JP2009148781A - Laser welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser welding method capable of efficiently performing stable welding excellent in welding quality irrespective of the size of a gap of a lap portion of a plurality of metal plates having a low melting point metal plating layer formed thereon by irradiating a welding target portion of the lap portion with a laser beam. <P>SOLUTION: The method includes: a first step of laser-welding the entire region of a welding target portion 14 of a lap portion 25 of a plurality of steel plates 16, 17 to a "×" type welding pattern 18 to be preheated and removing a zinc plating layer on the entire region of the welding target portion 14 by evaporation; and a second step of laser-welding the entire region to a "○" type welding pattern 19 passing through the outer end of the "×" type welding pattern 18 in a state where the entire region of the welding target portion 14 is pre-heated with the "×" type welding pattern 18. In this way, the amount of molten metal in pattern welding increases, and welding can be stably executed even if the gap of the lap portion 25 of the steel plates 16, 17 is large. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser welding method in which a plurality of metal plates are welded in a spot shape by irradiating a laser beam onto an overlapping portion of metal plates, and in particular, laser welding patterns having various shapes on a welding target portion of the overlapping portion. Weld.

  In laser welding, a plurality of metal plates can be welded in a spot shape by irradiating a superposed portion of the metal plates with a high energy density heat source of a narrow beam spot. Compared to spot welding, which is conventionally used for joining car bodies, etc., laser welding is non-contact welding, so it does not require an interference avoidance operation that avoids interference between the spot gun, jig and workpiece, unlike spot welding. So it is a highly efficient welding method.

  However, when welding by irradiating the laser beam to the welded part of the overlapped part of a plurality of galvanized steel sheets, if there is no gap in the overlapped part, the melting point of zinc is lower than the melting point of iron, so solidification is delayed, Immediately before or during the melting of the steel sheet, the zinc is evaporated in the welded part, and the zinc vapor vapor blows away the surrounding molten metal by pressure in the welded part. Is formed. In addition, the zinc vapor is left in the melted portion and becomes bubbles (blowholes or pits), resulting in a decrease in welding strength. On the other hand, when the gap between the steel plates is large, melt-off (edge breakage) occurs, and the welding target portion of the steel plate is not sufficiently joined, resulting in a decrease in welding strength.

In order to solve the above-described problems, Patent Document 1 discloses a laser welding method including a pre-process by series welding and laser light irradiation and a main welding process by laser welding in advance. In this laser welding method, in the series welding process, the resistance spot welding electrode is pressed from one side of the joining region of the galvanized steel sheet to evaporate and remove zinc, thereby forming the zinc removal region. Next, in the laser light irradiation step, the zinc removal region is irradiated with laser light in an in-focus or defocused state to remove zinc remaining in the zinc removal region and surrounding zinc, thereby widening the zinc removal region. In the main welding process, the zinc removal region is irradiated with laser light in a just-focus state to melt-bond a plurality of galvanized steel sheets.
JP 2006-110565 A

The laser welding method of Patent Document 1 is an inefficient welding method because the galvanized steel sheet is welded by a combination of series welding by resistance spot welding and laser welding, so that the process is complicated and a pre-processing process is required. It is. In addition, since the formation of the zinc removal region depends on the processing efficiency of the pre-processing, the accuracy of this pre-processing has a great influence on the welding quality of laser welding, and there is a risk of reducing the merit of laser welding. is there.
An object of the present invention is to irradiate a laser beam to a welding target portion of an overlapping portion of a plurality of metal plates on which low melting point metal plating is formed, regardless of the size of the gap between the overlapping portions of the metal plates. Provided is a laser welding method capable of efficiently performing stable welding with excellent quality.

  The laser welding method according to claim 1, wherein a plurality of metal plates including a metal plate on which a low melting point metal plating is formed are stacked, and a laser beam is irradiated to the overlapping portion of the metal plates to weld the plurality of metal plates in a spot shape. In the laser welding method, the laser beam is irradiated so as to form a first welding pattern in which the entire area of the welding target portion can be preheated in a region inside the outer periphery of the welding target portion having a substantially circular outer shape of the metal plate. A first step of welding and a second step of welding by irradiating with laser light so as to form an annular second welding pattern along the outer peripheral portion of the welding target portion are provided.

