CN117066819B

CN117066819B - An automatic pipe-to-pipe butt welding process for hydraulic stainless steel pipelines

Info

Publication number: CN117066819B
Application number: CN202310786072.2A
Authority: CN
Inventors: 侯晓楠; 杨尊熙; 邓立国; 张云龙; 展娜; 王玉梅; 张莉; 常明; 纪淑霞; 汪超; 张光; 赵乐鑫; 尹克; 褚琦; 张立涛; 李瑞蓉; 彭秉洲
Original assignee: Taian Aerospace Special Vehicle Co ltd
Current assignee: Taian Aerospace Special Vehicle Co ltd
Priority date: 2023-06-29
Filing date: 2023-06-29
Publication date: 2025-09-02
Anticipated expiration: 2043-06-29
Also published as: CN117066819A

Abstract

The invention discloses a pipe-pipe butt joint automatic welding process of a hydraulic stainless steel pipeline, which adopts the technical scheme of a fixing piece or a steel threaded air inlet joint with a clamping sleeve, realizes the butt joint automatic welding of a pipe joint with any clamping length and a steel pipe, and achieves the effect of 100% automatic welding proportion of the hydraulic pipeline. The invention also adopts the technical proposal of tungsten electrode gap gauge and adjusting the relative position between the tungsten electrode and the center of the groove, stabilizes the welding quality, solves the problem that the welding seam deviates from the center of the groove, and realizes the single-sided welding and double-sided forming effects. The invention also adopts the technical scheme of debugging welding parameters through an algorithm, so that reasonable welding parameters can be rapidly predicted when the product specification is changed, and the welding test times can be reduced. The effect of single-sided welding and double-sided forming of the hydraulic pipeline with the thickness of 2-4 mm and the same diameter or different diameters can be realized by reasonably adjusting the technological parameters.

Description

Automatic pipe-pipe butt welding process for hydraulic stainless steel pipeline

Technical Field

The invention relates to the technical field of pipeline welding, in particular to a pipe-pipe butt joint automatic welding process of a hydraulic stainless steel pipeline.

Background

The application of the automatic welding process of the pipe-pipe butt joint in China at present mainly focuses on a high-precision guide pipe in the aviation field, and the experience for a chassis hydraulic pipeline is less. The chassis pipeline mainly comprises a suspension hydraulic system pipeline, a steering hydraulic system pipeline, an engine pipeline, a speed change pipeline, a brake pipeline, a driving pipeline and the like, and is mainly made of stainless steel, and if the same welding parameters are adopted in the circumferential weld welding process because the stainless steel has low heat conductivity, the welding line is difficult to penetrate through in the early stage, the welding line temperature in the later stage is higher, burning-through is easy to generate, most pipelines are automatically welded by adopting the process parameters which are gradually decreased in sections, and the difficulty of debugging the process parameters is further improved along with the reduction of the pipe diameter and the increase of the wall thickness. The wall thickness of the aviation conduit is in the range of [0.6,1] mm, however, the wall thickness of the chassis pipeline is in the range of [2,4] mm, the wall thickness of the pipeline is larger, the diameter of the pipeline is in the range of [6,38] mm, the diameter variation range is large, and therefore, the chassis pipeline has more severe heat input control in the welding process. Due to the fact that the wall thickness is increased, the welding seam forming difficulty is correspondingly increased due to the fact that the molten pool is heavy in the vertical and overhead welding positions, and therefore the welding difficulty of the chassis hydraulic pipeline is high when the same welding quality is achieved.

Automatic welding equipment requires a certain length of linear distance on both sides of the weld to meet the clampable requirements of the equipment, hereinafter referred to as clampable length. In the closed pipe welding tongs welding equipment, the distance from the tungsten electrode to the outer wall of the welding tongs is required to be larger than or equal to the clamping length, and the open welding equipment is required to be larger in space at two sides of a welding seam, so that a welding gun rotating space is required to be reserved. In order to meet the assembly requirements of various systems of the chassis, the shapes of the hydraulic pipelines are various, the steel pipes near the welding seams often have shape distortion, and the joint length is correspondingly shortened. The welding equipment has a narrow operable space, the common open type welding equipment cannot be automatically welded, and the closed type pipe welding tongs welding equipment is generally not suitable for pipelines with the thickness of more than 3mm, and two types of welding tongs welding equipment are required to be used alternately. The manual welding has higher technical requirements for workers, and the welding quality is not easy to control. Meanwhile, the multi-section welding process parameter debugging method is complex, multiple test welding confirmation is needed, and the manpower and material resources are wasted in the debugging process. Therefore, how to obtain stable welding quality, and stability of controlling welding quality is a new problem which is mainly faced in the production of chassis pipelines.

The document CN103962684B discloses an automatic welding method of a hydraulic hard pipe assembly, but the automatic welding method has certain defects, the automatic welding proportion of the welding method described in the document is 85.6 percent, and the automatic welding of the hydraulic pipeline cannot be realized completely. Because the closed welding tongs can only weld the pipeline with the wall thickness smaller than 2mm, after the pipeline with the wall thickness larger than 2mm is subjected to backing welding by using the closed welding tongs, the pipeline is welded by using the open type automatic welding equipment and filler wire, and two kinds of equipment are required to be used for welding for two times, so that the production process is complex. Meanwhile, the joint is required to be processed under the condition of equal inner diameter and equal outer diameter of the guide pipe, the processing procedure is increased, and the butt welding scheme of the unequal-diameter joint cannot be provided.

Under the conventional argon arc welding process, the center of the tungsten electrode points to the center of the groove, but the center position of the tungsten electrode deviates from the forming centers of the front and back welding seams during welding of the hydraulic pipeline, the width of the back welding seam is 1-4 mm, and when the forming position of the back welding seam deviates greatly from the center of the groove, the root is not melted through, so that the penetration of the back welding seam is ensured, and the relative position of the tungsten electrode and the center of the groove is required to be adjusted. There is no unification of the mechanism of generation of such deviations, and the compensation method also lacks an effective solution.

In summary, in the prior art, an effective solution is not yet available for how to realize all automatic welding problems for hydraulic pipelines, and how to realize the aims of single-sided welding double-sided forming and unequal-diameter joint butt joint single-sided welding double-sided forming under one welding process of chassis hydraulic pipelines.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an automatic pipe-pipe butt joint welding process of a hydraulic stainless steel pipeline, which has the effect of realizing the welding of pipe joints and steel pipes with any clamping length and achieving the automatic welding proportion of 100 percent. The automatic welding process provided by the invention can realize the butt joint single-sided welding and double-sided forming of the equal-diameter or unequal-diameter pipe joint and the steel pipe, and achieves the effect of the I-level welding seam in QJ2865A-2014 'conduit welding technical condition'. The technical scheme adopted by the invention is as follows:

An automatic pipe-pipe butt welding process for a hydraulic stainless steel pipeline comprises the following steps:

The first step, sawing and blanking a stainless steel guide tube,

Secondly, flattening the opening of the catheter,

Thirdly, bending the conduit after flattening by a data hydraulic pipe bender,

Fourth, the catheter is cleaned,

Step five, carrying out positioning welding on the guide pipe and the welded pipe joint in a spot welding mode, adopting an argon arc welding machine to carry out positioning welding without filling wires, and cleaning the welded joint of the guide pipe and the joint to be welded by using an industrial acetone wet towel before welding;

the welding tongs are arranged on a welding tongs support, the welding tongs are closed pipe welding tongs, a fixing piece for clamping a pipeline is arranged on the welding tongs support or a steel threaded air inlet connector with a clamping end is directly clamped on the welding tongs, the fixing piece is a flat clamping piece or a concave clamping piece, and the flat clamping piece or the concave clamping piece respectively comprises an upper semicircle and a lower semicircle;

seventh, putting a tungsten electrode gap gauge into the welding tongs, and positioning the tungsten electrode after the tungsten electrode falls to the middle diameter position of the gap gauge.

And eighth, placing the pipeline into a welding tongs, adjusting the relative position of the groove center of the pipeline and a tungsten electrode according to the comparison result of the size and the material of the joint body of the pipe joint and the guide pipe, clamping the pipeline, and clamping the pipeline by adjusting the height of a set screw on the clamping piece of the upper half piece.

When the pipeline is too long, the other side of the steel pipe is placed on the steel pipe bracket.

And ninth, installing an air inlet device and an air outlet device of the protective air in the pipe.

And tenth, estimating the average heat input by using a formula according to the diameter and the wall thickness of the joint body, calculating the heat input value of each section by using the average heat input, setting the welding speed and the pulse time, reversely calculating the welding current values of the peak value and the base value by using the formula, inputting the welding program for trial welding, and adjusting the parameters according to the welding result until the welding quality is qualified.

And eleventh, automatically welding the guide pipes and the pipe joints which are welded in batches.

Preferably, the stainless steel hydraulic pipeline is made of austenitic stainless steel, the outer diameter range of the pipeline is 6-38 mm, the wall thickness of the pipeline is 2-4 mm, one side of the pipeline which is butted at two sides is a pipe joint, the other side of the pipeline is a stainless steel conduit, the joint body of the pipe joint is at least one of the outer diameter, the inner diameter and the wall thickness of the conduit, the same diameter or equal outer diameter and unequal inner diameter are adopted, a flat-end pipe joint is selected when the outer diameter of the pipe joint is equal to or greater than 1mm, a bevel pipe joint is adopted when the outer diameter of the pipe joint is greater than or equal to 1mm, the outer diameter, the inner diameter and the wall thickness of the pipe joint which are butted at two sides are the same, the difference between the outer diameter and the inner diameter is not greater than 2mm when the wall thickness is equal to one of the outer diameter and the inner diameter is not greater than 1mm.

