JP2020015052A - Welding method, welding device and welding steel plate - Google Patents

Abstract

To provide a welding method in which occurrence of spatter is suppressed in welding overlapped galvanized steel plates.SOLUTION: A first steel plate is welded to a second steel plate by irradiating a beam having a circumference of a high-energy beam surrounded with low energy to the steel plate while scanning the beam in a scanning direction. When a width of a weld bead in a joined part between the first steel plate and the second steel plate is defined as A in a cross section cut in a direction orthogonal to the scanning direction of a welded part, a width of a weld bead extending to outside, on a surface of the first steel plate more than the joined part, at a finishing point at which scanning of the beam is finished is defined as B1 in the cross section cut along the scanning direction of the welded part, and a width of the weld bead extending to outside, on the surface of the first steel plate more than the joined part, at a starting point at which the scanning of the beam is started is defined as B2 in the cross section cut along the scanning direction of the welded part, relational expressions of B1>A and B2>A are satisfied.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a welding method, a welding device, and a welded steel plate. In particular, the present invention relates to a technique for reducing the occurrence of spatter due to scattering of molten metal when performing superposition welding by heating superposed steel sheets with a laser.

  In recent years, in many fields including copiers and printers, parts obtained by superimposing and welding plated steel sheets having excellent corrosion resistance have been used. For example, a frame of a copying machine or a printer is often formed by laminating or butting inexpensive materials such as inexpensive galvanized steel sheets and joining them by welding. In such a case, laser welding, in which the amount of heat input is reduced as compared with other welding methods, and which enables high-speed welding with low distortion and high accuracy, is often applied.

  In laser welding, a laser beam is applied to the surface of the material to be welded. When the applied power density (laser output per unit area) exceeds a predetermined level, the temperature of the metal surface rises to the boiling point of the metal and the metal vapor Evaporates violently from the laser irradiation point, and a part is turned into plasma. At the irradiation point, the surface of the molten metal is dented by the reaction force of the evaporation, and the laser beam propagates in the depression while repeating reflection. Then, the depression is further deepened to form a keyhole, and a deep molten region can be formed in a short time.

  High-speed metal vapor is ejected from the keyhole formed at the irradiation point of the laser beam, and a region called a molten pool in which the metal is melted is formed around the keyhole. The molten pool is not limited to a so-called pond that exists in the natural world, and can take various shapes depending on laser irradiation conditions. Most of the irradiated laser light propagates through the keyhole, reaches the bottom surface, and heats this portion. Therefore, the temperature of the molten metal becomes highest inside the material to be welded. A large amount of metal evaporates from inside the keyhole, and high pressure is applied to the molten metal, so that convection occurs in the molten metal, but the convection is not always stable and may fluctuate. When the convection fluctuates, a phenomenon in which a part of the molten metal is caught in the high-speed steam blowout and scatters around, that is, spatter may occur.

  In addition, in order to secure the strength of welding, instead of irradiating a fixed point with laser light and performing spot welding, it is sometimes necessary to form a linear weld bead by irradiating while scanning laser light along a line. In many cases, this may make spatter more likely to occur. This is because the generation of the keyhole and the flow of the molten pool around the keyhole become unstable with the movement of the laser beam irradiation position. In particular, the molten metal melted at the tip in the scanning direction of the laser beam is liable to be caught in the high-speed steam blowout from the keyhole that is rapidly generated following the scanning, so that spatter is easily generated. Also, if the flow of the molten pool becomes unstable due to repeated expansion and contraction of the keyhole, etc., the shielding gas and air for preventing oxidation are taken into the molten metal to generate bubbles, and the bubbles remain trapped. It can also solidify and produce porosity.

  Further, particularly when galvanized steel sheets are overlapped and laser-welded, spattering may occur because the zinc plating in the overlapped portion is vaporized by laser heating and blows away the molten metal.

  Therefore, as an attempt to suppress spatter, for example, Patent Literature 1 discloses a welding method in which a laser beam is spirally scanned along a welding bead forming direction while rotating a laser beam at a high speed.

WO 2015/107664

  According to Patent Literature 1, a laser beam can be spirally scanned to form a molten pool having a wide surface side. The molten pool flows while rotating in the direction in which the laser beam travels, and a depression is formed behind the opening of the keyhole. This describes that the flow of the molten metal that blocks the opening of the keyhole from behind is suppressed, and the laser beam does not directly irradiate the molten metal in the vicinity of the opening, thereby reducing spatter. .

