Lap fillet welded joint, method for producing same, and automotive component

Abstract

This lap fillet welded joint comprises: a first steel sheet 11; a second steel sheet 12 overlapped onto the first steel sheet 11; and a weld bead 13 formed at a corner between a surface of the first steel sheet 11 and an end face of the second steel sheet 12. A zinc-based plating 15 having a thickness of 2.0 to 20.0 μm is provided on the surface of the first steel sheet 11 and / or a surface of the second steel sheet 12. A steady-state section 131 of the weld bead 13 has wavy weld toes 134, 135 and a porosity defect rate of less than 20.0%. In plan view of the lap fillet welded joint from the weld bead side, the amount of spatter adhesion at a particle size of 300 μm or more in a weld bead peripheral region within 20 mm from both ends of the weld bead in the length direction and within 60 mm from both ends of the weld bead in the width direction is 0.25 / cm2 or less.

Description

Overlap fillet weld joint and method for manufacturing the same, and automotive parts 【0001】 This invention relates to lap fillet weld joints, methods for manufacturing the same, and automotive parts. 【0002】 Arc welding, which uses an arc discharge, is used to join materials in various machine parts. For example, in automotive parts such as car suspension components, arc welding is often used for lap fillet welding of steel plates. In recent years, with the trend towards higher strength and thinner steel plates that make up automotive parts, the level of corrosion resistance required for lap fillet welded joints has also improved. For this reason, there is a growing need to use zinc-plated steel sheets, which have excellent corrosion resistance, as a material for lap fillet welded joints. 【0003】 When arc welding zinc-plated steel sheets to form lap fillet welds, zinc, which has a lower melting and boiling point than iron, evaporates into zinc vapor. This vapor remains in the molten pool as bubbles, and as the molten steel solidifies, it is known to create voids called porosity defects in the weld metal. If a large number of porosity defects occur, the joint strength decreases due to a reduction in the joint area. Furthermore, even if only a small number of porosity defects occur, if pits or irregularities exist on the surface of the weld metal, it may hinder electrodeposition coating and lead to coating defects. Therefore, countermeasures against porosity defects are essential for arc welds of zinc-plated steel sheets. In addition, if zinc vapor is mixed into the arc plasma, droplet transfer becomes unstable, and a lot of spatter is generated. If spatter adheres to the welded joint or jig, it leads to a decrease in production efficiency due to an increase in spatter removal processes, poor appearance, and thinning of the coating film. 【0004】Patent Document 1 discloses a TIG welding method for fillet joints using galvanized steel sheets or primer-coated steel sheets, characterized by employing a TIG arc that oscillates with a frequency of 10 Hz or higher and an amplitude of 3 mm or higher, employing welding conditions including an arc current value and welding speed that melt the base material surfaces constituting the lap joint of two base materials while not melting the joint corners, feeding the welding wire from the welding direction along the base material corners toward the molten pool to form weld metal, creating a gap in the joint corner between the wire and the base material, and welding while releasing zinc vapor generated on the base material surface near the joint corners close to the bottom of the molten pool to the outside through the gap.According to this welding method, welding can be performed without forming pores or pits by always maintaining a path for easily discharging zinc vapor or primer component vapor from the heat-affected zone adjacent to the molten pool of the closely adhering base material lap portion of the galvanized steel sheet or primer-coated steel sheet into the outside air. 【0005】 Japanese Patent Publication No. 2003-53544 【0006】 The technology described in Patent Document 1 requires that the joint corners not be melted. Therefore, according to the technology in Patent Document 1, it is difficult to ensure sufficient penetration depth of the weld bead. Furthermore, the technology in Patent Document 1 requires that TIG welding be used as the welding method. TIG welding is an arc welding method that uses non-consumable tungsten as an electrode to generate an arc plasma and introduces filler material such as welding wire into the arc plasma. Therefore, the technology disclosed in Patent Document 1 cannot be applied to consumable electrode type arc welding such as submerged arc welding. In order to suppress the occurrence of porosity defects in various parts, a technology applicable to various arc welding methods, not limited to TIG welding, is required. Moreover, Patent Document 1 does not particularly address the issue of spatter adhesion. 【0007】The present invention was made to solve the above-mentioned problems, and aims to provide lap fillet welded joints and automotive parts that have excellent corrosion resistance and fewer spatter and porosity defects. Furthermore, the present invention aims to provide a method for manufacturing lap fillet welded joints that have excellent corrosion resistance and fewer spatter and porosity defects when lap fillet welding zinc-plated steel sheets. 