JPH0825080A - Solid wire for welding and welding method - Google Patents

Abstract

PURPOSE:To obtain a solid wire for welding and welding method suitable to weld a high-tension steel sheet. CONSTITUTION:In this solid wire for welding, one kind of the element which is selected from C, Si, Mn, Ni, Cr, Mo, V, Nb, Ti, Al, Zr, Cu, B, Ca and rare earth element is specified, the balance consists of Fe and the carbon equivalent Weq expressed by the next formula is 0.15-0.7. Formula: Weq=[C]+[Si]/24+[Mn]/6+[Ni]/60+[Cr]/5+[Mo]/4+[V]/14+[Nb]+[Ti]/14. Where, [M] is the content of a component M in the wire (wt.%). Welding is executed by a single pass by using this wire, setting the welding voltage Va in a prescribed range and under the conditions that a welding current is 50-500A and welding speed is 5-250cm/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding solid wire and welding method suitable for welding thin high-strength steel sheets, and more particularly to a welding solid wire and welding method capable of obtaining a fillet weld having excellent joint fatigue characteristics. .

[0002]

2. Description of the Related Art Conventionally, solid wires are often used for fillet welding thin thin high strength steel sheets. However, no study has been made on the effect of the wire composition and welding conditions used for welding on the fatigue strength of welded joints.

[0003]

As described above, in the welding of the conventional high-strength steel sheet, the influence of the composition of the welding wire and the welding conditions on the fatigue strength of the welded joint is not taken into consideration. However, there is a problem in that the fatigue strength may not be sufficient. In this case, the original fatigue strength of the high-tensile steel plate cannot be exhibited.

The present invention has been made in view of the above problems, and it is possible to obtain a welded joint having excellent fatigue strength and to sufficiently utilize the original fatigue strength of a high-strength steel sheet. And a welding method.

[0005]

The solid wire for welding according to the present invention comprises C: 0.01 to 0.40% by weight and S
i: 0.05 to 2.00% by weight and Mn: 0.20 to 3.00% by weight, Ni: 0.5 to 5.0% by weight, Cr: 0.005 to 3.00% by weight %,
Mo; 0.10 to 2.00% by weight, V; 0.01 to 1.00% by weight, Nb; 0.01 to 1.00% by weight,
Ti; 0.01 to 1.00% by weight, Al; 0.01 to 1.00% by weight, Zr; 0.01 to 1.00% by weight, Cu; 0.05 to 1.50% by weight, B; 0.00
05 to 0.0500% by weight, Ca; 0.001 to 0.050% by weight and rare earth element; 0.001 to 0.
It contains at least one element selected from the group consisting of 050% by weight, regulates the P content to 0.05% by weight or less and the S content to 0.05% by weight or less, and balances iron and unavoidable. It is characterized by being made of impurities and having a carbon equivalent Weq represented by the following formula 1 of 0.15 to 0.70.

[0006]

## EQU1 ## Weq = [C] + [Si] / 24 + [Mn] / 6
+ [Ni] / 60 + [Cr] / 5 + [Mo] / 4 +
[V] / 14 + [Nb] + [Ti] / 14 where [M] is the content (% by weight) of the component M in the wire. The welding method according to the present invention uses the above solid wire for welding, The voltage Va is set within the range shown by the following mathematical formula 2, the welding current is 50 to 500 A, and the welding speed is 5 to 2
It is characterized by welding in one pass under the condition of 50 cm / min.

[0007]

## EQU2 ## VL≤Va≤VH However, VL and VH are expressed by the following equations 3 and 4, respectively.

[0008]

[Formula 3] VL = 7.96 × 10 ^-8 × A ³ −1.12 × 10 ^-4 × A ² +0.1
1 x A + 9.43 + P1 + P2-Weq x 5-4

[0009]

[Equation 4] VH = 7.96 × 10 ^-8 × A ³ −1.12 × 10 ^-4 × A ² +0.1
1 × A + 9.43 + P1 + P2 Further, A, P1 and P2 take the values shown in Table 1 below.

[0010]

[Table 1]

[0011]

The present inventors investigated the relationship between the weld bead shape and the fatigue strength, and found that the bead toe shape with respect to the base material had a close relationship with the fatigue strength of the joint. As a result, it was found that the larger the radius of curvature ρ of the bead toe, the higher the fatigue strength and the better the fatigue properties of the joint.

