CN107160051A - A kind of variable cross-section solid welding wire welded for consumable electrode - Google Patents

Abstract

A variable cross-section solid welding wire for melting electrode welding. The invention aims to solve the technical problems that in the current melting electrode welding method, it is difficult for the droplet to smoothly transition to the molten pool, and the control system is complicated, the process parameters are complex and the cost is high. . A variable cross-section solid welding wire for melting electrode welding of the present invention is composed of a plurality of thin-diameter sections and a plurality of thick-diameter sections, and the thin-diameter sections and thick-diameter sections are connected together alternately; The intersection of the lower end surface of the contact tip and the central axis of the solid welding wire is the coordinate origin O, and a one-dimensional coordinate system x-axis is established along the feeding direction of the solid welding wire. The variable-section solid welding wire used for melting electrode welding satisfies the following formula: And T(B) _≥Tmelt >T(C). The invention can realize the stable and precise control of the droplet transfer, thereby making the welding process stable and improving the welding quality.

Description

A variable cross-section solid welding wire for melting electrode welding

Background technique

Arc welding is an important thermal processing process widely used in industrial fields. According to whether the welding electrode melts, it can be divided into non-melting electrode welding methods (such as argon tungsten arc welding, plasma arc welding, etc.) and melting electrode welding methods (such as electrode arc welding, submerged arc welding, gas metal arc welding, etc.). Among them, submerged arc welding and gas shielded metal welding use automatic devices to feed welding wire, which is easy to automate and is more and more widely used in production.

In melting electrode welding, the welding wire is used as an electrode, and the workpiece (base material) is used as an electrode. A welding arc is established between the two electrodes, and the heat generated by the arc is used to melt the base material and the welding wire to form a molten pool, which is formed as the molten pool solidifies. Welds to connect two parts. At present, in the melting electrode welding process, the welding wire can be divided into two types: solid welding wire and flux cored welding wire. Among them, the solid welding wire is widely used, which is made by wire drawing process, and the cross section of the welding wire is uniform.

During the melting electrode welding process, how to ensure the stability of the welding arc and control the smooth transition of the molten droplets produced by the melting of the welding wire into the molten pool has always been a problem faced by welding workers. Although some control methods have been adopted, such as welding current waveform control, welding arc protection atmosphere control, welding wire withdrawal control, etc., most of them are not very ideal. There are also some control methods that have achieved good results, such as the cold metal transfer (CMT) process, which uses the joint control of welding current and wire withdrawal to control the droplet transfer well, but it brings a complex control system and relatively Many process parameters and high cost lead to the poor promotion and application of these processes.

Contents of the invention

The present invention aims to solve the technical problems that the droplet is difficult to smoothly transition to the molten pool in the current melting electrode welding method, as well as the technical problems of complex control system, complicated process parameters and high cost, and provides a variable cross-section for melting electrode welding. Solid wire.

A variable cross-section solid welding wire for melting electrode welding of the present invention is composed of a plurality of thin-diameter sections and a plurality of thick-diameter sections, the thin-diameter sections and thick-diameter sections are connected together alternately, and the thin-diameter sections and thick-diameter sections The diameter sections are all cylinders, and all the thin diameter sections have the same size, all the thick diameter sections have the same size, and the materials of the thin diameter section and the thick diameter section are the same;

For melting electrode gas shielded welding, take the intersection point of the lower end surface of the electric tip and the central axis of the solid welding wire as the coordinate origin O, and establish a one-dimensional coordinate system x-axis along the feeding direction of the solid welding wire, and the described used for melting electrode welding Variable cross-section solid welding wire satisfies the following formula:

x is the distance from the point on the central axis of the solid wire to the origin O, in mm;

T(x) is the wire temperature at point x, in °C;

e is a natural constant;

α is the temperature coefficient of resistance of the solid welding wire, the unit is ℃ ^-1 ;

T ₀ is room temperature, which is 25°C;