【0008】 The inventors of this invention conducted extensive research on lap fillet welding of zinc-plated steel sheets and, as a result, discovered that the above problems can be solved by performing lap fillet welding under specific conditions, leading to the completion of this invention. That is, the present invention is illustrated as follows. 【0009】 <1> A lap fillet welded joint comprising a first steel plate, a second steel plate superimposed on the first steel plate, and a weld bead formed at the corner between the surface of the first steel plate and the end face of the second steel plate, wherein a zinc-based plating with a thickness of 2.0 to 20.0 μm is provided on at least one of the surfaces of the first steel plate and the second steel plate, the steady portion of the weld bead has a wavy toe and a porosity of less than 20.0%, and when the lap fillet welded joint is viewed in plan from the weld bead side, the amount of spatter with a particle size of 300 μm or more in the weld bead peripheral region within 20 mm from both ends in the longitudinal direction of the weld bead and within 60 mm from both ends in the width direction of the weld bead is 0.25 particles / cm 2 The following is a lap fillet welded joint. 【0010】 <2> The zinc deposition amount of the zinc-based plating is 5 to 100 g / m². 2 The lap fillet welded joint described in <1>. 【0011】 <3> The lap fillet welded joint according to <1> or <2>, wherein the zinc-based plating contains 40% by mass or less of aluminum. 【0012】 <4> A lap fillet welded joint according to any one of <1> to <3>, wherein the thickness of the first steel plate and the second steel plate is 1.0 to 6.0 mm. 【0013】<5> The lap fillet welded joint according to any one of <1> to <4>, wherein the wavelength of the wavy toe is 0.03 to 0.20 mm. 【0014】 <6> A method for manufacturing an overlapped fillet welded joint, comprising the steps of overlapping a first steel plate and a second steel plate, and fillet welding the corner between the surface of the first steel plate and the end face of the second steel plate, wherein at least one of the surfaces of the first steel plate and the second steel plate is coated with a zinc-based plating having a thickness of 2.0 to 20.0 μm, the fillet welding is performed by pulse arc welding with a pulse peak current of 400 to 650 A, a pulse peak time of 0.5 to 2.0 msec, and a base current of 50 A or more while weaving the torch, and the weaving oscillation pattern satisfies either (A) or (B) below when viewed from the welding direction. (A) The torch is oscillated linearly at a frequency of 0.5 to 6.0 Hz and an amplitude of 0.1 to 6.0 mm, such that it is substantially perpendicular to the line connecting the tip of the torch and the corner. (B) When the direction parallel to the surface of the first steel plate is the transverse direction, the direction perpendicular to the surface of the first steel plate is the longitudinal direction, and the thickness of the second steel plate is T [mm], the plate is oscillated to trace a triangular trajectory under the conditions that the transverse movement is 0.1 to T [mm], the longitudinal movement is greater than 0 and less than or equal to T [mm], and the longitudinal movement ≤ transverse movement. 【0015】 <7> The zinc deposition amount of the zinc-based plating is 5 to 100 g / m². 2 The method for manufacturing a lap fillet welded joint as described in <6>. 【0016】 <8> The method for manufacturing a lap fillet welded joint according to <6> or <7>, wherein the pulse arc welding is performed with an average welding current of 130 to 300 A and a welding voltage of 10.0 to 30.0 V. 【0017】 <9> The method for manufacturing a lap fillet welded joint according to any one of <6> to <8>, wherein the pulsed arc welding is performed at a welding speed of 0.4 to 1.2 m / min. 【0018】 <10> The pulse arc welding is performed by alternately switching between forward and reverse feeding of the welding wire, a method for manufacturing an overlap fillet welded joint according to any one of <6> to <9>. 【0019】 <11> The pulsed arc welding is a method for manufacturing a lap fillet welded joint according to any one of <6> to <10>, wherein the pulsed arc welding has a short-circuit frequency of 100 times / second or less when the welding voltage is below 5V. 【0020】 <12> The method for manufacturing a lap fillet welded joint according to any one of <6> to <11>, wherein the pulsed arc welding is characterized in that the amount of spatter generated is 3.00 g / min or less. 【0021】 <13> An automotive part comprising an overlap fillet welded joint as described in any one of <1> to <5>. 【0022】 According to the present invention, it is possible to provide lap fillet welded joints and automotive parts that have excellent corrosion resistance and fewer spatter and porosity defects. Furthermore, according to the present invention, it is possible to provide a method for manufacturing lap fillet welded joints that have excellent corrosion resistance and fewer spatter and porosity defects when lap fillet welding zinc-plated steel sheets. 【0023】 This is a cross-sectional view of a lap fillet welded joint according to an embodiment of the present invention. This is a plan view of a lap fillet welded joint according to an embodiment of the present invention. This is a conceptual diagram illustrating a method for manufacturing a lap fillet welded joint according to an embodiment of the present invention. This is a conceptual diagram illustrating the weaving oscillation pattern. 