In the sixth step, the tungsten electrode is mounted on the rotor gear of the welding tongs, the axial direction of the tungsten electrode cannot be adjusted, and a proper fixing piece is required to be selected before the pipeline is mounted.

The clamping method of the steel threaded air inlet connector with the clamping end on the welding tongs is simple and convenient, in order to conduct more stable clamping at the connector of the pipe connector directly, a flat clamping piece or a concave clamping piece can be adopted, the concave clamping piece comprises a first-stage concave-retraction concave clamping piece and a second-stage concave-retraction concave clamping piece, the first-stage concave-retraction concave clamping piece is retracted into the clamping piece body to be 0-0.5 mm before the threads of the fastening bolt hole, the retraction diameter is larger than the maximum outer diameter of the pipe connector nut, the fastening bolt hole is moved out of the clamping piece by the second-stage concave-retraction clamping piece, and the fastening bolt hole is arranged along the radial direction.

Preferably, when the pipe joint can clamp a pipeline with the length smaller than the distance from the tungsten electrode to the outer wall of the welding tongs, a first-stage concave clamping piece or a second-stage concave clamping piece is adopted according to the reduction degree of the clampable length, the central hole of the concave clamping piece is the same as the outer diameter of the pipe joint or the steel pipe, and the total length or the clamping position from the tungsten electrode to the outer wall of the welding tongs to the outer wall of the joint is in the nut part of the pipe joint, the steel threaded air inlet joint with the clamping end is adopted for clamping on the welding tongs.

Further preferably, when the pipe joint can clamp a pipeline with the length longer than the distance from the tungsten electrode to the outer wall of the welding tongs, a flat clamping piece is selected, the central hole of the clamping piece is the same as the outer diameter of the pipe joint or the steel pipe, at the moment, a larger clamping area can be ensured, the clamping point is coplanar with the tongs, and the clamping force is larger.

When the length of the steel pipe which can be clamped is smaller than the distance from the tungsten electrode to the outer wall of the welding tongs, clamping pieces cannot be used for clamping, a clamping plate clamp is used at the moment, the clamping plate clamp comprises two U-shaped clamping plates, one U-shaped clamping plate is an aluminum alloy clamping plate, the other U-shaped clamping plate is a high-temperature-resistant flame-retardant nylon clamping plate, the aluminum alloy is required to be contacted with a guide pipe and the welding tongs to achieve a conductive effect, the high-temperature-resistant flame-retardant nylon clamping plate is arranged outside the aluminum alloy clamping plate and is intersected with the aluminum alloy clamping plate to prevent air leakage, and the nylon clamping plate is externally clamped on the welding tongs by an insulating clamp for fixing.

In the seventh step, the tungsten electrode gap gauge is a stepped cylinder, the middle cylinder is used for positioning the radial position of the tungsten electrode, the size of the middle diameter is determined by the method that the middle diameter = two side diameters +2 x tungsten electrode gap, the two side diameters represent the outer diameter of a joint body or the outer diameter of a guide pipe of a pipe joint of a pipeline, when the outer diameters of the two sides of the pipeline are different, the two side diameters take the outer diameter of a larger side, and the tungsten electrode gap refers to the distance from the tip of the tungsten electrode to the outer diameter of the pipeline on the side with the larger diameter. The tungsten electrode gap h is a function of the wall thickness of the pipeline, and h is expressed by the formula h=0.5×delta;

When the wall thickness of two sides of the pipeline is different, the numerical value is taken as the unit mm from the side with the larger wall thickness.

In the eighth step, the tungsten electrode is used as a reference to position the center of the groove, and the corresponding position range of the center of the groove relative to the tip of the tungsten electrode is +/-0.5 mm. The method for adjusting the relative positions of the tungsten electrode and the center of the groove according to the comparison result of the size and the material of the joint body and the guide pipe of the pipe joint comprises the steps that when the wall thickness of the joint body and the wall thickness of the guide pipe are different, the tungsten electrode is deviated to the large side of the wall thickness by an offset amount (0, 0.5 mm), when the wall thickness is the same, the tungsten electrode is deviated to the large side of the outer diameter by an offset amount (0, 0.5 mm), when the wall thickness is different, the large side of the wall thickness needs more energy to melt a base metal, when the wall thickness is the same, the large side of the outer diameter is provided with a transition groove, the slope of the groove surface promotes an arc to deviate downwards, and in order to ensure that the inner wall of the small side of the inner diameter is fully melted to form transition connection with the inner wall of the large side of the inner diameter, and the tungsten electrode is deviated to the large side of the outer diameter.

Specifically, the relative positions of the tungsten electrode and the groove center are adjusted through a movable pipeline, when the wall thicknesses of the joint body and the guide pipe are different, the movable pipeline enables the tungsten electrode to deflect to the side with the larger wall thickness, the deflection (0, 0.5) is achieved, when the wall thicknesses are the same, the movable pipeline enables the tungsten electrode to deflect to the side with the larger outer diameter, the deflection (0, 0.5) is achieved, when equal diameters (when the inner diameters and the outer diameters of two welding sides are equal), the tungsten electrode is deflected to the side with the high silicon content, the pipeline is used as a reference, when the silicon content of the joint body is smaller than 0.3%, the movable pipeline enables the tungsten electrode to deflect to the guide pipe (0, 0.3) millimeter, when the silicon content of the joint body and the steel pipe are both in the range of 0.3-0.4%, when the silicon content of the joint body is higher than 0.4%, the movable pipeline enables the tungsten electrode to deflect to the joint body (0, 0.3] millimeter, the silicon content can be estimated through the appearance of a welding seam, when the silicon content is smaller than 0.3%, and when the silicon content is smaller than 0.4%, the silicon content is higher than the bright surface of the welding seam is high.

In the ninth step, the air inlet side of the in-pipe protection air supply device can be provided with a perforated silica gel plug and a steel guide pipe, the silica gel plug is conical, the small diameter of the silica gel plug is more than 3mm smaller than the inner diameter of the pipe joint, and the large diameter of the silica gel plug is more than 1mm larger than the inner diameter of the pipe joint, the air inlet side of the in-pipe protection air supply device can also be provided with a steel threaded air inlet connector connected with the air supply pipe through a quick connector, the steel threaded air inlet connector is connected with a threaded sleeve through H/n fit, the threaded sleeve is in threaded fit with a nut of the pipe joint, one end of the air inlet connector is connected with the quick connector for the air supply pipe, the outer diameter of one end of the air inlet connector is smaller than 0.5mm smaller than the inner diameter of the pipe joint, the steel wire mesh is arranged in the air inlet connector, and the air outlet uniformity effect can be achieved.

Specifically, when the pipe joint can be clamped, the silica gel plug is adopted for air supply, the air supply steel pipe is connected to the air supply hose through the quick-connection joint, the air supply steel pipe is inserted into the silica gel plug, and the silica gel plug is arranged in the pipe joint.

The tenth step comprises the following steps:

(1) The method for estimating the average heat input by using a formula according to the diameter and the wall thickness of the joint body comprises the steps of recording at least five groups of welding parameter finishing lists which are qualified in welding when the pipe joint and the conduit are of different diameters and the wall thickness under the same material condition, listing the diameters, the wall thicknesses and the average heat input, taking the average heat input as dependent variables, fitting the diameters, the wall thicknesses and the average heat input by using a linear formula with the diameters and the wall thicknesses as independent variables, and obtaining a relational expression of the average heat input relative to the diameters and the wall thicknesses:

;

wherein, the D-pipeline outer diameter, when two sides of outer diameter are different, taking larger value, unit mm;

a. b, c, a constant obtained by a fitting formula;

Delta-wall thickness of the pipeline, wherein when the equal diameter of the pipeline is unequal, the wall thickness average value is obtained, and when the equal diameter of the pipeline is unequal, delta = wall thickness +0.5 radius difference is unit mm;

(2) Fitting a decreasing linear formula according to the number of segments of known pipeline penetration welding parameters of at least five groups and the heat input values of each segment to obtain a decreasing coefficient k of the heat input of each segment, and solving the average value of the decreasing coefficients of the heat input of each segment;

The heat input of each segment is gradually decreased, and is converted into a function of the segment through a fitting method to obtain a Qn formula, wherein Qn=k is n+b;

The k-slope is a constant obtained by fitting a formula, namely a decreasing coefficient of the heat input;

b-intercept, which is a constant obtained by a fitting formula;

n-number of segments;

The fitting method comprises the steps of recording welding parameters which are qualified by welding and have different diameters and wall thicknesses, calculating the heat input of each section, and linearly fitting the number of sections with the welding heat input of each section;

then the k values of different formulas are averaged to obtain the average value of the decreasing coefficients ;

Combining mean heat inputThe formula: Heat input of the estimated mean value Data substitutionA formula;

wherein, n is the number of segments, qn is the heat input of the nth segment,

Qn=* N+Q1, calculating to obtain Q1, thereby calculating the estimated heat input Qn of each segment;