  In this laser welding method, a plurality of metal plates including a metal plate on which a low melting point metal plating is formed are overlapped, and in the first step, laser is applied in a region inside the outer periphery of the welding target portion of the overlapped portion of the metal plates. Light is irradiated to form a first welding pattern. Next, in the second step, since the entire area of the welding target portion is preheated by the first welding pattern, laser light is irradiated along the outer peripheral portion of the welding target portion to form an annular second welding pattern. The low melting point metal plating can be evaporated at the time of the first welding pattern welding, and the amount of molten metal at the time of the second welding pattern processing can be increased.

  The laser welding method according to claim 2 is the laser welding method according to claim 1, wherein the first welding pattern includes a plurality of linear welding patterns intersecting at the center of the welding target portion, and the second welding pattern includes a plurality of linear welding patterns. It consists of the annular welding pattern which passes an outer side edge part, It is characterized by the above-mentioned.

  According to a third aspect of the present invention, there is provided a laser welding method according to the first aspect of the invention, wherein the first welding pattern is an annular welding pattern centered on the center of the welding target portion and surrounding an area of about 1/2 of the area of the welding target portion. It is characterized by becoming.

According to a fourth aspect of the present invention, there is provided the laser welding method according to the first aspect, wherein the first welding pattern is a spiral welding pattern that is spirally connected to the second welding pattern.
A laser welding method according to a fifth aspect is characterized in that, in any of the first to fourth aspects of the invention, the metal plate on which the low melting point metal plating is formed is a steel plate on which galvanization is formed.

  According to the first aspect of the present invention, in the first step, the outer shape of the metal plate becomes a first welding pattern in which the entire area of the welding target portion can be preheated in a region inside the outer periphery of the welding target portion having a substantially circular shape. In the second step, welding is performed by irradiating the laser beam so as to form an annular second welding pattern along the outer peripheral portion of the welding target portion. Laser welding that efficiently performs good welding with stable welding quality regardless of the size of the gap between the overlapping portions of the metal plates can be realized without requiring a pre-processing step for removal.

  That is, since laser welding is performed so that the entire welding target portion has a first welding pattern that can be preheated, the low melting point metal plating in the entire welding target portion can be removed by evaporation. In addition, since the entire area of the welding target portion is preheated by the first welding pattern, laser welding is performed so that an annular second welding pattern is formed along the outer peripheral portion of the welding target portion. Even when the amount of metal increases and the gap between the overlapping portions is large, welding can be stably performed. In addition, it is possible to supply molten metal to the defective part of the welding target part due to the explosion of the low melting point metal plating that occurs when there is no gap in the overlapped part, reducing the occurrence of internal defects and reliably preventing welding defects I can.

  According to invention of Claim 2, the 1st welding pattern consists of a some linear welding pattern which cross | intersects at the center of a welding object part, and the 2nd welding pattern passes the outer side edge part of a some linear welding pattern. Since it consists of an annular welding pattern, the whole area of the welding object can be preheated almost uniformly by a plurality of linear welding patterns, and the low melting point metal plating of the welding object can be reliably removed by evaporation. Also, since the welding of the annular welding pattern is performed in a state where the entire area of the welding target portion is preheated by the plurality of linear welding patterns, even when the amount of molten metal during welding increases and the gap between the overlapping portions is large Stable welding can be performed. Further, when there is no gap in the overlapped portion, the molten metal can be supplied to the defective portion due to the explosion of the low melting point metal plating, and a joint portion with high welding strength can be formed.

  According to invention of Claim 3, since the 1st welding pattern consists of an annular welding pattern centering on the center of a welding object part, and enclosing the area of about 1/2 of the area of a welding object part, The entire region can be preheated evenly, and the low-melting point metal plating of the welding target portion can be reliably removed by evaporation. In addition, the same effects as those of the first aspect are obtained.