  However, in the method described in Patent Literature 1, since the laser beam is spirally scanned, the laser beam once again forms the molten pool at a portion where the scanning orbits intersect. There is a possibility that rapid evaporation occurs and the molten metal is scattered.

Further, with the spiral scanning of the laser beam, each part of the material to be welded is intermittently heated, so that the temperature fluctuation of each part becomes complicated when viewed temporally, and the molten metal flows unstable. Waves that oscillate in synchronization with the helical scanning may be generated in the molten pool, and the keyhole may be more likely to be caught in the jet of high-speed steam that is jetted.
Therefore, the method described in Patent Literature 1 cannot always sufficiently suppress the occurrence of sputtering.

  The present invention is characterized in that a first steel sheet and a second steel sheet are stacked, and the high energy beam is irradiated on the first steel sheet while moving a beam surrounding the high energy beam with low energy in the scanning direction. A high-energy beam for irradiating the keyhole, irradiating the second steel plate with the first steel plate, and irradiating the second steel plate with the first steel plate. A steel plate is welded, and in a cross section of a welded portion in a direction perpendicular to the scanning direction, a width of a fusion zone at a joint between the first steel plate and the second steel plate is C, and a surface of the first steel plate Is a welding method, wherein D is greater than 2C, where D is the width of the fusion zone.

  Further, the present invention provides a method in which a first steel sheet and a second steel sheet are stacked, and the high energy beam is irradiated on the first steel sheet while scanning a beam surrounding a high energy beam with low energy in a scanning direction. The high-energy beam irradiating the keyhole penetrates the first steel plate and irradiates the second steel plate, and the first steel plate and the second 2, the width of a weld bead at the joint between the first steel plate and the second steel plate is A in a cross section obtained by cutting the welded portion in a direction perpendicular to the scanning direction, and the welded portion is welded. In a cross section taken along the scanning direction, at the end point where the scanning of the beam is completed, the width of a weld bead extending outward on the surface of the first steel plate from the joint is B1, In front of the weld In a cross section taken along the scanning direction, when a width of a weld bead extending outward on the surface of the first steel plate from the joint at the start point of starting the beam scanning is B2, > A and B2> A.

  Further, the present invention is a welded steel plate obtained by welding a first steel plate and a second steel plate along a line, and in a cross section obtained by cutting a welded portion in a direction perpendicular to the line, the first steel plate and the second steel plate are welded together. The width of the weld bead at the joint of the second steel sheet is A, and at a cross section obtained by cutting the weld along the line, at one end of the line, on the surface of the first steel sheet more than the joint. The width of the weld bead extending to B1 is B1, and at a cross section obtained by cutting the welded portion along the line, the other end of the line extends outward from the joint at the surface of the first steel plate. B1> A and B2> A, where B2 is the width of the existing weld bead.

  The present invention is also a welding apparatus for overlapping and welding a first steel plate and a second steel plate, wherein the first steel plate is scanned in a scanning direction with a beam surrounding a high energy beam with low energy. To irradiate the high energy beam irradiating part of the high energy beam to form a keyhole, the high energy beam irradiating the keyhole penetrates the first steel plate and irradiates the second steel plate, The first steel plate and the second steel plate are welded, and in a cross section obtained by cutting a welded portion in a direction orthogonal to the scanning direction, a weld bead at a joint between the first steel plate and the second steel plate is formed. In a cross section where the width is A and the welded portion is cut along the scanning direction, at a termination point at which the scanning of the beam is completed, a weld extending outward on the surface of the first steel plate from the joint at the end point. Bead width B1, a section of the welding portion cut along the scanning direction, and at a start point at which scanning of the beam is started, a welding bead extending outward on the surface of the first steel plate beyond the joining portion. When the width is B2, the beam is irradiated so that B1> A and B2> A.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a keyhole and the flow of the molten pool surrounding a keyhole become stable, generation | occurrence | production of a spatter can be suppressed, and the weld bead of a characteristic shape is formed.

(A) The typical sectional view which cut along the scanning direction of the laser beam the steel plate under welding of an embodiment. (B) The typical sectional view which cut the steel plate under welding of an embodiment along the direction perpendicular to the scanning direction of a laser beam. (A) The typical sectional view which cut along the scanning direction of the laser beam the steel plate after welding of an embodiment. (B) The typical sectional view which cut the steel plate after embodiment along the direction perpendicular to the scanning direction of the laser beam. (A) The typical sectional view which cut the steel plate under welding of comparative example 1 along the scanning direction of the laser beam. (B) A schematic cross-sectional view of the steel plate being welded in Comparative Example 1 cut along a direction orthogonal to the scanning direction of the laser beam. 9 is a table collectively showing Examples and Comparative Examples.

