JP7059803B2 - Lap welding method - Google Patents

Description

The present invention relates to a superposition welding method in which three or more metal plates constituting a member around a door opening of an automobile body are superposed and welded.

Conventionally, in the case of an automobile body, in order to improve the torsional rigidity of the body and reduce the amount of deformation in the event of a vehicle collision, the members around the door opening (various pillars, etc.) are made of multiple metal plates. It has a closed cross section structure. For example, a surface plate as a skin material is welded to the surface of a skeleton member having a closed cross-sectional structure. Therefore, as a member around the door opening, it is necessary to integrally weld three or more metal plates.

Patent Document 1 discloses that three metal plates are integrally joined by spot welding. Specifically, the center pillars that make up the vehicle body are composed of a center pillar inner panel, a center pillar outer reinforcement, and a side outer panel, and are closed by a center pillar outer reinforcement with a hat-shaped cross section and a center pillar inner panel with a substantially flat plate shape. Along with forming a cross-sectional structure, a side outer panel with a hat-shaped cross section is welded to the outside of the center pillar outer reinforcement. More specifically, the flange portions formed on the outer edges in the width direction of each panel are overlapped with each other, and these flange portions are integrally joined by spot welding.

Japanese Unexamined Patent Publication No. 2014-73769

However, when three or more metal plates (in the case of Patent Document 1, the center pillar inner panel, the center pillar outer reinforcement and the side outer panel) are joined only by spot welding, the welding nugget formed by this spot welding is used. Since it is necessary to form over each metal plate, it is necessary to increase the diameter of this weld nugget. Therefore, it is necessary to increase the width dimension of the flange portion of each panel (larger than the required diameter of the welding nugget), the center pillar becomes large, and it is difficult to reduce the weight of the vehicle body.

In addition, when most of the rigidity of the vehicle body is borne by the closed cross-sectional structure composed of the center pillar inner panel and the center pillar outer reinforcement, it is preferable to reduce the thickness of the side outer panel to reduce the weight of the vehicle body. When trying to form a welded nugget, there is a limit to how thin the side outer panel can be. That is, in general, the weld nugget is formed in the substantially central portion in the plate thickness direction of each of the overlapped panels. Therefore, when trying to form a weld nugget even on the side outer panel, a certain amount of plate is also formed on this side outer panel. Thick dimensions are required. This also made it difficult to reduce the weight of the vehicle body. Specifically, if the ratio of the plate thickness dimension of the side outer panel to the total plate thickness dimension (the plate thickness dimension of the entire superimposed panel) is less than 1/5, a weld nugget is formed even on the side outer panel. Will be difficult. For this reason, when joining metal plates to each other only by spot welding, it is necessary to set this ratio to 1/5 or more, and there is a limit to reducing the thickness of the side outer panel and reducing the weight of the vehicle body.

The present invention has been made in view of this point, and an object thereof is to reduce the weight of the vehicle body while obtaining sufficient vehicle body rigidity when three or more metal plates are laminated and welded. It is an object of the present invention to provide a feasible lap welding method.

The solution of the present invention for achieving the above object is a surface plate located on the vehicle body surface side, which constitutes a member around the door opening of the vehicle body, and a first surface plate adjacent to the vehicle interior side of the surface plate. Each of three or more metal plates including the vehicle body structure plate and the second vehicle body structure plate adjacent to the vehicle interior side of the first vehicle body structure plate extends along the opening edge of the door opening. A flange portion that is continuous with the outer edge of the main body portion and extends along the opening edge of the door opening is provided, and the flange portions of the metal plates are overlapped with each other, and these flange portions are overlapped with each other. Welding is premised on the lap welding method. Then, in this lap welding method, the flange portion of the first vehicle body structure plate is overlapped with the flange portions of the first vehicle body structure plate, the second vehicle body structure plate, and the surface plate . And the flange portion of the second vehicle body structural plate are joined by spot welding at a plurality of locations along the opening edge of the door opening, and after the spot welding step, welding by the spot welding is performed. At a plurality of locations including the locations between the locations, the flange portion of the surface plate and the flange portion of the first vehicle body structural plate , each of which is irradiated with a laser beam from the surface plate side and melted by the laser beam. A molten pool made of molten metal is agitated by scanning the laser beam to perform a laser welding step of joining the flange portion of the surface plate and the flange portion of the first vehicle body structural plate, and the laser is performed. The center position of the laser welded portion in the welding process is in the width direction orthogonal to the direction along the opening edge of the door opening in each of the flange portion of the surface plate and the flange portion of the first vehicle body structure plate. It is set to a position closer to the main body than the center position of the main body and to a position closer to the main body than the center position in the width direction in the welding nugget generated by spot welding in the spot welding step. The welding pitch of the laser welded portion in the laser welding step is set to be smaller than the welding pitch of the welded portion in the spot welding step .

Due to this specific matter, when the surface plate, the first vehicle body structure plate, and the second vehicle body structure plate constituting the members around the door opening of the vehicle body are overlapped and welded, first, these metal plates are overlapped with each other. In this state, the first vehicle body structure plate and the second vehicle body structure plate are joined by spot welding at a plurality of locations along the opening edge of the door opening. After that, laser welding is performed by irradiating laser light from the surface plate side at a plurality of locations including the locations between the welded portions in this spot welding to join the surface plate and the first vehicle body structural plate. In the laser welding at this time, the molten metal made of the molten metal of the surface plate and the first vehicle body structure plate melted by the laser beam is agitated by scanning the laser beam. As a result, the surface tension of the molten metal forming the molten pool causes the molten metal to gather together and intervene between the surface plate and the first vehicle body structural plate, and these surface plates and the first body structure plate are intervened. It is welded to the vehicle body structure plate.

