RU2366551C2 - Method to weld together pipes by friction - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: in compliance with proposed method, pipes to be welded together are arranged so that their end faces form a circular gap. Clamp is revolved over the end faces of pipes and heat pressure is applied to fixed pipes to eliminate aforesaid gap. Upset-forging the pipes together allows an interference fit joint.

EFFECT: higher strength of welded joint.

2 cl, 2 dwg, 1 ex

Description

The invention relates to drilling equipment and relates to the hardening of the welded connection of tubular parts, mainly drill pipes with drill lock parts - a nipple and a coupling, the diameter of which exceeds the diameter of the pipe.

The closest analogue adopted for the prototype is known, the connection of tubular parts by friction welding, containing a lock part (nipple and sleeve) and a pipe with mating welded ends (see GOST R 50278-92 “Drill pipes with welded joints. Technical conditions”). In this device, before the welding operation, to strengthen the welded joint, the ends of the pipe are planted, i.e. thicken. However, the planting of the pipe from two ends leads to its appreciation up to 30%. In addition, the endurance limit of the upset pipe ends is reduced to 20% (see, for example, test results for alternating bending of the smooth and upset pipe part with a diameter of 146 mm from steel of strength group D in the book by A.E. Saroyan. “Drill columns in deep drilling ". M.," Nedra ", 1979, p. 117, Table 5). This is due to the deterioration of the macrostructure of the metal as a result of a change in the direction of its layering from the most favorable parallel to the perpendicular to the axis of the pipe, i.e. to the most unfavorable.

The objective of the invention is to increase the strength of the welded joint of tubular parts by increasing the cross section of the welded joint due to the material of the parts of the lock - nipple and coupling.

To solve this problem, in the connection of tubular parts by friction welding, containing a lock part and a pipe with mating welded ends, an annular protrusion with an internal conical bore is made on the nipple from the side of the mating end, and a reciprocal external conical groove is made on the pipe at the mating welded end with the ability to fit with a large guaranteed interference fit of the mentioned surfaces after contact of the ends of the nipple and the pipe.

The invention is illustrated by drawings, which depict:

figure 1 - connection of tubular parts to friction welding.

figure 2 - connection of tubular parts after friction welding.

An annular protrusion 3 with an inner conical bore 4 is made on the nipple 1, and a reciprocal external conical groove 5 is provided on the pipe 2. The nipple 1 is set against the mating ends 6 of the nipple 1 and the pipe 2, and a diametrical gap 7 is formed between the conical surfaces, which it is eliminated during the heating pressure operation, and during the subsequent forging pressure operation, their landing is formed with a large guaranteed interference fit.

The inventive device allows to solve the problem.

Indeed, in the claimed connection of tubular parts, due to the fact that an annular protrusion with an internal bore is made on the nipple from the side of the mating end, and a reciprocal external conical groove is made on the pipe at the mating welded end, which, by friction welding, come into contact with a large guaranteed interference fit, are formed two load-bearing sections - along the weld and conical connection, and the total resistance moment of these sections is close to the moment of resistance of the section of the upset end tr to prototype (prototype apparatus), and the total bending moment is higher as the material strength of the annular flange section exceeds the cross section of the pipe end planted prototype.

Thus, there is an increase in the strength of the welded joint of tubular parts.

In addition, a friction welding method is provided for the foregoing joining of tubular parts.

A known method of friction welding of the connection of tubular parts containing a lock part and a pipe with mating welded ends, including installing them at point-blank ends, rotating the lock part while creating heating pressure on it while the pipe is stationary, and after stopping rotation, forging pressure. In this method, a pipe with upset ends is used, i.e. to strengthen the weld, the ends of the pipe are thickened (see GOST R 50278-92 “Drill pipes with welded joints. Specifications”). However, the landing of the pipe from two sides leads to its appreciation. In addition, the endurance limit of the upset pipe ends is reduced to 20%. This is due to the deterioration of the macrostructure of the metal as a result of a change in the direction of its layering from the most favorable parallel to the perpendicular to the axis of the pipe, i.e. to the most unfavorable.

The objective of the invention is to increase the strength of the welded joint of tubular parts by increasing the cross section of the welded joint due to the material of the parts of the nipple lock and coupling.

To solve this problem, in a method of friction welding of a connection of tubular parts containing a lock part and a pipe with mating welded ends, including installing them in the abutment ends, rotating the lock part while creating heating pressure on it while the pipe is stationary, and after stopping the rotation, forging pressure , when installing before welding the details of the lock with the inner conical surface and the pipe with the counter outer conical surface, the ends face up, a diametrical joint is formed between their conical surfaces set, at a pressure which eliminate the heating, and after stopping rotation during subsequent forging operations provide landing conical surfaces with great tightness guaranteed.

