TW201800171A - ARC welding method of steel sheet with molten zinc based plating and method for producing welding member - Google Patents

Abstract

To provide an arc welding method for hot-dip galvanized steel sheets and a method for manufacturing welded members through which excellent appearance of welded parts and welding strength are achieved. The present arc welding method welds together hot-dip galvanized steel sheets through a pulse arc welding method. With this welding method, the steel sheets are welded together such that the distance from the distal end of the welding wire (2) to the portion to be welded of the abutting part (7) of the hot-dip galvanized steel sheets, which are the objects to be welded, is a length at which the welding wire (2) and the welding pool (3) generated at the abutting part (7) will not short-circuit each other, and at which the arc will not extinguish.

Description

Arc welding method of molten Zn-based plated steel plate and manufacturing method of welded member

The present invention relates to an arc welding method for a molten Zn-based plated steel sheet, a method for manufacturing a welded member, and a welded member.

Since the molten zinc-based plated steel sheet (fused Zn-based plated steel sheet) has good corrosion resistance, it is generally used in a wide range of applications starting with building and automobile components. Among them, since a molten Zn-Al-Mg plated steel sheet containing Al in an amount of 1% by mass or more can maintain excellent corrosion resistance for a long period of time, the demand for a material that replaces the conventional molten Zn-based plated steel sheet has increased. In addition, the Al concentration in the plating layer of the conventional molten Zn-based plated steel sheet is usually 0.3% by mass or less (see JIS G3302).

When a molten Zn-based plated steel sheet is used for a building member, an automobile member, or the like, an arc welding method is often used for assembly. However, when arc welding of a molten Zn-based plated steel sheet, welding spatters, pits, and pores (hereinafter, pores are included in the pits unless otherwise specified) are often noticeably generated, and arc weldability is deteriorated. This is because Zn has a lower boiling point (about 906 ° C) than the melting point of Fe (about 1538 ° C). Therefore, Zn vapor is generated during arc welding to make the arc unstable, and welding spatters and pores are likely to occur. In addition, if (a) to (c) of FIG. 7 are used to describe the welding spatter, the pit, and the air hole, it will be as follows. That is, as shown in FIG. 7 (a), the welding spatter 111 is, for example, slag or metal particles scattered from the welding wire 102 or the molten pool 103 when the steel plate 101‧101 'is welded. As shown in FIG. 7 (b), the pores 112 are pores included in the welding beads 106. This welding bead 106 refers to a portion that is solidified by cooling the molten metal (a part of the base material and the molten portion of the weld metal) during welding, and is a welding metal that metallurgically joins the materials to be welded to each other. Meanwhile, as shown in FIG. 7 (c), the dent 113 refers to a dent formed by an air hole appearing on the surface of the welding bead 106.

When the welding spatter adheres to the plating surface of the molten Zn-based plated steel sheet, not only the appearance of the welded portion is impaired, but also the portion where the welding spatter adheres becomes the starting point of corrosion. Therefore, if a large amount of welding spatter adheres, the corrosion resistance significantly decreases and becomes a problem. At the same time, it is necessary to have a process of removing welding spatter with a wire brush or the like, which increases costs. On the other hand, if the generation of pores is significant, the welding strength decreases and becomes a problem.

In particular, in a member requiring long-term corrosion resistance, although a molten Zn-based plated steel sheet having a high adhesion amount per unit of 90 g / m ² or more is used on each side, the more the plating adhesion amount per side is, The larger the amount of Zn vapor during arc welding, the more significant the generation of welding spatters and pores.

In addition, in this specification, regarding the amount of plating adhesion of each surface of the molten Zn-based plated steel sheet, the amount of plating adhesion is small as the unit adhesion amount is low, and the number of plating adhesion amount is described as Unit attachment is high.

As a method for suppressing the generation of welding spatter and pores during welding of a molten Zn-based plated steel sheet, a pulse arc welding method using a welding wire as an electrode has been proposed. According to this pulse arc welding method, droplet transfer from a welding wire used as an electrode to a substrate is changed to spray transfer, and small particles of the droplet can suppress welding spatter. At the same time, while the molten pool (the part of the bead before solidification) is stirred by the pulse arc, the molten pool is pushed down and the molten pool becomes thin, thereby promoting the discharge of Zn vapor and suppressing the generation of pores.

For example, Patent Documents 1 and 2 disclose a pulsed arc welding method in which the pulse current waveforms such as the composition, peak current, peak period, and frequency of a welding wire are controlled within an appropriate range, and welding spatter is suppressed.