  Hereinafter, a welding method, a welding device, and a welded steel plate according to embodiments of the present invention will be described with reference to the drawings. In the embodiment, as an example, a frame used for a copying machine, a printer product, or the like is formed by overlapping and welding plated steel sheets having excellent corrosion resistance. For example, it is a lap welding frame manufactured using two galvanized steel sheets having a thickness of 1.0 mm.

  FIGS. 1A and 1B are schematic cross-sectional views showing a laser beam irradiation method according to the embodiment and a molten state of two galvanized steel sheets which are workpieces. FIG. 1A is a cross-sectional view of a portion to be irradiated along the scanning direction of laser light, and FIG. 1B is a cross-sectional view of the portion to be irradiated along a direction orthogonal to the scanning direction of laser light. It is sectional drawing. In the figure, 1 is a front steel plate as a first steel plate, 2 is a rear steel plate as a second steel plate, 3 is a laser beam, 4 is a keyhole, 5 and 6 are weld pools, and 7 is a shim which is a spacer. , 8 are gaps, 9 is a laser scanning direction, 10 is a metal vapor flow, and 11 is a cooled and solidified weld bead. As the front steel plate 1 and the rear steel plate 2, for example, a galvanized steel plate is used.

  In the embodiment, the laser light 3 is irradiated from a laser light source (not shown). As the laser light source, for example, a fiber laser having a wavelength of 1070 to 1080 [nm] can be used. Laser light of other wavelengths other than this may be used. A laser beam is generated from a laser oscillator (not shown), and is condensed by a beam scanner and a condensing lens via a laser beam intensity distribution conversion optical system, and the laser beam 3 is applied to the surface of the superimposed frame of the galvanized steel sheet. Irradiate. Instead of a beam scanner, a condensing optical system having a built-in light intensity distribution conversion optical system connected to a fiber laser may be attached to the robot and driven to irradiate the surface of the frame with laser light.

  At the irradiation point of the laser beam 3, zinc on the surface melts and evaporates as the temperature rises, and then the steel plate as the base material melts and evaporates. In a portion where the light intensity is high near the center of the irradiation point of the laser beam 3, the metal evaporates, the molten pool becomes concave due to the reaction force of the evaporation, and a hole called a keyhole 4 is formed. Pond 5 spreads. With the irradiation of the laser beam, the keyhole 4 gradually becomes deeper, penetrates the galvanized steel sheet on the front side, and the zinc in the overlapped portion also melts and evaporates. In the present embodiment, by providing a gap 8 between the two galvanized steel sheets by using a shim 7 or the like, zinc vapor escapes from the gap 8, and the molten steel sheet is blown off to generate spatter. I do not have it. Thus, the keyhole 4 penetrates the front steel plate 1 and reaches the rear steel plate 2. At this time, a molten pool 5 is also formed between the front steel plate 1 and the rear steel plate 2, and the two steel plates are welded.

  In the laser light 3 of the present embodiment, a light intensity distribution is formed in the high intensity laser light near the center and the low intensity laser light around the center by the laser light intensity distribution conversion optical system. A large area molten pool 6 is formed on the surface of the front steel plate 1. In order to form a linear weld bead and increase the welding strength, the laser beam 3 is scanned on the surface of the steel sheet along a laser scanning direction 9 in a linear trajectory, and is applied to the front steel sheet 1 and the rear steel sheet 2. Is formed and welded with a linear weld bead 11. That is, a beam surrounding the high energy beam with low energy is irradiated on the steel sheet while moving in the scanning direction to form a linear weld bead.

  In the present embodiment shown in FIG. 1, a laser beam having a lower power density than the center is irradiated onto a large area which is twice or more the irradiation diameter of the laser beam 3 at the center where the keyhole 4 and the molten pool 5 are formed. Perform welding. In the present embodiment, the surface of the front side steel plate 1 in the periphery of the keyhole 4 is widely heated to form a molten pool also in the periphery, and the pressure of the molten pool to narrow the opening of the keyhole is reduced. , To increase the opening diameter of the keyhole. Since a large opening diameter can be ensured, the pressure at which the metal vapor flow 10 blows out can be reduced, and the molten metal around the keyhole 4 can be prevented from being entangled in the vapor flow and scattered. Further, in the molten pool, the temperature difference between the deep part near the bottom of the keyhole and the shallow part near the surface can be reduced, and convection can be suppressed. Therefore, spatter can be greatly reduced.

