JP2019089099A - Composite welding method of zinc-based plated steel sheet - Google Patents

Abstract

To provide a composite welding method for forming an excellent weld bead, in which generation of a weld defect is suppressed.SOLUTION: In a composite welding method by laser welding for performing butt welding of a zinc-based plated steel sheet and by arc welding, the laser welding is performed in advance of the arc welding, and either means between pulse arc-welding means for applying a welding-current in a pulsed manner and wire feed control means for repeating regular sending and reverse sending of a welding wire is used, as the arc welding.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite welding method of a zinc-based plated steel sheet.

  The zinc-based plated steel sheet is obtained by plating zinc or a zinc alloy on the surface of the steel sheet. Because of their excellent corrosion resistance, they are widely used in construction members, automotive members, mechanical members and the like.

  When the plated steel plate is welded, zinc heat is generated from the plating layer by the welding heat, which is trapped in the weld metal and causes the beads to frequently generate pores (blow holes) such as porosity and surface craters. When the pores advance to the surface and form an opening (pit), the property of the bead surface is deteriorated. The pores and openings are collectively referred to as "blow holes" hereinafter.

  Furthermore, when applying the arc welding method, spattering occurs frequently because the generated zinc vapor destabilizes the arc. In addition, the arc welding method has a problem that the penetration is shallow and the welding speed is slow.

  While laser welding does not require a filler metal, it requires high butt accuracy. Furthermore, there is a problem that an undercut easily occurs on the surface of the weld bead. The laser welding method is keyhole welding using a laser beam. When the laser beam is irradiated, the zinc vaporizes the zinc from the galvanized layer, and the zinc vapor blows away the molten steel in the molten pool and the zinc vapor intrudes into the molten steel, resulting in a large number of blow holes in the weld bead. Occur.

  When weld defects such as the above-described blow holes, pits, undercuts, etc. occur in the weld bead, the mechanical strength at the weld will be reduced. Therefore, application of a composite welding method using laser welding and arc welding in combination to zinc-based plated steel sheets has been proposed (see, for example, Patent Document 1).

Patent Document 1 discloses galvanized steel plates having a thickness of less than 0.2 to 6.0 mm and having a galvanization amount of 10 to 120 g / m ² or galvanized steel sheets having the same plate thickness and the same galvanization amount and the like A welding method including a step of irradiating a laser at a portion to be welded and a step of performing gas metal arc welding after the step of laser irradiation in lap welding with metal and lap fillet welding is described. When an arc is irradiated to the vicinity of the melting portion and the evaporation portion formed by the irradiation of the laser beam, the arc discharge is stably generated and concentrated on the laser irradiation portion, and high speed welding can be performed. Therefore, in lap fillet welding of galvanized steel sheets, it is described that only the upper plate end portion can be welded and welding can be performed with almost no melting of the galvanized layer of the lap portion.

JP 2002-66774 A

  In general, arc welding has disadvantages such as slow welding speed, shallow penetration, high heat input and large thermal deformation, and frequent spattering, as compared with laser welding. Therefore, laser welding and arc welding are used in combination. Even in the case of the combined welding method, it is required to control the arc welding so that a good weld bead can be formed. Although patent document 1 has shown the welding condition which specified the range of the irradiation position and the irradiation angle regarding irradiation of a laser beam and irradiation of gas metal arc welding, it does not disclose the welding conditions other than that.

  Therefore, the present invention provides a composite welding method for forming a good weld beat in which the occurrence of welding defects is suppressed, focusing on the control of the arc welding in the composite welding method using both laser welding and arc welding. The purpose is to

  When welding a galvanized steel sheet by a composite welding method using both laser welding and arc welding, the present inventors use the control means for pulse arc welding or wire feeding of the arc welding to obtain blow holes and spatters. And the like, it has been found that the occurrence of weld defects such as can be suppressed and good weld beads can be formed, and the present invention has been completed. Specifically, the present invention provides the following.

(1) The present invention is a composite welding method by laser welding and arc welding for butt welding of a zinc-based plated steel sheet, wherein the laser welding is performed prior to the arc welding and welding current is used as the arc welding. The method is a composite welding method of a zinc-based plated steel sheet using pulse arc welding means for applying pulsatively in a pulse form or wire feeding control means for repeating forward feeding and reverse feeding of a welding wire.