As shown in FIG. 1A, a base material 2 is superposed on a weld base material 1 and the base materials 1 and 2 are welded by horizontal fillet welding to a bead 3.
When the bead is formed, the bead toe portion 4 has a downwardly convex shape and is curved with a radius of curvature ρ, as shown in an enlarged view in FIG. The larger the radius of curvature ρ of the bead toe 4, the smoother the skirt of the bead 3 contacts the base material 1.

In FIG. 2, the abscissa represents the radius of curvature ρ of the toe, and the ordinate represents the time strength (in the case where the joint composed of the base materials 1 and 2 is not broken even if it is bent 10 ⁶ times). It is a graph which shows the fatigue test result by taking the upper limit of the stress between the materials 1 and 2. This fatigue test method is carried out by using a plane bending fatigue tester and applying both sine wave stress as a stress load. The steel plate (base material) is a thin high-strength steel plate (50k
gf class high strength steel HT50 and 80 kgf class high strength steel HT
80). As is clear from FIG. 2, as the radius of curvature ρ of the toe portion increases, the time strength σ increases,
It can be seen that the fatigue strength increases.

Based on the above findings, the present invention has developed a welded solid wire having a large bead toe radius of curvature ρ in the welding of thin plate high-strength steel, whereby fatigue strength is extremely high and good. I tried to obtain a large joint.

The inventors of the present invention have conducted extensive studies in order to solve the above problems, and as a result, have found a carbon equivalent Weq derived from the wire composition and a range of an appropriate welding voltage Va at which an appropriate curvature radius at the toe portion can be obtained. The present invention has been completed by finding that there is a correlation between the two. Further, in the present invention, the range in which a more favorable bead toe radius of curvature is obtained is defined for other welding execution conditions within the proper welding voltage range, advancing and receding angles, and torch angles. Figure 3 shows base materials 1 and 2
FIG. 3 shows a state in which the welding torch 5 is moved in the direction shown by the arrow in the drawing and welded when the edges are overlapped and horizontal fillet welding is performed. In FIG. 3, the inclination angle of the welding torch with respect to the horizontal direction is θ2, and the angle of inclination with respect to the direction perpendicular to the welding line is the advance angle θ1.

Next, the reason for adding the components of the composition of the solid wire defined in the present invention and the reason for limiting the composition will be explained.

C (Carbon) C improves the strength of steel. However, considering the yield of the wire component in the weld metal, if the content is less than 0.01% by weight, the desired strength of the weld metal cannot be secured. On the other hand, when the C content exceeds 0.40% by weight, the weldability is deteriorated, high carbon martensite is generated, and the toughness is deteriorated. Therefore, the C content is 0.01 to 0.40% by weight.

Si (Si) Si is an element that is effective in increasing the strength of steel and has a strong deoxidizing effect. By containing Si in the wire, generation of bubbles and oxidation of the weld metal can be prevented. However, if the Si content is less than 0.05% by weight, the above effect cannot be obtained. On the other hand, S
If the i content exceeds 2.00% by weight, the toughness of the weld metal deteriorates significantly. Therefore, the Si content is set to 0.05 to 2.00% by weight.

Mn (Manganese) Mn has an effect of improving both strength and toughness of steel by actions such as solid solution strengthening, transformation strengthening and grain refinement strengthening. However, if the Mn content is less than 0.20% by weight, the above effect cannot be obtained. On the other hand, when the Mn content exceeds 3.00% by weight, primary crystal grain boundaries develop to cause grain boundary fracture, resulting in significant deterioration in crack resistance and toughness. Therefore, the Mn content is 0.20 to 3.0
0% by weight.

If the P (phosphorus) P content exceeds 0.050% by weight, the solid solution of P in ferrite not only impairs the toughness of the matrix but also causes weld cracking. For this reason,
It is necessary to regulate the P content to be 0.050% by weight or less.

S (Sulfur) When the S content exceeds 0.050% by weight, the ductility of the weld metal part and the crack resistance of the weld metal part are deteriorated as in the case of P. Therefore, the S content is 0.050
It is necessary to make it less than or equal to the weight%.

Furthermore, in addition to the above essential elements, the following elements can be selected and added in one or more kinds to improve the mechanical properties of the weld metal, in particular, improve the strength and ductility, and strengthen the toughness. .