The inventive method allows to solve the problem.

Indeed, in the inventive method, due to the fact that the detail of the lock 1 with its conical surface 4 comes into contact with the counter conical surface 5 of the pipe 2 with a large guaranteed interference fit, two load-bearing sections are formed in the connection of the tubular parts - along the weld and the conical connection with a large guaranteed tightness, and the total moment of resistance of these sections is close to the moment of resistance of the section of the upset end of the pipe of the prototype (the method according to the prototype), and the total bending moment is higher, since Ruggedness material cross section exceeds the cross section of the annular flange upset pipe end prototype.

Thus, there is an increase in the strength of the welded joint of tubular parts

An example of the implementation of the friction welding of tubular parts. For example (Fig. 1), we take the parameters of the welded joint of the parts — the pipe and nipple of the drill pipe lock PN 114 × 9 of strength group E with an external upset: the pipe wall thickness is 8.6 mm, the outer and inner diameters of the upset ends are 130 and 94.5, respectively mm (see GOST R 50278-92, Table 2), the temporary resistance of the pipe material (strength group E) and the lock nipple (40KhMFA steel) respectively 689 MPa (see ibid., p.12) and 981 MPa (see GOST 27834 "Welded joints for drill pipes. Technical conditions", p.7).

In the claimed design (Figure 1), we take the wall thickness of the welded ends of the pipe 1 and nipple 2, equal to 7.6 mm To do this, we end the pipe 1 with the formation of an end face with a diameter of 112 mm, and at the end of the nipple 2 we create a response end with the same outer and inner diameter, as a result of which the cross-sectional area of the welded ends is 24.9 cm ² . The annular protrusion 3 in the section passing through the weld has an outer diameter D = 130 mm, and the inner diameter d of the protrusion is due to the parameters of the cavity intended to accommodate the inner burr.

According to the technological process of friction welding (see. Friction welding: Handbook / V.K. Lebedev et al. - L.: Engineering. Leningrad. Department, 1987. - 236 pp. Ill. "). pressure and axial movement of the heating with rotation are 6640 kgf and 12.7 mm, respectively; the same when forging after stopping rotation - 13280 kgf and 2.3 mm. In total, the axial movement of the nipple to the pipe during the welding process is 15 mm.

The conical mating surfaces 4 and 5 are taken to be 30 mm long with a taper of 1: 15 = 0.066. The diametrical gap 7 on the conical surfaces when installing the parts with the ends 6 in the focus will be:

12.7.0666 = 0.84 mm

This gap is eliminated as a result of heating pressure with a force of 6640 kgf when moving the nipple with rotation to the pipe to a length of 12.7 mm (Figure 2), and a large guaranteed interference fit for forging pressure with a movement of 2.3 mm

2.3.0.066 = 0.15 mm

This interference fit fits H9 / z8.

To create such an interference fit together with the forging operation, additional force is required. According to the data of I.A. Birger (see Birger I.A. et al. “Strength Analysis of Machine Parts: Handbook - 4th ed., Revised and enlarged. - M.: Mechanical Engineering, 1993, p. 98” ) this force F can be found from the expression

F = q _m · µ · π · d _cf · l _s / c, (1)

where q _m is the contact pressure on the landing surface (for landings with a large guaranteed tightness q _m = 40 MPa = 392 kgf / cm ² );

µ = 0.15 - coefficient of friction;

d _av = 113 mm = 11.3 cm - the average diameter of the landing surface;

l _p = 30 mm = 3 cm - the length of the landing surface;

k = 1.5 - gearing safety factor.

After substituting the values in the formula (1), we obtain the value F = 4173 kgf.

Therefore, the pressure of the forging in the welding process, taking into account the force necessary to create a guaranteed large interference on the conical surfaces of the welded tubular parts, should be taken equal to:

13280 + 4173 = 17453 kgf.

The strength of the connection of the pipe with the nipple is estimated by the limiting alternating bending moment (M _before ) of a dangerous section, i.e. section passing through the weld. It is represented by two sections: directly along the seam and along the annular ledge.

For a section directly along the seam of a smooth (without upsetting) pipe end with a nipple M _{before. w} determined from the dependence

M _{prev. w} = (σ _{-1) K D} · W _w

where (σ _-1 ) _D is the endurance limit of a butt welded joint of a full-scale drill pipe with upset ends when tested for alternating bending; for a pipe with a diameter of 114 mm (σ _-1 ) _D = 9 kgf / mm ² = 900 kgf / cm ² (see Saroyan A.E. Drill columns in deep drilling. M: "Nedra", 1979, p. 117, table 5);

To _в = 1,2 is the ratio of the endurance limits of the smooth and upset sections of the drill pipe (see ibid. Test data for pipes with a diameter of 146 mm of strength group D smooth and with upset ends);

W _W - the moment of resistance to bending of the weld, cm ³ .