In the spot welding step, since the welded portion is sandwiched by the spot welded electrode, the deformation of the surface plate due to this causes the surface plate and the first vehicle body structural plate to be in the region between the spot welded portions. The gap between them tends to be large, but due to the stirring of the molten pool by scanning the laser beam described above, the molten metal fills the gap between the surface plate and the first vehicle body structural plate, and these surface plates and the first The vehicle body structure plate of No. 1 will be welded well.

It should be noted that this laser welding is also effective when there is no gap between the surface plate and the first vehicle body structural plate. That is, when the metal plate is a galvanized steel plate, in the conventional general laser welding, when there is no gap between the surface plate and the first vehicle body structural plate, zinc vapor is generated inside the molten metal. There was a risk of explosion and a hole in the joint, but according to the laser welding according to this solution, there is no gap between the surface plate and the first vehicle body structural plate. However, the zinc vapor is satisfactorily discharged by stirring the molten pool, and it is possible to suppress the formation of holes in the joint portion.

As described above, according to the lap welding method according to the present solution, three or more metal plates can be integrally joined by the combined use of spot welding and laser welding. That is, since it is not necessary to join three or more metal plates only by spot welding, it is not necessary to increase the diameter of the welding nugget (since it is not necessary to form a welding nugget over each metal plate, the welding nugget is not required). It is not necessary to increase the diameter of the metal plate), and the width dimension of the joint portion (for example, the flange portion) of each metal plate can be reduced to reduce the weight of the vehicle body. Further, since the surface plate and the first vehicle body structure plate are joined by laser welding, it is not necessary to form a welding nugget in the surface plate by spot welding, and the wall thickness of the surface plate can be reduced. This also makes it possible to reduce the weight of the vehicle body. Then, in spot welding, the welding pitch may be reduced because there is a possibility that a current flowing through the welded portion to be welded may flow into an already welded welded portion existing in the vicinity of the welded portion. Although there were restrictions, it is possible to secure sufficient vehicle body rigidity by using laser welding that is not restricted by this welding pitch. As described above, according to the present solution, when three or more metal plates are superposed and welded, it is possible to reduce the weight of the vehicle body while obtaining sufficient vehicle body rigidity.

Further, the condition of the laser beam in the laser welding step is such that the surface plate and the first vehicle body structure plate can form the molten pool without the laser beam penetrating the surface plate. It is preferable that the value is set to melt.

According to this, in the laser welding process, the surface plate and the first vehicle body structure plate are melted with the minimum amount of laser light energy required to form a molten pool. It can be welded to the structural plate.

Further, at least one of the first vehicle body structure plate and the second vehicle body structure plate is made of an ultra-high tension steel plate, and the surface plate is larger than the first vehicle body structure plate and the second vehicle body structure plate. In the case of a steel plate having a low hardness, in the laser welding step performed after the spot welding step, the surface plate and the first first are irradiated with a laser beam to the outside of the heat-affected zone around the welded portion in the spot welding. It is preferable to join the body structure plate of the above. The ultra-high-strength steel plate referred to here is, for example, an ultra-high-tensile material or a hot stamping material.

Generally, when an ultra-high-strength steel plate is spot-welded, the heat-affected zone around the welded portion has a lower hardness than the base metal (the portion not affected by heat) due to the influence of heat generated during welding. In such a portion where the hardness is low, stress tends to be concentrated when an external force is applied, and there is a possibility that sufficient member strength cannot be secured. In view of this point, in the present solution, by performing a laser welding process, the outside of the heat-affected zone around the welded portion in spot welding is heated (heat-affected zone), so that the periphery of the heat-affected zone is tempered. Therefore, the hardness of this portion can be brought close to the hardness of the heat-affected zone. As a result, stress is less likely to be concentrated on the heat-affected zone when an external force is applied, and the strength of the member can be improved.

In the present invention, when three or more metal plates including a surface plate, a first body structure plate and a second body structure plate are overlapped and welded, the first body structure plate and the second vehicle body are welded by spot welding. After joining with the structural plate, the surface plate and the first vehicle body structure melted by irradiating the laser beam from the surface plate side at a plurality of locations including the portion between the welded portions in this spot welding. A molten pool made of molten metal of the plate is agitated by scanning with a laser beam so that these surface plates and the first vehicle body structural plate are joined. As a result, each metal plate can be joined with high joint strength while reducing the width dimension of the joint portion (for example, the flange portion) of each metal plate and making the surface plate thinner, thereby providing sufficient vehicle body rigidity. It is possible to reduce the weight of the car body while obtaining it.

It is a side view which shows the vehicle body manufactured by the welding method which concerns on embodiment. It is sectional drawing of the center pillar along the line II-II in FIG. It is a schematic block diagram which shows the laser welding apparatus used for laser welding. It is a side view for demonstrating the welding work of a body skeleton. It is a side view of the vehicle body for demonstrating the spot welding place in a spot welding process. FIG. 6A is an enlarged view showing a spot welded portion at the end of the spot welding process, and FIG. 6B is a cross-sectional view taken along line BB in FIG. 6A. It is a side view of the vehicle body for demonstrating the laser welding part in a laser welding process. It is sectional drawing of the flange part of the center pillar for demonstrating the laser welding process. 9 (a) is an enlarged view showing a laser welded portion at the end of the laser welding process, and FIG. 9 (b) is a cross-sectional view taken along line BB in FIG. 9 (a). It is a figure corresponding to FIG. 6B at the time of completion of a spot welding process in a modification. It is a figure which shows the result of having measured the hardness in the one-dot chain line AA portion in FIG. FIG. 9 is a view corresponding to FIG. 9 at the end of the laser welding process in the modified example. It is a figure which shows the result of having measured the hardness in the one-dot chain line AA portion in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present embodiment describes a case where the lap welding method according to the present invention is applied to welding metal plates constituting a center pillar (sometimes called a B pillar) which is a member around a door opening of a vehicle body. .. The lap welding method according to the present invention can also be applied to welding of metal plates constituting other members (for example, rockers described later) around the door opening of the vehicle body.