Specifically, assuming that the width of a fusion zone that joins the front steel plate 1 and the rear steel plate 2 is C and the width of the fusion zone on the surface of the front steel plate 1 is D, the laser is irradiated under the condition that D> 2C. Light 3 is irradiated.
According to the present embodiment in which a laser beam having a low power density is scanned and irradiated while encircling a laser beam having a high power density, a heated portion of the front steel sheet 1 is so formed that the laser power density gradually increases. The laser light is irradiated. Since the portion located in front of the keyhole in the laser scanning direction 9 is preheated by the laser beam having the low power density, the portion located in front of the keyhole is compared with the case where only the laser beam having the high power density is scanned. A large weld pool is generated stably. Examples and comparative examples will be described later. The present embodiment can reduce the occurrence of sputtering as compared with a case where only a laser beam having a high power density is scanned and irradiated. Compared with the case where a small molten pool and a keyhole grow rapidly due to rapid heating by a laser beam having a high power density, in the present embodiment, the molten pool in front of the keyhole is stable, so that it interferes with the following keyhole. This is because the entrainment in the steam flow is suppressed.

  A galvanized steel sheet welded by performing laser welding according to the present embodiment will be described with reference to the drawings. FIG. 2A is a cross-sectional view of a welded steel plate after welding along a scanning direction of laser light, and FIG. 2B is a welding view after welding along a direction orthogonal to the scanning direction of laser light. It is sectional drawing which cut the steel plate.

  A in FIG. 2B is the width of the weld bead at the joint when the weld is cut in a direction perpendicular to the laser scanning direction. B1 in FIG. 2A is the end point of the laser scanning, that is, the weld bead portion extending outside the joint when the weld is cut along one end of the linear weld bead along the laser scanning direction. Width. B2 in FIG. 2A is a starting point of laser scanning, that is, a weld bead extending outside the joint when the weld is cut along the laser scanning direction at the other end of the linear weld bead. The width of the part.

In the present embodiment, since welding is performed by scanning along the line while encircling the laser beam having a high power density at the center with the laser beam having a lower power density than the center, the width B1 and the width B2 of the welding bead are both larger than the width A. It has the feature of. That is, B1> A and B2> A, and there is a feature that spatter adheres little.
Hereinafter, specific examples of the present embodiment and comparative examples will be described with reference to the drawings.

[Example 1]
In the deep penetration type laser welding of the present embodiment, two galvanized steel sheets having a thickness of 1 [mm] are superposed with a shim having a thickness of 0.3 [mm] therebetween to control the gap, and the wavelength is 1070 [nm]. ] Was used. Nitrogen is used as a shielding gas to prevent oxidation of the molten metal. The shielding gas is not limited to nitrogen, and may be an inert gas such as Ar (argon) or He (helium), or a mixed gas thereof.

The welding conditions are as follows: the laser output of the laser oscillator is 3000 [W], the beam diameter is 0.5 [mm], and the energy density at the peripheral portion is made smaller than that at the central portion by a beam profile conversion optical system. Specifically, the power density (laser output per unit area) within the beam spot diameter of 0.2 [mm] is set to 2.0 × 10 ⁶ [W / cm ² ], and the power density at the outer peripheral portion is set to 7 × 10 ⁶ [W / cm ² ]. 0.0 × 10 ⁵ [W / cm ² ]. The welding speed, that is, the scanning speed of the laser beam is 5 [m / min], the length of the welding bead is 6 [mm], and the flow rate of the shielding gas is 5.0 [l / min] to 30.0 [l / min]. Can be set as appropriate within the range.

  Under the above conditions, the superposed steel sheets were irradiated with a laser beam to obtain a joined body. As a result of measuring the amount of spatter from the change in mass before and after welding of the joined body, the amount of spatter in the example was about 1.8 [mg]. Next, a tensile shear test was performed on the joined body composed of the two obtained steel sheets in order to evaluate welding strength. In the tensile shear test, the tensile shear strength of the joined body was about 309 [kgf].

  The welding bead shapes performed under the above welding conditions are as follows: A in FIG. 2B is about 1.2 [mm], B1 in FIG. 2A is about 1.5 [mm], and B2 is about 1.4 [mm]. [Mm]. B1 and B2 are both A or more.