Where σ ₀ is the resistivity of the solid wire at room temperature, in mm Ω; c is the specific heat of the solid wire material, in J/(g °C); ρ is the density of the solid wire material, in g/mm ³ ;

v is the wire feeding speed, the unit is mm/s;

j is the current density, the unit is A/mm ² , j=I/S, I is the current through the solid welding wire, that is, the welding current, and S is the cross-sectional area of the solid welding wire;

And T(B) _≥Tmelting >T(C), point B is the midpoint of the truncation of the thin-diameter section farthest from the contact tip on the central axis, point C is the thick-diameter section farthest from the contact tip on the central axis The midpoint of the above section, Tmelt is the _melting point of the solid welding wire;

For point B: x _B ＝L ₀ -L ₂ -0.5×L ₁ ; for point C: x _C ＝L ₀ -0.5×L ₂ , L ₀ is the dry elongation length of solid welding wire, L ₂ is the thick diameter section The length of , L ₁ is the length of the narrow diameter section;

The dry elongation of the welding wire refers to the distance from the end of the welding wire to the end of the contact tip.

During the steady feeding process of the solid welding wire, the temperature of the solid welding wire reaches a quasi-steady state, that is, the temperature of the welding wire is only related to the position x and has nothing to do with time.

The invention proposes a solid welding wire with variable cross-section, which can form uniform molten droplets after melting in the welding process and transition into the molten pool, which is beneficial to the stability of the welding process and the improvement of welding quality.

Principle of the present invention:

When performing metal gas shielded welding, in the part of the dry elongated welding wire, under the action of the welding current flowing through the welding wire, resistance heat will be generated, which will become part of the heat of the melting welding wire. In the case of the variable cross-section solid welding wire proposed by the present invention, by rationally designing the cross-sectional area and length of the welding wire at the variable cross-section, the resistance of the dry elongated part of the welding wire can be mainly concentrated at the small cross-section, so that the resistance heat generated there Increase, the temperature rises to exceed the melting point of the welding wire and melts, at the same time, the temperature of the lower welding wire rises and leaves the welding wire, and under the action of the arc heat, molten droplets are formed and transition to the molten pool. As the welding wire is fed, the arc will jump to the welding wire At the place where the segment falls off, the above process will be repeated to form a stable droplet transfer process.

The obtaining process of above-mentioned formula of the present invention is as follows:

The solid welding wire is preheated by the resistance heat Q _r to realize the increase of the internal energy Q _of the solid welding wire. Because the specific heat capacity of the welding wire changes very little with temperature, such as the specific heat capacity of the H08CrMnVA welding wire with a temperature variation coefficient of 10 ^-4 orders of magnitude, in order to simplify the analytical formula of the temperature field of the hot wire, it is easy to understand, the present invention considers the specific heat capacity to be a constant, and does not consider the effect of the arc on Thermal action of the welding wire.

Take any place x on the central axis of the solid welding wire and its microelement dx at the forward end, the preheating temperature of the solid welding wire is generated under the action of resistance heat. The transient heat balance equation satisfied by the micro-elements of the dx segment in the time dt is:

Q _r = Q _inside (1)

According to Joule's law, the current through the solid welding wire is I, the resistivity of the solid welding wire is σ, and the resistance heat Q _r generated by the micro-element with the cross-sectional area of the solid welding wire S in the time dt satisfies:

In the dt time, the internal energy increment Q _{of the} microelement satisfies:

Q _inner = cρSdxdT (3)

In the formula: c - the specific heat of the solid welding wire material;

ρ——the density of solid welding wire material;

According to v=dx/dt, v is the wire feeding speed, and the transient heat balance equation of formula (1), it can be obtained:

Note j=I/S, that is, j represents the current density of the solid welding wire, which can be satisfied by the preheating temperature obtained by heating the solid welding wire by resistance:

The resistivity of solid wire varies with temperature as follows:

σ(T)=σ ₀ (1+αT) (6)

σ ₀ is the resistivity of solid welding wire at 25°C, let Substitute formula (6) into formula (5) to get:

According to the initial condition T(t=0)=T ₀ , we get:

Equation (8) expresses the expression of the preheating temperature of the solid welding wire under the action of resistance heat.