(3) The peak heat input and the base heat input for each segment are calculated based on the following formulas:

Since the average heat input of each segment is equal to the sum of the peak current heat input and the base current heat input, i.e., the nth segment heat input qn=qp [ Tp/(tp+tb) ]+qb [ Tb/(tp+tb) ];

Wherein Qp-peak heat input, qb-base heat input, tp-peak pulse time, tb-base pulse time, tb: tp is selected from 1 to 3, preferably 1;

The ratio range Qp of the peak heat input to the base heat input is 2-5, preferably 3;

(4) The peak current and the base current are calculated based on the following formula:

Heat input formula q=η×i×u/V/1000;

wherein Q is welding input, and the unit is KJ/mm;

Eta-effective utilization rate of electric arc thermal power, 0.9 is obtained according to empirical value argon arc welding;

i is welding current, the peak current is marked by Ip, the base value current is marked by Ib, the unit is A, ip is 2-5;

u is welding voltage, peak voltage is marked by Up, base voltage is marked by Ub, unit V;

v-welding speed in mm/s, wherein the welding speed is adjusted within the range of 1-2.5 mm/s;

the voltage formula is obtained through a fitting mode, the formula of the welding equipment with the same type is universal, and the fitting is needed again when the brand or model of the equipment is replaced:

U=d×h+e×I+f;

The h-tungsten electrode gap is the distance from the tip of the tungsten electrode to the outer diameter of the pipeline, and when the outer diameters of two sides of the pipeline are different, the outer diameter of the pipeline is the outer diameter big side, and the unit mm;

The welding equipment d, e and f with the same model are constants;

The fitting method comprises the steps of respectively recording voltage values fed back by equipment under different tungsten electrode gaps and current values, and then linearly fitting the corresponding relation between the tungsten electrode height, the current value and the voltage value to obtain a voltage calculation formula;

the tungsten electrode gap h is a function of the wall thickness of the pipeline, and h is expressed by the formula h=0.5×delta ;

Wherein, when the wall thickness of the two sides of the pipeline is different, the delta-wall thickness is measured as the unit mm on the side with larger wall thickness,

Calculating peak heat input Qp and base heat input Qb of each section, substituting a voltage formula, and setting a tungsten electrode gap value and a welding speed to calculate peak current Ip and base current Ib of each section;

Preferably, the heat input is inversely related to the sulfur content in the material, and as the sulfur content is reduced to ensure penetration, the welding current can be increased or the welding speed can be reduced, and the adjustment range is +/-10%.

And writing a welding current calculation formula into the EXCEL table, and rapidly calculating the welding current of each section of peak value and base value by using a single variable solving and a cycle statement of a macro command to generate a welding parameter table.

Preferably, the welding procedure is divided into 5-9 sections, the welding procedure starts clockwise from 3 o' clock, 1 section is an arc leading section, the arc leading section is 10 degrees, the middle is a welding section with an angle of 40-80 degrees, the last section is an arc receiving section, the number of the welding sections is not counted, the arc receiving angle is 90-120 degrees, and the current is attenuated to zero.

Furthermore, the invention also adopts the technical proposal of the welding tongs bracket and the steel pipe bracket, which has the effects of conveniently positioning and clamping the steel pipe and supporting the overlong steel pipe in an auxiliary way.

Compared with the prior art, the invention has the beneficial effects that:

The invention designs the technical means of concave clamping pieces, clamping plates or steel threaded air inlet connectors with different specifications, realizes the butt joint automatic welding of pipe joints with any clamping length and steel pipes, obtains 100% automatic welding of hydraulic pipelines, has the effect of achieving single-sided welding and double-sided forming by only using one type of equipment and one-time welding, and can meet the clamping and welding requirements of 24-degree conical heads and 37-degree ball head common brands (such as Eton, su Jiangge and the like) welding type hydraulic pipe joints. Can be suitable for closed pipe welding equipment of different brands such as AMI, MK, hua Heng, baoli Su Di and the like.

2, Adopting a technical means of debugging welding parameters through an algorithm, and having the effects of rapidly predicting reasonable welding parameters when changing materials or changing pipeline specifications, rapidly debugging proper technological parameters and reducing welding test times, and realizing single-sided welding and double-sided forming of hydraulic pipelines with equal diameters or unequal diameters of thickness (2-4) by reasonably adjusting the technological parameters;

the invention also adopts the technical means of the back air supply device and the air outlet device, which has the advantages of fully protecting the back welding seam, simultaneously utilizing the air pressure difference principle to play a role in supporting the flat welding seam, and achieving the effect that the appearance of the welding seam is flat and even and the top is free from collapse;

The welding quality is stabilized by adopting the technical scheme of adjusting the relative position between the tungsten electrode and the center of the groove by adopting the tungsten electrode gap gauge, the problem that the welding seam deviates from the center of the groove is solved, and the single-sided welding and double-sided forming effects are realized. The adjusting step comprises the seventh step of adjusting the radial diameter of the tungsten electrode according to the pipe joint of the pipeline and the outer diameter of the steel pipe, and the eighth step of adjusting the tungsten electrode bias according to the pipeline size and the material composition through the adjustment of the axial position of the pipeline.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.

FIG. 1 is a flow chart of a tube-to-tube butt automatic welding process for a hydraulic stainless steel pipeline;

FIG. 2 is a schematic diagram of a hydraulic stainless steel pipeline structure, wherein FIG. (a) is a schematic diagram of a hydraulic stainless steel pipeline structure in a butt joint mode with equal outer diameter and unequal inner diameter;

wherein 001 is a pipe joint, 002 is a steel pipe to be welded, and 003 is a tungsten electrode;

FIG. 3 is a schematic diagram of clamping a hydraulic pipeline, wherein 301 is the clampable length of a pipe joint, 302 is the distance from a tungsten electrode to the outer wall of a welding tongs, 303 is the clampable length of a steel pipe, and 004 is the welding tongs;

FIGS. 4 (a) -4 (f) are clamping solutions for different pipeline sizes;

FIG. 4 (a) is a flat clip-on length grippable solution;

figure 4 (b) is a level 1 retracting concave clip-grippable length-hour solution,

Figure 4 (c) is a level 2 retracting concave clip-grippable length-hour solution,

FIG. 4 (d) is a view of the steel threaded air intake fitting clamping position with the clamping end above the union nut;

FIG. 4 (e) is a solution with a gripping end of a steel threaded air intake fitting gripping location outside the fitting;

FIG. 4 (f) is a clamping solution of a clamping plate clamp-steel pipe without a clampable straight-edge guide pipe;

Wherein 005 is an upper clamping piece and 006 is a lower clamping piece;

401-threaded holes, 402-clamping sleeves, 403-threaded sleeves, 404-air inlet connectors, 405-set aside pipe joint nut assembling and disassembling clamping length, 406-clamping positions, 407-pipe joint nut outer diameters, 408-aluminum alloy clamping plates, 409-high-temperature-resistant flame-retardant nylon clamping plates and 410-insulating clamps;

FIG. 5 is a schematic illustration of the use of a holder bracket and a steel tube bracket, wherein 501-holder bracket, 502-tube bracket, 503-rotating handle, 504-rotating pallet;

FIG. 6 is a schematic view of a tungsten electrode gap and a schematic view of a tungsten electrode gap used therein, wherein FIG. (a) is a schematic view of a tungsten electrode gap and FIG. (b) is a schematic view of a tungsten electrode gap used therein, 601-a mid-diameter position, 602-a tungsten electrode gap;

FIG. 7 shows an in-pipe protective gas inlet device, wherein FIG. (a) shows an in-pipe protective gas inlet device, a silica gel plug and a steel pipe, and FIG. (b) shows an in-pipe protective gas inlet device, a steel screwed joint, 701 a silica gel plug, 702 a gas supply steel pipe, 703 a quick connector, 704 a gas supply hose, 705 a steel wire mesh;

FIG. 8 shows an in-tube shielding gas outlet apparatus, wherein 801-the inner core portion, 802-the spacing portion, 803-the handle portion;

FIG. 9 is a schematic diagram of a weld current partition;

FIG. 10 is a photograph of a metallographic test of a welded joint, wherein (a) is a metallographic specimen, (b) is a joint structure, 200X, and (c) is a fused region structure, 500X;

FIG. 11 is a graph of tungsten height, current, voltage fit.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In a typical implementation mode of the invention, a process flow chart is shown in fig. 1, a pipeline structure schematic diagram is shown in fig. 2, the pipeline structure schematic diagram is in a butt joint mode of a pipe joint and a conduit, the pipeline structure schematic diagram (a) is in a butt joint mode of equal outer diameters and unequal inner diameters, and the pipeline structure schematic diagram (b) is in a butt joint mode of equal wall thicknesses and unequal outer diameters and inner diameters. One side of the pipeline which is butted at the two sides is a pipe joint 001, the other side is a steel pipe 002 to be welded, the steel pipe to be welded is a stainless steel hydraulic conduit, the material is austenitic stainless steel, the outer diameter range of the pipeline is 8mm to 38 mm, the wall thickness of the pipeline is 2 mm to 4 mm, a flat-end pipe joint is selected when the pipeline has equal diameter or equal diameter and unequal inner diameter, and a bevel pipe joint is adopted when the difference value between the outer diameter of the pipe joint and the outer diameter of the conduit is more than or equal to 1 mm. The outer diameter, inner diameter and wall thickness of the two side butt joint steel pipe and the pipe joint are required to have the same size, when the wall thickness is the same, the difference between the outer diameter and the inner diameter is not more than 2 mm, and when one of the outer diameter and the inner diameter is the same, the wall thickness difference is not more than 1 mm.