  According to the invention of claim 4, since the first welding pattern is a spiral welding pattern that is spirally connected to the second welding pattern, the entire area of the welding target portion can be preheated almost uniformly and the low melting point of the welding target portion. Metal plating can be reliably removed by evaporation. In addition, the same effects as those of the first aspect are obtained.

  According to the invention of claim 5, since the metal plate on which the low melting point metal plating is formed is a steel plate on which galvanization is formed, a welded portion of a galvanized steel plate having excellent welding quality and high antirust effect is formed. be able to. In addition, the same effects as in the first to fourth aspects are achieved.

  The present embodiment is a laser welding method in which a plurality of metal plates including a metal plate on which a low melting point metal plating is formed are overlapped, and a laser beam is irradiated to the overlapped portion of the metal plates to weld the plurality of metal plates in a spot shape. This is an example when the present invention is applied.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the laser welding apparatus 1 includes a laser oscillator 2, a scanner processing head 3, and a control device 4 for controlling them.
The laser oscillator 2 outputs laser beams LA having various energy densities based on an output control command instructed from the control device 4. The laser beam LA output from the laser oscillator 2 is transmitted to the scanner processing head 3 via the transmission fiber 5. At this time, the laser beam LA having a spread angle depending on the laser oscillator 2 and the transmission fiber 5 is transmitted to the scanner processing head 3.

The scanner processing head 3 adjusts the focus of the laser beam LA output from the laser oscillator 2 according to the laser beam position control command from the control device 4, and the laser beam is applied to the welding target portion 14 in the metal plate overlapping portion 25. LA is irradiated to form a weld locally. Here, examples of the laser beam LA include a YAG laser and a CO ₂ laser, and the YAG laser is more excellent in absorbing light energy with respect to metal than the CO ₂ laser.

  In the casing 6 of the scanner processing head 3, a movable collimating lens 7, a fixed mirror 8, a movable mirror 9, a condensing lens 10, a cover slide 11 and the like are disposed. The collimating lens 7 is a lens that collimates the laser beam LA in order to condense the laser beam LA by the condensing lens 10, and the inside of the casing 6 is moved in the vertical direction (Z-axis direction) by an actuator (not shown). It is movable.

  The movable mirror 9 is provided so as to be tiltable in the X-axis direction and the Y-axis direction by the X-axis motor 12 and the Y-axis motor 13. The X-axis motor 12 and the Y-axis motor 13 are constituted by servo motors or the like. The laser beam LA transmitted to the collimating lens 7 is reflected by the fixed mirror 8 toward the movable mirror 9, and is reflected by the X-axis motor 12 and the Y-axis motor 13 from the movable mirror 9 whose mirror angle is changed, and thereby the condenser lens 10. It is condensed with. Therefore, the laser beam LA that has been collected can be irradiated to the welding target portion 14 of the overlapping portion 25 of the plurality of metal plates while moving at high speed by changing the angle of the movable mirror 9 to form a laser welded portion. It becomes possible.

  As shown in FIG. 1, the focal length FL in the Z-axis direction, which is the distance from the condenser lens 10 to the position where the laser beam LA is most condensed, is adjusted by the vertical movement of the collimator lens 7 and the condenser lens 10. Is done. The portion with the smallest outer diameter of the laser spot diameter becomes a heat source portion with a high energy density, and the energy density of the laser beam LA decreases as the distance from the heat source portion increases. The scanner processing head 3 can be attached to a robot arm (not shown) as required.

  The output control of the laser oscillator 2 by the control device 4 is configured such that the energy density of the laser beam LA is adjusted in synchronism with the position control command of the scanner processing head 3. Switching between the low-density energy laser beam LA and the high-density energy laser beam LA is performed by transmitting an electrical signal from the control device 4 to the laser oscillator 2.

Next, a laser welding method using the above laser welding apparatus 1 will be described.
As the metal plate, steel plates 16 and 17 on which zinc plating 15 of a low melting point metal lower than the melting point of iron is formed are employed. The steel plates 16 and 17 on which the galvanized plate 15 is formed have rust prevention performance and are used in various fields such as automobile bodies. Zinc has a melting point of 419.5 ° C. and a boiling point of 930 ° C. Iron has a melting point of 1535 ° C and a boiling point of 2750 ° C.