(2) The present invention is a welding method in which the pulse arc welding means repeatedly applies a current waveform of a peak current (IP) and a base current (IB) with a period (PF), and the following equation (1) The composite welding method of the zinc-based plated steel plate as described in (1) whose average welding current (I) shown by these is the range of 100-300A. I = (IP + IB) / PF (1)

(3) The present invention is the composite welding method of a galvanized steel sheet according to (1), wherein the wire feeding control means has a welding wire speed of 200 to 500 mm / s.

(4) In the present invention, the zinc-based plating according to any one of (1) to (3), wherein the arc welding uses a gas obtained by mixing 2 to 30% by volume of carbon dioxide gas with argon gas as a shielding gas. It is a composite welding method of a steel plate.

(5) The present invention is the composite welding method of a galvanized steel sheet according to any one of (1) to (4), wherein the butt welding is performed on a joint having no gap.

(6) In the present invention, the blow hole occupancy rate in the welded portion after welding is 10% or less, and the spatter adhesion amount around the weld portion is 20 or less per 100 mm × 50 mm in (1) to (5) It is a composite welding method of a zinc system plating steel sheet given in either.

(7) The method according to any one of (1) to (6), wherein the tensile strength of the welded portion is at least 1.3 times the tensile strength of the main portion. It is.

  According to the present invention, the occurrence of weld defects such as blow holes and spatters can be suppressed, and a good weld bead can be formed. Therefore, the external appearance of a welding part is favorable and there exists a useful effect that it is excellent in joint intensity.

It is a schematic diagram for describing the embodiment according to the present invention, (a) is a plan view showing a joint part along a welding direction, (b) is a joint from a direction perpendicular to the welding direction It is the figure which showed the part. It is a figure for demonstrating calculation of a blowhole occupancy rate. It is a figure for demonstrating the evaluation test which measures the tensile strength of a welding part.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited by these descriptions.

  The present invention is a composite welding method by laser welding and arc welding for butt welding of a zinc-based plated steel plate, wherein the laser welding is performed prior to the arc welding and welding is performed, and the welding current is pulsed as the arc welding. It is preferable to use any means of pulse arc welding means applied to the wire or wire feed control means for repeating forward feeding and reverse feeding of the welding wire.

  FIG. 1 shows an embodiment according to the present invention. FIG. 1 (a) is a plan view showing the joint portion along the welding direction 14, and FIG. 1 (b) is a schematic view showing the joint portion from the direction perpendicular to the welding direction 14. . Two galvanized steel plates 1 are combined in a T-shape and welded by laser welding and arc welding.

  In laser welding, the laser beam 11 is irradiated from the tip of a laser irradiation means (not shown). Arc welding is consumable electrode type arc welding using a shielding gas containing argon gas. An arc is generated at the arc electrode provided at the tip of the arc torch 12, and the tip of the arc electrode is melted and transferred to the molten pool. The arc electrode is supplied by a welding wire. The arc torch is provided with an electrode supply device and an arc control device (not shown).

  When welding using a zinc-based plated steel sheet 1, as shown in FIG. 1A, laser welding with the laser beam 11 precedes along the welding direction 14, and arc welding with the arc torch 12 follows. As you move each welding means. The laser welding is preceded and the arc welding is followed by separating the target position of laser welding from the target position of arc welding by the distance 13 and the arc of the arc welding is attracted to the laser, so evaporation of zinc-based plating occurs. The range is narrowed, less susceptible to zinc vapor, and the arc is stabilized. Then, the penetration becomes deep and penetrates the plate thickness, and the zinc vapor escapes to the back surface side, so that the generation amount of blow holes and pits in the weld bead is reduced. Furthermore, since the filler metal (welding wire) is continuously supplied to the welding bead by arc welding, undercutting can be prevented. As described above, according to the present invention, the occurrence of welding defects such as blow holes, pits, undercuts and the like can be prevented, so that the reduction in the strength of the welded portion is suppressed. In addition, arc welding has a large amount of gap that can be welded compared to laser welding, and the welding operation is simplified in that high positional accuracy is not required at the time of butting. In addition, as shown to (b) of FIG. 1, in order to escape the zinc vapor from a zinc-based plating layer at the time of welding, you may provide the clearance gap 4 in a coupling part.

