JP2008149330A - Laser welding joint and joined body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser welding joint in which no deformation is caused through excess heat input into joining members by a laser beam, and to provide a joined body welded by laser with this joint. <P>SOLUTION: This joint is a laser welding joint formed in the joining members 1A, 1B for the purpose of joining the butted weld zone of the end faces 13, 14 of these members 1A, 1B by laser welding or laser arc hybrid welding. In the welding ends of the joining members 1A, 1B, a projected part 15 is formed projecting on the side of a laser irradiation face so that the welding end faces 13, 14 are continuous and then, on the laser irradiation face of the projected part 15, a welding groove 16 is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a welded joint for laser welding for laser welding or laser-arc hybrid welding of a member to be joined made of, for example, aluminum or an aluminum alloy material, and in particular to prevent distortion due to excessive heat input of a laser beam. The present invention relates to a joint for laser welding and a joined body welded by the joint.

For the production of vehicle bodies such as railway vehicles and automobiles, for example, MIG welding or friction stir welding is used for joining members to be joined such as aluminum alloy plates. However, in MIG welding, the heat input to the members to be joined increases, and the effect of distortion on welding becomes large when joining plate members having a thickness of several millimeters.
On the other hand, friction stir welding is preferable because distortion due to welding is small because the amount of heat input is small, but the welding speed is about the same as MIG automatic welding and it cannot be increased in speed, and it is difficult to reduce the production cost. is there.

On the other hand, friction stir welding and the like can be considered in addition to laser and arc welding for the production of car bodies such as railway vehicles and automobiles. For example, when a hollow extruded profile that is a member to be joined is used and a structure for a railway vehicle is formed as a joined body, the hollow extruded profile has a joint strength and rigidity that can withstand the load from a rotating tool during construction. Therefore, it is difficult to reduce the weight. Therefore, at present, laser welding or laser / arc hybrid welding in which laser welding, TIG welding, or MIG welding is combined is expected as a joining method for suppressing high-speed joining and the accompanying heat input to the joint. Further, in laser welding or the like, since there is no weight increase for securing the strength of the joint, it is expected that the vehicle body of a railway vehicle or the like can be reduced.
JP 2005-138153 A

  However, when aluminum or aluminum alloys are joined by welding using a laser, they have a high thermal conductivity, so there is a problem that the heat from the laser irradiated to the joint is dispersed before the joint is sufficiently melted. It was. That is, although aluminum and aluminum alloys have a low melting point, if sufficient heat is applied to the joint, a large amount of energy enters the member to be joined, causing distortion. In addition, since aluminum and aluminum alloys have a high heat transfer coefficient and a high reflectivity of the laser beam, the laser beam is reflected and it is difficult to concentrate energy on the joint.

  By the way, laser welding and laser hybrid welding have an advantage that the joining speed can be increased by heat input to the joining portion by laser. However, if it is difficult to concentrate energy on the joint, such a merit is also halved. That is, it is necessary to irradiate the laser beam for a sufficient time while suppressing the feed rate of the laser beam so that the joint can be sufficiently melted.

  Therefore, the present invention provides a joint for laser welding in which distortion is not caused by excessive heat input to a member to be joined by a laser beam and a joined body laser-welded by the joint in order to solve such a problem. For the purpose.

The welded joint for laser welding according to the present invention is formed on the joined member in order to join the joined portion where the joined end faces of the joined members are butted together by laser welding or laser-arc hybrid welding, The joining end portion of the member to be joined is formed with a convex portion protruding on the laser irradiation surface side so that the joining end surface is continuous, and a welding groove is formed on the laser irradiation surface side of the convex portion. It is characterized by that.
In the laser-welded joint according to the present invention, it is preferable that the weld groove has a V-shaped cross section by an inclined surface formed on the laser irradiation surface side of the convex portion.
In the joint for laser welding according to the present invention, the member to be joined is preferably made of aluminum or an aluminum alloy material.

The joined body of the present invention comprises a member to be joined provided with a welded joint for laser welding that joins a joined portion in which joined end faces are butted together by laser welding or laser-arc hybrid welding, and is joined by the laser welding In the joint, a convex portion projecting on the laser irradiation surface side is formed at the joint end portion of the member to be joined so that the joint end surface is continuous, and a welding groove is formed on the laser irradiation surface side of the convex portion. It is characterized by being.
In the joined body of the present invention, the member to be joined is preferably made of aluminum or an aluminum alloy material.

  According to the present invention, when the projection is irradiated with the laser beam, heat is concentrated by preventing diffusion of heat by the laser beam, and heat is efficiently transmitted in the depth direction of the joint. In addition, since the laser beam applied to the welding groove on the surface of the convex portion repeatedly reflects on the left and right slopes, the joint portion is efficiently heated. Therefore, when a joined body is formed by laser welding or laser / arc hybrid welding, it is possible to prevent distortion from being caused by excessive heat input to the member to be joined by the laser beam.