After the substitution of quantities, we have

M _{prev. w} = 900 · 1.2 · 0.1 (11.20 ⁴ -9.68 ⁴ ) / 11.20 = 67068 kgf · cm = 6573 Nm

For the cross section of the annular protrusion M _{before. in} determined from the dependence

where W _in = 0,1 (D ⁴ -d ⁴ ) / D is the moment of resistance to bending, cm ³ ;

D and d - outer and inner diameter of the annular protrusion, cm;

σ _-1 ^and = 0.4σ _in (see Belyaev N.M. Resistance of materials, M., 1958, p. 733) is the tensile strength in bending of a standard smooth specimen for 40KhMFA steel from which the nipple is made, kgf / cm ² ;

σ _in = 981 MPa = 10010 kgf / cm ² - temporary resistance of the material of the nipple;

α _kD = 1.2 is the actual stress concentration coefficient (concentration factor: risks from the cutter on the outer surface of the annular protrusion, see Belyaev N.M., p.743, table 37);

α _m = 1,6 - scale factor (see ibid., p. 747).

To determine the inner diameter d of the annular protrusion included in the value of W _in in the expression (2), it is necessary to have the parameters of the annular cavity designed to accommodate the inner burr. We take the length of this cavity equal to 2 cm. Its inner diameter is 112 mm, and the outer one is the desired value of d, i.e. the inner diameter of the annular protrusion. Bearing in mind that the total value of the displacement of the nipple at the heating pressure and forging pressure is 15 mm = 1.5 cm, we find the total volume of the formed grata

(11.20 ² -9.68 ² ) 0.785 1.5 = 37.4 cm ³

Considering that half of the formed grata is located in the cavity, we find the value of d from the following equality

(d ² -11.20 ² ) 0.7852 = 37.4.5.5

Taking into account the values d = 117 mm obtained from this equality and, bearing in mind that the outer diameter of the annular protrusion is D = 130 mm, we determine the value of We for this section

W _in = 0.1 (13.0 ⁴ -11.7 ⁴ ) / 13.0 = 75.6 cm ³

Then the value of M _pred.v for the cross section of the annular ledge according to the expression (2) will be equal

M _{prev. c} = 75.6 · 0.4 · 10010 / 1.2 · 1.6 = 157658 kgf · cm = 15450 Nm.

The total ultimate bending moment of the dangerous section will be equal to

M _{prev. sums} = M _{prev. w} + M _{before c} = 6573 + 15450 = 22023 Nm

In the prototype M _{before the height} for the weld of the pipe PN 114 × 9 is determined from the dependence

M _{prev. height} = (σ _-1 ) _D · W _height ,

where (σ _-1 ) _D = 9 kgf / mm ² = 900 kgf / cm ² (see Saroyan A.E. Drill columns in deep drilling. M., Nedra, 1979, p. 117, Table 5).

W _height = 0.1 (13.0 ⁴ -9.45 ⁴ ) / 13.0 = 158.3 cm ³

After the substitution of quantities, we have

M _{prev. h} = 900158.3 = 142470 kgfcm = 13962 Nm

The ratio of ultimate bending alternating moments of the claimed connection of tubular parts and prototype is

22023/13962 = 1.6

The proposed method of friction welding of tubular parts provides a significant increase in the strength of the welded joint and a decrease in the cost of drill pipes as a result of the abolition of the upsetting operation of their ends.

Claims (2)

1. The connection of tubular parts for friction welding, comprising a lock part and a pipe with mating welded ends, characterized in that the lock part is bored from the mating end side to form an annular protrusion having an inner conical surface, and the pipe at the mating welded end is machined to form a response the outer conical surface, while said conical surfaces are placed with the possibility of their landing with a guaranteed interference fit after welding the parts of the lock and pipe. 2. A method of friction welding of the connection of tubular parts containing a lock part and a pipe with mating ends to be welded, including installing them at point-blank ends, rotating the lock part with applying heating pressure to it while the pipe is stationary, and after stopping rotation, forging pressure, characterized in that on the parts of the lock from the side of the mating end, an annular protrusion with an inner conical surface is preliminarily performed, and on the pipe, a reciprocal outer conical surface, set their ends in p with the formation of a diametrical gap between their conical surfaces, which is eliminated when the heating pressure is applied, and the forging pressures ensure that said conical surfaces are fitted with a guaranteed tightness.

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