The main process steps are as follows:

firstly, sawing and blanking a stainless steel guide pipe, wherein the blanking mode can be selected from a portable pipeline cutting machine, a metal circular sawing machine, a cooling liquid and a laser pipe cutting machine;

secondly, flattening the guide pipe by a flattening machine, wherein the flatness of the end of the flattened pipe is less than or equal to 0.2mm;

Thirdly, bending the conduit after flattening by a data hydraulic pipe bender, arranging an extension section on the conduit to meet the clamping requirement of equipment, sawing the extension section after shaping, selecting automatic or manual sawing and cutting according to the structural form, flattening the conduit again after sawing, and clamping the conduit with a flattening machine for flattening the conduit with the length of the flattening machine, wherein the flatness of the pipe end after flattening is less than or equal to 0.2mm, flattening the conduit with an electric polishing machine or file for less than 10mm, and the flatness of the pipe end after flattening is less than or equal to 0.5mm;

fourthly, a pneumatic pipeline cleaning gun is used for shooting high-density polyurethane bullets which are more than about (10-30)% of the inner diameter of the pipe into the guide pipe, the bullets are used for carrying out the surplus matters in the pipe in the movement process of the pipe, and dirt such as dust in the pipe and fine scrap iron and the like carried in the cutting process are cleaned, and the cleaning times are carried out until the dirt on the surface of the sponge bullets is discharged;

and fifthly, using an argon arc welding machine to weld the formed guide pipe and the welded pipe joint without filling wires in a positioning way, cleaning the welded joint of the guide pipe and the joint by using an industrial acetone wet towel before welding, positioning welding spots (3-4) which are required to be uniformly distributed on the periphery of the pipe, wherein the diameter (3-4) of each welding spot is equal to or smaller than the diameter (3-4) of each welding spot, the height of each welding spot is not larger than 0.3mm of the surface of a base metal, and polishing the welding spots by using a file when the height of each welding spot exceeds the surface of the base metal, wherein the maximum butt joint gap after positioning is smaller than 0.5 mm, and the maximum misalignment amount is smaller than 0.5 mm.

And a sixth step of installing the welding tongs on the welding tongs support as shown in fig. 5, clamping the two sides of the butt joint with unequal diameters by using clamping pieces with different inner hole diameters, clamping the pipeline with the clamping length of the pipe joint (the clamping length of the pipe joint is shown as 301 in fig. 3) being larger than the distance from the tungsten electrode to the outer wall of the welding tongs as shown as 302 in fig. 3, adopting the technical scheme of a flat clamping piece as shown as fig. 4 (a), installing a flat end set screw in the threaded hole 401 of the upper clamping piece 005, the effect is that the screw protruding after the upper clamping piece 005 and the lower clamping piece 006 are closed tightly presses the pipeline, clamping the pipeline with the clamping length of the butt joint being smaller than the distance from the tungsten electrode to the outer wall of the welding tongs as shown in fig. 4 (b), clamping the clamping length of the pipe joint with a first-stage or second-stage indentation concave clamping piece is slightly smaller than that of a common joint, adopting the technical scheme of the first-stage indentation concave clamping piece, and inwards retracting the central shaft of the upper clamping piece 005 and the lower clamping piece 006 of the first-stage indentation concave clamping piece to the front 0.5mm before the screw threads of the set screw hole 401, the diameter is larger than the maximum outer diameter of the pipe joint, and the clamping piece is located at the position of the joint with the clamping piece and the clamping end being close to the flange and the bevel of the flange.

As shown in fig. 4 (a), a workpiece error of 3-5 mm is generally reserved between the clamping piece and the pipe joint nut, so as to overcome the dimension accumulated error of workpiece parts and positioning welding.

If the total length of the pipe joint is smaller, as shown in fig. 4 (c), a two-stage retraction clamping piece is adopted, wherein the first stage retraction clamping piece is retracted to be 1.5mm in front of the clamping piece mounting surface, the retraction diameter is larger than the maximum outer diameter of the pipe joint nut, the second stage retraction moves out the tightly fixed threaded hole 401 from the clamping piece, and the inner diameter of the central hole of the concave clamping piece is the same as the outer diameters of the pipe joint and the steel pipe;

If the width of the welding tongs of the welding equipment is larger, when the clamping length of the pipe joint is smaller than the distance from the tungsten electrode to the outer wall of the welding tongs, the technical scheme of the steel threaded air inlet joint with the clamping end can also be adopted, when the clamping position of the clamping piece is above the nut of the pipe joint, the steel threaded air inlet joint 404 with the clamping sleeve is adopted, as shown in fig. 4 (d), the clamping sleeve and the threaded sleeve are matched in an H/n mode, the outer diameter of the clamping sleeve 402 is the same as the diameter of an inner hole of the flat clamping piece, the clamping sleeve is used for clamping instead of the outer diameter part of a pipeline, the inner diameter of the clamping sleeve 402 is larger than the outer diameter 407 of the nut of the pipe joint, the effect is that the nut of the pipe joint can be screwed with the threaded sleeve 403, the clamping sleeve 402 cannot cover the outer nut of the pipe joint after being installed, the clamping length 405 of the nut of the pipe joint is set, the clamping sleeve is convenient for the dismounting of the nut of the pipe joint and the steel threaded air inlet joint with the clamping end is adopted, and the clamping sleeve is matched in an H/n mode, the clamping position 406 in the figure is adopted, and the tightness is ensured in a matched mode.

The inside protection gas supply device has the advantages that the gas outlet structure is a stepped steel rod, the inner core part is deep into the pipe joint, the diameter is smaller than the inner diameter (1-1.5) of the steel pipe, the choke resistance is achieved, the limiting part is larger than the inner diameter of the pipe joint, the diameter of the handle part is not limited, and the diameter can be equal to the inner core.

When the welding tongs are clamped outside the pipe joint, namely the pipe joint is arranged inside the welding tongs, a steel threaded air inlet joint 404 with a clamping end is adopted, as shown in fig. 4 (e), when the clamping position of the clamping piece of the welding tongs is out of the length range of the pipe joint, the clamping end is added to the threaded sleeve, the outer diameter of the clamping end is the same as the inner hole of the flat clamping piece, the clamping end is used for replacing the clamping of the pipe joint, and the threaded sleeve with the clamping end can be processed into a step shape according to the requirements of the clamping piece;

For the situation that the clamping cannot be performed due to the fact that the distance between the bending part and the welding line is smaller on one side of the steel pipe, the clamping technical scheme of the clamping plate clamp is adopted, as shown in fig. 4 (f), the clamping plate clamp is two U-shaped clamping plates, the inner width of each U-shaped clamping plate is identical to the diameter of the steel pipe, the effect is that the distance between the steel pipe and the clamping side is not limited by the concentric requirement of clamping plates, one clamping plate is made of aluminum alloy, one clamping plate is made of high-temperature-resistant flame-retardant nylon, the aluminum alloy clamping plate 408 is grounded and is in contact with a guide pipe and a welding clamp, the conductive effect is achieved, the high-temperature-resistant flame-retardant nylon clamping plate 409 is arranged outside the aluminum alloy clamping plate and is crossed with the aluminum alloy clamping plate to prevent air leakage, and the nylon clamping plate external insulation clamp 410 is clamped on the welding clamp for fixing, and the effect is used for preventing short circuit of the clamping plates.

Seventh, a tungsten electrode gap gauge 602 is placed in the welding tongs, and the tip of the tungsten electrode 003 is dropped to the middle diameter position 601 to position the tungsten electrode. The conventional method is to locate the radial position of the tungsten electrode in a visual manner, and due to larger error, the inventor designs a tungsten electrode gap gauge 602 as shown in fig. 6 (a), wherein the tungsten electrode gap gauge 602 is a cylinder with a ladder-type structure, two ends of the cylinder are supported and fixed by the lower half piece of the clamping piece, and the middle cylinder is used for locating the radial position of the tungsten electrode, as shown in fig. 6 (b), and is used for quickly and accurately locating the tungsten electrode gap. The size of the middle diameter is determined by the following method that when the outer diameters of two sides are the same, the middle diameter D=the diameter of two sides+2×the tungsten electrode gap h, wherein the tungsten electrode gap h is the distance from the tip of a tungsten electrode to the outer diameter of a pipeline, when the outer diameters of two sides of the pipeline are different, the outer diameter of the pipeline is the large outer diameter side, the tungsten electrode gap h is a function of the wall thickness of the pipeline, and the formula is h=0.5×deltaWhen the wall thicknesses of two sides of a pipeline are different, the numerical value is the unit mm of the side with the larger wall thickness, the tolerance of 0.2mm is related, the tolerance of less than phi 16mm can be increased by 0.2mm without adding 0.2mm and the requirement of more than or equal to phi 16mm, the welding quality stability can be improved by avoiding tungsten adhesion in the welding process through proper tungsten electrode gap, and the welding quality stability is improved.