Advantages of the present invention:

Compared with conventional solid welding wire, the variable cross-section solid welding wire for melting electrode welding of the present invention will bring the following advantages:

1. Match the appropriate welding parameters, without using other control measures, it can realize the stable and precise control of the droplet transfer, so as to make the welding process stable and improve the welding quality;

2. The solid welding wire of the present invention can reduce the temperature of molten droplets. Compared with conventional welding wires, it can generally reduce the temperature by 200°C to 300°C, thereby reducing alloy burning loss during welding and improving weld quality;

3. As the droplet temperature decreases, the temperature of the welding pool will also decrease, which will improve the metallurgical process of the welding pool, reduce the amount of gas dissolved, and thereby reduce defects such as welding pores;

4. For the thick welding wire, after adopting the variable section design, the flexibility of the welding wire can be improved, the rigidity of the thick welding wire can be reduced, and the winding and feeding of the thick welding wire can be facilitated.

Description of drawings

Fig. 1 is a schematic diagram of the variable cross-section solid welding wire used for melting electrode welding of the present invention when performing gas shielded welding of the melting electrode, 1 is a wire feeder, 2 is a variable cross-section solid welding wire for melting electrode welding, and 3 is a conductive tip , 4 is the gas shielding nozzle, 5 is the shielding gas, 6 is the dry extension part of the welding wire, 7 is the arc, 8 is the welding power supply, and 9 is the workpiece;

Figure 2 is a partial schematic diagram of the variable cross-section solid welding wire used for metal electrode welding in test 1 when gas shielded metal welding is performed, 3 is the contact tip, 8 is the welding power supply, and 2-1 is the variable cross-section used for metal electrode welding The thin-diameter section of the solid welding wire, 2-2 is the thick-diameter section of the variable-section solid welding wire used for melting electrode welding.

detailed description

Specific embodiment 1: This embodiment is a variable cross-section solid welding wire for melting electrode welding, which is specifically composed of a plurality of thin diameter sections and a plurality of thick diameter sections, and the thin diameter sections and thick diameter sections are connected together alternately. Both the thin diameter section and the thick diameter section are cylinders, and all the thin diameter sections have the same size, all the thick diameter sections have the same size, and the materials of the thin diameter section and the thick diameter section are the same;

For melting electrode gas shielded welding, take the intersection point of the lower end surface of the electric tip and the central axis of the solid welding wire as the coordinate origin O, and establish a one-dimensional coordinate system x-axis along the feeding direction of the solid welding wire, and the described used for melting electrode welding Variable cross-section solid welding wire satisfies the following formula:

x is the distance from the point on the central axis of the solid wire to the origin O, in mm;

T(x) is the wire temperature at point x, in °C;

e is a natural constant;

α is the temperature coefficient of resistance of the solid welding wire, the unit is ℃ ^-1 ;

T ₀ is room temperature, which is 25°C;

Where σ ₀ is the resistivity of the solid wire at room temperature, in mm Ω; c is the specific heat of the solid wire material, in J/(g °C); ρ is the density of the solid wire material, in g/mm ³ ;

v is the wire feeding speed, the unit is mm/s;

j is the current density, the unit is A/mm ² , j=I/S, I is the current through the solid welding wire, that is, the welding current, and S is the cross-sectional area of the solid welding wire;

And T(B) _≥Tmelting >T(C), point B is the midpoint of the truncation of the thin-diameter section farthest from the contact tip on the central axis, point C is the thick-diameter section farthest from the contact tip on the central axis The midpoint of the above section, Tmelt is the _melting point of the solid welding wire;

For point B: x _B ＝L ₀ -L ₂ -0.5×L ₁ ; for point C: x _C ＝L ₀ -0.5×L ₂ , L ₀ is the dry elongation length of solid welding wire, L ₂ is the thick diameter section The length of L ₁ is the length of the thin diameter section.