Prior Art Documents [Patent Documents] [Patent Documents 1] Japanese Laid-Open Patent Gazette "Japanese Patent Application Laid-Open No. 9-206984 (published on August 12, 1997)" [Patent Literature 2] Japanese Laid-Open Patent Gazette "Japanese Patent Application Laid-Open No. 2013- Bulletin 184216 (published on September 19, 2013) ''

[Summary of the Invention] [Problems to be Solved by the Invention] However, in Patent Documents 1 and 2, only the molten Zn-based plated steel sheet with a low coating adhesion amount per unit of 45 g / m ² is disclosed. In the examples, there is no description of a method for suppressing welding spatter and pores of a molten Zn-based plated steel sheet having a high unit adhesion amount.

As described above, although the plating adhesion amount of the molten Zn-based plated steel sheet is increased and the corrosion resistance is excellent, welding spatters and pores are remarkably generated during arc welding, thereby deteriorating the appearance and welding strength of the welded portion. In view of this situation, the present invention provides an arc welding method for a molten Zn-based plated steel sheet, a method for manufacturing a welded member, and a welded member, which can suppress arc welding even if the unit adhesion amount of the molten Zn-based plated steel sheet is high. The occurrence of welding spatters and pores, and the appearance and welding strength of the welded part are excellent.

[Means to solve the problem] The present inventors obtained knowledge after detailed research results, which are related to the welding of molten Zn-based plated steel plates. When performing arc welding using the pulse welding method, the welding wire is appropriately adjusted by The distance from the tip to the welding target portion of the contact portion between the Zn-based plated steel plates to be welded can suppress the welding spatter from the plated adhesion amount of the molten Zn-based plated steel plate from a low unit adhesion amount to a high unit adhesion amount. Production of materials and stomata. Based on this knowledge, the present invention has been completed.

That is, the arc welding method of the molten Zn-based plated steel sheet of the present invention is a pulsed arc welding method that generates an arc by alternately supplying a peak current and a base current to weld the molten Zn-based plated steel sheets to each other. The arc welding method is characterized in that the distance from the tip of the welding wire to the welding target portion of the contact portion between the Zn-based plated steel plates to be welded does not cause short circuit between the welding wire and the molten pool generated at the contact portion. The fused Zn-based plated steel sheets are welded to each other at a length such that the arc does not extinguish.

The method for manufacturing a welded member of the present invention is a method for manufacturing a welded member that welds molten Zn-based plated steel plates to each other by a pulse arc welding method, and is characterized in that the plating adhesion of each side of the molten Zn-based plated steel plate The amount is 15 g / m ² or more and 250 g / m ² or less. The distance from the tip of the welding wire to the welding target portion of the contact portion between the Zn-based plated steel plates to be welded is 2 mm to 20 mm, and a pulse is generated. The peak current of the arc welding current is 350A to 650A, the pulse period is 1ms to 20ms, and the aforementioned molten Zn-based plated steel plates are welded to each other by pulse arc welding. [Effect of the invention]

According to the present invention, there is provided an arc welding method for a molten Zn-based plated steel sheet, a method for manufacturing a welded member, and a welded member. Even if the unit adhesion amount of the molten Zn-based plated steel sheet is high, welding spatters and pores can be suppressed during arc welding. Production, and the appearance and welding strength of the welded part are excellent.

[Embodiments for Implementing the Invention] Hereinafter, embodiments of the present invention will be described. In addition, the following description is for a clearer understanding of the purpose of the invention, and the invention is not limited unless otherwise specified. At the same time, in this application, "A ~ B" means above A and below B.

In the following description, in order to make the arc welding method for a molten Zn-based plated steel sheet according to an embodiment of the present invention easy to understand, first, the arc welding phenomenon in the conventional arc welding method without pulses will be described with reference to FIG. 6. The outline of a general pulse arc welding method is demonstrated based on FIG.1 and FIG.2. The principle of the pulsed arc welding according to the embodiment of the present invention is the same as the principle of the general pulsed arc welding method.

FIG. 6 is a cross-sectional view schematically showing an arc welding phenomenon in the conventional pulsed arc welding method. As shown in FIG. 6, in the arc welding method without a pulse, for example, when welding a molten Zn-based plated steel sheet 201 · 201 ′, the droplets 205 generated from the welding wire 202 are brought into contact with the molten pool (short-circuited) and transferred. A short-circuit transfer has occurred. At this time, in the mixed portion of the droplet 205 and the molten pool, a large amount of welding spatter is generated by the ejection of Zn vapor. At the same time, pores are generated in large quantities because Zn vapor is not easily removed.

Next, an outline of a general pulse arc welding method will be described. FIG. 1 is a diagram schematically showing a pulse current waveform in the pulse arc welding method. As shown in FIG. 1, the pulsed arc welding method is an arc welding method in which a peak current IP and a base current IB are alternately supplied. The peak current IP can be set above a critical current of a droplet transfer. The time during which the peak current IP flows is taken as the peak period PP, and the pulse period of the pulse current formed by the peak current IP and the base current IB is taken as the period PFQ. If the peak current IP is set to be greater than the critical current, the effect of tightening the molten droplet at the tip of the wire by electromagnetic force (Pinch effect) is generated, and the melting of the tip of the wire is caused by the electromagnetic pinching effect. Tightening of the droplets causes the droplets to become small particles and enables droplet transfer (spray transfer) to be carried out with correct rules for each pulse cycle. Thereby, the droplet system is smoothly transferred to the molten pool, and generation of welding spatter is suppressed.