Al (Aluminum) Al is an element having a deoxidizing effect on steel. However, A
If the 1 content is less than 0.01% by weight, the deoxidizing effect is not sufficient. On the other hand, when the Al content exceeds 1.00% by weight, a large amount of Al ₂ O _3, which is a deoxidation product, remains in the weld metal, so that the deoxidization effect disappears and the toughness significantly increases. to degrade. Therefore, when containing Al,
Its content is 0.01 to 1.00% by weight. The amount of unavoidable impurities is less than 0.01% by weight.

Ni (Nickel) Ni is an element effective for improving the toughness and strength of the weld metal. However, if the Ni content is less than 0.5% by weight, the above effect cannot be obtained. On the other hand, if the Ni content exceeds 5.0% by weight, primary grain boundaries develop and, conversely, embrittlement occurs. Therefore, when Ni is contained,
Its content is 0.5 to 5.0% by weight. The amount of unavoidable impurities is less than 0.5% by weight.

Cr (Chromium) Cr has the effects of strengthening the weld metal portion and improving the corrosion resistance and the high temperature strength by the oxide film. However, if the Cr content is less than 0.005% by weight, the above effect cannot be obtained. Further, the Cr content is 3.
If it exceeds 00% by weight, the self-hardening property is increased and the crack resistance is deteriorated. Therefore, when Cr is contained, its content is set to 0.005 to 3.00% by weight. The amount of unavoidable impurities is less than 0.005% by weight.

Mo (Molybdenum) Mo has the effect of enhancing the hardenability of the weld metal and contributes to the improvement of its strength. However, if the Mo content is less than 0.10% by weight, the above effect cannot be obtained. On the other hand, when the Mo content exceeds 2.00% by weight, carbides are formed and the toughness is significantly reduced. Therefore, when Mo is contained, its content is set to 0.10 to 2.00% by weight. In addition, the amount of unavoidable impurities is 0.
It is less than 10% by weight.

Ti, Zr (Titanium, Zirconium) Ti and Zr are both strong deoxidizing agents and prevent oxidation of the deposited metal. Further, since Ti and Zr form an oxide, they are effective in increasing the strength due to the precipitation effect and improving the toughness due to the refinement of the structure. However, the Ti content is 0.0
If it is less than 1% by weight, the above-mentioned effect cannot be obtained, and if the Ti content exceeds 1.00% by weight, the weldability is deteriorated and the toughness is significantly lowered due to the formation and precipitation of carbides. . Further, similarly to this, the Zr content is 0.
Even when the amount is less than 01% by weight, the above effect cannot be obtained, and when the Zr content exceeds 1.00% by weight, the weldability is deteriorated and the toughness is significantly reduced due to the formation and precipitation of carbides. . Therefore, when Ti is contained, the content is 0.01 to 1.00% by weight, and when Zr is contained, the content is 0.01 to 1.00% by weight.
And The inevitable impurities of Ti and Zr are less than 0.01% by weight, respectively.

Nb, V (Niobium, Vanadium) Nb and V are added for increasing strength, improving high temperature strength and improving toughness. However, if Nb and V are less than 0.01% by weight, respectively, this effect cannot be expected.
If it exceeds 0% by weight, toughness and crack resistance are deteriorated due to the formation of carbide. Therefore, Nb and V in the wire
The content of each is 0.01 to 1.00% by weight.

When Nb and V are not added and are allowed only as unavoidable impurities, the amount of these unavoidable impurities is less than 0.01% by weight.

Cu (Copper) Cu has a function of forming an amorphous film having an anticorrosion effect. This effect is not recognized when the Cu content is less than 0.05% by weight, and the effect is saturated when the Cu content exceeds 1.50% by weight, and adverse effects such as weld cracking occur. Therefore, the Cu content of the wire is 0.05 to 1.50% by weight.

When Cu is contained as an unavoidable impurity, the amount of the unavoidable impurity is 0.05% by weight.
Less than

When the wire is plated with Cu, the Cu content including the amount of plated Cu is calculated as C of the wire.
u content.

Ca (calcium) and rare earth elements (RE
M) Ca and REM are elements that are mainly effective in increasing the strength of weld metal, improving ductility, and stabilizing the arc, and for that purpose, each must be contained in an amount of 0.001% by weight or more. However, if each of these elements is added in an amount of more than 0.050% by weight, the amount of non-metallic inclusions in the steel increases and the ductility deteriorates. Therefore, the Ca and REM contents of the wire are 0.001 to 0.050% by weight, respectively. In addition, REM
(Rare earth element) refers to all elements having atomic numbers 57 to 71.