Embodiment 2: This embodiment differs from Embodiment 1 in that: the variable cross-section solid welding wire used for melting electrode welding is H08CrMnVA welding wire. Others are the same as the first embodiment.

Embodiment 3: This embodiment differs from Embodiment 1 or Embodiment 2 in that: the variable cross-section solid welding wire used for melting electrode welding is H08Mn ₂ Si welding wire. Others are the same as those in Embodiment 1 or 2.

Embodiment 4: This embodiment differs from Embodiments 1 to 3 in that: the variable cross-section solid welding wire used for melting electrode welding is H13CrMoA welding wire. Others are the same as one of the specific embodiments 1 to 3.

Embodiment 5: This embodiment differs from Embodiments 1 to 4 in that: the variable cross-section solid welding wire used for melting electrode welding is H08MnA welding wire. Others are the same as one of the specific embodiments 1 to 4.

The present invention is verified with following test:

Test 1: This test is a variable cross-section solid welding wire used for melting electrode welding. Specifically, it is composed of multiple thin-diameter sections and multiple thick-diameter sections. The thin-diameter sections and thick-diameter sections are connected together alternately. Both the thin diameter section and the thick diameter section are cylinders, and all the thin diameter sections have the same size, all the thick diameter sections have the same size, and the materials of the thin diameter section and the thick diameter section are the same;

For melting electrode gas shielded welding, take the intersection point of the lower end surface of the electric tip and the central axis of the solid welding wire as the coordinate origin O, and establish a one-dimensional coordinate system x-axis along the feeding direction of the solid welding wire, and the described used for melting electrode welding Variable cross-section solid welding wire satisfies the following formula:

x is the distance from the point on the central axis of the solid wire to the origin O, in mm;

T(x) is the wire temperature at point x, in °C;

e is a natural constant;

α is the temperature coefficient of resistance of the solid welding wire, the unit is ℃ ^-1 ;

T ₀ is room temperature, which is 25°C;

Where σ ₀ is the resistivity of the solid wire at room temperature, in mm Ω; c is the specific heat of the solid wire material, in J/(g °C); ρ is the density of the solid wire material, in g/mm ³ ;

v is the wire feeding speed, the unit is mm/s;

j is the current density, the unit is A/mm ² , j=I/S, I is the current through the solid welding wire, that is, the welding current, and S is the cross-sectional area of the solid welding wire;

Point B is the midpoint of the line section of the thin diameter section farthest from the contact tip on the central axis, point C is the midpoint of the line section of the thick diameter section farthest from the contact tip on the central axis, and T is the solid _welding wire. melting point;

For point B: x _B ＝L ₀ -L ₂ -0.5×L ₁ ; for point C: x _C ＝L ₀ -0.5×L ₂ , L ₀ is the dry elongation length of solid welding wire, L ₂ is the thick diameter section The length of L ₁ is the length of the thin diameter section.

The solid welding wire is H08CrMnVA, then ρ=7.8×10 ^-3 g/cm ³ , c=0.42J/g·℃, σ ₀ =9.7×10 ^-5 mm·Ω, α=6.45×10 ^-3 ℃ ^-1 , substituted into the above formula to get:

Note: d is the diameter of the solid welding wire in mm, the unit of I is A, the unit of x is mm, and the unit of v is mm/s.