Fig. 2 is a cross-sectional view schematically showing a pulse arc welding phenomenon. Here is an example of fillet welding through a lap joint. As shown in FIG. 2, in the pulsed arc welding method in which the peak current value is appropriately set, since the droplets 5 of the small particles are spray-transferred from the welding wire 2 to the melting pool 3, short-circuiting is unlikely to occur. At the same time, the molten pool 3 directly below the arc is pushed down by the pulsed arc 4 and is stirred while the depth of the molten pool is thinned to promote the discharge of Zn vapor and suppress the generation of welding spatters and pores. The portion cooled and solidified by the molten pool 3 becomes a bead 6.

To further explain, in such a pulsed arc welding method, the distance between the front end of the welding wire 2 and the molten pool 3, that is, because the shorter the arc length becomes, the more effectively the pulsed arc 4 pushes the molten pool 3 downwards It is large and can promote the discharge of Zn vapor. However, if the arc length is too short, the front end of the welding wire 2 and the molten pool 3 form a short circuit and a spark is generated, the molten pool 3 is blown away and a large amount of welding spatter is generated. In particular, when the unit adhesion amount of the molten Zn-based plated steel sheet system is high, since the amount of Zn vapor generated increases, even if the pulse arc welding method is used, Zn vapor cannot be removed from the molten pool 3 and stays in the molten pool 3. Zn vapor is sprayed out in a single stream and ripples are generated in the molten pool 3, and a short circuit occurs with the front end of the welding wire 2 and the generation of welding spatter becomes significant.

Therefore, in the present invention, a short circuit between the tip of the welding wire 2 and the molten pool 3 is prevented, and even if the unit adhesion amount of the molten Zn-based plated steel sheet system is high, the influence of Zn vapor can be suppressed and droplet transfer can be stabilized, and Suppression of welding spatters and pores.

The meaning of the terms of the pulsed arc welding method in this specification is as follows. That is to say, generally in various arc welding methods, although a pulse voltage can be applied and a pulse arc can be generated, in such various pulse arc welding methods, the pulse arc welding method of the present invention uses a pulsed metal active gas (MAG, Metal Active Gas (MIG) welding method and pulse metal inert gas (MIG) welding method are targeted. That is, the present invention relates to a pulsed arc welding method, which uses an electric arc generated between a welding wire and a substrate to perform welding while melting the welding wire and the substrate at the same time. There is shielding gas.

This embodiment will be described in detail below.

[Position relationship between contact portions between welding wire and molten Zn-based plated steel sheet before welding] In the pulsed arc welding method of molten Zn-based plated steel sheet according to this embodiment, based on FIG. The positional relationship between the contact portions of the plated steel sheets will be described.

(A) of FIG. 3 schematically shows the arc welding method for a molten Zn-based plated steel sheet according to an embodiment of the present invention. When fillet welding is performed through a lap joint, the welding wire 2 and the molten Zn-based plated steel sheet 1 1 'A sectional view of the positional relationship between the contact portions 7 of each other. Fig. 3 (b) is a cross-sectional view schematically showing the positional relationship between the contact portion 7 of the welding wire 2 and the molten Zn-based plated steel plate 1‧1 'during fillet welding through the T-joint 2. Each of (a) and (b) in FIG. 3 shows a state before welding while showing a vertical cross section with respect to the welding direction.

As shown in (a) and (b) of FIG. 3, before welding, the molten Zn-based plated steel sheet 1 and the molten Zn-based plated steel sheet 1 'that are the object of welding can be arranged in various joint shapes. In FIG. 3 (a), it is arranged as an overlap joint, and in FIG. 3 (b), it is arranged as a T-shaped joint. Between the arranged molten Zn-based plated steel sheet 1 and the molten Zn-based plated steel sheet 1 ', a contact portion 7 is formed as a contact surface that contacts each other. Here, in the contact portion 7, the end portion closest to the tip of the welding wire 2 is referred to as a corner portion 7a. The corner portion 7a is a portion where a bead 6 (see Fig. 4) is formed in a portion where the molten Zn-based plated steel sheet 1 and the molten Zn-based plated steel sheet 1 'are adjacent to each other. In more detail, in the case of a lap joint, the corner portion 7a refers to a flat surface including a side surface of the end portion of the molten Zn-based plated steel sheet 1 'disposed on the top surface of the molten Zn-based plated steel sheet 1 and the top. Interlaced parts. In the case of a T-joint, the corner portion 7a refers to the plane of the molten Zn-based plated steel sheet 1 'which is erected on the top surface of the molten Zn-based plated steel sheet 1 and contains a wide surface that is slightly perpendicular to the top surface. The aforementioned staggered portions of the top surface.