[Example 2]
In Example 2, the power density within a beam spot diameter of 0.2 [mm] was 1.7 × 10 ⁶ [W / cm ² ], and the power density at the outer peripheral portion was 8.0 × 10 ⁵ [W / cm]. ² ], except that two steel plates were joined under the same conditions as in Example 1. The bonded body thus formed was subjected to the measurement of the spatter amount and the tensile shear test in the same manner as in Example 1. The amount of spatter was about 1.9 [mg], and the tensile shear strength was about 318 [kgf].

  The weld bead shape of Example 2 under the above welding conditions is such that A in FIG. 2B is about 1.2 [mm], B1 in FIG. 2A is about 1.6 [mm], and B2 is about 1 [mm]. .4 [mm]. B1 and B2 are both A or more.

[Example 3]
In the third embodiment, the beam diameter is φ2.0 [mm], the power density within the beam spot diameter 0.2 [mm] is 1.7 × 10 ⁶ [W / cm ² ], and the power density in the outer peripheral portion is 1.7 × 10 ⁶ [W / cm ² ]. Was set to 2.0 × 10 ⁵ [W / cm ² ]. Otherwise, the two steel plates were joined under the same conditions as in Example 1. The bonded body thus formed was subjected to the measurement of the spatter amount and the tensile shear test in the same manner as in Example 1. The sputter amount was about 2.1 [mg] and the tensile shear strength was about 304 [kgf].

  Under the above welding conditions, the weld bead shape of Example 3 is such that A in FIG. 2B is about 1.1 [mm], B1 in FIG. 2A is about 2.4 [mm], and B2 is about 2 [mm]. 0.3 [mm]. B1 and B2 are both A or more.

[Comparative Example 1]
In Comparative Example 1, the power density of the laser beam within the beam spot diameter of 0.2 [mm] was uniformly applied to 2.0 × 10 ⁶ [W / cm ² ], and the outer periphery was irradiated with a small power density. Do not irradiate laser light. The two steel plates were joined under the same conditions as in Example 1 except for the laser light irradiation conditions. The bonded body thus formed was subjected to the measurement of the spatter amount and the tensile shear test in the same manner as in the example. The sputter amount was about 8.4 [mg], and the tensile shear strength of the joined body was about 306 [kgf].

  In the weld bead shape of Comparative Example 1 created under the above welding conditions, A in FIG. 2B is about 1.1 [mm], B1 in FIG. 2A is about 0.9 [mm], and B2 is B in FIG. It is about 0.9 [mm]. B1 and B2 are both smaller than A.

  In the laser welding of Comparative Example 1, as shown in FIG. 3B, when viewed in a cross section in a direction perpendicular to the scanning direction, a weld pool 5 is formed around the keyhole 4 and the periphery, and the vicinity of the irradiation point of the laser beam 3 Is heated by this plasma, and the penetration width of the surface is slightly widened. However, the spread of the penetration width of the surface with respect to the joining portion (through portion) is smaller than that of the embodiment.

  Further, as shown in FIG. 3A, when viewed in a cross section in a direction along the scanning direction, the width of the fusion portion in front of the keyhole in the scanning direction of the laser beam 3 is narrow. Also, the width of the fusion zone behind the keyhole is as wide as that of FIG. 3B, and is smaller than that of the embodiment.

  In Comparative Example 1, the laser beam 3 is mainly irradiated to the tip of the keyhole 4 during laser welding, and heat input occurs, so the temperature near the tip of the keyhole 4 is high. Further, in the molten pool, the molten metal is pushed by the reaction force of the evaporative gas, and convection from the high temperature portion toward the irradiation surface occurs. As a result, the flow of the molten metal is disturbed, and ripples and the like are observed on the surface of the molten pool. At this time, a part of the molten metal is caught in the high-speed metal vapor stream 10 blown out from the keyhole 4 at a high speed, and spatter occurs. Further, when scanning with the laser beam 3, a part of the molten metal existing in the scanning direction loses an escape route, and is caught in the high-speed metal vapor flow 10 blown out from the keyhole 4, thereby generating spatter. The width B1 and the width B2 of the formed weld bead are both smaller than the width A.

[Summary of Examples and Comparative Examples]
FIG. 4 shows the laser beam irradiation conditions, the amount of sputtering, and the bonding strength of Examples 1, 2, and 3 and Comparative Example 1 in a table. It can be seen that Examples 1, 2, and 3 all generate less spatter than Comparative Example 1 and realize the same or higher bonding strength.