The tungsten electrode is preferably cerium tungsten, thorium tungsten and lanthanum tungsten have no differential effect on welding quality and stability, and is preferably a high-durability and non-radiative cerium tungsten electrode, and the cerium tungsten has the following structure: the tip end of the tungsten electrode is axially polished to be (30-35) DEG, the diameter of the end plane is (0.2-0.3) mm, the polishing lines are consistent with the axial direction, and a tungsten electrode polishing machine with angle scales is used for polishing.

Eighth step, put into the soldering terminal with the pipeline, when the pipeline overlength, on the pipeline bracket was placed to the steel pipe opposite side, pipeline bracket height-adjustable, soldering terminal support 501 (bump-proof frame and support have been removed in the figure) and pipeline bracket 502 place the mode as shown in fig. 5, pipeline bracket 502 sets up rotatory handle 503 height-adjusting, pipeline bracket 502 top sets up rotatable layer board 504 of V type, its effect lies in that the pipeline shape is complicated, suitable height can keep the pipeline position level in the soldering terminal, reduces the soldering terminal atress.

The steel pipe is moved in the welding tongs, and the relative positions of the groove center and the tungsten electrode tip are adjusted according to the sizes and the material compositions of the pipe joint and the steel pipe, and the reason is that the positions of the tungsten electrode tip, the front welding line center (outer welding line center) and the back welding line center (inner welding line center) deviate, the width of the back welding line can be 1mm at minimum, the root is not melted through when the deviation between the forming position of the back welding line and the groove center is large, and the relative positions of the groove center and the tungsten electrode tip are required to be adjusted in order to ensure the penetration of the back welding line. The center of the groove is within +/-0.5 mm of the tip of the tungsten electrode. The relative position of the groove center and the tip of the tungsten electrode is adjusted according to the pipeline size, when the wall thickness of the pipe joint and the wall thickness of the steel pipe are different, the tungsten electrode is deviated to the side with large wall thickness by an offset (0, 0.5) millimeter, when the wall thickness is the same, the tungsten electrode is deviated to the side with large outer diameter by the offset (0, 0.5) millimeter, as described in the embodiment 5 and the embodiment 6, the principle is that when the wall thickness is different, the side with large wall thickness needs more energy to melt the base metal, and when the wall thickness is the same, the inner wall of the side with large inner diameter needs to be melted to flow to the inner wall of the side with small inner diameter to form transition connection.

The components of the steel pipe and the joint have obvious influence on the welding effect, the steel pipe is generally stable in the commodity feeding component of the same manufacturer, the pipe joint is different in components according to the standard or the manufacturer, even if the pipe joint meets the national standard, the components of the joint and the steel pipe are difficult to ensure to be completely the same due to different manufacturers, different processing modes, non-uniform raw materials and the like, the tungsten electrode tip pointing position is adjusted by adopting the following method in order to ensure that the root part of the back welding seam is penetrated, and the tungsten electrode tip pointing position is difficult to ensure to be completely the same:

The pointed position of the tungsten electrode tip is regulated according to the pipe joint and the steel pipe material composition, the method is that when the equal diameter welding is carried out (when the inner diameter and the outer diameter of the two welding sides are equal), the tungsten electrode is deviated to the side with high silicon content, the silicon content of the steel pipe is 0.3 percent to 0.4 percent as the benchmark, when the silicon content of the joint is less than 0.3 percent, the tungsten electrode is deviated to the steel pipe (0, 0.3 millimeter; when the silicon content of the joint is similar to that of the steel pipe and is in the range of 0.3% -0.4%, the tungsten electrode is not biased; when the silicon content of the joint is higher than 0.4%, the tungsten electrode should be deviated to the pipe joint (0, 0.3) millimeter, the silicon content can be estimated by the appearance of the welding seam, when the silicon content is less than 0.3%, the welding seam presents a bright surface, when the silicon content is higher than 0.4%, the welding seam presents a matt surface, as described in the example 7, the comparative example 2 and the example 4, the principle is that when the silicon content of two sides is different, siO ₂ generated by deoxidization is higher on the side with high silicon content, siO ₂ is an oxidizing active agent, the surface tension temperature coefficient of a molten pool can be positive, meanwhile, the spot area of an anode of the molten pool is reduced because SiO ₂ is a non-metallic oxide, the conductivity is poor, the arc conductive channel is reduced, the arc is deviated to the side with low silicon content, the arc molten pool is deviated to the side with low silicon content (Bian Chungong and the stainless steel A-TIG welding surface tension measurement and penetration increase mechanism is researched [ D ]. Lanzhou university, 2020:0-61), and therefore, in order to ensure that the root penetration of the tungsten electrode should be deviated to the side with high silicon content.

The air inlet device and the air outlet device are selected according to the product size, the purity of the protective gas is more than or equal to 99.99%, the flow rate of the protective gas outside the pipe is (30-40) cubic feet/hour, the flow rate of the protective gas inside the pipe is (15-20) cubic feet/hour, the air supply time is advanced by (10-15) seconds, and the air supply time is delayed by (20-35) seconds.

When the pipe joint 001 can be clamped, the air inlet device for protecting air in the pipe can adopt the technical scheme that a silica gel plug is adopted for air supply, as shown in fig. 7 (a), an air supply steel pipe 702 is connected to an air supply hose 704 through a quick-connection joint 703, the air supply steel pipe 702 is inserted into the silica gel plug 701, the silica gel plug 701 is arranged in the pipe joint 001, the silica gel plug has a small diameter which is more than 3mm smaller than the inner diameter of the pipe joint, and a large diameter which is more than 1mm larger than the inner diameter of the pipe joint, and the air inlet device has the advantages of low cost, firm installation, quick replacement and convenient purchase. The air inlet device of the protection air in the pipe can also adopt a steel threaded joint, as shown in fig. 7 (b), one end of the steel threaded joint is connected to a pipe joint, the other end of the steel threaded joint is connected with an air supply joint, the end part of the air supply joint is provided with a steel wire mesh 705, and the other end of the air supply joint is connected to the protection air inlet pipe through a quick-plug joint. The device has the advantages that the device is firm in installation and not falling off, the air in the pipe is discharged more uniformly through the steel wire mesh 705, the device is suitable for pipelines with larger pipe diameters, the screw thread screwing is needed, and the convenience is lower than that of a silica gel plug scheme. When the pipe joint cannot be clamped, the technical scheme of the steel threaded air inlet joint with clamping is needed, and the structure is shown in fig. 4 (d) (e), so that the air supply requirement is met and the clamping solution is provided.

The other side of the pipeline is provided with a protective gas outlet device in the pipeline, the structure is shown in figure 8, and the placing mode is shown in figure 5. The device is characterized in that the structure of the protecting gas supplying device in the pipe is a stepped steel bar, the protecting gas supplying device in the pipe comprises an inner core part 801, a limiting part 802 and a handle part 803 which are sequentially connected, the inner core part 801 stretches into a pipe joint, the diameter of the inner core part is smaller than the inner diameter (1-1.5) mm of the pipe joint, the limiting part 802 is larger than the inner diameter of the pipe joint, and the diameter of the handle part 803 is not limited (can be equal to the diameter of the inner core). The pipe inner protection gas supply device has the advantages that the pipe inner protection gas supply device is only placed into the pipe without threaded connection, and the installation is convenient. The diameter of the air outlet device is smaller than the inner diameter (1-1.5) of the pipe joint, a part of pipe orifice area is blocked to play a role in blocking flow, the air outlet quantity is smaller than the air inlet quantity to enable positive air pressure to be formed in the pipe, and the effect of adjusting weld joint formation can be achieved when the air outlet device is used in combination with the flow of protective gas in the pipe.

The welding current partition is divided into 9 sections according to the angle, the welding pipe is surrounded by about one and a half circles, the current in the different sections is different, the welding starting position is welded clockwise from the 3 o 'clock position, the welding seam is only sealed by 1/4 when the welding seam is welded to the 6 o' clock position, the forming of the welding seam is not affected by the small air pressure in the pipe, the welding seam is sealed by 3/4 when the welding seam is welded to the 12 o 'clock direction, the air pressure in the pipe can be larger than the air pressure outside the pipe, the positive air pressure can hold molten pool metal when the welding seam is welded to the horizontal position, the welding seam collapse at the position near the 12 o' clock is avoided, and the current gradually decreases to 0 after the 9 th section. The air supply time (10-15) is advanced and the air supply time (20-35) is retarded. The principle of the welding clamp is that air in the welding clamp and air in the steel pipe can be discharged by feeding air in advance, and the welding seam is ensured to be under the inert gas protection atmosphere during welding. The delayed air supply can accelerate the cooling of the welding seam, and the welding simulation calculation is carried out by taking the welding of a pipeline with the diameter of 20 as an example, and the initial welding position is 0 degrees. The welding was ended at 33 seconds, and the tungsten electrode returned to the starting position at 50 seconds, starting the time-lapse air supply. The maximum weld temperature at the start of the time delay plenum was already below 450 ℃. The austenitic stainless steel material is free from intergranular corrosion after the temperature is below 450 ℃, and is cooled for 20 to 35 seconds and then the temperature is reduced to about 300 ℃, so that the welding seam is free from oxidative discoloration when being contacted with air.

And tenth, estimating the average heat input by using a formula according to the components, the diameter and the wall thickness of the welded joint, calculating the heat input value of each section by using the average heat input, setting the welding speed and the pulse time, inversely calculating the welding current value of the peak value and the base value by using the formula, inputting the welding program for trial welding, and adjusting parameters according to the welding result until the welding quality is qualified.