In other words, in a state where the molten Zn-based plated steel sheet 1 and the molten Zn-based plated steel sheet 1 'are arranged in an arbitrary joint shape, the corner portion 7a means that the molten Zn-based plated steel sheet 1 and the molten Zn The arc-irradiated portion of the plated steel sheet 1 'is also called the welding target portion. Further, in the case of a joint shape butt joint, the welding target portion means a surface facing the end portion of the molten Zn-based plated steel sheet 1 and the end portion of the molten Zn-based plated steel sheet 1 '. 2 side edge (edge line).

As described above, it is important to control the arc length within an appropriate range to suppress the occurrence of welding spatter caused by the short-circuit between the tip of the welding wire 2 and the molten pool 3. However, referring to FIG. 2 again, because the molten pool 3 is pushed down by the pulsed arc 4 effect, the molten pool 3 is almost the same as the waveform of the pulsed arc 4 and moves up and down in a very short time, so it is used in welding. Determining and managing the arc length itself is difficult. Therefore, in the present invention, as shown in (a) and (b) of FIG. 3, from the wire tip 2a which is the tip of the wire 2 to the contact portion 7 between the Zn-based plated steel sheets before welding, the wire 2 side The distance D to the corner portion 7a is set to a length that does not cause short circuit between the welding wire 2 and the molten pool 3, and a length that does not extinguish the pulse arc 4.

Here, for example, in the case of performing pulsed arc welding with respect to the joint shape as shown in (a) and (b) of FIG. 3, the welding wire 2 is moved in a vertical direction with respect to the paper surface and the welding target portion is moved. Sequential welding. Therefore, the distance D indicates the length of a perpendicular line extending from the tip portion 2a of the welding wire as a point to the welding target portion (the corner portion 7a or the edge portion on the welding wire 2 side) that is a line. The straight line passing through the central axis of the welding wire 2 does not necessarily need to pass through the corner portion 7a, and the straight line may pass near the corner portion 7a. Therefore, in a broad sense, the above-mentioned distance D refers to a point where the straight line passing through the central axis of the welding wire 2 intersects between the point (welding target portion) of the molten Zn-based plated steel plate 1 or the molten Zn-based plated steel plate 1 'and the wire tip portion 2a. distance.

In this way, in the arc welding method of the molten Zn-based plated steel sheet according to this embodiment, the distance D from the wire tip 2a to the corner 7a is maintained at a level that does not cause short circuit between the wire 2 and the molten pool 3. Length without welding the arc without extinguishing the arc. In this method, instead of measuring the length of the arc itself, welding can be performed while maintaining the above-mentioned distance D. Even if the unit adhesion amount of the molten Zn-based plated steel sheet system is high, the welding during arc welding can be suppressed with a simple structure. Spatters and blowholes.

In the arc welding method for a molten Zn-based plated steel sheet according to this embodiment, it is preferable to set the distance D from the wire tip 2a to the corner 7a to be 2 to 20 mm. If the distance D is less than 2 mm, a short circuit occurs between the welding wire 2 and the molten pool 3 and welding spatter is generated. If welding spatter is generated, the molten pool 3 is pushed down and cannot be stirred, so that Zn vapor cannot be discharged, and pores are also generated. On the other hand, if the distance D is greater than 20 mm, an arc extinguishment occurs, that is, so-called arc interruption. If an arc interruption occurs, a short circuit occurs between the welding wire 2 and the molten pool 3, and a spark is generated when the pulsed arc 4 is ignited again, and the molten pool 3 is blown away and a welding spatter is generated. Next, when the pulsed arc 4 is extinguished, the molten pool 3 is pushed down and cannot be stirred, so that Zn vapor cannot be discharged, and pores are also generated. In addition, if the distance D is greater than 20mm, because the arc is widened and the pinch effect is weakened by the electromagnetic force, the droplet 5 becomes difficult to be cut off. As a result, the droplet 5 is coarsened and suspended large particles are welded. Splashes.

Here, when the molten Zn-based plated steel sheet is arc-welded, since the metal system of the wire tip portion 2a is transferred to the molten pool 3, the tip of the wire 2 gradually retracts to the voltage supply side toward the wire 2. The above-mentioned distance D can be changed in accordance with various welding conditions, and not only a unique value can be obtained. It can be adjusted within a range of 2 to 20 mm by adjusting the supply speed of the welding wire 2, the peak current IP and the period PFQ described later.