The inevitable impurities of Ca and REM are less than 0.001% by weight, respectively.

B (Boron) B is an element which, when added in a trace amount, makes the structure fine and imparts excellent low temperature toughness. However, if the content is less than 0.0005% by weight, such an effect cannot be expected. On the other hand, if B is contained in an amount of more than 0.0500% by weight, the weld crack resistance is significantly deteriorated. Therefore, the content of B is 0.
It is 0005 to 0.0500% by weight. The unavoidable impurities of B are less than 0.0005% by weight.

Carbon equivalent Weq: 0.15≤Weq≤0.70 When the carbon equivalent Weq is less than 0.15, the weld metal at the toe and the base metal are compatible with each other under any welding condition. Poor, bad toe shape. Therefore, good fatigue characteristics cannot be expected. As the carbon equivalent Weq increases, the toe shape becomes smoother, but if the carbon equivalent exceeds 0.70, the welding workability is poor and a normal weld cannot be obtained. For this reason, Weq is set to 0.15 to 0.70.

The carbon equivalent Weq is preferably 0.25 to 0.70, more preferably the carbon equivalent Weq is 0.35 to 0.70.

The carbon equivalent is calculated on the basis of the above formula 1. For each component term in this definition formula of Weq, the content is substituted even if the component is an unavoidable impurity. . For each component, if the content is below the detection limit, 0 is substituted.

Next, the welding conditions of the welding method of the present invention will be described.

Welding current A: 50 to 500 A In general arc welding, when the welding current is less than 50 A, the arc is unstable and welding is impossible. Therefore, the lower limit of the welding current is set to 50A. If the welding current exceeds 500 A, problems such as defective shield and defective bead shape are likely to occur. Therefore, the upper limit of the welding current is 500A.

Welding speed γ: 5 cm / min to 250 cm / min If the welding speed is less than 5 cm / min, the arc becomes buried in the molten weld metal under any welding condition, and the arc becomes unstable. The bead shape deteriorates. Therefore, the lower limit of the welding speed is 5 cm / min. If the welding speed exceeds 250 cm / min, the welding speed is too high and the arc does not continue, resulting in a humping bead. Therefore, 250 cm / min is set as the upper limit of the welding speed.

Welding voltage: VL≤Va≤VH However, these VL, Va, and VH are represented by the above-mentioned equations 2, 3, and 4. That is, Va = adequate welding voltage (V) VH = 7.96 × 10 ⁻⁸ × A ³ −1.12 × 10 ⁻⁴ × A ² + 0.11 × A +
9.43 + P ₁ + P ₂ -Weq × 5−4 VL = 7.96 × 10 ⁻⁸ × A ³ −1.12 × 10 ⁻⁴ × A ² + 0.11 × A +
9.43 + P1 + P2 Moreover, A, P1 and P2 take the values shown in Table 1, and carbon equivalent W
eq is represented by Equation 1 above.

FIG. 4 is a graph showing the relationship between the welding voltage, the carbon equivalent Weq, and the radius of curvature ρ, with the horizontal axis representing the welding voltage and the vertical axis representing the radius of curvature ρ. As shown in FIG. 4, as the welding voltage increases, the radius of curvature ρ of the bead toe increases, and the fatigue strength of the welded joint improves.

However, when the voltage becomes higher than the voltage VH determined by the welding current, the shield gas composition, and the welding speed, undercutting occurs and the joint becomes defective. Therefore, the upper limit of the proper welding voltage Va is a value defined by VH.

On the contrary, the radius of curvature ρ of the toe portion becomes smaller as the welding voltage becomes lower. However, the tendency depends on the wire composition. The inventors have found that a wire having a larger carbon equivalent defined by Weq has a larger radius of curvature ρ at the toe of the bead at the same voltage. From FIG.
It can be seen that the fatigue strength rapidly deteriorates when the curvature radius ρ of the toe portion is less than 0.05 mm. From this, the toe radius of curvature ρ = 0.0 required to obtain good fatigue strength
The minimum welding voltage at which 5 mm is obtained is defined as VL, and this is the lower limit of the proper welding voltage. VL is a function of the carbon equivalent Weq in addition to the welding current, the shield gas composition and the welding speed. At a welding voltage below VL, the radius of curvature of the toe is small, and as a result, the fatigue strength of the joint is small.
From the above, the proper welding voltage is VL or more and VH or less.

