JP2009166066A - Solid wire for pulse mag welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid wire for pulse MAG welding which is adequately fit for a member to be welded formed of a thin steel sheet, and capable of obtaining excellent weld bead of wide bead width even when a gap is large. <P>SOLUTION: The solid wire for pulse MAG welding has a composition consisting of, by mass to the total mass of the wire, <0.10% Si, 0.01-0.15% C, 1.80-2.50% Mn, 0.001-0.070% S, ≤0.030% P, ≤0.010% O, and the balance Fe with inevitable impurities. The wire contains one or two of Ti and Al of ≤0.20%. Further, the wire contains ≤0.30% Mo. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid wire for pulse MAG welding, and when applied to the welding of thin steel plates, the width of the weld bead is wide, the conformability of the toe portion is good, and the groove gap of the welded portion (hereinafter referred to as a gap). ) Is related to a pulsed MAG welding solid wire which can obtain a good welding bead even in a wide case.

Gas shielded arc welding using a solid wire is highly efficient, and a weld metal with good mechanical performance and a good weld bead can be obtained. In addition, pulse MAG welding using a mixed gas such as Ar + CO ₂ , Ar + O ₂ or Ar + CO ₂ + O ₂ has recently been increasing in order to reduce the amount of spatter generated and ensure high-speed weldability. In the pulse MAG welding method, a peak current that is a high current and a base current that is a low current are generated periodically and alternately to melt the wire during the peak current period and melt droplets during the base current period. It is a welding method intended to be transferred to. By controlling the peak current, the peak time, etc., the melting energy of the wire is made appropriate, and the amount of spatter generated is reduced by shifting to 1 pulse-1 drop.

  These weldings are widely used in the automobile industry, etc., where thin plates with a thickness of 0.5 to 6.0 mm are used. For the purpose of further improving productivity, automation by a welding robot is frequently used, and the welding speed is 1 m / min. It is often welded at the above high speed. Therefore, the amount of welding heat input is very small, the cooling rate is high, and the width of the weld bead is narrow and tends to be a convex weld bead. Furthermore, in the welding of automobiles and the like, the gap between the members tends to become wide due to the complicated shape of the joint. Under such circumstances, it is required to perform stable welding satisfying the gap resistance.

  Conventionally, various techniques described in JP-A-9-99390 (Patent Document 1) and JP-A-10-24389 (Patent Document 2) have been disclosed for the purpose of performing welding with a good bead shape. Yes. However, when the welding wire described in the above technique is used for welding under high-speed welding conditions, the familiarity with the steel plate is poor, and the molten metal solidifies before the width of the weld bead is increased. Tends to be narrow and convex bead. Furthermore, since the width of the weld bead is narrow, there is a problem that welding cannot be performed when the gap between the members is wide.

Further, in the welding wire described in Japanese Patent Laid-Open No. 2002-346787 (Patent Document 3), although the amount of spatter can be reduced, the bead width does not increase when the gap between the members is wide, and the gap resistance is It is not satisfactory.
JP-A-9-99390 Japanese Patent Laid-Open No. 10-24389 JP 2002-346787 A

  An object of the present invention is to provide a solid wire for pulse MAG welding in which a good weld bead having a wide bead width can be obtained even when the gap is wide in pulse MAG welding of a thin steel plate. .

  The gist of the present invention is mass% with respect to the total mass of the wire, Si: less than 0.10%, C: 0.01 to 0.15%, Mn: 1.80 to 2.50%, S: 0.001 to It is characterized by containing 0.070%, P: 0.030% or less, O: 0.010% or less, the other being composed of Fe and inevitable impurities. Further, the total content of one or two of Ti and Al is 0.20% or less. Furthermore, the solid wire for pulse MAG welding is characterized by containing Mo in an amount of 0.30% or less.

  According to the solid wire for pulse MAG welding of the present invention, it is possible to obtain a flat and wide bead shape with little spatter generation, good conformity with a welding member, in welding thin steel plates. Even when the gap is wide, a good weld bead having a wide bead width can be obtained.

  In order to solve the above-mentioned problems, the present inventors made a prototype of a solid wire in which various components were changed, and investigated in detail the effect of the component composition on pit generation, bead width, and gap resistance. As a result, the following knowledge was obtained. The generation of pores such as pits can be prevented by adding Si, Mn, Al, Ti, etc., which have a strong deoxidizing action, but if a large amount of Si is contained, the weld bead width becomes narrow. Therefore, by reducing the Si content and adding appropriate amounts of Mn, Al, Ti, etc., the surface tension and viscosity of the weld metal are optimized, and the familiarity with the welded member is improved, so that a flat and wide weld bead can be obtained. can get. Furthermore, it has been found that the amount of spatter generated can be reduced by adding appropriate amounts of C, S and Mo.