【0024】 The embodiments of the present invention will be described in detail below. The present invention is not limited to the embodiments described below, and it should be understood that modifications, improvements, etc., made to the embodiments described below, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention, also fall within the scope of the present invention. In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. 【0025】<Layer Fillet Weld Joint> Figure 1 is a cross-sectional view (a cross-sectional view perpendicular to the weld line of the weld metal) of a layer fillet weld joint according to an embodiment of the present invention. Figure 2 is a plan view of the layer fillet weld joint according to an embodiment of the present invention. As shown in Figures 1 and 2, the layer fillet weld joint according to an embodiment of the present invention comprises a first steel plate 11, a second steel plate 12, and a weld bead 13 (weld metal) formed at the corner between the surface of the first steel plate 11 and the end face of the second steel plate 12. The weld bead 13 is formed to join the surface of the first steel plate 11 and the end face of the second steel plate 12. A heat-affected zone 14 is formed around the weld bead 13. Here, in this specification, "steel plate" is a concept that includes not only plate-shaped members but also plate-shaped parts of members having a three-dimensional shape. Therefore, for example, the flange portion of a hat-shaped member also corresponds to "steel plate" in this specification. 【0026】 A zinc-based plating 15 is provided on at least one of the surfaces of the first steel plate 11 and the second steel plate 12. In Figure 1, a configuration in which the zinc-based plating 15 is provided on both surfaces (bottom and top) of the first steel plate 11 and on one surface (bottom: the surface overlapping the first steel plate 11) of the second steel plate 12 is shown as an example. However, the zinc-based plating 15 may be provided only on one surface (top: the surface overlapping the second steel plate 12) of the first steel plate 11, or only on one surface (bottom) of the second steel plate 12. By providing the zinc-based plating 15 in such positions, porosity defects in the weld bead 13 can be suppressed. In addition, by providing the zinc-based plating 15 on the surface of the first steel plate 11, the corrosion resistance of the lap fillet weld joint is improved. The zinc-based plating 15 may also be applied to the other surface of the second steel plate 12 (the top surface: the surface opposite to the surface overlapped with the first steel plate 11) and to the end faces of the first steel plate 11 and the second steel plate 12. From the viewpoint of improving the corrosion resistance of the lap fillet weld joint, it is preferable that the zinc-based plating 15 be applied to the entire surface of the first steel plate 11 and the second steel plate 12 (excluding the portion where the weld bead 13 is formed). Here, in this specification, "surface of the steel plate" means a surface perpendicular or substantially perpendicular to the thickness direction of the steel plate. Also, "end face of the steel plate" means a surface parallel or substantially parallel to the thickness direction of the steel plate. 【0027】Herein, in this specification, zinc-based plating 15 means a plating with a composition mainly composed of zinc, and optionally further containing elements such as Si, Al, Mg, and Fe. Furthermore, a composition in which zinc-based plating 15 is mainly composed of zinc means a composition in which the most abundant element in zinc-based plating 15 is zinc. The zinc content in zinc-based plating 15 is not particularly limited as long as zinc is the main component, but is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more. 【0028】 The zinc-based plating 15 preferably contains aluminum. The inclusion of aluminum further improves the corrosion resistance of the lap fillet welded joint. The aluminum content in the zinc-based plating 15 is not particularly limited, but is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. 【0029】 The content of each element in the zinc-based plating 15 can be measured by the following method. First, an acid solution is obtained by stripping and dissolving the zinc-based plating 15 using an acid containing an inhibitor that suppresses corrosion of the steel material (first steel plate 11 and second steel plate 12). Next, the obtained acid solution is subjected to ICP analysis. This allows the content of each element in the zinc-based plating 15 to be determined. The type of acid is not particularly limited as long as it can dissolve the zinc-based plating 15. Note that the content of each element measured by the above means is the average content of each element in the entire zinc-based plating 15. 【0030】 The amount of zinc deposited on the zinc-based plating 15 is not particularly limited, but is preferably 5 to 100 g / m². 2 More preferably 10 to 80 g / m 2This is how the corrosion resistance of lap fillet welded joints is improved by controlling the amount of zinc deposition within this range. Here, the amount of zinc deposition in the zinc-based plating 15 is determined by the following method. First, the zinc-based plating 15 is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the steel material (first steel plate 11 and second steel plate 12). Next, the mass change [g] before and after the treatment is multiplied by the ratio of zinc in the zinc-based plating 15 obtained by the above method (zinc content [mass%] / 100) and the area [m²] of the part where the zinc-based plating 15 was formed is calculated. 