Thickness of thin high-strength steel plate 0.5 to 7.0 m
When the m plate thickness exceeds 7.0 mm, it becomes difficult to perform welding in one pass, and a large current is required, so that the shield property is deteriorated and the bead shape is apt to occur. On the contrary, if the plate thickness is less than 0.5 mm, it cannot be welded by solid wire welding. Therefore, the thickness of the thin high-tensile steel plate is set to 0.5 to 7.0 mm.

Advance angle θ1 of welding torch: 0 ° to 30 ° Angle of welding direction of welding torch (advance receding angle) θ1 (Fig. 3)
When the angle of refraction is smaller than 0 °, the bead becomes convex and the width tends to be insufficient, and the radius of curvature of the toe portion also becomes small, leading to a reduction in fatigue strength. As the advancing angle θ1 increases, the radius of curvature of the toe increases, but when the advancing angle θ1 exceeds 30 °, the arc becomes unstable and undercut occurs. Therefore, the advancing angle θ1 of the torch is set to 0 ° or more and 30 ° or less.

Welding torch tilt angle θ2: 30 ° to 60 ° If the angle (tilt angle) θ2 (see FIG. 3) between the torch and the lower plate exceeds 60 °, the toe curvature radius ρ becomes small, Further, the arc is focused on the lower plate, so that the so-called easily comes off. The radius of curvature ρ of the toe portion increases as the inclination angle decreases, but if the angle of inclination is less than 30 °, the bead is likely to be convex, resulting in poor shape. Therefore, the torch tilt angle θ
2 is 30 to 60 °.

[0049]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples. Using a solid wire having the chemical composition shown in Table 2 below, lap fillet welding was performed under the test conditions shown in Table 3 below and the welding conditions shown in Table 4 below, and fatigue test pieces of the joint were collected. However, A to H are solid wire numbers.

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

The bead of this fatigue test piece was 2 per condition.
It was sampled at 0 places and the curvature radius ρ of the toe portion was measured at a magnification of 50 times. The radius under each condition was a representative diameter with a cumulative probability of 50% or more. The results of these tests are also shown in Table 4.

As shown in Table 4, (1) Examples 1 to 3, 4 to 6, 7 to 9, 10 to 12 and 1
Nos. 3 to 15 and 16 to 23 all have the chemical composition and Weq of the solid wire satisfying the limited range of the present invention, and as a result, the bead toe curvature radius ρ becomes 0.05 mm or more, and good fatigue properties are obtained. It became a joint to have.

(2) Comparative Examples 24, 26, 28, 30, 3
In No. 2, since the welding voltage is lower than VL, the radius of curvature of the toe portion becomes smaller than 0.05 mm, and as a result, the joint becomes inferior in fatigue characteristics and is defective.

(3) Comparative Examples 25, 27, 29, 31, 3
In No. 3, since the welding voltage is higher than VH, the curvature radius of the toe is large, but undercut occurs,
It is defective as a welded joint.

(4) In Comparative Example 34, the curvature radius ρ of the toe portion showed a good value, but the Weq exceeded the limited range of 0.15 to 0.70. Therefore, the strength became excessive and low temperature cracking occurred. If cracks occur in the welded part, the joint is defective.

(5) In Comparative Example 35, Weq is in a limited range of 0.1.
It is below 5 to 0.70. Therefore, although the welding voltage satisfies the limited range, the bead shape is poor, the radius of curvature of the toe portion is less than 0.05 mm, and the fatigue property is poor.

(6) In Comparative Example 36, the radius of curvature ρ of the toe portion showed a good value, but among the components of the solid wire,
Since Si and Mn were lower than the limits of the present invention, the welding workability was remarkably poor, and deoxidation became insufficient, resulting in oxidized poor beads.

FIG. 4 shows a test in which the welding current, the plate thickness, the torch advance / retreat angle and the torch tilt angle are the same among these test results (Examples 1 to 15 and Comparative Examples 24 to 3).
3) shows the relationship among welding voltage, Weq, and bead toe curvature radius ρ.

FIG. 5 also shows the relationship between the carbon equivalent Weq and the proper welding voltage range Va. This Figure 5
The proper welding voltage Va is the upper limit value VH and the lower limit value VL.
It is shown as the area between and.