Mean heat inputThe formula:;

wherein, n is the number of sections, qn is the heat input of the nth section;

The nth stage heat input qn=qp [ Tp/(tp+tb) ]+qb [ Tb/(tp+tb) ];

wherein qp—peak heat input;

Qb-base heat input, tp-peak pulse time, tb-base pulse time, f-pulse frequency, f=1/(tp+tb).

According to pages 149 of the third edition, volume 1, FIGS. 5-29 of the welding manual, the ratio of the base value to the peak pulse time Tb to Tp is generally 1-3, 1 being taken in the present invention. Pulse time is a function of wall thickness tp=tb=δmax/10;

wherein, delta is the wall thickness of the pipeline, and when the wall thicknesses of two sides of the pipeline are different, delta takes a larger value delta max, and the unit is mm.

The stainless steel pulse argon arc welding is generally low-frequency pulse, and as the wall thickness is increased, the pulse time is increased, namely the pulse frequency is reduced, so that the penetration depth can be increased, and the arc stability is improved.

The welding speed adjustment range is 1-2.5 mm/s;

According to a 149 th page table 5-2 of a third edition volume 1 of a welding manual, welding speed V and pulse frequency f are required to be matched with each other, so that welding spots can be guaranteed to have a certain overlapping amount, continuous and compact welding seams are obtained, an interpolation method is used for calculating a pulse frequency and speed corresponding relation table, and the speed regulation range of the corresponding pulse frequency in the range of the patent wall thickness is (1-2.5) mm/s.

And the ratio range Qp: qb of the peak heat input and the base heat input is 2-5.

According to the heat input formula, the heat input is proportional to the current. Thus, the heat input ratio relationship of the peak value and the base value may be the same as the current ratio relationship. According to the welding manual pulse amplitude ratio F=ip to Ib of 5-10, the maximum current which can be output by the closed pipe welding machine is not higher than 200 amperes due to the large wall thickness of the welded pipeline, and the range of the value of Ip to Ib is 2-5 in order to reduce the peak current value and maintain the penetration welding heat input value. Because the heat input is a function of the current, the ratio range of Qp to Qb is 2-5 with reference to the current ratio;

The estimated mean heat input is converted by fitting to a function of diameter and wall thickness, 。

D is the outer diameter of the pipeline, and when the outer diameters of the two sides are different, a larger value is taken as a unit mm;

a. b, c-are constants obtained by a fitting formula;

Delta-wall thickness of pipeline, which is the average value of wall thickness when the pipeline is equal in diameter and unequal in diameter, delta=wall thickness+0.5 radius difference, unit mm.

The fitting method is that the welding parameters of the pipe joint and the conduit with different diameters and wall thicknesses under the same material condition are recorded, the average heat input value is calculated, and the average heat input is fitted by using a linear formula to obtain the formula of the average heat input about the diameters and the wall thicknesses.

The estimated heat input of each segment is gradually decreased, and the Qn _{Estimation of} formula is obtained by converting the heat input into a function of the segment through a fitting method, wherein Qn=k×n+b.

K-slope, which is a constant derived from the fitting equation, i.e., a decreasing coefficient of heat input;

b-intercept, a constant derived from the fitting equation.

The fitting method comprises the steps of recording welding parameters which are qualified by welding under different diameters and wall thicknesses, calculating heat input of each section, and linearly fitting the number of the sections and the welding heat input of each section.

Then the k values of different formulas are averaged to obtain the average value of the decreasing coefficients. The estimated mean heat input calculated from the diameter and wall thicknessThe estimated heat input Qn of each segment can be calculated by performing a backward calculation in accordance with the decreasing coefficient and the number of segments.

The voltage formula is obtained through a fitting mode, the formula of the welding equipment with the same type is universal, and the fitting is needed again when the brand or model of the equipment is replaced.

For example, the voltage formula of MK-200 welding machine is U=0.775×h+0.048×I+5.9;

h-tungsten electrode gap, when the outer diameters of two sides of the pipeline are different, the outer diameter of the pipeline is the larger side, and the unit mm

The fitting method comprises the steps of recording voltage values fed back by the equipment under the current values when different tungsten electrode gaps are respectively recorded, and performing linear fitting on the corresponding relation among the tungsten electrode height, the current values and the voltage values to obtain a voltage calculation formula. For example, under the conditions of 1, 1.2, 1.5 and 2 mm, corresponding voltage values between 140 amperes and 20 amperes of current are recorded, and linear fitting is performed by software to obtain a formula.

The tungsten electrode gap h is a function of the wall thickness of the pipeline, and h is expressed by the formula h=0.5×delta;

Delta-wall thickness, when the wall thickness of two sides of pipeline is different, the numerical value is taken as one side with large wall thickness, unit mm,

The reduction of the tungsten electrode gap is beneficial to improving the arc stability, the tungsten adhesion risk exists during welding of the too small tungsten electrode gap, and according to the product tolerance and the welding wall thickness range of the patent, the welding quality of the tungsten electrode gap in a half wall thickness range is stable.

And calculating the peak heat input Qp and the base heat input Qb of each section according to the relation between Qn _{Estimation of} and the peak base heat input ratio, substituting a voltage formula, setting the tungsten electrode gap value and the welding speed, and calculating the peak current Ip and the base current Ib of each section.

The heat input is inversely related to the sulfur content in the material, and as the sulfur content is reduced to ensure penetration, the welding current can be integrally increased or the welding speed can be reduced, and the adjustment range is +/-10%.

In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail with reference to specific embodiments.

Example 1 automatic welding was performed using MK-200 pipe welder and some chassis hydraulic line as examples, the pipe joint material was SUS304, and the steel pipe material was 1Cr18Ni9Ti.

Example 2 automated welding was performed using an AMI-M207A pipe welder and some chassis hydraulic tubing as examples.

Example 2 differs from example 1 in that the apparatus AMI-M207A used in example 2 has a larger width of the jaws and a larger grippable length is required for the clamping.

TABLE 1 automatic welding ratio using MK-200 chassis hydraulic lines

TABLE 2 automated welding ratio using AMI-M207A chassis hydraulic lines

It can be seen from tables 1 and 2 that the process has an automatic welding solution for a zero grippable length using different welding equipment, and a 100% automatic welding ratio can be achieved.

Performance test was performed on the welded joint of example 1 above:

1) Visual inspection, namely, the welded weld is uniform and full, no macroscopic defect exists, the recess of the weld is not more than 25% of the wall thickness, and the weld of the pipeline with the serial number 2 and the pipeline with the serial number 3 is cut, so that the single-sided welding and double-sided forming effect can be obtained under the condition of equal-diameter and unequal-diameter welding, and the transition of the weld is uniform.

2) And (3) oil pressure test, namely pressing for 10min under 25MPa, maintaining the pressure for 30min, and ensuring that the welding line of the pipeline is intact without oil leakage.

3) And the X-ray flaw detection is carried out on the joint, so that the welding defects such as air hole slag inclusion and the like are avoided, and the I-level welding seam requirement in QJ2865A-2014 'technical condition of conduit welding' is met. The pipeline flaw detection bottom plates with the specifications of phi 20 and phi 10 have the advantages that the brightness inside the welding seam is uniform, no circular or strip-shaped shadow exists, and the welding seam quality is good.

4) And (3) tensile test, namely carrying out full-pipe tensile test results on the steel pipe with the diameter smaller than phi 38, wherein the results are shown in the table 3 and meet the tensile strength requirement in GB/T14976-2002 stainless steel seamless pipe for fluid transportation, and the fracture position is a weld joint.

5) In the metallographic test, a sequence number 6 phase sample is shown in fig. 10 (a), the appearance of a molten pool is clearly visible, and the complete penetration of a welding line is illustrated. FIG. 10 (b) is a photograph of the structure of a welded joint under a light mirror, wherein the upper right part of the drawing is a weld joint structure, the lower left part is a parent metal structure, and the middle transition region is a fusion zone structure. White is an austenitic structure and black is a delta-ferritic structure. The austenitic stainless steel weld joint contains a certain amount of delta-ferrite, so that the directionality of austenitic columnar crystals can be cut off, and the tissue toughness and the hot cracking resistance are improved. It can be seen from fig. 10 (c) that the fusion zone is relatively uniform and has no coarse columnar crystals along the fusion line, which is advantageous for the comprehensive mechanical properties of the welded joint. The metallographic structure is good, no air holes and cracks exist, and the structure is austenite and ferrite.

TABLE 3 results of full tube tensile test

In order to enable those skilled in the art to more clearly understand the technical solution of the protection gas outlet device of the present invention, the technical solution of the present invention will be described in detail with reference to specific example 3 and comparative example 1.

Example 3 phi 12 x 2 pipe joint and pipe butt joint

The flow rate of the protective gas in the pipe is 15-20 cubic feet/hour, the gas supply time is advanced by 10-15 seconds, and the gas supply time is delayed by 20-35 seconds. The silica gel plug in-tube shielding gas supply device and the in-tube shielding gas outlet device are used.

Comparative example 1 phi 12 x 2 pipe joint and steel pipe butt joint

Comparative example 1 differs from example 3 in that comparative example 1 does not use an in-pipe shielding gas outlet device

According to the welding forming effect graphs of the comparative example 1 and the example 3, it can be seen that under the condition that the flow rate of the protective gas in the pipe is 15-20 cubic feet/hour, the flat welding seam is collapsed under the action of gravity without using the protective gas outlet device in the pipe, and the flat welding seam is formed flat by the air pressure supporting surface with the use of the protective gas outlet device in the pipe.