2 By dividing by [ ], the amount of zinc deposited on the zinc-based plating 15 can be determined. 【0031】 The thickness of the zinc-based plating 15 is 2.0 to 20.0 μm, preferably 3.0 to 20.0 μm, more preferably 5.0 to 20.0 μm, and even more preferably 7.0 to 20.0 μm. By controlling the thickness in this way, it is possible to improve the corrosion resistance of the lap fillet weld joint while ensuring the jointability between the surface of the first steel plate 11 and the end face of the second steel plate 12. The thickness of the zinc-based plating 15 is determined by the following method. First, a treatment is performed to strip and dissolve the zinc-based plating 15 using an acid containing an inhibitor that suppresses corrosion of the steel material (first steel plate 11 and second steel plate 12). Next, the amount of mass change before and after the treatment is measured over the area [m²] of the portion where the zinc-based plating 15 was formed. 2 The amount of zinc-based plating 15 is determined by dividing by [ ]. Next, the amount of zinc-based plating 15 obtained in this way and the specific gravity of the metal contained in the zinc-based plating 15 are used to convert it into the thickness of the zinc-based plating 15. 【0032】 The thickness of the first steel plate 11 and the second steel plate 12 is not particularly limited, but for example, when the lap fillet welded joint is used in an automobile part, the thickness of the first steel plate 11 and the second steel plate 12 is preferably 1.0 to 6.0 mm, more preferably 1.5 to 5.5 mm, and even more preferably 2.0 to 5.0 mm. The thickness of the first steel plate 11 and the second steel plate 12 can be determined using a micrometer or calipers. Alternatively, the thickness of the first steel plate 11 and the second steel plate 12 may be determined by microscopic observation of a cross-section taken after cutting the lap fillet welded joint. 【0033】As shown in Figure 2, the weld bead 13 has a steady portion 131, a starting portion 132, and a ending portion 133. The starting portion 132 and the ending portion 133 correspond to the ignition and extinction of the welding arc, and are formed when the arc plasma is unstable, so their width and shape are non-uniform. The starting portion 132 is not particularly limited, but for example, it is the area within 15 mm from the starting end of the weld bead 13. Similarly, the ending portion 133 is not particularly limited, but for example, it is the area within 15 mm from the end. The steady portion 131 is the area other than the starting portion 132 and the ending portion 133. 【0034】 The steady portion 131 of the weld bead 13 has wavy toes 134 and 135. Here, wavy refers to a shape in which concave and convex portions appear alternately and periodically, as shown in Figure 2. This wavy shape of the toes 134 and 135 is a result of pulse arc welding while weaving the torch. The wavy shape of the toes 134 and 135 makes it easier to distribute the stress applied to the weld bead 13, thereby improving the fatigue strength of the lap fillet weld joint. 【0035】 The wavelength W of the wavy toes 134 and 135 is not particularly limited, but is preferably 0.03 to 0.20 mm. By controlling the wavelength W of the wavy toes 134 and 135 within this range, the fatigue strength of the lap fillet weld joint can be stably improved. The wavelength W of the wavy toes 134 and 135 can be determined by microscopic observation of the wavy toes 134 and 135. 【0036】 The steady-state portion 131 of the weld bead 13 has a porosity defect rate of less than 20.0%, preferably 18.0% or less, and more preferably 15.0% or less. By keeping the porosity defect rate below 20.0%, the joint strength of the lap fillet weld joint can be improved, and defects in electrodeposition coating can also be suppressed. The porosity defect rate in the steady-state portion 131 of the weld bead 13 is measured by the following procedure. First, an X-ray transmission image of the steady-state portion 131 of the weld bead 13 is taken. This allows for the confirmation of porosity defects contained in the weld bead 13. Next, the total length of the porosity defects along the weld bead 13 is measured. Then, the porosity defect rate can be calculated by dividing the total length of the porosity defects by the length of the steady-state portion 131. 【0037】 The lap fillet welded joint according to an embodiment of the present invention has an adhesion amount of spatter with a particle size of 300 μm or more in the peripheral region 16 (see FIG. 2) of the weld bead within 20 mm from both ends in the length direction of the weld bead 13 and within 60 mm from both ends in the width direction of the weld bead 13 of 0.25 pieces / cm 2 Preferably 0.21 pieces / cm or less 2 More preferably 0.17 pieces / cm or less 2 or less. Here, the peripheral region 16 of the weld bead within 20 mm from both ends in the length direction of the weld bead means a region located within 20 mm from the start end 132 and the end end 133 of the weld bead 13. Also, the peripheral region 16 of the weld bead within 60 mm from both ends in the width direction of the weld bead 13 means a region located within 60 mm from the stop ends 134 and 135 of the steady part 131 of the weld bead. With the adhesion amount of spatter within this range, it can be said that there is little spatter, so that defective appearance and thinning of the coating film can be suppressed. In addition, since there is no need to perform a spatter removal process, the production efficiency can be increased. The adhesion amount of spatter of the lap fillet welded joint can be calculated by photographing the appearance of the lap fillet welded joint, obtaining the number of spatters with a particle size of 300 μm or more in the peripheral region 16 of the weld bead, and dividing by the area of the peripheral region 16 of the weld bead. Note that the particle size of the spatter is calculated as an equivalent circle diameter. 