In this way, by setting the distance D from the tip portion 2a of the welding wire to the corner portion 7a to 2 to 20 mm, even if the unit adhesion amount of the molten Zn-based plated steel sheet is high, it is possible to effectively suppress welding spatters and pores. An arc welding method of a fused Zn-based plated steel sheet which is produced and capable of achieving excellent appearance and welding strength of a welded portion can be realized.

Next, preferable specific examples of various conditions used in the arc welding method of the molten Zn-based plated steel sheet according to this embodiment will be described.

[Peak current] The peak current IP for generating a pulse arc is preferably set in a range of 350 to 650A. For example, when the supply speed of the welding wire 2 is 15 m / min or more, if the peak current IP is less than 350A, the welding wire 2 is insufficiently melted, and the welding wire 2 is supplied excessively so that the distance D is less than 2 mm. At the same time, the arc force becomes weak, and the stirring effect of the molten pool 3 pushing down becomes weak. In contrast, if the peak current IP is greater than 650A, the welding wire 2 is excessively melted so that the distance D is greater than 20 mm, and arc interruption or coarsening of the droplet 5 occurs.

[Period] It is preferable to set the PFQ of the pulse in the pulse arc in the range of 1 to 20 ms. If the period PFQ becomes shorter, the number of times the molten pool 3 is pushed down by the pulsed arc 4 increases, and the discharge of Zn vapor can be promoted. However, if the period PFQ becomes too short, when the supply speed of the welding wire 2 is slow (for example, 3 m / min or less), the welding wire 2 is melted so much that the distance D is greater than 20 mm, and arc interruption or droplets occur. Roughening of 5. As a result, droplet transfer becomes unstable, and welding spatter is generated. On the other hand, if the period PFQ becomes too long, the welding wire 2 will not melt enough to cause the distance D to be less than 2 mm, a short circuit will occur between the welding wire 2 and the molten pool 3, and welding spatter will be generated. At the same time, because the number of times that the molten pool 3 is pushed down by the pulsed arc 4 is reduced, Zn vapor is not discharged, so welding spatters and pores are generated.

[Shield gas] In the pulse welding method, in order to transfer the droplet spray, an Ar-CO ₂ mixed gas can be used as the shield gas. This shielding gas can also be used to block the arc in welding and the surroundings of the molten pool from the atmosphere. The shielding gas of this embodiment also uses an Ar-CO ₂ mixed gas. As for the Ar-CO ₂ mixed gas, Ar-30 vol% CO ₂ gas, Ar-20 vol% CO ₂ gas, Ar-10 vol% CO ₂ gas, or Ar-5 with a further decreased CO ₂ concentration can also be used. % CO ₂ gas.

Meanwhile, in the present embodiment, when the pulsed MIG welding method is used, the protective gas system is argon or an argon-helium mixed gas.

[Joint shape] In addition to fillet welding of the lap joint shown in FIG. 3 (a) and fillet welding of the T-shaped joint shown in FIG. 3 (b), the present invention is also applicable to corner joints, cross joints, The shape of any of the connectors, such as a patch connector and a flare connector. At the same time, the invention can also be used for butt welding of butt joints, angle joints, cross joints and T-joints.

[Molten Zn-based plated steel sheet] The molten Zn-based plated steel sheet to be welded in this embodiment is preferably a molten Zn-plated steel sheet, an alloyed molten Zn-plated steel sheet, a molten Zn-Al plated steel sheet, or a molten Zn- A hot-dip galvanized steel sheet, such as an Al-Mg plated steel sheet, containing Zn as a main component of the plating layer.

Among molten Zn-based plated steel sheets, molten Zn-Al-Mg plated steel sheets are suitable because they contain Al: 1.0 to 22.0% by mass, Mg: 0.05 to 10.0% by mass, and have excellent corrosion resistance. In order to suppress the formation and growth of the Zn ₁₁ Mg ₂ series phase which is the cause of the decrease in the appearance and corrosion resistance of the plating layer, the plating layer of the molten Zn-Al-Mg plated steel sheet may also be added with Ti: 0.002 to 0.1 mass% B: 0.001 to 0.05 mass%. At the same time, in order to suppress the excessive growth of the Fe-Al alloy layer generated at the interface between the original plate surface and the plating layer, and to improve the adhesion of the plating layer during processing, Si can be added up to 2.0% by mass.

[Plating adhesion amount] When the plating adhesion amount of the molten Zn-based plated steel sheet is small, the system is disadvantageous in terms of maintaining the corrosion resistance of the plated surface for a long period of time and sacrificing the anticorrosive effect. After various reviews, it was found that it is more effective to set the plating adhesion amount on each side to 15g / m ² or more. On the other hand, if the plating adhesion amount on each side exceeds 250 g / m ² , the amount of Zn vapor generated becomes excessive, and even if the arc welding method of the molten Zn-based plated steel sheet according to this embodiment is used, welding spatters and pores are suppressed. It is also difficult to generate the metal oxide, so the plating adhesion amount per surface is preferably 250 g / m ² or less.