  As shown in FIGS. 1 and 2, a superposition of the upper steel plate 16 and the lower steel plate 17 on which the galvanizing 15 is formed is handled by a robot (not shown), and the irradiation range A of the laser welding apparatus 1 is reached. Deploy. For example, the irradiation range A is 300 mm in diameter, and the outer diameter of the laser spot is 0.6 mm. The position of the scanner processing head 3 itself is fixed. Next, the laser beam LA is irradiated to the welding target portion 14 of the overlapping portion 25 of the upper steel plate 16 and the lower steel plate 17 to weld a plurality of galvanized steel plates in a spot shape.

  In the first step, focusing on the spot welding diameter in the region inside the outer periphery of the welding target portion 14 whose outer shape is substantially circular, the upper surface of the upper steel plate 16 has a melting point of iron (1535 ° C.) or higher. A laser beam LA having a high energy density is irradiated. Then, the laser beam LA is moved and irradiated at a high speed by changing the angle of the movable mirror 9 along the spot welding diameter, and the laser welding LA is applied to the spot welding diameter at the center of the welding target portion 14. A plurality of intersecting linear welding patterns (first welding patterns), for example, a “×” type welding pattern 18 shown in FIG. 3 is formed, and heat at the time of “×” type welding pattern welding is a portion to be welded. It spreads toward the outer peripheral side of 14, and the whole region of the welding object part 14 is heated substantially.

  At the time of laser welding, if there is no gap in the overlapping portion 25 of the upper steel plate 16 and the lower steel plate 17, the melting point of zinc is lower than the melting point of iron and solidification is delayed immediately before or during melting of the steel plate. The zinc plating 15 of 14 evaporates, and this zinc vapor remains as bubbles (blowholes or pits) in the welding target portion 14 or blows off the surrounding molten metal by pressure and blows away. By this explosion, the zinc plating 15 of the welding target portion 14 is removed to the outside. Defects such as holes due to explosions are formed in the welding target portion 14. On the other hand, when the gap between the overlapping portions 25 of the upper steel plate 16 and the lower steel plate 17 is large, the zinc plating 15 evaporated during laser welding is discretely removed from the welding target portion 14 toward the outer peripheral side.

  Next, in the second step, the outer peripheral portion of the welding target portion 14 is focused, and the upper surface of the upper steel plate W1 is irradiated with a laser beam LA having a high energy density. Then, the laser beam LA is moved and irradiated at high speed along the outer peripheral portion of the welding target portion 14 due to the change in the angle of the movable mirror 9, and passes through the outer end portions of the plurality of linear welding patterns by this laser welding. An annular welding pattern (second welding pattern), for example, as shown in FIG. 3, a “◯” shaped annular welding pattern 19 that passes through the outer end of the “×” shaped welding pattern is formed. . As a result, a weld portion having a weld pattern in which a “◯” shape is locally formed around the “x” shape is formed in the overlapping portion 25 of the upper steel plate 16 and the lower steel plate 17.

  During laser welding, the amount of molten metal is increased by performing laser welding in a state where the entire welding target portion 14 is preheated, and there is no gap in the overlapping portion 25 of the upper steel plate 16 and the lower steel plate 17. Molten metal is supplied to the defect site | part of the welding target part 14 by the explosion of the zinc plating 15 of the generated welding target part 14. FIG. Further, the bubbles remaining in the welding target portion 14 are reheated to evaporate and become discrete.

  On the other hand, when the gap between the overlapping portion 25 of the upper steel plate 16 and the lower steel plate 17 is large, since the laser welding is performed in a state in which the entire area of the welding target portion 14 is preheated, the amount of molten metal is increased, and in a stable state. The welding joining by laser welding will be performed.