【0038】 The lap fillet welded joint according to an embodiment of the present invention is composed of a first steel plate 11 and a second steel plate 12 provided with a zinc-based plating 15, so it has excellent corrosion resistance. Also, the lap fillet welded joint according to an embodiment of the present invention has few porosity defects, so it has excellent joint strength and electrodeposition coating properties. Furthermore, the lap fillet welded joint according to an embodiment of the present invention has little spatter, so it can suppress a decrease in production efficiency, defective appearance, coating defects, etc. due to an increase in the spatter removal process. Therefore, the lap fillet welded joint according to an embodiment of the present invention can be used in various applications that require the above-described effects. Examples of applications include building materials, automotive parts, etc., and it is particularly preferably an automotive part. 【0039】<Method for Manufacturing Overlap Fillet Weld Joint> The overlap fillet weld joint having the above characteristics is manufactured by performing overlap fillet welding under specific conditions. A conceptual diagram for explaining the manufacturing method of this overlap fillet weld joint is shown in FIG. 3 (a view in plan view), and its details will be described below. The manufacturing method of the overlap fillet weld joint according to an embodiment of the present invention includes a step of overlapping a first steel plate 11 and a second steel plate 12 (hereinafter referred to as "overlapping step"), and a step of performing fillet welding on the corner between the surface 111 of the first steel plate 11 and the end face 121 of the second steel plate 12 (hereinafter referred to as "fillet welding step"). In the overlapping step, the first steel plate 11 and the second steel plate 12 are overlapped in the plate thickness direction such that the end face 121 of the second steel plate 12 is disposed on the surface 111 of the first steel plate 11. In the fillet welding step, the end face 121 of the second steel plate 12 and the surface 111 of the first steel plate 11 are fillet welded to form a weld bead 13. During fillet welding, the first steel plate 11 and the second steel plate 12 remain in an overlapped state. Further, the weld bead 13 is formed so as to join the end face 121 of the second steel plate 12 and the surface 111 of the first steel plate 11. 【0040】 On at least one of the surface 111 of the first steel plate 11 and the surface of the second steel plate 12 used in the manufacturing method of the overlap fillet weld joint according to an embodiment of the present invention, a zinc-based plating 15 having a thickness of 2.0 to 20.0 μm is provided. Thereby, the corrosion resistance of the overlap fillet weld joint is improved. Further, the zinc-based plating 15 may also be provided on the end face of the first steel plate 11 and the end face 121 of the second steel plate 12. Thereby, the corrosion resistance of the overlap fillet weld joint is further improved. Since the details of the zinc-based plating 15 are as described above, the description thereof is omitted. 【0041】The fillet welding process is performed by pulsed arc welding. Since zinc-based plating 15 is provided on at least one of the surfaces 111 of the first steel plate 11 and the second steel plate 12, zinc in the zinc-based plating 15, which has a lower melting point and boiling point than iron, evaporates during pulsed arc welding. If zinc vapor enters the molten pool and remains there while the molten pool solidifies, porosity defects will occur in the weld bead 13. The molten pool is a pool of molten metal formed by heat such as arc plasma during welding. Furthermore, if zinc vapor is mixed into the arc plasma, droplet transfer becomes unstable, generating a lot of spatter, which adheres to the lap fillet weld joint and jig. Spatter is a deposit formed from droplets of molten metal scattered or airborne during welding. To solve these problems, the conditions for the fillet welding process are specified as described below. 【0042】 Fillet welding is performed by pulsed arc welding while weaving the torch 20. The pulse conditions for pulsed arc welding are a pulse peak current of 400 to 650 A, a pulse peak time of 0.5 to 2.0 msec, and a base current of 50 A or more. By performing pulsed arc welding under these pulse conditions, droplet transfer becomes smoother, and the generation of spatter can be suppressed. From the viewpoint of stably ensuring this effect, the pulse peak current is preferably 450 to 600 A, more preferably 500 to 550 A, the pulse peak time is preferably 0.7 to 1.8 msec, more preferably 0.8 msec or more and less than 1.5 msec, and still preferably 0.9 to 1.4 msec, and the base current is preferably 55 A or more, more preferably 60 A or more. The upper limit of the base current is preferably less than 80 A, and more preferably 75 A or less. Furthermore, while there are no particular limitations on other pulsed arc welding conditions, it is preferable that the average welding current is 130 to 300 A, the welding voltage is 10.0 to 30.0 V, and the welding speed is 0.4 to 1.2 m / min, and more preferably that the average welding current is 150 to 280 A, the welding voltage is 15.0 to 28.0 V, and the welding speed is 0.6 to 1.2 m / min. By performing pulsed arc welding under these conditions, the above effects can be more stably ensured. 