[Welding wire] The welding wire 2 is preferably JIS Z3312 YGW11 or JIS Z3312 YGW12. In addition to these, various solid-cored wires specified in JIS Z3312 may be used, and other types of materials may also be used. For example, non-plated wires, flux-cored wires, slag-based wires, and the like can also be used.

As the diameter of the welding wire 2, for example, a diameter of 1.2 mm can be used, and a diameter in the range of 0.8 to 1.6 mm can also be used.

In this embodiment, the supply speed of the welding wire 2 is set to a range of 3 m / min or more and 15 m / min or less. This can prevent the welding wire 2 from becoming insufficiently fused and the welding wire 2 from being excessively fused. The supply speed of the welding wire 2 described above can be set in accordance with the set value of the average welding current.

[Welding speed] The welding speed can be set to 0.4m / min, and it can also be set in the range of 0.1 ~ 2.0m / min in accordance with various welding conditions.

[Porosity Occupancy and Number of Welding Sputters] According to the arc welding method of the molten Zn-based plated steel sheet according to this embodiment, it is possible to suppress the occurrence of welding spatters and pores and weld the molten Zn-based plated steel sheets to each other. A welded member formed by the welding can be provided. The evaluation of the welded member (porosity occupancy and number of welding spatter adhesion) will be described with reference to FIGS. 4 and 5.

Fig. 4 is a plan view illustrating a method for measuring a porosity in a welded member 10 in which molten Zn-based plated steel sheets are welded to each other 1‧ '. As shown in Fig. 4, a welding bead 6 is formed in a welded member 10 obtained by welding a molten Zn-based plated steel sheet 1 and a molten Zn-based plated steel sheet 1 ', and most of the beads 6 have air holes 6a. At the same time, the length in the long-side direction (welding line direction) of the bead 6 is taken as the length L, and the length of the i-th air hole starting from one end portion of the bead 6 is taken as di. Here, when the shape of the joint is, for example, a T-joint, the molten Zn-based plated steel sheet 1 and the molten Zn-based plated steel sheet 1 'shown in Fig. 4 are welded vertically in a three-dimensional manner.

According to the design and construction manual for the construction sheet welding joints (architecture design and construction manual editing committee), if the sum of the lengths of the air holes 6a shown in FIG. 4 is summarized, If the total value Σdi (mm) of the lengths of all the pores 6a formed in the bead 6 is added and the pore occupation ratio Br calculated by the following formula (1) is 30% or less, the welding strength is considered to be no problem. . The pore occupation ratio Br of the welded member 10 of the present invention is 30% or less, and has excellent welding strength.

Br = (Σdi / L) × 100 ･ ･ ･ (1) (here, di: the length of the i-th air hole observed in the aforementioned bead, L: the length of the bead).

Fig. 5 is a plan view illustrating a method for measuring the number of welding spatters in a welded member 10 in which molten Zn-based plated steel sheets are welded to each other 1 · 1 '. As shown by the dotted line in FIG. 5, if the number of welding spatters in the area 8 with a length of 100 mm and a width of 100 mm centered on the welding bead 6 is 20 or less, the welding spatter is not obvious, and the effect on the corrosion resistance is not significant. Also very small. Here, the center of the region 8 may also be used as the center of the welding bead 6, and 100 mm in length means 50 mm from the side of the welding bead 6 in one direction (the molten Zn-based plated steel sheet 1) and the other direction (the Zn-based plating). The side of the steel plate 1 ') is 50mm. At this time, when the shape of the joint of the welding member 10 is, for example, a T-joint, the length of 100 mm in the region 8 may also mean that the bead 6 is used as the center and each of them extends 50 mm in the right direction. Meanwhile, the width of 100 mm means the width of the region 8 in the same direction as the long-side direction of the bead 6.

The number of welding spatter adhered in the region 8 of the welding member 10 of the present invention is 20 or less, and the welding appearance and corrosion resistance are excellent.

(Summary) As described above, in the arc welding method for a molten Zn-based plated steel sheet according to this embodiment, the distance is preferably 2 mm or more and 20 mm or less.

Next, in the arc welding method for a molten Zn-based plated steel sheet according to this embodiment, the peak current is preferably 350 A to 650 A, and the pulse period is preferably 1 ms to 20 ms.

Meanwhile, in the arc welding method for a molten Zn-based plated steel sheet according to this embodiment, the plating layer of the molten Zn-based plated steel sheet may include Zn as a main component and contain 1.0% by mass or more and 22.0% by mass or less of Al .

Furthermore, in the arc welding method of the molten Zn-based plated steel sheet according to the present embodiment, the plating layer of the molten Zn-based plated steel sheet preferably contains Mg of not less than 0.05% by mass and not more than 10.0% by mass.