(Vehicle body configuration)
FIG. 1 is a side view showing a vehicle body 10 manufactured by the lap welding method according to the present embodiment. In FIG. 1, the front side of the vehicle body is indicated by an arrow FR, and the upper side of the vehicle body is indicated by an arrow UP.

As shown in FIG. 1, in the vehicle body 10, the rocker 11 extends along the front-rear direction of the vehicle body at the lower portion of the vehicle body side portion. The front pillar 12 extends upward from the front end portion of the rocker 11. Further, the center pillar 13 extends upward from the central portion of the rocker 11 in the front-rear direction of the vehicle body. Further, the rear pillar 14 extends upward from the rear end portion of the rocker 11. The rear pillar 14 is integrally formed with the rear fender panel 15. A roof side rail 16 extending along the front-rear direction of the vehicle body is joined (welded) to the upper end portion of the front pillar 12, the upper end portion of the center pillar 13, and the upper end portion of the rear pillar 14.

The front side portion of the rocker 11, the front pillar 12, the front side portion of the roof side rail 16, and the center pillar 13 form a substantially rectangular front side door opening 61 when viewed from the side surface of the vehicle body. Further, the rear side portion of the rocker 11, the center pillar 13, the rear side portion of the roof side rail 16, and the rear pillar 14 form a substantially rectangular rear side door opening 62 when viewed from the side surface of the vehicle body. That is, these rockers 11, front pillars 12, center pillars 13, rear pillars 14, and roof side rails 16 are members around the door opening of the vehicle body.

(Composition of center pillar)
FIG. 2 is a cross-sectional view of the center pillar 13 along the line II-II in FIG. As shown in FIG. 2, the center pillar 13 is adjacent to the side outer panel 7 as a surface plate located on the vehicle body surface side and the inside in the vehicle width direction (the vehicle interior side of the side outer panel 7) with respect to the side outer panel 7. The center pillar outer reinforcement 8 as the first vehicle body structural plate is arranged adjacent to the inner side in the vehicle width direction (the vehicle interior side of the center pillar outer reinforcement 8) with respect to the center pillar outer reinforcement 8. The center pillar inner panel 9 is integrally welded to each other.

The center pillar outer reinforcement 8 is made of a steel plate, and its cross-sectional shape is a hat shape that is open inward in the vehicle width direction. That is, the center pillar outer reinforcement 8 extends inward in the vehicle width direction from the first plate portion 81 extending in the vehicle body front-rear direction and the vehicle body vertical direction, and the front edge of the first plate portion 81 on the vehicle body front side. Front side second plate portion 82, rear side second plate portion 83 extending inward in the vehicle width direction from the end edge of the first plate portion 81 on the rear side of the vehicle body, and the tip edge of the front side second plate portion 82 (vehicle). The front flange portion 84 extending from the inner tip edge in the width direction toward the front side of the vehicle body, and extending toward the rear side of the vehicle body from the tip edge (inner tip edge in the vehicle width direction) of the rear second plate portion 83. A rear flange portion 85 is provided. The first plate portion 81, the front side second plate portion 82, and the rear side second plate portion 83 constitute a pillar main body portion of the first vehicle body structure plate according to the present invention. That is, the flange portions 84 and 85 are continuously formed on both outer edges of the pillar main body portion in the width direction.

Further, the center pillar inner panel 9 is made of a flat plate-shaped steel plate. The width dimension (dimension in the vehicle body front-rear direction) of the center pillar inner panel 9 substantially matches the dimension in the vehicle body front-rear direction of the center pillar outer reinforcement 8. The center pillar inner panel 9 is a main body portion (pillar main body) facing the first plate portion 81 and the second plate portions 82, 83, respectively, in a state of being welded to the center pillar outer reinforce 8 (state shown in FIG. 2). A portion) 91, a front flange portion 92 welded to the front flange portion 84 of the center pillar outer reinforcement 8, and a rear flange portion 93 welded to the rear flange portion 85 of the center pillar outer reinforcement 8. There is. That is, these flange portions 92 and 93 are continuously formed on both outer edges of the main body portion 91 in the width direction. By welding the center pillar outer reinforcement 8 and the center pillar inner panel 9 in this way, a closed cross-sectional structure is formed by both of them.

The side outer panel 7 is made of a steel plate and is a plate material constituting the design surface of the center pillar 13. Further, the side outer panel 7 has a hat shape in which the cross-sectional shape is open inward in the vehicle width direction, similarly to the center pillar outer reinforcement 8. That is, the side outer panel 7 extends along the vehicle body front-rear direction and the vehicle body vertical direction, and the first plate portion 71 and the first plate portion thereof are overlapped with the outer surface of the first plate portion 81 of the center pillar outer reinforcement 8. The front second plate portion 72 and the first plate extending inward in the vehicle width direction from the front edge of the vehicle body in 71 and being overlapped with the outer surface of the front second plate portion 82 of the center pillar outer reinforcement 8. A rear second plate portion 73 that extends inward in the vehicle width direction from the rear end edge of the portion 71 and is overlapped with the outer surface of the rear second plate portion 83 of the center pillar outer reinforcement 8. ing. Further, the side outer panel 7 extends from the tip edge of the front second plate portion 72 toward the front side of the vehicle body, and the front flange portion 74 superposed on the outer surface of the front flange portion 84 of the center pillar outer reinforcement 8. The rear flange portion 75 extends from the tip edge of the rear second plate portion 73 toward the rear side of the vehicle body and is overlapped with the outer surface of the rear flange portion 85 of the center pillar outer reinforce 8. The first plate portion 71, the front side second plate portion 72, and the rear side second plate portion 73 constitute the pillar main body portion of the surface plate according to the present invention. That is, the flange portions 74 and 75 are continuously formed on both outer edges of the pillar main body portion in the width direction.