【0043】Pulse arc welding is preferably carried out with a short - circuit frequency below 5 V of the welding voltage being 100 times per second or less. By controlling the short - circuit frequency within this range, the scattering of molten metal can be suppressed, making it easier to reduce the generation of spatter. From the perspective of stably ensuring this effect, the short - circuit frequency is more preferably 90 times per second or less, and even more preferably 80 times per second or less. 【0044】 Pulse arc welding is preferably carried out while alternately switching between forward and reverse feeding of the welding wire. By performing the wire feeding control of the welding wire in this way, the fluctuation of the molten pool becomes large and the discharge of zinc vapor is promoted, making it easier to reduce the generation of spatter and porosity defects. Note that the welding wire is not particularly limited, and those known in the relevant technical field can be used. 【0045】 As arc welding, it is preferable to use MAG (Metal Active Gas) welding. Among arc weldings, TIG (Tungsten Inert Gas) welding and plasma arc welding are non - consumable electrode type weldings, so it is impossible to realize the stirring of the molten pool combining weaving and droplet transfer. Different from MAG welding, MIG (Metal Inert Gas) welding uses an inert gas mainly composed of argon or helium as the shielding gas, but the gas is expensive. Also, due to the tendency of the arc to spread, sufficient penetration may not be obtained in some cases. MAG welding does not have these drawbacks. 【0046】The weaving oscillation pattern is performed such that it satisfies either (A) or (B) below when viewed from the welding direction. A conceptual diagram (a schematic diagram as viewed from the welding direction) for explaining this weaving oscillation pattern is shown in Figure 4. (A) The torch 20 is oscillated linearly so as to be approximately perpendicular to the line L connecting the tip and the corner, under the conditions of a frequency of 0.5 to 6.0 Hz and an amplitude of 0.1 to 6.0 mm. "Approximately perpendicular" means perpendicular (90°) ± 10°, preferably perpendicular (90°) ± 5°. (B) When the direction parallel to the surface 111 of the first steel plate 11 is the horizontal direction X, the direction perpendicular to the surface 111 of the first steel plate 11 is the vertical direction Y, and the thickness of the second steel plate 12 is T [mm], the torch is oscillated to trace a triangular trajectory under the conditions that the movement in the horizontal direction X is 0.1 to T [mm], the movement in the vertical direction Y is greater than 0 and less than or equal to T [mm], and the movement in the vertical direction Y ≤ the movement in the horizontal direction X. By performing weaving with the above-described oscillation patterns (A) or (B), the oscillation of the molten pool is increased, promoting the discharge of zinc vapor, thereby reducing spatter and porosity defects. In particular, weaving with oscillation pattern (B) can increase the oscillation of the molten pool more than weaving with oscillation pattern (A), thus further reducing spatter and porosity defects. 【0047】 In oscillation pattern (A), the frequency is preferably 1.0 to 5.0 Hz and the amplitude is preferably 0.5 to 5.0 mm, and the frequency is more preferably 1.5 to 4.0 Hz and the amplitude is more preferably 1.0 to 4.0 mm. In oscillation pattern (A), the torch angle at the start of welding is preferably 40 to 65°. In this specification, "torch angle" means the angle formed by the surface 111 of the first steel plate 11 and the line L connecting the tip and corner of the torch 20. In oscillation pattern (B), the movement in the lateral direction X is preferably 0 to 6.0 [mm] and the movement in the vertical direction Y is preferably greater than 0 and 6.0 [mm] or less, and the movement in the lateral direction X is more preferably 0.5 to 5.0 [mm] and the movement in the vertical direction Y is more preferably 0.1 to 5.0 [mm]. 【0048】A gap (hereinafter referred to as "plate gap") may exist between the first steel plate 11 and the second steel plate 12. However, if the oscillation of the molten pool is made too large, the molten metal will easily flow into the plate gap, reducing the effectiveness of suppressing sputter and porosity defects. Therefore, when there is a plate gap, it is preferable to set the frequency of the oscillation pattern (A) to 0.5 to 6.0 Hz and the amplitude to 0.1 to 4.0 mm. Furthermore, it is preferable to set the movement in the lateral direction X to 0.1 to 4.0 mm and the movement in the vertical direction Y to greater than 0 and less than or equal to 4.0 mm in the oscillation pattern (B). 