In order to make it clear to the person skilled in the art the relation between heat input and sulfur content according to the present invention, the present invention will be described in detail with reference to specific example 4 and comparative example 2.

Example 4 phi 16 x 2 pipe joint (SUS 316L sulfur content 0.0165%) and phi 16 x 2 (1 Cr18Ni9 Ti) steel pipe were butt-jointed.

Comparative example 2 phi 16 x 2 pipe joint (SUS 316L sulfur content 0.0015%) was butted with phi 16 x 2 (1 Cr18Ni9 Ti) steel pipe.

Comparative example 2 differs from example 4 in that the sulfur content of the joint of comparative example 2 is low, the two sets of pipes are welded using the same welding parameters, example 4 is welded using an overall 3% reduction in current, and comparative example 2 is welded using a 9% increase in current.

According to the welding forming effect graphs of the comparative example 2 and the example 4, the welding effect is the same, the same welding effect is achieved, the heat input used in the example 4 is reduced by 12% compared with that in the comparative example 2, the heat input required by the example 4 is reduced, the higher the sulfur content is, the less the heat input is required, the difficulty of measuring the material components in the welding production process is high, the welding current or the welding speed of each section can be integrally improved or reduced by integrally adjusting the welding current or the welding speed of each section according to the welding effect through the first part of trial welding, and the welding effect of full penetration is achieved.

The principle is that the sulfur element can raise the surface tension of molten pool, when sulfur content is high, the molten metal flows to the center of molten pool, and the liquid metal band flows to the center of weld joint with heat, so that the heat is conducted to wall thickness direction to increase the penetration and reduce the melting width. When the sulfur content is low, the surface tension is small, the liquid metal flows around the molten pool along with the temperature rise, the heat is dispersed along with the liquid metal, the penetration is reduced, and the welding seam is widened.

In order to enable those skilled in the art to more clearly understand the technical solution of the present invention for aligning the pipe dimension with the tungsten electrode, the technical solution of the present invention will be described in detail with reference to specific examples 5 and 6.

Example 5 phi 22 x2 pipe joint (SUS 304) and phi 20 x2 (1 Cr18Ni9 Ti) steel pipe were butt-jointed with tungsten electrode biased toward the pipe joint by 0.3mm.

Example 6 phi 20 x 2.5 pipe joint (SUS 304) and phi 20 x 2 (1 Cr18Ni9 Ti) steel pipe were butted, with tungsten electrode biased toward the pipe joint by 0.3mm.

In the embodiment 5, the tungsten electrode is positioned and biased to the side with large outer diameter during pipeline welding, and according to the relative positions of the tungsten electrode and the welding seam after welding and the internal welding seam forming diagram after cutting, the welding seam is biased to the joint by the tungsten electrode, the center of the internal welding seam and the external welding seam is biased to the side of the steel pipe under the slope of the groove, and the double-sided forming effect of single-sided welding can be achieved after the welding is biased. In the embodiment 6, the tungsten electrode position is deviated to the side with large wall thickness during pipeline welding, the center of the welded outer welding seam is identical to the tungsten electrode position according to the relative positions of the tungsten electrode and the welding seam after welding, and the inner welding seam forming graph after cutting shows that the center of the inner welding seam is deviated to the side of the steel pipe due to melting transition, so that the single-sided welding double-sided forming effect can be achieved after the deviation.

In order to enable those skilled in the art to more clearly understand the technical scheme of aligning the material components of the present invention with tungsten, the technical scheme of the present invention will be described in detail with reference to specific example 7, example 4 and comparative example 2.

Example 7 phi 16 x 2 pipe joint (SUS 304) and phi 16 x 2 (1 Cr18Ni9 Ti) steel pipe were butt-jointed and tungsten electrode centered.

Comparative example 2 phi 16 x 2 pipe joint (SUS 316L) and phi 16 x 2 (1 Cr18Ni9 Ti) steel pipe were butted, with tungsten electrode biased toward the pipe joint by 1.1mm.

Example 4 phi 16 x 2 pipe joint (SUS 316L) and phi 16 x 2 (1 Cr18Ni9 Ti) steel pipe were butt-jointed with tungsten electrode biased toward the pipe joint by 0.7mm.

The difference between example 7 and example 4 and comparative example 2 is that the silicon content of the joint is different, the silicon content of the steel pipe is less different, the main components of the materials are shown in Table 4, and the welding effect record is shown in Table 5.

Table 4 joint and catheter composition table

Table 5 table of silicon content and weld offset

In the embodiment 7, the tungsten electrode points to the center of the groove during pipeline welding, the center of the visible outer welding seam deviates from the center of the steel pipe after welding, the center of the inner welding seam further deviates from the center of the steel pipe after cutting, and the tungsten electrode is proved to deviate to the side with high silicon content during equal-diameter welding, so that the center of the welding seam at the back surface can be ensured to be at the center of the groove.

In the tungsten electrode deflection tube in the pipeline welding of the comparative example 2, the silicon content in the tube joint is not greatly different from that of the steel tube, the center of an external welding line is deflected to the joint after the welding is finished, the center of an internal welding line is further deflected to the joint after the cutting, and the forming graph of an internal welding line is further deflected to the joint, so that the tungsten electrode is deflected to the steel tube, a back groove with overlarge deflection can be still covered by the welding line, and the tungsten electrode is deflected to the side with high silicon content in the equal-diameter welding.

Example 4 tungsten electrode bias tube during pipeline welding, the silicon content in the pipe joint is similar to that of a steel tube. After welding, the center of the visible outer weld joint is slightly deviated to the joint, the deviation of the joint is smaller, the inner weld joint is identical to the center of the outer weld joint in the internal weld joint forming diagram after cutting, but the local weld joint is deviated from the joint, and only the joint is arranged on a pipeline, so that the deviation degree of the center of the weld joint is small when the silicon content is similar, and the tungsten electrode deviation cannot be excessively large.

The principle is that when the silicon contents of two sides are different, siO ₂ generated by deoxidization on the side with high silicon content is higher, siO ₂ is an oxidizing active agent, so that the surface tension temperature coefficient of a molten pool is positive, meanwhile, as SiO ₂ is a nonmetallic oxide, the conductivity is poor, the spot area of an anode of the molten pool is reduced, an arc conducting channel is reduced to cause arc shrinkage, the arc is deflected to the side with low silicon content, and a back weld joint is deflected to the side with low silicon content, so that the tungsten electrode is deflected to the side with high silicon content for ensuring root penetration.

In order to enable those skilled in the art to more clearly understand the technical solution of estimating welding parameters according to the present invention, the technical solution of the present invention will be described in detail with reference to specific embodiment 9.

Example 9 the pipe joint Φ20×2.5 material 316L of the equal diameter, the pipe joint Φ20×2 material 1Cr18Ni9Ti welding parameters were estimated by a formula, and the estimated data welding effect was tested.

1) For example, several parameters of pipeline penetration welding are known, and the parameters are arranged to list the diameter, wall thickness and average heat input, as shown in Table 6. A minitab fit was used to determine the relationship between the mean heat input and the pipe diameter wall thickness according to table 6. Equation fitting using multiple regression yields a mean heat input (KJ/mm) = -0.1776+0.0074 x diameter+ 0.1526 x wall thickness.

TABLE 6 heat input data for penetration welds

2) The average heat input = -0.1776+0.0074×20+0.1526×2.25 (average 2.25 over 2.5 and 2.0) can be obtained by inputting the pipe diameter and wall thickness into the formula (average 2.25) = 0.314 (KJ/mm)

3) Fitting a decreasing linear formula according to the number of segments of known pipeline penetration welding parameters and the heat input values of each segment can obtain the decreasing coefficient k of the heat input of each segment, and the average value of the decreasing coefficients of the heat input of each segment is obtained, as shown in Table 6. Assuming that the welding is performed in 9 segments, the heat input of 9 segments can be found according to the decreasing coefficient, as shown in table 7.

4) The peak base value heat input ratio 3 (the empirical data ratio is between 2 and 5, and 3 is frequently taken for the convenience of calculation) is taken, and the peak value and base value heat input values of each section can be obtained according to the fact that the heat input of each section of the average value heat input is equal to the sum of the peak value heat input and the base value heat input, as shown in table 7.

5) The relation between the voltage and the current of the equipment and the gap between tungsten electrodes is calculated, fitting can be carried out according to the data of the welding equipment, such as an MK-200 pipe welder, and when the tungsten electrodes with the heights of 1, 1.2, 1.5 and 2mm are high, the voltage parameters of 140 amperes to 20 amperes of the current can be fitted to obtain a voltage formula of U (V) =0.775×the gap between tungsten electrodes (mm) +0.048×the current (A) +5.9. Linear model Polynomial (multi-form approximation) was selected, X (tungsten height), Y (current) index was 1, LAR was selected for robust type, and the fitted graph was as shown in fig. 11:

6) The relationship between the pulse time and the plate thickness is that the peak pulse time(s) =the base pulse time(s) =the wall thickness/10 (mm), and the ratio of the peak pulse time to the base pulse time, namely the pulse width ratio is 1. The relation between the heat input and the welding current and the voltage is that the welding input (KJ/mm) =0.9×welding current (A) ×welding voltage (V)/welding speed (mm/s)/1000, the welding current adjusting range is that the base value current (15-90) A and the peak value current (45-180A), and the welding voltage is in a functional relation with the welding current and the tungsten electrode gap.