In addition, in the arc welding method of the molten Zn-based plated steel sheet according to this embodiment, the composition of the plating layer of the molten Zn-based plated steel sheet preferably satisfies Ti: 0.002 to 0.1 mass%, and B: 0.001 to 0.05 mass. A condition selected from the group consisting of%, Si: 0 to 2.0% by mass, and Fe: 0 to 2.5% by mass.

At the same time, in the arc welding method of the molten Zn-based plated steel sheet according to this embodiment, arc welding can be performed so that the pore occupation ratio Br shown in the following formula (1) is 30% or less and 100 mm in length with the bead as the center. In the area with a width of 100 mm, the number of welding spatter adhesion is 20 or less.

Br = (Σdi / L) × 100 ･ ･ ･ (1) (here, di: the length of the i-th air hole observed in the aforementioned bead, L: the length of the bead).

[Examples] Four types of molten Zn-based plated steel plates shown in Table 1 were used to form overlapping fillet welded joints and perform pulse arc welding. As the welding wire 2, JIS Z3312 YGW12 with a diameter of 1.2 mm was used, and the welding speed was set to 0.4 m / min, the bead length was set to 180 mm, and the overlapping portion was set to 30 mm.

[Table 1]

At the same time, during welding, a high-speed camera was used under the following conditions to photograph a portion including the tip portion of the welding wire 2 and the contact portion 7 between the welding wire 2 side and the contact portion 7 of the Zn-based plated steel plate before welding. The distance D from the tip portion of the welding wire 2 to the corner portion 7a is measured. After performing pulsed arc welding, the number of welding spatter adhered and the pore occupation ratio Br were measured by the aforementioned method.

[Photographic conditions for high-speed cameras] High-speed cameras: (limited stock) Laser light source for visualization M310 manufactured by Novitec: CAVLUX HF manufactured by Cavitra Inc. Pulse wavelength: 810nm Photography frames: 4000 frames / second

Tables 2 and 3 show the types of molten Zn-based plated steel sheets, pulse arc welding conditions, the distance D from the tip of the welding wire 2 to the corner 7a, the number of welding spatters, and the pore occupation rate. Measurement results of Br.

Table 2 uses a molten Zn-6% Al-3% Mg plated steel sheet as the molten Zn-based plated steel sheet, and shows the type of shielding gas, peak current IP, period PFQ, and the distance from the tip of the welding wire 2 to the corner 7a. The results of investigations on the number of welding spatter adhered and the pore occupation ratio Br as a function of the distance D up to this point.

[Table 2]

The distance D, the peak current IP, and the period PFQ in the No. 1-20 embodiment of the present invention are less than 20, and the pore occupation rate is less than 30%. In this example, it was found that a welded member in which welding spatters and pores are suppressed and the appearance and welding strength of the welded portion are excellent can be obtained.

On the other hand, in the comparative examples No. 21 to 26 where the distance D, the peak current IP, and the periodic PFQ are outside the scope of the present invention, welding spatters and pores are generated remarkably, and welding with excellent appearance and welding strength of the welded portion cannot be obtained. member.

Table 3 shows the types of molten Zn-based plated steel plates with various plating compositions and adhesion amounts, and welding under various pulsed arc welding conditions and distances D, and showing the number of welding spatter adherence and pore occupation ratio Br. Findings.

[table 3]

As shown in Nos. 27 to 39, the distance D, the peak current IP, the period PFQ, and the plating adhesion amount from the tip of the welding wire 2 to the corner portion 7a are all within the scope of the present invention. In any welded member made of molten Zn-based plated steel sheet, welding spatters and pores are suppressed. In particular, we know that in Nos. 35 to 38, from a low unit adhesion amount of the plating adhesion amount of 15 g / m ^{2 to} a high unit adhesion amount of the plating adhesion amount of 250 g / m ² , Since the pores are all suppressed, an arc-welded member of a molten Zn-based plated steel sheet excellent in the appearance and welding strength of the welded portion can be obtained.

In contrast, in the comparative examples No. 40 to 48 in Table 3, the plating adhesion amount is 250 g / m ² which exceeds the upper limit of the present invention, even if the distance D from the tip of the welding wire 2 to the corner 7 a and the peak current IP The cycle PFQ is within the scope of the present invention, because Zn vapor is remarkably generated, and the occurrence of welding spatters and pores cannot be suppressed. Therefore, an arc-welded member of a molten Zn-based plated steel sheet having excellent appearance and welding strength cannot be obtained.