【0049】 In pulse arc welding performed under the above conditions, the spatter generation rate is preferably 3.00 g / min or less, more preferably 2.90 g / min or less, and even more preferably 2.80 g / min or less. With a spatter generation rate within this range, the spatter adhering to the lap fillet weld joint can also be reduced. The spatter generation rate [g / min] is determined by collecting the spatter generated during arc welding in a collection box, measuring its mass [g], and dividing it by the welding time [minutes]. 【0050】 The method for manufacturing lap fillet welded joints according to an embodiment of the present invention is suitable for manufacturing lap fillet welded joints used in various applications because it reduces the occurrence of spatter and porosity defects when lap fillet welding zinc-plated steel sheets (first steel sheet 11 and second steel sheet 12 provided with zinc plating 15). In particular, this manufacturing method can suppress spatter from adhering to the lap fillet welded joint and jig, thus eliminating problems such as decreased production efficiency due to an increased spatter removal process, poor appearance, and poor painting. 【0051】<Automotive Parts> Automotive parts according to an embodiment of the present invention are equipped with the above-described lap fillet welded joint. Since this automotive part uses a lap fillet welded joint made of zinc-plated steel sheets (first steel sheet 11 and second steel sheet 12 provided with zinc-plated 15), it has excellent corrosion resistance. Furthermore, since the automotive part according to an embodiment of the present invention uses a lap fillet welded joint with suppressed porosity defects, it has excellent joint strength and electrodeposition coating properties. Moreover, since the automotive part according to an embodiment of the present invention uses a lap fillet welded joint with less spatter generation, it has high production efficiency and can suppress appearance defects, coating defects, etc. 【0052】 The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples. 【0053】 Overlap fillet welding was performed under various conditions using two identical steel plates (first steel plate and second steel plate) that were fully coated with zinc-based plating. Overlap fillet welding was performed by fillet welding the corners between the surface of the first steel plate and the end face of the second steel plate to form a weld bead, thereby obtaining an overlap fillet welded joint. The characteristics of the obtained overlap fillet welded joints are shown in Table 1, and the welding conditions are shown in Table 2. In Table 1, each characteristic of the overlap fillet welded joint was determined by the method described above. In Table 2, for the weaving oscillation pattern, "A" indicates that the above-described oscillation pattern (A) was performed, "B" indicates that the above-described oscillation pattern (B) was performed, and "--" indicates that no weaving was performed. In oscillation pattern (A), the torch angle at the start of welding was set to 45°. 【0054】 【0055】 【0056】 As shown in Tables 1 and 2, the lap fillet welded joints of Examples 1 to 5, which were fabricated by performing lap fillet welding under predetermined weaving and pulsed arc conditions, exhibited low spatter adhesion and a low porosity defect rate. 【0057】In contrast, the lap fillet welded joints of Comparative Examples 1 and 2 had a high porosity defect rate because weaving was not performed during lap fillet welding. Furthermore, when weaving was not performed during lap fillet welding, the porosity defect rate did not decrease sufficiently even when wire feeding control was performed by alternately switching between forward and reverse feeding of the welding wire (Comparative Example 2). The lap fillet welded joint of Comparative Example 3 had a small thickness of zinc-based plating, resulting in less spatter and porosity defects compared to the other examples and comparative examples. As a result, the amount of spatter adhesion was small and the porosity defect rate was low. However, the lap fillet welded joint of Comparative Example 3 had insufficient corrosion resistance due to the small thickness of the zinc-based plating. In Comparative Example 4, the frequency and amplitude of the weaving oscillation pattern (A) were large, so the weaving promoted the discharge of zinc vapor and reduced the porosity defect rate. On the other hand, in Comparative Example 4, the torch movement was too large, resulting in many short circuits, and the amount of spatter was large because the amount of Zn adhesion in the zinc-based plating was large. Therefore, the lap fillet welded joint in Comparative Example 4 had a large amount of spatter adhesion. 【0058】In Comparative Example 5, the pulse peak current of the pulsed arc welding was too low, resulting in a weak effect on oscillating the molten pool. As a result, the lap fillet weld joint in Comparative Example 5 had a high porosity defect rate. In Comparative Example 6, the pulse peak time of the pulsed arc welding was too short, resulting in a weak effect on oscillating the molten pool. As a result, the lap fillet weld joint in Comparative Example 6 had a high porosity defect rate. In Comparative Example 7, the pulse peak current of the pulsed arc welding was too high and the pulse peak time was too long, resulting in large oscillating of the molten pool, many short circuits, and a large amount of spatter generation. As a result, the lap fillet weld joint in Comparative Example 7 had a large amount of spatter adhesion. In Comparative Example 8, the lateral X and vertical Y movements of the weaving oscillation pattern (B) were too large, resulting in many short circuits and a large amount of spatter generation. As a result, the lap fillet weld joint in Comparative Example 8 had a large amount of spatter adhesion. In addition, in Comparative Example 8, because there was a gap between the plates, the molten pool easily flowed into the gap, resulting in a high porosity defect rate. In Comparative Example 9, the vertical Y-direction movement of the weaving oscillation pattern (B) was too large, resulting in frequent short circuits and a large amount of spatter generation. Consequently, the lap fillet weld joint in Comparative Example 9 had a large amount of spatter adhesion. 