Hereinafter, the reason for limitation of the solid wire component composition for pulse MAG welding of this invention is demonstrated.
Si: Less than 0.10% by mass Si is an important element for widening the bead width by acting as a deoxidizing element and greatly affecting the surface tension and viscosity of the molten metal. In order to investigate the influence of the Si amount on the bead width, a wire having a different Si content is used, and the gap between the end portion of the upper plate 1 and the surface of the lower plate 2 shown in FIG. Welding was performed under welding conditions. The wire component is C: 0.04 to 0.08% by mass (hereinafter referred to as “%”) and Mn: 1.98 to 2.05%, and the target position of the wire is the corner of the lap joint. The angle θ of the welding torch 3 was 60 °.

溶接後、図２に示す溶接ビードの幅をＷ、下板２の表面から溶接ビード４の一番盛り上がった部分の高さをＨとして、溶接ビードの形状係数Ｈ／Ｗを測定した。なお、ビード形状係数Ｈ／Ｗは０．４０未満でビード幅が広くなり良好なビードとなる。

After welding, the weld bead shape factor H / W was measured with the width of the weld bead shown in FIG. 2 being W and the height of the most raised portion of the weld bead 4 from the surface of the lower plate 2 being H. The bead shape factor H / W is less than 0.40, the bead width is widened, and a good bead is obtained.

  FIG. 3 shows the relationship between the Si content and the bead shape factor H / W. As the Si content increases, the bead shape factor H / W increases and the bead shape factor H / W satisfies less than 0.40. In order to achieve this, Si needs to be less than 0.10%. When Si is 0.10% or more, particularly under high-speed welding conditions, the surface tension and viscosity of the molten metal are increased, and the conformity with the welded member is deteriorated, so that the bead shape factor H / W is 0.40 or more. The bead shape becomes convex and the bead width becomes narrow. Therefore, Si is less than 0.10%. In addition, although the minimum of Si is not specifically limited, It is preferable that it is 0.005% or more from steelmaking cost.

C: 0.01 to 0.15%
C has a function of stabilizing the arc and making the droplets fine. If C is less than 0.01%, the stability of the arc cannot be ensured, and if it exceeds 0.15%, not only the spatter is increased, but also the weld metal is markedly hardened and the crack resistance is deteriorated. Therefore, C is set to 0.01 to 0.15%.

Mn: 1.80 to 2.50%
Mn is an important element as a deoxidizing element, and if it is less than 1.80%, the deoxidizing effect cannot be obtained and pits are generated. On the other hand, if it exceeds 2.50%, the surface tension and viscosity of the weld metal increase excessively, and a wide bead cannot be obtained. Therefore, Mn is 1.80 to 2.50%.

S: 0.001 to 0.070%
S lowers the viscosity and surface tension of the droplet and facilitates the removal of the droplet from the wire, thereby reducing the size of the droplet and reducing spatter. Further, S has an effect of flattening the bead shape and improving the familiarity of the toe portion. If S is less than 0.001%, the effect cannot be obtained. However, when S exceeds 0.070%, cracks occur in the weld metal. Therefore, S is 0.001 to 0.070%.

P: 0.030% or less P is an impurity, an element that causes cracks in the weld metal due to an increase in P. If it exceeds 0.030%, hot cracking may occur.
O: 0.010% or less O has the effect of stabilizing the arc and reducing the size of the droplets. However, if it exceeds 0.010%, the short-circuit time becomes longer and the arc stability is lowered, resulting in frequent spattering. In addition, pits are generated and the amount of slag generated on the bead surface is increased to deteriorate the bead appearance.

Total of one or two of Ti and Al: 0.20% or less Ti and Al act as deoxidizing elements even when added in a small amount. In addition, there is an effect of improving the familiarity between the weld metal and the base material. However, if the total of one or two of Ti and Al exceeds 0.20%, the bead shape becomes convex and the bead width becomes narrow. In addition, a large amount of slag is generated, deteriorating the bead appearance.

Mo: 0.30% or less Mo is an element that refines the structure of the weld metal and improves toughness. Furthermore, the inclusion of Mo improves the droplet formation, stabilizes the transfer, and reduces the amount of spatter generated. However, if it exceeds 0.30%, the weld metal is hardened and the toughness is reduced, and the droplet formation is poor, the transition becomes unstable, and the amount of spatter generated increases. Therefore, Mo is 0.30% or less.

Hereinafter, the effects of the present invention will be described more specifically with reference to examples.
First, Table 2 shows the chemical composition of the trial wire obtained by vacuum melting the raw steel, forging, rolling, wire drawing, annealing, copper plating, drawing to a product diameter of 1.2 mm, and winding with a spool.