Setting welding speed to 2.4mm/s, and welding peak value/base value for 0.25s (welding time=wall thickness/10=2.5/10=0.25 s), wherein the tungsten electrode gap is 1.5 (tungsten electrode gap= (0.5×wall thickness)=(0.5×2.5)=1.4Taking 1.5) the peak base current was obtained by inverse solving the heat input equation and the voltage equation using EXCEL, as shown in table 7.

TABLE 7 Peak and base Heat inputs from mean Heat inputs

7) And inputting the generated welding parameters into welding equipment for trial welding, performing endoscopic examination, completely penetrating the pipeline welding seam, slightly sinking the welding seam, fine-adjusting welding current, and performing trial welding again to finally generate the parameters shown in table 8. Suitable welding parameters can be obtained by predicting the parameters only twice.

Table 8 welding parameters

From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

1) Compared with the prior art, the invention has the beneficial effects that by adopting the technical means of designing the concave clamping pieces, clamping plates or steel threaded air inlet connectors with different specifications, 100% automatic welding of the hydraulic pipeline is realized, the equal-diameter and unequal-diameter pipe joint and the steel pipe single-side welding double-side forming can be realized, and the invention has the effect of only using one device and one-step welding forming.

2) The invention adopts the technical means of debugging welding parameters through an algorithm to obtain the effect of quickly debugging proper technological parameters when changing materials or pipeline specifications.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The automatic pipe-pipe butt welding process for the hydraulic stainless steel pipeline is characterized by comprising the following steps of:

firstly, sawing and blanking a stainless steel guide pipe;

secondly, flattening the guide pipe;

thirdly, bending the conduit after flattening;

Fourth, cleaning the guide pipe;

Fifthly, positioning welding the guide pipe and the welded pipe joint by adopting an argon arc welding machine without filling wires;

Seventh, putting a tungsten electrode gap gauge into the welding tongs, and positioning the tungsten electrode after the tungsten electrode falls to the middle diameter position of the gap gauge;

The eighth step, the pipeline is put into a welding tongs, and the relative position of the groove center of the pipeline and a tungsten electrode is adjusted according to the comparison result of the size and the material of the joint body of the pipe joint and the guide pipe, and the pipeline is clamped;

a ninth step of installing an air inlet device and an air outlet device of the protective gas in the pipe on the pipeline;

tenth, estimating the average heat input by using a formula according to the diameter and the wall thickness of the joint body, calculating the heat input value of each section by the average heat input, setting the welding speed and the pulse time, inversely calculating the welding current value of each section of peak value and base value by the formula, inputting the welding program for trial welding, and adjusting parameters according to the welding result until the welding quality is qualified;

2. The automatic pipe-pipe butt welding process of the hydraulic stainless steel pipeline according to claim 1, wherein the stainless steel pipeline is made of austenitic stainless steel, the pipeline outer diameter range is 6-38 mm, the pipeline wall thickness is 2-4 mm, one side of the pipeline which is in butt joint at two sides is provided with a pipe joint, the other side is provided with the stainless steel pipeline, the joint body of the pipe joint and the pipe are at least one of the same size, flat-end pipe joints are selected when the pipe joint and the pipe joint have equal diameters or equal outer diameters and unequal inner diameters, and groove pipe joints are adopted when the difference value between the pipe joint outer diameter and the pipe outer diameter is more than or equal to 1 mm.

3. The automatic pipe-pipe butt welding process of the hydraulic stainless steel pipeline according to claim 1, wherein in the sixth step, the concave clamping piece comprises a first-stage retraction concave clamping piece and a second-stage retraction concave clamping piece, wherein the first-stage retraction concave clamping piece is retracted into the clamping piece body to be 0-0.5 mm before the screw thread of the fastening bolt hole, and the retraction diameter is larger than the maximum outer diameter of the pipe joint nut;

when the pipe joint can clamp a pipeline with the length smaller than the distance from the tungsten electrode to the outer wall of the welding tongs, a first-stage concave clamping piece or a second-stage concave clamping piece is adopted according to the reduction degree of the clampable length;

when the pipe joint can clamp a pipeline with the length longer than the distance from the tungsten electrode to the outer wall of the welding tongs, a flat clamping piece is selected and is used for clamping, clamping piece center hole and pipe joint the outer diameter of the steel pipe is the same as that of the steel pipe.

4. The automatic pipe-pipe butt welding process of the hydraulic stainless steel pipeline according to claim 1, wherein when the clampable length of the steel pipe is smaller than the distance from the tungsten electrode to the outer wall of the welding tongs, a clamping plate clamp is adopted, the clamping plate clamp comprises two U-shaped clamping plates, one U-shaped clamping plate is an aluminum alloy clamping plate, the other U-shaped clamping plate is a high-temperature-resistant flame-retardant nylon clamping plate, the aluminum alloy clamping plate is in contact with the guide pipe and the welding tongs, the high-temperature-resistant flame-retardant nylon clamping plate is arranged outside the aluminum alloy clamping plate and is intersected with the aluminum alloy clamping plate, and the high-temperature-resistant flame-retardant nylon clamping plate is clamped on the welding tongs by an external insulation clamp.

5. The automatic welding process for the pipe-pipe butt joint of the hydraulic stainless steel pipeline according to claim 1, wherein in the seventh step, the tungsten electrode gap gauge is a cylinder with a ladder-shaped structure, the middle cylinder is used for positioning the radial position of a tungsten electrode, the middle diameter size is determined by the following method that the middle diameter = two side diameters +2 x tungsten electrode gap, the two side diameters represent the outer diameter of a joint body or the outer diameter of a guide pipe of a pipe joint of the pipeline, when the outer diameters of the two sides of the pipeline are different, the two side diameters take the outer diameter of a larger side, and the tungsten electrode gap refers to the radial distance from the tip of the tungsten electrode to the outer diameter of the pipeline with the larger side diameter.

6. The automatic pipe-pipe butt welding process of a hydraulic stainless steel pipe according to claim 1, wherein in the eighth step, according to the comparison result of the size and the material of the joint body and the conduit of the pipe joint, the method for adjusting the relative position of the tungsten electrode and the center of the groove is that when the wall thickness of the joint body and the conduit is different, the tungsten electrode is deviated to the side with large wall thickness by an offset (0, 0.5) millimeter, when the wall thickness is the same, the tungsten electrode is deviated to the side with large outer diameter by an offset (0, 0.5) millimeter, when the equal diameter welding is performed, the tungsten electrode is deviated to the side with high silicon content, based on the silicon content of the pipe between 0.3% and 0.4%, when the silicon content of the joint body is less than 0.3%, the tungsten electrode is deviated to the conduit (0, 0.3) millimeter, when the silicon content of the joint body and the conduit is within the range of 0.3-0.4%, the tungsten electrode is not deviated to the joint body (0.3) by the moving the pipe.

7. The automatic pipe-pipe butt welding process for hydraulic stainless steel pipeline according to claim 1, wherein in the ninth step, the air inlet device for protecting air in the pipe adopts a silica gel plug for air supply or a steel screw joint for air supply, the air supply steel pipe is connected to the air supply hose through a quick connector when the pipe joint can be clamped by adopting the silica gel plug for air supply, the air supply steel pipe is inserted into the silica gel plug, and the silica gel plug is installed in the pipe joint.

8. The automatic pipe-pipe butt welding process for hydraulic stainless steel pipeline according to claim 1, wherein the tenth step comprises the following steps:

;

a. b, c, a constant obtained by a fitting formula;

b-intercept, which is a constant obtained by a fitting formula;

n-number of segments;

wherein, n is the number of segments, qn is the heat input of the nth segment,

wherein, qp-peak heat input, qb-base heat input, tp-peak pulse time, tb-base pulse time, tb: tp is selected from 1 to 3;

the ratio range Qp of the peak heat input to the base heat input is 2-5;

Heat input formula q=η×i×u/V/1000;

wherein Q is welding input, and the unit is KJ/mm;

U=d×h+e×I+f;

The welding equipment d, e and f with the same model are constants;

The peak heat input Qp and the base heat input Qb of each segment are calculated, then the peak heat input Qp and the base heat input Qb are brought into a voltage formula, and the peak current Ip and the base current Ib of each segment can be calculated by setting the tungsten electrode gap value and the welding speed.

9. The automatic pipe-pipe butt welding process for hydraulic stainless steel pipes according to claim 1, wherein the heat input is inversely related to the sulfur content in the material, and the welding current is increased or the welding speed is decreased as the sulfur content is reduced to ensure penetration, and the adjustment range is +/-10%.

10. The automatic pipe-pipe butt welding process of the hydraulic stainless steel pipeline according to claim 1, wherein the welding procedure is divided into 5-9 sections, the welding procedure starts clockwise from 3 o' clock, the 1 section is an arc guiding section, the arc guiding section is 10 degrees, the middle is a welding section, the angle is 40-80 degrees, the last section is an arc receiving section, the number of welding sections is not counted, and the arc receiving angle is 90-120 degrees, and the current is attenuated to zero.