【0059】 As can be seen from the above results, the present invention provides lap fillet welded joints and automotive parts that have excellent corrosion resistance and fewer spatter and porosity defects. Furthermore, the present invention provides a method for manufacturing lap fillet welded joints that have excellent corrosion resistance and fewer spatter and porosity defects when lap fillet welding zinc-plated steel sheets. 【0060】 11 First steel plate 111 Surface 12 Second steel plate 121 End face 13 Weld bead 131 Steady section 132 Starting section 133 End section 134, 135 Toe section 14 Heat-affected zone 15 Zinc plating 16 Area around the weld bead 20 Torch

Claims

First steel plate and, The second steel plate is superimposed on the first steel plate, A weld bead formed at the corner between the surface of the first steel plate and the end face of the second steel plate. A lap fillet welded joint comprising, A zinc-based plating with a thickness of 2.0 to 20.0 μm is provided on at least one of the surfaces of the first steel plate and the second steel plate. The steady portion of the weld bead has a wavy toe and a porosity defect rate of less than 20.0%. When the aforementioned lap fillet weld joint is viewed from the weld bead side in a plan view, the amount of spatter with a particle size of 300 μm or more adhering to the weld bead peripheral region within 20 mm from both ends in the longitudinal direction of the weld bead and within 60 mm from both ends in the width direction of the weld bead is 0.25 particles / cm². 2 The following is a lap fillet welded joint. 　 The zinc deposition amount of the aforementioned zinc-based plating is 5 to 100 g / m². 2 The lap fillet welded joint according to claim 1. 　 The lap fillet welded joint according to claim 1 or 2, wherein the zinc-based plating contains 40% by mass or less of aluminum. 　 The lap fillet welded joint according to claim 1 or 2, wherein the thickness of the first steel plate and the second steel plate is 1.0 to 6.0 mm. 　 The lap fillet welded joint according to claim 1 or 2, wherein the wavelength of the wavy toe is 0.03 to 0.20 mm. 　 The process of overlapping the first steel plate and the second steel plate, A process of fillet welding the corner between the surface of the first steel plate and the end face of the second steel plate. A method for manufacturing a lap fillet welded joint comprising: A zinc-based plating with a thickness of 2.0 to 20.0 μm is provided on at least one of the surfaces of the first steel plate and the second steel plate. The aforementioned fillet welding is performed by pulse arc welding with a pulse peak current of 400 to 650 A, a pulse peak time of 0.5 to 2.0 msec, and a base current of 50 A or more, while weaving the torch. A method for manufacturing a lap fillet welded joint, wherein the weaving oscillation pattern satisfies either (A) or (B) below when viewed from the welding direction. (A) The torch is oscillated linearly under the conditions of a frequency of 0.5 to 6.0 Hz and an amplitude of 0.1 to 6.0 mm, such that it is approximately perpendicular to the line connecting the tip of the torch and the corner. (B) When the direction parallel to the surface of the first steel plate is the transverse direction, the direction perpendicular to the surface of the first steel plate is the longitudinal direction, and the thickness of the second steel plate is T [mm], the plate is oscillated to trace a triangular trajectory under the conditions that the transverse movement is 0.1 to T [mm], the longitudinal movement is greater than 0 and less than or equal to T [mm], and the longitudinal movement ≤ transverse movement. 　 The zinc deposition amount of the aforementioned zinc-based plating is 5 to 100 g / m². 2 The method for manufacturing a lap fillet welded joint according to claim 6. 　 The method for manufacturing a lap fillet welded joint according to claim 6 or 7, wherein the pulsed arc welding is performed with an average welding current of 130 to 300 A and a welding voltage of 10.0 to 30.0 V. 　 The method for manufacturing a lap fillet welded joint according to claim 6 or 7, wherein the pulsed arc welding is performed at a welding speed of 0.4 to 1.2 m / min. 　 The method for manufacturing a fillet welded joint according to claim 6 or 7, wherein the pulsed arc welding is performed by alternately switching between forward and reverse feeding of the welding wire. 　 The method for manufacturing a fillet welded joint according to claim 6 or 7, wherein the pulsed arc welding has a short-circuit frequency of 100 times / second or less when the welding voltage is below 5V. 　 The method for manufacturing a fillet welded joint according to claim 6 or 7, wherein the pulsed arc welding generates 3.00 g / min or less of spatter. 　 An automobile part comprising a lap fillet welded joint according to claim 1 or 2.

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