  As described above, according to the present invention, a laser beam having a low power density such that a keyhole is not generated around the periphery while forming a deep melt with a laser having a high power density at the center to secure good bonding strength. Heat with. Thereby, the temperature distribution is reduced, the turbulence of the convection of the molten pool is suppressed, and the spatter generated when the molten metal is caught in the high-speed steam ejected from the keyhole can be reduced.

[Other embodiments]
Embodiments of the present invention are not limited to the embodiments described above, and many modifications and combinations are possible within the technical idea of the present invention.
For example, an object to be welded is not limited to a galvanized steel sheet, but can be applied to other metals or overlap welding of a metal and a resin. Further, the present invention is applicable not only to lap welding but also to butt welding.

1 front steel plate / 2 back steel plate / 3 laser beam / 4 keyhole / 5 molten pool / 6 molten pool / 7 shim / 8 ... Gap / 9 ... Laser scanning direction / 10 ... Metal vapor flow / 11 ... Cooled and welded bead / A ... When cut in a direction perpendicular to the laser scanning direction Width of weld bead at joint / B1... Width of weld bead portion extending outside the joint when cut along the laser scanning direction at the end point of laser scanning / B2. The width of the weld bead that extends outside the joint when cut along the laser scanning direction at the start of irradiation

Claims (4)

Stack the first steel sheet and the second steel sheet,
Irradiating the first steel plate while moving a beam surrounded by low energy around the high energy beam in the scanning direction,
Melting the irradiation part of the high energy beam to form a keyhole, the high energy beam irradiating the keyhole penetrates the first steel plate and irradiates the second steel plate; Welding the steel sheet and the second steel sheet,
In the cross section of the welded portion in a direction perpendicular to the scanning direction, the width of the fusion zone at the joint between the first steel plate and the second steel plate is C, and the width of the fusion zone at the surface of the first steel plate is C D
D> 2C,
A welding method characterized in that: Stack the first steel sheet and the second steel sheet,
Irradiating the first steel sheet while scanning in the scanning direction a beam surrounding the high energy beam with low energy,
Melting the irradiation part of the high energy beam to form a keyhole, the high energy beam irradiating the keyhole penetrates the first steel plate and irradiates the second steel plate; Welding the steel sheet and the second steel sheet,
In a cross section of the welded portion cut in a direction orthogonal to the scanning direction, a width of a weld bead at a joint between the first steel plate and the second steel plate is A,
In a cross section obtained by cutting the welded portion along the scanning direction, at an end point where the scanning of the beam is completed, the width of a weld bead extending outward on the surface of the first steel plate beyond the joint portion is set to B1. age,
In a cross section obtained by cutting the welded portion along the scanning direction, at a start point where the beam scanning is started, a width of a weld bead extending outward on the surface of the first steel plate beyond the joint portion is set to B2. And when
B1> A and B2> A,
A welding method characterized in that: A welded steel plate obtained by welding a first steel plate and a second steel plate along a line,
In a cross section obtained by cutting a welded portion in a direction perpendicular to the line, a width of a weld bead at a joint between the first steel plate and the second steel plate is A,
In a cross section obtained by cutting the welded portion along the line, at one end of the line, a width of a weld bead extending outward on the surface of the first steel plate from the joint portion is B1,
In a cross section obtained by cutting the welded portion along the line, at the other end of the line, when the width of a weld bead extending outward on the surface of the first steel plate from the joint is B2,
B1> A and B2> A,
A welded steel sheet, characterized in that: A welding device for overlapping and welding a first steel plate and a second steel plate,
Irradiating the first steel sheet while scanning in the scanning direction a beam surrounding the high energy beam with low energy,
Melting the irradiation part of the high energy beam to form a keyhole, the high energy beam irradiating the keyhole penetrates the first steel plate and irradiates the second steel plate; Welding the steel sheet and the second steel sheet,
In a cross section of the welded portion cut in a direction orthogonal to the scanning direction, a width of a weld bead at a joint between the first steel plate and the second steel plate is A,
In a cross section obtained by cutting the welded portion along the scanning direction, at an end point at which scanning of the beam is completed, the width of a weld bead extending outward on the surface of the first steel plate beyond the joint portion is set to B1. age,
In a cross section obtained by cutting the welded portion along the scanning direction, at a start point where scanning of the beam is started, a width of a weld bead extending outward on the surface of the first steel plate from the joint portion is set to B2. And when
Irradiating the beam such that B1> A and B2> A,
Welding equipment characterized by the above-mentioned.

Images