表２のワイヤを用いて水平姿勢による重ねすみ肉継手のビード形状試験を行い、ビード形状およびピットの発生を調査した。さらに横向姿勢による重ねすみ肉継手の耐ギャップ性試験を行い、架橋可能なギャップ幅を調査した。

The bead shape test of the lap fillet joint in a horizontal posture was performed using the wires in Table 2, and the occurrence of the bead shape and pits was investigated. In addition, a gap resistance test was conducted on the overlapped fillet joint in the horizontal orientation, and the gap width that can be cross-linked was investigated.

  In the bead shape test, a weld length of 500 mm was welded between the end portion of the upper plate 1 and the surface of the lower plate 2 shown in FIG. 1 under the welding conditions shown in Table 1 (1). The number of pits generated on the surface of the formed weld bead was investigated. The target position of the wire was the corner of the lap joint, and the angle θ of the welding torch 3 was 60 °. The bead shape factor H / W was less than 0.40, and the bead width was widened.

  In the gap resistance test, as shown in FIG. 4, a spacer 7 was sandwiched between the front plate 5 and the rear plate 6 to form a joint having a test piece length of 500 mm. At this time, welding was performed so that the gap length G1 = 2 mm widened to G2 = 4 mm. Welding was started from the gap length G1 = 2 mm side under the welding conditions shown in Table 1 (2) until the molten metal could not be cross-linked. As shown in FIG. 5, the welding was performed by setting the angle on the rear plate 6 side of the front plate 5 as a target position and setting the angle θ of the welding torch 3 to 30 °. The weldable gap at this time was measured, and a weldable gap of 3 mm or more was evaluated as good. Further, the arc state and the amount of spatter generated were sensory including a bead shape test, and the presence or absence of hot cracking was visually evaluated. The results are summarized in Table 3.

表１および表３中ワイヤ記号Ｗ１〜Ｗ７が本発明例、Ｗ８〜Ｗ１５は比較例である。

In Tables 1 and 3, wire symbols W1 to W7 are examples of the present invention, and W8 to W15 are comparative examples.

  In the wire symbols W1 to W7, which are examples of the present invention, the total amount of wire components Si, C, Mn, S, P, O, Ti and Al and Mo are appropriate amounts, so the arc is stable and the amount of spatter generated is small. The result was very satisfactory with no bead formation, a wide bead shape with a low bead shape factor H / W, and good gap resistance.

  In the comparative example, since the wire symbol W8 had a low C, the arc was unstable and the amount of spatter generated was large. Since the wire symbol W9 has a high C, the amount of spatter generated is large. Since the wire symbol W10 has a low Mn, pits occurred. Moreover, since S was low, the amount of spatter was large, the bead shape factor H / W was high, and the weldable gap was narrow. Since the wire symbol W11 had a high Mn, the bead shape factor H / W was high and the weldable gap was narrow.

  Since the wire symbol W12 has a high S and the wire symbol W13 has a high P, high temperature cracking occurred in both cases. Moreover, since the wire symbol W13 has a large sum of Al and Ti, the bead shape factor H / W is high, the weldable gap is narrow, the slag generation amount is large, and the bead appearance is also poor. Since the wire symbol W14 is high in O, the arc is unstable, the spatter generation amount is large, pits are generated, the slag generation amount is large, and the bead appearance is also poor. Since the wire symbol W15 has a large amount of Si, the bead shape factor H / W was high and the weldable gap was narrow. Moreover, since there was much Mo, spatter generation amount was large.

It is a figure which shows the wire aim position of the lap fillet joint welding used for the Example of this invention. It is explanatory drawing which measures bead shape factor H / W in the Example of this invention. It is a figure which shows the relationship between Si content and bead shape factor H / W. It is a figure which shows the test plate of the horizontal lap joint used for the Example of this invention. It is a figure which shows the wire aim position of the horizontal lap joint in the Example of this invention.

Explanation of symbols

1 Upper plate 2 Lower plate 3 Welding torch 4 Weld bead 5 Front plate 6 Rear plate 7 Spacer θ Torch angle W Bead width H Bead height G Gap length


Patent Applicant Nippon Steel & Sumikin Welding Co., Ltd.
Attorney Attorney Shiina and others 1

Claims (3)

In mass% with respect to the total mass of the wire, Si: less than 0.10%, C: 0.01 to 0.15%, Mn: 1.80 to 2.50%, S: 0.001 to 0.070% P: 0.030% or less, O: 0.010% or less, the other being Fe and inevitable impurities, a solid wire for pulse MAG welding. The solid wire for pulse MAG welding according to claim 1, wherein the total content of one or two of Ti and Al is 0.20% or less. The solid wire for pulse MAG welding according to claim 1 or 2, characterized by containing Mo in an amount of 0.30% or less.

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