Due to the influence of heat conduction, the resistance heat generated by itself is transmitted to the thick diameter section through heat conduction at both ends of the thin diameter section close to the thick diameter. Therefore, the temperature at the midpoint of the thin diameter section is calculated here, and the temperature at this point is less affected by heat conduction. , it is considered that the temperature at the midpoint on the thin diameter segment is the highest. The thick-diameter section also calculates the temperature at the midpoint. Assuming that the melting point of the H08CrMnVA welding wire is 1400°C, in order to make the temperature at point B reach the melting point, the heating length x _{B of point B} and its diameter d ₁ must satisfy the following formula:

T(B)=1400℃>T(C), deduced

The welding current is 150.5A, x _B is 13mm, the length L _{1 of} the thin diameter section is 1mm, the diameter d ₁ is 0.75mm, the wire feeding speed v is 8m/min, the length L ₂ of the thick diameter section is 2mm, and d ₂ is 0.9mm , then x _C is 14.5mm, T(B)=1407°C, T(C)=413°C, point B will melt before point C, realizing automatic droplet transfer.

Claims (5)

1. a kind of variable cross-section solid welding wire welded for consumable electrode, it is characterised in that the variable cross-section welded for consumable electrode is solid Welding wire is made up of multiple thin diameter sections and multiple wide sections, and thin diameter section and wide section alternately link together, described thin diameter section It is cylinder with wide section, and all thin diameter section sizes are the same, all wide section sizes are the same, thin diameter section and wide section Material it is identical；

Connect for gas metal-arc welding, the intersection point for taking the lower surface of ignition tip and the axis of solid welding wire is the origin of coordinates O, one-dimensional coordinate system x-axis is set up along the feeding direction of solid welding wire, and described is used for the variable cross-section solid welding wire that consumable electrode is welded Meet following formula：

<mrow> <mi>T</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mi>&amp;alpha;</mi> </mfrac> <mo>&amp;lsqb;</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <msub> <mi>&amp;alpha;T</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <msup> <mi>&amp;alpha;Aj</mi> <mn>2</mn> </msup> <mfrac> <mi>x</mi> <mi>v</mi> </mfrac> </mrow> </msup> <mo>-</mo> <mn>1</mn> <mo>&amp;rsqb;</mo> </mrow>

X be solid welding wire axis on point apart from origin O distance, unit is mm；

T (x) is the welding wire temperature of x points, and unit is DEG C；

E is natural constant；

α is the temperature-coefficient of electrical resistance of solid welding wire, and unit is DEG C^-1；

T₀It is room temperature, is 25 DEG C；

Wherein σ₀For the resistivity of solid welding wire at room temperature, unit is mm Ω；C is the specific heat of solid welding wire material, Unit is J/ (g DEG C)；ρ is the density of solid welding wire material, and unit is g/mm³；

V is wire feed rate, and unit is mm/s；

J is current density, and unit is A/mm², j=I/S, I is the electric current i.e. welding current by solid welding wire, and S is solid welding wire Cross-sectional area；

And T (B) >=T_{It is molten}＞ T (C), B point is, farthest away from the midpoint of the thin diameter section of ignition tip institute's transversal section on axis, C points are Farthest away from the midpoint of wide section institute's transversal section on axis of ignition tip, T_{It is molten}For the fusing point of solid welding wire；

For B points：x_B=L₀-L₂-0.5×L₁；For C points：x_C=L₀-0.5×L₂, L₀For the stem elongation length of solid welding wire, L₂ For the length of wide section, L₁For the length of thin diameter section.

2. a kind of variable cross-section solid welding wire welded for consumable electrode according to claim 1, it is characterised in that described It is H08CrMnVA welding wires for the variable cross-section solid welding wire that consumable electrode is welded.

3. a kind of variable cross-section solid welding wire welded for consumable electrode according to claim 1, it is characterised in that described It is H08Mn for the variable cross-section solid welding wire that consumable electrode is welded₂Si welding wires.

4. a kind of variable cross-section solid welding wire welded for consumable electrode according to claim 1, it is characterised in that described It is H13CrMoA welding wires for the variable cross-section solid welding wire that consumable electrode is welded.

5. a kind of variable cross-section solid welding wire welded for consumable electrode according to claim 1, it is characterised in that described It is H08MnA welding wires for the variable cross-section solid welding wire that consumable electrode is welded.