(Pulse arc welding)

As arc welding, it is preferable to use pulse arc welding. A stable arc is obtained, and small droplets transfer to the molten pool in a constant cycle, reducing spatter. In addition, since the molten pool is vibrated in pulses, the discharge of zinc vapor is promoted, which is effective in reducing blow holes and pits. Also, while ordinary arc welding does not stabilize the arc, spattering occurs frequently, while pulse arc welding stabilizes the arc due to the high current of the pulse, so spattering is reduced.

The present invention is a welding method in which the pulse arc welding means applies a current waveform of a peak current (IP) and a base current (IB) repeatedly with a period (PF), and the average welding current (I) is Formula (1) of
I = (IP + IB) / PF (1)

  In arc welding, the current value, voltage value, and their waveforms applied to the arc electrode are adjusted. In pulse arc welding, current waveforms of peak current (IP) and base current (IB) are repeatedly applied with a period (PF). The average welding current in the pulse arc welding is obtained by a value obtained by dividing the peak current (IP) and the base current (IB) in the current waveform by the period (PF), as in equation (1).

  The average welding current is preferably in the range of 100 to 300A. When the average welding current is less than 100 A, droplet transfer from the welding wire tip to the molten pool becomes unstable, and spatter occurs frequently. When it exceeds 300 A, the droplet becomes large at the wire tip, and when the droplet is transferred to the molten pool, spatter occurs frequently. In order to obtain an average welding current in the range of 100 to 300 A, the peak current (IP) can be set in the range of 350 to 500 A, the base current (IB) 25 to 100 A, and the cycle (PF) in 2 to 4 ms.

(Wire feed)
In the present invention, it is preferable to use a wire feeding control means which repeats forward feeding and reverse feeding of the welding wire. It is preferable to control the wire speed when repeating forward and reverse feeding of the welding wire to be in the range of 200 to 500 mm / s. If the welding wire speed is less than 200 mm / s, the droplet at the welding wire tip and the molten pool are separated too much, and the droplet moves from a high position to the molten pool, so spatter tends to occur frequently. On the other hand, if the welding wire speed exceeds 500 mm / s, spatters are likely to occur frequently because the droplet contacts the molten pool before it leaves the welding wire tip. Also, the forward and reverse speeds of the welding wire may be the same or different, but it is preferable to move at substantially the same speed. The moving distance of the welding wire can be selected in the range of 1.5 to 5.0 mm, for example, about 2.5 mm.

(Shield gas for arc welding)
Arc welding preferably uses a shielding gas from the viewpoint of the stability of the arc and the oxidation of the weld metal. As the shield gas, an inert gas such as argon gas can be used, or a mixed gas of argon gas and carbon dioxide gas (CO ₂ gas) can be used. For example, a gas in which 2 to 30% by volume of carbon dioxide gas is mixed with argon gas can be used. Generally, arc welding using a mixed gas of argon gas and CO ₂ gas as a shielding gas is called MAG welding (mag welding), and arc welding using an inert gas such as argon gas is MIG welding (mig welding) It is called.

(Near gap of joint)
There may be gaps in the joint to weld through the plate. In the composite welding according to the present invention, a good weld can be obtained even if welding is performed without providing a gap in the joint. When the material plate thickness is thin, for example, 9 mm or less, it is not necessary to widen the gap. On the other hand, even in the case of setting the gap, it is possible to join even about twice the gap which can be joined by laser welding. Generally, with regard to the gap of the joint portion, in the case of laser welding, up to 0.3 mm is considered to be joinable, whereas the composite weld according to the present invention is able to join up to 0.8 mm.

(welded part)
The composite welding method according to the present invention is preferable in that the area occupied by the blow hole is reduced, and a welded portion with a reduced amount of sputter deposition around the welded portion can be obtained. Therefore, a joint is obtained in which the tensile strength of the weld is 1.3 times or more the tensile strength of the main body. The blowhole occupancy means a numerical value measured by the method of the evaluation test described later. The blow hole occupancy rate is preferably 10% or less, more preferably 7% or less, 5% or less, 3% or less, or 2% or less. The amount of sputter deposition around the weld is preferably 40 or less per 100 mm × 50 mm, and more preferably 30 or less, 20 or less, or 10 or less.