Regarding the relationship between the plate thickness dimensions of the side outer panel 7, the center pillar outer reinforcement 8 and the center pillar inner panel 9, the center pillar outer reinforcement 8 has the largest plate thickness dimension among these members, and the side The outer panel 7 is set to have the smallest plate thickness. For example, the center pillar outer reinforcement 8 has a plate thickness dimension set to a predetermined value in the range of 2.4 mm to 3.0 mm, and the center pillar inner panel 9 has a plate thickness dimension set to a predetermined value in the range of 1.1 mm to 2.3 mm. Is set, and the plate thickness dimension of the side outer panel 7 is set to a predetermined value in the range of 0.3 mm to 1.0 mm. Further, the ratio of the total plate thickness dimension (the sum of the plate thickness dimensions of each of the side outer panel 7, the center pillar outer reinforcement 8 and the center pillar inner panel 9) to the plate thickness dimension of the side outer panel 7 is "5" or more. The plate thickness dimension is set. Since the center pillar outer reinforcement 8 and the center pillar inner panel 9 are members that are responsible for the vehicle body rigidity, the plate thickness is set so that sufficient vehicle body rigidity can be obtained. Further, the side outer panel 7 is a plate material constituting the design surface of the center pillar 13, and is for setting a small plate thickness dimension to contribute to weight reduction of the vehicle body weight. The maximum value is set to "10" as the setting range of the ratio of the plate thickness dimension. This value is not limited to this.

(Laser welding equipment)
As will be described later, the side outer panel 7, the center pillar outer reinforcement 8, and the center pillar inner panel 9 are integrally joined by using spot welding and laser welding in combination. Spot welding is performed by a spot welding device, and laser welding is performed by a laser welding device. These welding devices are arranged at a welding process location on the vehicle body manufacturing line, and the spot welding device is arranged on the upstream side of the vehicle body manufacturing line with respect to the laser welding device. Therefore, after spot welding (welding of each part of the vehicle body 10) is performed by the spot welding device, laser welding is performed by the laser welding device.

Since a general spot welding device that has been well known has been used, the description thereof is omitted here (see, for example, Japanese Patent Application Laid-Open No. 2008-290149).

Unlike general laser welding, the laser welding apparatus is such that a molten pool made of molten metal melted by a laser beam is agitated by scanning the laser beam. The term "scanning" as used herein means changing the irradiation position while irradiating the laser beam. This welding method is generally called LSW (laser screw welding). Hereinafter, the laser welding apparatus will be described.

FIG. 3 is a schematic configuration diagram showing the laser welding apparatus 1. As shown in FIG. 3, the laser welding apparatus 1 includes a laser oscillator 2, a laser scanner 3, a welding robot 4, and a robot controller 5.

The laser oscillator 2 produces a laser beam. The generated laser light is guided to the laser scanner 3 via the optical fiber cable 21. As the laser beam, for example, a carbon dioxide gas laser, a YAG laser, a fiber laser, or the like can be used.

The laser scanner 3 irradiates the work W (for example, the center pillar 13) with the laser beam guided through the optical fiber cable 21 (see the one-dot chain line in FIG. 3). A lens group (not shown) and a plurality of mirrors are housed inside the laser scanner 3. The lens group includes a collimated lens for making the laser light parallel, a condensing lens for condensing the laser light so as to focus at the processing point of the work W (a predetermined laser irradiation position on the work W), and the like. Is provided. Further, each mirror is configured to be rotatable about one rotation axis. It is possible to scan the laser beam with these mirrors and scan the laser beam within a predetermined range of the work W. Each mirror can be configured using, for example, a galvano mirror.

As described above, the laser welding according to the present embodiment is laser screw welding (LSW). That is, the laser beam is scanned over the entire circumference around the center position of the welded portion (welded portion) of the work W, and the welded portion is melted to perform welding. The scanning of the laser beam will be performed by each of the mirrors.

The welding robot 4 is configured to make the laser scanner 3 movable. The welding robot 4 is composed of an articulated robot. Specifically, the present embodiment includes a base 41, a rotation mechanism (not shown) housed inside the base 41, joints 42, 43, 44, and arms 45, 46, 47. .. The rotation operation of the rotation mechanism and the swing operation of the arms 45, 46, 47 at the joints 42, 43, 44 make it possible to move the laser scanner 3 in any direction.

The robot controller 5 stores information (information such as the amount of rotation angle of each joint 42, 43, 44) for moving the laser scanner 3 toward the welded portion by offline teaching in advance. Then, when the vehicle body is transported to the welding process location on the vehicle body manufacturing line, the welding robot 4 operates based on the information according to the control signal from the robot controller 5, so that each welding location is sequentially subjected to. LSW will be performed.

(Welding operation)
Next, a welding operation for manufacturing the vehicle body 10 will be described. In particular, here, a welding operation for integrally joining the side outer panel 7, the center pillar outer reinforcement 8 and the center pillar inner panel 9 constituting the center pillar 13 will be mainly described.

In this welding operation, a body skeleton welding process, a spot welding process, and a laser welding process are sequentially performed on the vehicle body manufacturing line.

FIG. 4 is a side view for explaining the welding process of the body skeleton. As shown in FIG. 4, in the welding process of the body skeleton, the skeleton members 11', 12', 13', 16'of the rocker 11, the front pillar 12, the center pillar 13, and the roof side rail 16 are integrally connected to each other. Will be welded. In FIG. 4, the skeleton member 13'of the center pillar 13 and the skeleton member 16'of the roof side rail 16 are already welded. The outer panel (side outer panel 7 in the center pillar 13), which is the skin material, has not yet been welded to the skeleton members 11', 12', 13', 16', and the reinforcement (in the center pillar 13). Is a member having a closed cross-sectional structure in which the center pillar outer reinforcement 8) and the inner panel (center pillar inner panel 9 in the case of the center pillar 13) are welded (temporarily fixed).