Next, the effect verification test of the joint part of the various welding patterns laser-welded by the laser welding method of the Example mentioned above is demonstrated based on FIG.
[Work material]
A 440 galvanized steel sheet having a thickness of 1.4 mm was prepared as a metal plate.
[Welding method]
Based on the laser welding method using the laser welding apparatus 1 described above, a plurality of galvanized steel plates are overlapped, and laser light LA having an energy density equal to or higher than the melting point of iron is applied to the welding target portion 14 of the overlapped portion of the galvanized steel plates. Irradiation was performed, and a plurality of galvanized steel sheets were melt-joined in a spot shape.

[Welding pattern]
After welding the “×” type welding pattern, the joint portion of the “◯” type annular welding pattern (25.7 mm welding) passing through the outer end portion of this “×” type welding pattern was welded. As welding patterns of the comparative examples, the joints of a linear welding pattern (20 mm welding) and a C-shaped welding pattern (20 mm welding) were welded respectively.

[Test and evaluation of bonding strength]
The tensile shear strength of the joints of various shapes of weld patterns was measured. As shown in FIG. 4, when there is a gap (0.1 mm to 0.4 mm) that allows zinc vapor to escape from the welding target part in the overlapping part of the steel plates, the joints of all the welding patterns exhibit high shear strength. It was. On the other hand, when there was no gap in the overlapped portion of the steel plates (0.0 mm) or when the gap was large (0.5 mm to 0.8 mm), only the joint portion of the welding pattern of the example showed high shear strength. On the other hand, in the joint portion of the linear type or C-shaped welding pattern, the shear strength decreases as the gap between the overlapping portions of the steel plates increases. In particular, when the size of the gap between the overlapping portions is 0.5 mm or more, it is considered that the edge breakage or the welding target portion of the steel plate is not sufficiently welded and a welding failure occurs.

  From this verification test result, two effects could be confirmed by welding the welding pattern of the example. The first effect is that X-type welding provides a preheating effect and galvanizing removal effect on the welded part 14, and the amount of molten metal is increased by ○ -type welding in the preheating state, which occurs during X-type welding. It can be confirmed that molten metal is supplied to defective parts such as perforations due to galvanized explosion of the welded part, and a weld with high welding strength is formed even when there is no gap in the overlapped part of the steel plates It was. Also, as a second effect, robust welding is possible even when the amount of molten metal during ○ -type welding increases due to the preheating effect in X-type welding and the gap between the overlapping parts of the steel plates is large, and high bonding is achieved. It was confirmed that a joint having strength was formed. Furthermore, the effect of reducing the occurrence of spatter during ○ -type welding was also confirmed by the preheating effect in X-type welding.

The effect of the laser welding method of the Example demonstrated above is demonstrated.
In the first step, laser welding is performed so that the entire area of the welding target portion 14 has an “×” type welding pattern 18 that can be preheated, so that the zinc plating 15 in the entire area of the welding target portion 14 can be removed by evaporation. Further, in the second step, in the state where the entire area of the welding target portion 14 is preheated by the “×” type welding pattern 18, Therefore, even if the amount of molten metal at the time of welding pattern welding is increased and the gap between the overlapping portions 25 of the steel plates 16 and 17 is large, welding can be performed stably.

  In addition, molten metal can be supplied to a defective portion such as a hole in the welding target portion 14 due to the blasting of the zinc plating 15 that occurs when there is no gap in the overlapping portion 25 of the steel plates 16 and 17, thereby reducing the occurrence of internal defects. In addition, it is possible to reliably prevent welding defects. As a result, regardless of the size of the gap between the overlapping portions 25 of the steel plates 16 and 17, laser welding excellent in welding quality and stable can be performed efficiently.

Next, a modified example in which the above embodiment is partially modified will be described.
1) The welding pattern is not limited to the shape shown in the embodiment, and various types of welding patterns can be applied. In particular, the heat during the first welding pattern welding is from the center of the welding target portion 14 to the outer periphery. A welding pattern that spreads radially is effective.