  When T-shaped butt welding is performed by arc welding, two-pass welding needs to be performed, whereas the composite welding according to the present invention is useful in that T-shaped butt welding can be performed in one pass.

  Hereinafter, examples of the present invention will be described. The invention is not limited to the following description.

The evaluation test regarding this embodiment used the double-sided zinc-based plated steel plate whose thickness is 4.5 mm. The material strength of the steel plate is 400N grade. The said zinc-based plating is a Zn-Al-Mg composition, and the adhesion amount on a steel plate surface is about 90 g / m < ² >. From the said plated steel plate, the to-be-welded material of the dimension of length 200 mm and width 100 mm was cut out, and it used for the welding described below.

  Composite welding using laser welding and arc welding in combination was preceded by laser welding. Arc welding in composite welding includes wire control and arc welding (a method of welding while repeating forward and reverse feeding of welding wire), pulse arc welding (pulsed welding current is applied in addition to ordinary arc welding means). Method) is used. Furthermore, only arc welding and only laser welding were performed to compare with composite welding. As a welding wire, YGW-12 equivalent goods of wire diameter phi 1.2 mm were used. The welded test material is cut out of a test body of dimensions 180 mm long and 50 mm wide from the region including the weld, and appearance observation, measurement of blow hole occupancy, strength ratio of weld as described below Used for evaluation tests such as measurement of

(Appearance observation)
The surface of the weld was observed, and as the amount of sputter deposition on the bead surface, the number of sputters in an area of 100 mm × 50 mm arbitrarily selected around the weld was measured.

  The weld was cut and the cross section was observed visually. The case where there was no defect such as undercut on the front bead and the back bead was stably formed was evaluated as good.

  On the back side opposite to the steel plate surface subjected to butt welding, zinc in the plating layer may evaporate due to heat at the time of welding, and the plating layer may disappear. The evaporation width (mm) of the plating layer on the back surface was measured.

(Blowhole occupancy rate)
The percentage of blow holes present in the cross section of the weld was measured. As shown in FIG. 2, the lengths a1, a2, etc. of the individual blow holes observed in the weld bead were measured. As shown below, the blowhole occupancy rate (%) was calculated by dividing the total of the measured blowhole lengths by the bead length L.

  Blowhole occupancy rate (%) = [(a1 + a2 + a3 + a4 +...) / L] × 100

(Strength ratio of welds)
FIG. 3 schematically shows a test method for measuring the strength of the weld. After making a test piece to the test piece and making the test piece 2 thinned to a thickness that does not cause breakage of the base material at the time of the test, welding is performed with the zinc-based plated steel sheet 1 by each welding method A welded assembly for tensile testing was made. Using this welded assembly, a tensile test was conducted by applying a load to the test piece 2 in the tensile direction 5 shown in FIG. By this tensile test, fracture occurred at the weld 3 of the welded assembly, and the tensile strength of the weld was obtained. Moreover, it used for the tensile test using the test piece 2 which made the plate | board thickness of the plated steel plate thin, and measured the tensile strength of the base material similarly. From these measured values, the ratio between the “tensile strength of the welded portion” and the “tensile strength of the base material” (hereinafter referred to as “the strength ratio of the welded portion”) was calculated.

<Test Example 1> When Pulsed Arc Welding Means was Used Laser welding and arc welding were used in combination, and composite welding in which laser welding preceded arc welding was applied to a test sample. Laser welding emitted a laser beam with an output of 4 kW. In the arc welding, a shield gas was used to perform mag welding in which a pulsed welding current was applied. The welding conditions for arc welding are shown in Table 1 in addition to the base current (A), peak current (A), average welding current (A) and period (ms), the voltage is 26 V, shield gas type is Ar + 10 volume% CO ₂ , the flow rate was 20 L / min, the front and rear angle was 20 ° forward, and the torch angle was 20 °. The welding speed was 1.0 m / min, and the joint gap was 0 mm. The test body obtained by these welding was used for the predetermined evaluation test. The results of the evaluation test are shown in Table 1.

  As shown in Table 1, laser welding performs composite welding prior to arc welding, and by using pulse arc (pulse mug) welding means in arc welding, a weld with a small blow hole occupancy rate and a small amount of spatter adhesion was gotten. The test A3 to the test A10 having an average current of 100 to 300 A had a blow hole occupancy rate in a low range of 4% or less, and a sputter deposition amount in a low range of 20 or less.