The front end of the skeleton member 11'of the rocker 11 is at the lower end of the skeleton member 12'of the front pillar 12, and the central portion of the skeleton member 11'of the rocker 11 in the vehicle body front-rear direction is at the lower end of the skeleton member 13'of the center pillar 13. The front end of the skeleton member 16'of the roof side rail 16 is joined to the upper end of the skeleton member 12'of the front pillar 12 by spot welding to form a body skeleton.

FIG. 5 is a side view of the vehicle body 10 for explaining a spot welded portion in the spot welded process. “◯” in FIG. 5 represents a spot welded portion. In the spot welding process, an outer panel (side outer panel 7 in the center pillar 13) is superposed on the body skeleton configured by the welding process of the body skeleton, and these two metal plates (in the center pillar 13) are superposed. The center pillar outer reinforcement 8 and the center pillar inner panel 9) and the outer panel (in the case of the center pillar 13, the side outer panel 7) are overlapped with each other.

Explaining the spot welding process in the center pillar 13, as shown in FIG. 2, the front flange portion of the center pillar outer reinforce 8 is on the outer surface (outer surface in the vehicle width direction) of the front flange portion 92 of the center pillar inner panel 9. 84 are overlapped, and the front flange portion 74 of the side outer panel 7 is superposed on the outer surface (outer surface in the vehicle width direction) of the front flange portion 84 of the center pillar outer reinforcement 8, and these three flange portions 92 are overlapped. , 84, 74 are sandwiched by the welding gun of the spot welding device, and the spot welding operation is performed. Similarly, the rear flange portion 85 of the center pillar outer reinforcement 8 is overlapped with the outer surface (outer surface in the vehicle width direction) of the rear flange portion 93 of the center pillar inner panel 9, and the center pillar outer reinforcement 8 is overlapped. The rear flange portion 75 of the side outer panel 7 is superposed on the outer surface (outer surface in the vehicle width direction) of the rear flange portion 85, and these three flange portions 93, 85, 75 are connected by the welding gun of the spot welding device. The spot welding operation is performed in the pinched state. Spot welding is performed on other members (rocker 11 and the like) in the same manner.

Welding points in this spot welding are a plurality of points in the longitudinal direction of each flange portion 92, 84, 74, 93, 85, 75 (direction along the opening edge of the door openings 61, 62), and in this direction. It is set to a position where there are equal intervals. Further, the center position of the welded portion in this spot welding is set to the center position in the width direction of the flange portions 92, 84, 74, 93, 85, 75. In addition, the distance between welded parts (welding pitch) in this spot welding causes a diversion (a phenomenon in which the current flowing through the welded part to be welded flows into the already welded welded part existing in the vicinity of the welded part). It is set by experiment or simulation as a dimension that can secure sufficient vehicle body rigidity and joint strength within a range that does not exist. That is, the dimensions are set so that the torsional rigidity of the vehicle body can be sufficiently obtained and the amount of deformation at the time of a vehicle collision can be reduced.

FIG. 6A is an enlarged view showing a spot welded portion (spot welded portion in the front flange portions 74, 84, 92) at the end of the spot welding process, and FIG. 6B is a diagram in FIG. 6A. It is sectional drawing along the line BB. In FIG. 6B, the spot welding electrodes E and E at the time of spot welding are shown by virtual lines. As shown in these figures, when the spot welding process is performed, weld nuggets N and N are formed at substantially the center of each of the overlapped flange portions 74, 84 and 92 in the plate thickness direction, and the center pillar outer reinforcement is formed. The front flange portion 84 of 8 and the front flange portion 92 of the center pillar inner panel 9 are integrally welded. Further, the welded portions of the flange portions 74, 84, 92 are sandwiched by the spot weld electrodes E and E, and the deformation of the front flange portion 74 of the side outer panel 7 (deformation due to the pressure welding of the spot weld electrodes E and E) causes the welded portions. In the region between the welded parts (welded nugget N, N forming parts) in spot welding, the gap between the front flange portion 74 of the side outer panel 7 and the front flange portion 84 of the center pillar outer reinforcement 8 becomes large. ing. The same condition is obtained at the spot welded portions of the rear flange portions 75, 85, 93. In such a state, the laser welding process described later is performed.

FIG. 7 is a side view of the vehicle body 10 for explaining the laser welding portion in the laser welding process. “●” in FIG. 7 represents a laser welded portion with respect to the center pillar 13. In the laser welding process, laser light is irradiated from the laser scanner 3 of the laser welding device 1 to predetermined locations of the flange portions 74 and 75 of the side outer panel 7, and the flange portions of the side outer panel 7 and the center pillar outer reinforcement 8 are respectively. 74, 84, 75, 85 are melted and these are integrally joined. Further, the welding pitch of the welded portion in this laser welding is set to be smaller than the welded pitch of the welded portion in the spot welding. Specifically, there are welded parts in this laser welding on both sides of the flange portions 74, 84, 75, 85 in the longitudinal direction (direction along the opening edges of the door openings 61, 62) with respect to the welded parts in spot welding. It has been set. That is, the welding points in laser welding are set at a plurality of points including the points between the welding points in spot welding. The welding pitch of this laser welding is an interval at which the bonding strength between the side outer panel 7 and the center pillar outer reinforcement 8 can be sufficiently secured, and the productivity (the time required for the laser welding process is minimized) is taken into consideration. The dimensions are set by experiment or simulation. Further, the center position of the welded portion in this laser welding is set to a position closer to the pillar main body portion than the center position in the width direction of the flange portions 74, 84, 92, 75, 85, 93. ..

Hereinafter, this laser welding process will be described.

FIG. 8 is a cross-sectional view of each front flange portion 74, 84, 92 of the center pillar 13 for explaining the laser welding process. This cross section is an intermediate position between the formed portions of the weld nuggets N and N, and a gap is generated between the flange portions 74, 84 and 92 due to the pinching (pressure welding) by the spot weld electrodes E and E. The part (corresponding to the cross-sectional part along the line VIII-VIII in FIG. 6) is shown.