  For example, as shown in FIG. That is, the first welding pattern is centered on the center of the welding target portion 14 and is to be welded so that the preheating at the time of the first welding pattern welding is uniformly transmitted to the first welding pattern region and the second welding pattern region. The annular welding pattern 21 is formed of an annular welding pattern 21 that surrounds an area that is approximately ½ of the area of the portion 14. By this welding pattern, the preheating effect in which the heat at the time of the first welding pattern welding spreads over the entire area of the welding target portion 14 and the galvanization evaporation removing effect are obtained, and the amount of molten metal at the time of the second welding pattern welding is increased. A robust welded portion can be formed with respect to the gap between the welded portions 14 of the steel plates 16 and 17.

  In this case, when the radius of the first welding pattern is xR and the radius of the second welding pattern is R, the radius of the first welding pattern is about 0 with respect to the radius R of the second welding pattern. .707R, it is considered that the first welding pattern region and the second welding pattern region are preheated equally by the first welding pattern surrounding a half area of the welding target portion 14.

2] Alternatively, as shown in FIG. In other words, the first welding pattern may be a spiral welding pattern 22 that is spirally connected to the second welding pattern 23. By this welding pattern, the preheating effect that the heat at the time of the first welding pattern welding spreads over the entire area of the welding target portion 14 and the galvanization evaporation removing effect are obtained, and the amount of molten metal at the time of the second welding pattern welding is increased.

3] In the embodiment, the low melting point metal plating is the zinc plating 15. However, zinc alloy plating, magnesium alloy plating having a boiling point of 109 ° C., aluminum alloy plating, etc. may be used. The present invention can be applied to any low melting point metal plating having a melting point lower than that of the base material.

4] In the example, the welding target portion 14 of the upper steel plate 16 and the lower steel plate 17 on which the zinc plating 15 was formed was laser-welded, but the upper steel plate on which the zinc plating 15 was not formed and the zinc plating were formed. The welding target portion 14 of the lower steel plate 17 may be laser welded. Further, the lower steel plate may be a plurality of sheets, and they may be formed with galvanization or not formed.

5] The laser welding method of the present invention can be applied to production lines of automobiles, railway vehicles, aircrafts, etc., and is not intended to limit the field of application or the range of uses.
6] In addition, those skilled in the art can implement embodiments in which various modifications are added to the embodiment without departing from the spirit of the present invention, and the present invention includes such modifications. is there.

It is a figure which shows the outline | summary of a laser welding apparatus, and the outline | summary of a scanner processing head. It is an expansion perspective view of the welding object part of the overlap part of a galvanized steel plate. It is an enlarged view of the 1st welding pattern and the 2nd welding pattern. It is data which shows the tensile shear strength of a junction part. It is a figure which shows the welding pattern which concerns on a change form. It is a figure which shows the welding pattern which concerns on a change form.

Explanation of symbols

LA laser beam 14 welding target portion 15 galvanized 16, 17 steel plates 18, 21, 22 first welding pattern 19, 23 second welding pattern
25 Superposition part

Claims (5)

In a laser welding method in which a plurality of metal plates including a metal plate on which a low-melting point metal plating is formed are overlapped, and a plurality of metal plates are welded in a spot shape by irradiating a laser beam on the overlapping portion of the metal plates,
A first step of welding by irradiating a laser beam in a region on the inner side of the outer periphery of the welding target portion having a substantially circular outer shape of the metal plate so as to form a first welding pattern capable of preheating the entire welding target portion. When,
Next, a laser welding method comprising: a second step of welding by irradiating a laser beam so as to form an annular second welding pattern along the outer peripheral portion of the welding target portion.   The first welding pattern is composed of a plurality of linear welding patterns intersecting at the center of the welding target portion, and the second welding pattern is composed of an annular welding pattern passing through the outer ends of the plurality of linear welding patterns. The laser welding method according to claim 1, wherein:   2. The laser welding method according to claim 1, wherein the first welding pattern is formed of an annular welding pattern that is centered on the center of the welding target portion and surrounds an area that is approximately ½ of the area of the welding target portion. .   2. The laser welding method according to claim 1, wherein the first welding pattern is a spiral welding pattern that is spirally connected to the second welding pattern.   The laser welding method according to any one of claims 1 to 4, wherein the metal plate on which the low melting point metal plating is formed is a steel plate on which galvanization is formed.

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