<Test Example 2> When Wire Feed Control Means was Used Laser welding and arc welding were used in combination, and composite welding in which laser welding preceded arc welding was applied to a test sample. Laser welding emitted a laser beam with an output of 4 kW. In arc welding, welding was performed by repeating forward and reverse feeding of the welding wire. The welding wire speeds are as shown in Table 2, and the welding wire speeds at the time of forward feeding and at the time of reverse feeding were the same. The moving distance of the wire was about 2.5 mm. In addition, welding conditions for arc welding are: average current 180A, voltage 20V, shield gas type Ar + 10% by volume CO ₂ , flow rate 20L / min, front and back angle 20 ° front, torch angle 20 ° The The welding speed was 1.0 m / min, and the joint gap was 0 mm. The test body obtained by these welding was used for the predetermined evaluation test. The results of the evaluation test are shown in Table 2.

  As shown in Table 2, the laser beam welding performs composite welding prior to arc welding, and by using a wire feeding control means that repeats forward feeding and reverse feeding of the welding wire, the blow hole occupancy rate is small and spatter adhesion Less welds were obtained. The test body B2 to test body B6 having a welding wire speed of 200 to 500 mm / s had a blow hole occupancy rate in a low range of 4% or less, and a sputter deposition amount in a low range of 20 or less.

Test Example 3 Comparison of Composite Welding Method and Arc Only Welding Method Next, the composite welding method according to the present invention was compared with a conventional welding method. Test body A9 of Test Example 1 and Test body B4 of Test Example 2 were selected as examples of the present invention. As a conventional method, only mag welding was performed, and specimens C1 and C2 were obtained according to the welding conditions shown in Table 3. Using these test pieces, the amount of sputter deposition, the Bulllow hole occupancy rate, the strength ratio of the weld, and the plating evaporation width on the back surface were each measured. The results are shown in Table 3.

  The invention examples of the test body A9 and the test body B4 corresponding to the welding method of the present invention showed a low sputter deposition amount and a blow hole occupancy rate, and exhibited a high strength ratio. Since evaporation of the zinc-based plating did not occur on the back surface, it was useful in that the corrosion resistance was maintained. On the other hand, the comparative example of the test bodies C1 and C2 which does not correspond to the welding method of this invention was inferior to the example of this invention. The specimens C1 and C2 had low sputter deposition amounts and blow hole occupancy rates, low strength ratios, and plating evaporation occurred on the back surface.

DESCRIPTION OF SYMBOLS 1 Zinc-based plated steel plate 2 Test piece 3 Weld 4 Gap in joint 5 5 Tension direction 11 Laser beam 12 Arc torch 13 Distance of aiming position 14 Welding direction

Claims (7)

  A composite welding method by laser welding and arc welding for butt welding of a zinc-based plated steel sheet, wherein the laser welding is performed prior to the arc welding and the pulse for applying a welding current in a pulse shape as the arc welding A composite welding method of a zinc-based plated steel sheet using arc welding means or wire feeding control means for repeating forward feeding and reverse feeding of a welding wire. The pulse arc welding means is a welding method in which a current waveform of a peak current (IP) and a base current (IB) is repeatedly applied by a period (PF), and the average welding current represented by the following equation (1) The composite welding method of the zinc-based plated steel plate according to claim 1, wherein I) is in the range of 100 to 300A.
I = (IP + IB) / PF (1)   The method according to claim 1, wherein the wire feeding control means has a welding wire speed of 200 to 500 mm / s.   The composite welding method for a zinc-based plated steel sheet according to any one of claims 1 to 3, wherein the arc welding uses, as a shielding gas, a gas obtained by mixing 2 to 30% by volume of carbon dioxide gas with argon gas.   The composite welding method of a galvanized steel sheet according to any one of claims 1 to 4, wherein the butt welding is performed on a joint having no gap.   The zinc-based plated steel plate according to any one of claims 1 to 5, wherein a blow hole occupancy rate in a welded portion after welding is 10% or less, and a spatter adhesion amount around the welded portion is 20 or less per 100 mm x 50 mm. Composite welding method.   The composite welding method of the zinc-based plated steel plate according to any one of claims 1 to 6, wherein the tensile strength of the welded portion is 1.3 times or more the tensile strength of the main body portion.

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