When the laser welding is started, the laser light emitted from the laser scanner 3 of the laser welding apparatus 1 is irradiated toward the surface of the side outer panel 7. At this time, the laser welding apparatus 1 scans the irradiated laser so that a circular shape (the shape when the side outer panel 7 is viewed from the front is circular) is formed by the region occupied by the irradiation locus of the laser beam, and FIG. As shown in (a) and (b), the metal material of the front flange portion 74 of the side outer panel 7 and the metal material of the front flange portion 84 of the center pillar outer reinforcement 8 are melted to form a molten pool over both of them. (First scan). In this case, the conditions of the laser beam (the amount of the laser beam, the focal position of the laser beam, etc.) are the same as that of the front flange portion 74 of the side outer panel 7 without the laser beam penetrating the front flange portion 74 of the side outer panel 7. It is set by experiment or simulation as a value that enables melting of the front flange portion 84 of the center pillar outer reinforcement 8. For example, the focal position of the laser beam is the surface of the front flange portion 74 of the side outer panel 7, and in this state, about half of the front flange portion 84 of the center pillar outer reinforcement 8 is melted in the thickness direction. Is set to. It should be noted that these are not limited to this. Further, in the present embodiment, the circular shape is formed by the irradiation locus of the laser beam, but it may be an elliptical shape or the like.

After that, the laser welding apparatus 1 agitates and flows the molten metal in the molten pool by scanning the laser beam. That is, the laser beam is scanned so as to rotate in a predetermined direction (direction of arrow R in FIG. 8C) around the axis P penetrating the center of the molten pool (second scanning). As a result, the molten metal is agitated in the molten pool. At this time, the molten pool is formed in a mortar shape by the molten metal flowing in the circumferential direction. At the same time, swells of molten metal occur in the molten pool. The molten metal swell is gathered by the surface tension of the molten metal to form a joint without perforations or separation beads, whereby the front flange portion 74 of the side outer panel 7 and the center pillar outer reinforcement 8 are formed. The front flange portion 84 of the above is integrally welded. The rear flange portion 75 of the side outer panel 7 and the rear flange portion 85 of the center pillar outer reinforcement 8 are also integrally joined by the same laser welding.

FIG. 9 (a) is an enlarged view showing a laser welded portion (laser welded portion in the front flange portions 74, 84, 92) at the end of the laser welding process, and FIG. 9 (b) is a diagram in FIG. 9 (a). It is sectional drawing along the line BB. As shown in these figures, when the laser welding process is performed, the laser beam irradiation point (laser light irradiates) between the front flange portion 74 of the side outer panel 7 and the front flange portion 84 of the center pillar outer reinforcement 8. The laser welded part is joined at (L in the figure).

The laser welding in the present embodiment is characterized in that the above-mentioned second scan is performed after the above-mentioned first scan.

If only the first scan is performed, the metal material of the front flange portion 74 of the side outer panel 7 is continuously melted by this scan, whereas the metal material of the front flange portion 84 of the center pillar outer reinforcement 8 ( The molten metal) is gradually cooled, and since stirring and mixing is not performed between the cooled portion and the newly melted portion, the melting becomes insufficient and the molten metal is completely melted. There is a risk that there will be metal materials that did not exist. Further, in the depth direction of the molten pool, there is a difference in the degree of melting between the metal material of the front flange portion 74 of the side outer panel 7 and the metal material of the front flange portion 84 of the center pillar outer reinforcement 8. The degree of melting as a whole becomes non-uniform, and it is difficult for bubbles to be discharged in the molten pool, so that many bubbles are present in the bead. As a result, sufficient bonding strength may not be obtained. Further, since stirring and mixing are not performed between the cooled portion and the newly melted portion, the elements in both portions are not sufficiently diffused, segregation occurs, and the temperature between the two portions is high. Due to the difference, the metallographic structure becomes non-uniform. This may also make it impossible to obtain sufficient bonding strength.

In the present embodiment, by performing the second scan after the first scan, the molten metal swells while flowing due to the scanning of the laser beam in the molten pool, so that the molten pool is sufficiently melted. It is stirred and mixed, and bubbles are discharged well. Further, since the molten pool undulates while flowing by scanning with laser light, the molten pool is sufficiently melted and stirred and mixed, the elements are sufficiently diffused, segregation is suppressed, and the temperature is made uniform. It is possible to prevent the tissue from becoming uneven. Thereby, sufficient bonding strength can be obtained.

As described above, in the present embodiment, three metal plates (side outer panel 7, center pillar outer reinforcement 8, center pillar inner panel 9) can be integrally joined by the combined use of spot welding and laser welding. can. That is, since it is not necessary to join three metal plates only by spot welding, it is not necessary to increase the diameter of the welding nugget (since it is not necessary to form a welding nugget over each metal plate, the welding nugget of the welding nugget is not required. It is not necessary to increase the diameter), and the width dimension of the flange portions 74, 84, 92, 75, 85, 93, which are the joints of the metal plates 7, 8 and 9, can be reduced to reduce the weight of the vehicle body. can. Further, since the side outer panel 7 and the center pillar outer reinforcement 8 are joined by laser welding, it is not necessary to form a welding nugget in the side outer panel 7 by spot welding, and the thickness of the side outer panel 7 can be reduced. This also makes it possible to reduce the weight of the vehicle body. In spot welding, there is a restriction in reducing the welding pitch because the above-mentioned diversion may occur, but by using laser welding that is not restricted by this welding pitch, a sufficient vehicle body can be used. It is possible to ensure rigidity. As described above, according to the present embodiment, when the side outer panel 7, the center pillar outer reinforcement 8, and the center pillar inner panel 9 are superposed and welded, the weight of the vehicle body is reduced while obtaining sufficient vehicle body rigidity. Is possible.