1‧1 ', 101‧101', 201‧201'‧‧‧fused Zn-based plated steel
2, 102, 202‧‧‧ Welding wire
2a‧‧‧ tip of the wire (tip of the wire)
3.103‧‧‧Melting Pool
4‧‧‧ pulse arc
5,205‧‧‧melt
6.106‧‧‧weld beads
7‧‧‧Contact
7a‧‧‧Corner (welding target)
8‧‧‧ area (area where the number of welding spatters can be counted)
10‧‧‧ Welded components
111‧‧‧welding spatter
112‧‧‧ Stomata
113‧‧‧Pit
D‧‧‧distance
L‧‧‧ length of welding beads
di‧‧‧ length of the ith pore
IP‧‧‧Peak current (A)
PP‧‧‧Peak period (ms)
PFQ‧‧‧ period (ms)
IB‧‧‧Base current

[Fig. 1] A diagram schematically showing a pulse current waveform in the pulse arc welding method. [Fig. 2] A sectional view schematically showing a pulse arc welding phenomenon. [Fig. 3] (a) is a schematic view showing an arc welding method of a molten Zn-based plated steel sheet according to an embodiment of the present invention. When fillet welding is performed through a lap joint, a wire and molten Zn-based plating are performed. A cross-sectional view of the positional relationship between the contact portions of the clad steel plates; (b) A cross-sectional view schematically showing the positional relationship during fillet welding through a T-shaped joint. [Fig. 4] It is a plan view explaining a method for measuring a porosity occupancy ratio in a welded member in which molten Zn-based plated steel plates are welded to each other. [Fig. 5] A plan view explaining a method for measuring the number of welding spatters in a welding member in which molten Zn-based plated steel plates are welded to each other. [Fig. 6] A cross-sectional view schematically showing an arc welding phenomenon in a conventional arc welding method without a pulse. [Fig. 7] (a) is a sectional view schematically showing a welding spatter; (b) is a sectional view schematically showing a pore; (c) is a sectional view schematically showing a pit.

1‧1’‧‧‧ molten Zn-based plated steel sheet

2‧‧‧ Welding Wire

2a‧‧‧ tip of the wire (tip of the wire)

7‧‧‧Contact

7a‧‧‧Corner (welding target)

D‧‧‧distance

Claims (8)

An arc welding method for molten Zn-based plated steel plates is an arc welding method for welding fused Zn-based plated steel plates to each other by a pulsed arc welding method in which peak current and base current are alternately supplied to generate an arc. It is characterized in that the distance from the tip of the welding wire to the welding target portion of the contact portion between the Zn-based plated steel plates that are the welding target is a length that does not cause short circuit between the welding wire and the molten pool generated at the contact portion, The molten Zn-based plated steel sheets are welded to each other for a length that the arc does not extinguish. The arc welding method for a molten Zn-based plated steel sheet according to claim 1, wherein the distance is 2 mm or more and 20 mm or less. The arc welding method for a molten Zn-based plated steel sheet according to claim 1 or 2, wherein the aforementioned peak current is 350A or more and 650A or less, and the pulse period is 1ms or more and 20ms or less. The arc welding method for a molten Zn-based plated steel sheet according to any one of claims 1 to 3, wherein the plating layer of the molten Zn-based plated steel sheet contains Zn as a main component and contains 1.0% by mass or more and 22.0% by mass or less of Al. The arc welding method for a molten Zn-based plated steel sheet according to claim 4, wherein the plating layer of the molten Zn-based plated steel sheet contains Mg of 0.05% by mass or more and 10.0% by mass or less. The arc welding method for a molten Zn-based plated steel sheet according to claim 5, wherein the composition of the plating layer of the molten Zn-based plated steel sheet satisfies Ti: 0.002 to 0.1% by mass, B: 0.001 to 0.05% by mass, Conditions selected from one or more of the group consisting of Si: 0 to 2.0% by mass and Fe: 0 to 2.5% by mass. The arc welding method for a molten Zn-based plated steel sheet according to any one of claims 1 to 6, wherein the arc welding is performed so that a pore occupation ratio Br represented by the following formula (1) is 30% or less, and The number of welding spatters attached to the center of the bead with a length of 100 mm and a width of 100 mm is less than 20; Br = (Σdi / L) × 100 ･ ･ ･ (1) (here, di: in the aforementioned bead The length of the i-th pore observed in the L (the length of the bead). A method for manufacturing a welded member, which is a method for manufacturing a welded member in which molten Zn-based plated steel plates are welded to each other by a pulse arc welding method, characterized in that the plating adhesion of each side of the aforementioned molten Zn-based plated steel plate is The amount is 15 g / m ² or more and 250 g / m ² or less. The distance from the tip of the welding wire to the welding target portion of the contact portion between the Zn-based plated steel plates to be welded is 2 mm to 20 mm, and a pulse is generated. The peak current of the arc welding current is 350A to 650A, the pulse period is 1ms to 20ms, and the aforementioned molten Zn-based plated steel plates are welded to each other by pulse arc welding.