The chemical compositions of the weld metal parts obtained in this test were within the ranges shown in Table 5 below.
However, in Table 5, Examples 1 to 3 and Comparative Example 2
In the case of 4 and 25, Examples 4 to 6 and Comparative Examples 26 and 27
In the case of Examples 7 to 9 and Comparative Examples 28 and 29,
In the case of Examples 10 to 12 and Comparative Examples 30 and 31, are Examples 13 to 15, Examples 16 to 23, Comparative Examples 32 and 3.
In the case of 3, is the case of Comparative Example 34, is the case of Comparative Example 35, and is the case of Comparative Example 36.

[0063]

[Table 5]

[0064]

As described above, according to the present invention, the solid wire composition and the carbon equivalent Weq are defined within a predetermined range, and further, the welding voltage, the welding current and the welding speed are defined within the appropriate ranges, and thus welding is performed. , The radius of curvature of the toe of the bead can be increased, and it is extremely effective as a welding wire for thin plate high-strength steel. By using the welding wire and welding method of the present invention, the fatigue characteristics of welded joints are significantly improved. Can be made.

[Brief description of drawings]

FIG. 1 is a schematic view showing a radius of curvature ρ of a bead toe portion.

FIG. 2 is a graph showing a relationship between a toe radius of curvature ρ and temporal strength.

FIG. 3 is a schematic diagram illustrating a welding method.

FIG. 4 is a graph showing a mutual relationship between welding voltage, carbon equivalent Weq, and radius of curvature ρ.

FIG. 5 is a graph showing the relationship between carbon equivalent Weq and appropriate welding voltage Va.

[Explanation of symbols]

 1, 2: base material 3; bead 4; toe portion 5; torch

Claims (5)

[Claims] 1. C: 0.01 to 0.40% by weight, S
i: 0.05 to 2.00% by weight and Mn: 0.20 to 3.00% by weight, Ni: 0.5 to 5.0% by weight, Cr: 0.005 to 3.00% by weight %,
Mo; 0.10 to 2.00% by weight, V; 0.01 to 1.00% by weight, Nb; 0.01 to 1.00% by weight,
Ti; 0.01 to 1.00% by weight, Al; 0.01 to 1.00% by weight, Zr; 0.01 to 1.00% by weight, Cu; 0.05 to 1.50% by weight, B; 0.00
05 to 0.0500% by weight, Ca; 0.001 to 0.050% by weight and rare earth element; 0.001 to 0.
It contains at least one element selected from the group consisting of 050% by weight, regulates the P content to 0.05% by weight or less and the S content to 0.05% by weight or less, and balances iron and unavoidable. Carbon equivalent W consisting of impurities and represented by the following formula
A solid wire for welding, wherein eq is 0.15 to 0.70. Weq = [C] + [Si] / 24 + [Mn] / 6 + [N
i] / 60 + [Cr] / 5 + [Mo] / 4 + [V] / 1
4+ [Nb] + [Ti] / 14 where [M] is the content of the component M in the wire (% by weight) 2. The solid wire for welding according to claim 1 is used, the welding voltage Va is set within the range shown by the following mathematical formula, the welding current is 50 to 500 A, and the welding speed is 5 to 2.
A welding method characterized by welding in one pass under the condition of 50 cm / min. VL ≦ Va ≦ VH, where VL = 7.96 × 10 ⁻⁸ × A ³ −1.12 × 10 ⁻⁴ × A ² + 0.11 × A +
9.43 + P1 + P2-Weq x 5-4 VH = 7.96 x 10 ^-8 x A ³ -1.12 x 10 ^-4 x A ² + 0.11 x A +
9.43 + P1 + P2 A; Welding current P1; P1 = 0 when shield gas composition consists of CO ₂ and inevitable impurities, shield gas composition is Ar; 5
In the case of a mixed gas containing 0 volume% or more and the balance being at least one gas selected from the group consisting of CO ₂ , O ₂ and He and an unavoidable impurity, P 1 = −
2, P1 = -1 P2 for other shield gas compositions; P2 = 0 for welding speed r of 50 cm / min or less,
When the welding speed r exceeds 50 cm / min, P2 = -r /
25 + 2 3. The material to be welded has a thickness of 0.5 to 7.0 m.
The high-strength steel sheet of m is a welding method according to claim 2. 4. The advancing angle θ1 of the welding torch is 0 to 30 °.
The welding method according to claim 2 or 3, wherein 5. The inclination angle θ2 of the welding torch is 30 to 6
It is 0 degree, The welding method of any one of Claims 2 thru | or 4 characterized by the above-mentioned.