Further, in the spot welding process, since the welded portion is sandwiched by the spot weld electrodes E and E, the deformation of the side outer panel 7 due to this causes the side outer panel 7 and the center pillar in the region between the spot welded portions. The gap between the outer reinforcement 8 tends to be large, but the molten metal fills the gap between the side outer panel 7 and the center pillar outer reinforcement 8 by stirring the molten pool by scanning the laser beam described above. , These side outer panels 7 and the center pillar outer reinforcement 8 can be welded well.

It should be noted that this laser welding is also effective when there is no gap between the side outer panel 7 and the center pillar outer reinforcement 8. That is, when the side outer panel 7 and the center pillar outer reinforcement 8 are galvanized steel plates, zinc vapor explodes inside the molten metal when there is no gap between the panels in the conventional general laser welding. However, according to the laser welding according to the present embodiment, even if there is no gap between the side outer panel 7 and the center pillar outer reinforcement 8, there is a risk that a hole will be formed in the joint portion. By stirring the molten pool, zinc vapor is satisfactorily discharged, and it is possible to prevent holes from being formed in the joint portion.

Further, in the present embodiment, the spot welded portion in the spot welded process and the laser welded portion in the laser welding process can be individually designed. In other words, the positional relationship between these spot welds and the laser welds does not have to correspond exactly, and the spot welds constrain the laser welds, or conversely, the laser welds constrain the spot welds. Is not given. Therefore, after performing the spot welding process, the vehicle body 10 can be conveyed to the laser welding process location to perform the laser welding process. That is, when the spot welded part restricts the laser welded part (for example, when spot welding and laser welding are performed at the same place), the vehicle body is used to ensure the position accuracy of the laser welded part. It is necessary to continuously perform the spot welding process and the laser welding process without transporting the body. In this case, it is difficult to secure an installation space for a welding device for performing each process at the same welding process location, which is not practical. In the present embodiment, each process can be carried out at individual welding process points, which is highly practical.

Further, in the present embodiment, it is formed by spot welding by setting the center position of the welded portion by spot welding to the center position in the width direction of each flange portion 92, 84, 74, 93, 85, 75. The welding nugget N can be set to a size that effectively utilizes the length dimension of the flange portions 92, 84, 74, 93, 85, 75 in the width direction. For example, the diameter of the weld nugget N and the length dimension of the flange portions 92, 84, 74, 93, 85, 75 in the width direction can be made substantially equal. Therefore, it is sufficient that the diameter of the weld nugget N is secured as the length dimension of the flange portions 92, 84, 74, 93, 85, 75 in the width direction, and the flange portions 92, 84, 74, 93, 85. , 75 It is possible to prevent the length dimension in the width direction from becoming longer than necessary. As a result, the length dimension of the flange portions 92, 84, 74, 93, 85, 75 in the width direction is shortened while sufficiently obtaining the joint strength between the center pillar outer reinforcement 8 and the center pillar inner panel 9 by spot welding. It can contribute to the weight reduction of the car body.

Further, in the present embodiment, the center position of the welded portion by laser welding is set to a position closer to the pillar main body portion than the center position in the width direction of each flange portion 92, 84, 74, 93, 85, 75. As a result, when an external force is applied, the side outer panel 7 and the center pillar outer reinforcement 8 are separated from the pillar main body side toward the flange portions 84, 74, 85, 75 (so-called mouth). Opening) can be effectively suppressed, and sufficient bonding strength between the side outer panel 7 and the center pillar outer reinforcement 8 can be obtained.

Further, in the present embodiment, the conditions of the laser beam in the laser welding process (the amount of the laser beam, the focal position of the laser beam, etc.) are satisfied with the side outer panel 7 and the center pillar without the laser beam penetrating the side outer panel 7. Since the outer reinforcement 8 is set to a value that allows the formation of a molten pool, the side outer panel 7 and the center pillar outer reinforcement are used with the minimum amount of laser light energy required to form the molten pool. 8 can be welded.

-Modification example-
Next, a modification will be described. In this modification, the center pillar outer reinforcement 8 is used as a hot stamping material (ultra-high-strength steel plate).

Generally, in spot welding, a heat-affected zone (hereinafter referred to as HAZ) whose hardness is lower than that of the base metal (the part not affected by heat) around the welding nugget due to the influence of heat generated during welding. ) Is formed. This softening of HAZ is particularly remarkable in spot welding to ultra-high-tensile materials and hot stamping materials whose tensile strength is equal to or higher than a predetermined value.

FIG. 10 is a diagram corresponding to FIG. 6B at the end of the spot welding process when the side outer panel 7 is a mild steel plate, the center pillar outer reinforcement 8 is a hot stamping material, and the center pillar inner panel 9 is a high-tensile material. In FIG. 10, the region surrounded by the alternate long and short dash line around the weld nuggets N and N is the HAZ portion (hereinafter, may be referred to as the HAZ softened zone), and the base metal (the portion not affected by heat). The hardness is lower than that of the above, and it is a region where stress is likely to be concentrated when an external force is applied. Further, FIG. 11 shows the results of measuring the hardness of the HAZ softened portion and the other portions (results of measuring the hardness of the alternate long and short dash line AA portion in FIG. 10). H in FIG. 11 is a portion corresponding to the HAZ softened zone.

In the past, after spot welding, tempering was performed by furnace heating, post-energization spot welding, etc. to bring the hardness of the HAZ softened part closer to the other parts, but these lead to a longer processing time. It wasn't good because it was there.

In this modification, when performing the laser welding process after the spot welding process is completed, as shown in FIG. 12, the position outside the heat-affected zone (HAZ softened zone) around the welding nugget (welding point) N in spot welding. Is set to the laser irradiation position, and LSW is performed in the same manner as in the case of the above embodiment.

By carrying out this laser welding process, the outside of the HAZ softened zone is heated (heat-affected zone), so that the periphery of the HAZ softened zone is backfired, and the hardness of this portion is brought closer to the hardness of the HAZ softened zone (the hardness is lowered). Can be done). FIG. 13 shows the result of measuring the hardness of the HAZ softened portion and the other portion (result of measuring the hardness of the one-dot chain line AA portion in FIG. 12). H in FIG. 13 is a portion corresponding to the HAZ softened zone. The broken line in FIG. 13 is the hardness before the laser welding process is performed, and the solid line is the hardness after the laser welding process is performed. As shown in FIG. 13, the periphery of the HAZ softened zone is tempered to reduce the hardness, so that when an external force is applied, stress is less likely to be concentrated on the HAZ softened zone, and the strength of the member is improved. Can be done.

As described above, in this modification, the laser welding step of joining the side outer panel 7 and the center pillar outer reinforcement 8 is performed, and at the same time, the area around the HAZ softened zone is tempered by heating the outside of the HAZ softened zone. , The hardness around the HAZ softened zone can be made close to the hardness of the HAZ softened zone. Therefore, the strength of the member can be improved without prolonging the processing time.

In this modification, the case where the center pillar outer reinforcement 8 is used as the hot stamping material has been described, but the center pillar inner panel 9 may be used as the hot stamping material. Further, both the center pillar outer reinforcement 8 and the center pillar inner panel 9 may be used as hot stamping materials. Further, at least one of the center pillar outer reinforcement 8 and the center pillar inner panel 9 may be made of an ultra-high-tensile material.

-Other embodiments-
It should be noted that the embodiments and modifications disclosed this time are examples in all respects and do not serve as a basis for limited interpretation. Therefore, the technical scope of the present invention is not construed solely by the embodiments and the modifications, but is defined based on the description of the claims. In addition, the technical scope of the present invention includes all modifications within the meaning and scope equivalent to the scope of claims.

For example, in the embodiment and the modification, the case where the present invention is applied as a lap welding method for integrally joining the metal plates constituting the center pillar 13 has been described. The present invention is not limited to this, and stacking for integrally joining other members constituting the door opening, for example, the metal plates constituting the rocker 11, the front pillar 12, the rear pillar 14, the roof side rail 16, and the like. It can also be applied as a welding method.

Further, in the embodiment and the modification, the center position of the welded portion in spot welding is set to the center position in the width direction of the flange portions 92, 84, 74, 93, 85, 75. The present invention is not limited to this, and the center position of the welded portion in spot welding is closer to the pillar body portion than the center position in the width direction of the flange portions 92, 84, 74, 93, 85, 75. It may be set to .

Further, in the embodiment and the modification, a case where three metal plates (side outer panel 7, center pillar outer reinforcement 8 and center pillar inner panel 9) are laminated and welded has been described. The present invention is not limited to this, and can be applied to the case where four or more metal plates are laminated and welded. In this case, a metal plate other than the side outer panel (surface plate) 7 is joined by spot welding, and the side outer panel 7 and a metal plate adjacent to the side outer panel 7 (for example, the center pillar outer reinforcement 8) are joined by laser welding. ..

The present invention is applicable to lap welding in which panels constituting pillars around a door opening of a vehicle body are integrally joined.

1 Laser welding device 10 Vehicle body 11 Rocker 12 Front pillar 13 Center pillar 14 Rear pillar 16 Roof side rail 61 Front side door opening 62 Rear side door opening 7 Side outer panel (surface plate)
8 Center Pillar Outer Reinforce (1st body structure plate)
9 Center pillar inner panel (second body structure plate)
74,84,92 Front flange 75,85,93 Rear flange

Claims (3)

A surface plate located on the vehicle body surface side, a first vehicle body structure plate adjacent to the vehicle interior side of the surface plate, and a vehicle interior of the first vehicle body structure plate, which constitute members around the door opening of the vehicle body. Each of the three or more metal plates including the second body structure plate adjacent to the inside is continuous with the main body portion extending along the opening edge of the door opening and the outer edge of the main body portion, and the door. It is a lap welding method in which a flange portion extending along the opening edge of the opening portion is provided, the flange portions of the metal plates are overlapped with each other , and these flange portions are welded.
The flange portion of the first vehicle body structure plate and the second vehicle body structure plate in a state where the flange portions of the first vehicle body structure plate, the second vehicle body structure plate, and the surface plate are overlapped with each other. A spot welding step of joining the flange portions of the above by spot welding at a plurality of locations along the opening edge of the door opening.
After the spot welding step, the flange portion of the surface plate and the flange portion of the surface plate melted by irradiating the laser beam from the surface plate side at a plurality of locations including the locations between the welded portions in the spot welding. A molten pool made of molten metal of each of the flange portions of the first vehicle body structure plate is stirred by scanning the laser beam to obtain the flange portion of the surface plate and the flange portion of the first vehicle body structure plate . And perform a laser welding process to join
The width of the laser welded portion in the laser welding step is such that the center position thereof is orthogonal to the direction along the opening edge of the door opening in each of the flange portion of the surface plate and the flange portion of the first vehicle body structure plate. It is set to a position closer to the main body than the center position in the direction and closer to the main body than the center position in the width direction in the welding nugget generated by spot welding in the spot welding process. Welding
A lap welding method characterized in that the welding pitch of a laser welded portion in the laser welding step is set to be smaller than the welding pitch of the welded portion in the spot welding step . In the lap welding method according to claim 1,
The condition of the laser beam in the laser welding step is that the surface plate and the first vehicle body structure plate are melted so as to enable the formation of the molten pool without the laser beam penetrating the surface plate. A lap welding method characterized by being set to a value. In the lap welding method according to claim 1 or 2,
At least one of the first vehicle body structure plate and the second vehicle body structure plate is made of an ultra-high-strength steel plate, and the surface plate is harder than the first vehicle body structure plate and the second vehicle body structure plate. Made of low steel plate
In the laser welding step performed after the spot welding step, the surface plate and the first vehicle body structure plate are joined by irradiating the outside of the heat-affected zone around the welded portion in the spot welding with a laser beam. A spot welding method characterized by this.

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