  Next, an embodiment of a laser-welded joint according to the present invention and a joined body will be described below with reference to the drawings. First, FIG. 5 is a view showing a railway vehicle structure constituted by members to be joined using the joint for laser welding according to the present embodiment. This railcar structure 80 that is a joined body includes a side structure 81 that forms left and right surfaces, a roof structure 82 that forms a roof, and a wife structure 83 that forms surfaces that close both ends in the longitudinal direction of the vehicle body. , And a frame 84 that forms the floor surface. In the side structure 81 and the roof structure 82, a plurality of extruded hollow members 88 having a length corresponding to one of the vehicle bodies are welded and joined in the width direction (the left-right direction in the drawing, the same applies hereinafter). In addition, the joined body may be other than a railcar structure or a railcar having an outer plate in which a member to be joined is a flat plate.

  Here, FIG. 1 is a diagram showing a laser-welded joint for extruded hollow shapes that are members to be joined. The extruded hollow profiles 1A and 1B are profiles made of an aluminum alloy formed by extrusion molding, and correspond to the extruded hollow profiles 88 constituting the railway vehicle 80. Laser welded joints shown in the drawings are formed on the left end and the right end of the extruded hollow members 1A and 1B, respectively. The extruded hollow members 1A and 1B are obtained by connecting the upper surface plate 2 and the lower surface plate 3 by ribs (not shown) and are closed in the width direction by the end ribs 5 and 6 positioned at the left and right end portions, respectively. It has a shape.

  From the end rib 5 of the extruded hollow member 1A, the joining protrusions 11 and 11 are formed on the extensions of the upper surface plate 2 and the lower surface plate 3, respectively, and from the end rib 6 of the extruded hollow member 1B. The joining protrusions 12 and 12 are formed so as to protrude between the joining protrusions 11 and 11. Accordingly, when the extruded hollow members 1A and 1B are joined, the joining projections 12 and 12 are fitted between the joining projections 11 and 11 as shown in the figure, and the joining projections 11 and 11 are joined to the joining end face 13 and the other upper surface. The face plate 2 and the joining end face 14 of the lower face plate 3 are brought into contact with each other.

  Furthermore, in this embodiment, the convex part 15 is formed in the joining end surfaces 13 and 14 part which is abutted. The convex portion 15 protrudes on the laser irradiation surface side in the vertical direction of the drawing, and is formed continuously in the longitudinal direction of the extruded hollow members 1A and 1B penetrating the drawing. Therefore, this laser welding joint is a joint having a shape in which the laser irradiation portion is raised from the other surface. Here, FIG. 2 is an enlarged view of a joint portion of the laser welding joint joint. In the extruded hollow members 1A and 1B, for example, the plate thickness t1 of the upper surface plate 2 and the lower surface plate 3 and the plate thickness t2 of the bonding projections 11 and 12 are 3 mm. On the other hand, the convex part 15 formed in the joint is formed with a width b of 2 mm and a height h of 1 mm.

  The reason why the projection 15 is provided at the joint is to concentrate the heat of the irradiated laser beam. This is because, on a flat surface without the projections 15, even if the bonding part is heated by laser beam irradiation, heat is diffused in aluminum having a high thermal conductivity, and the bonding part cannot be heated sufficiently. In particular, in the case of the extruded hollow shape members 1A and 1B, the upper surface plate 2 and the lower surface plate 3 to which the laser is irradiated are formed in a wide plate shape, so that heat easily escapes and it is difficult to concentrate heat on the joint. It is.

  By the way, when the member to be joined is aluminum or the like, it is not only the high heat transfer coefficient that makes it difficult to concentrate the heat at the joint irradiated with the laser. The high reflectivity of the laser beam is also a problem. This is because even if the projections 15 and 15 are irradiated, if the laser beam is reflected many times, the effect of the bent protrusion shape will be halved. Therefore, in the present embodiment, in addition to the convex portion 15, the joint shape further utilizes reflection. That is, the upper surface of the convex portion 15 is inclined toward the joint end faces 13 and 14 respectively, so that the reflected laser beam is concentrated on the joint portion. Therefore, the upper surface of the convex portion 15 is inclined toward the joining end faces 13 and 14, and a V-shaped welding groove 16 is formed along the joining line as shown in the figure at the time of joining.

Therefore, when the joints of the extruded hollow shapes 1A and 1B are combined with each other, the joining end surfaces 13 and 14 are abutted, and the convex portions 15 and 15 are projected on the surface side of the upper surface plate 2 and the lower surface plate 3 which are laser irradiation surfaces. The weld groove 16 appears on the upper surface. In laser welding or the like, a laser beam is irradiated onto the welding groove 16 of the convex portions 15 and 15 and a shielding gas is simultaneously injected.
The welding method may be joining by laser / arc hybrid welding combining laser welding and MIG welding. In laser / arc hybrid welding, the welding groove 16 is also irradiated with a laser beam. A shield gas is supplied from the front in the traveling direction, and welding is performed by supplying a MIG arc by a MIG torch at the rear in the traveling direction.

  In the laser welding joint according to this embodiment, when the convex portion 15 is irradiated with the laser beam, the convex portion 15 is heated intensively. This is because the surface of the convex portion 15 is not continuous in the plane direction, so that heat diffusion due to the laser beam is prevented and heat is efficiently transmitted in the depth direction of the joint portion. Furthermore, in this embodiment, since the V-shaped welding groove 16 is formed on the surface of the convex portion 15, the irradiated laser beam repeatedly reflects on the left and right slopes, so that the joint is efficiently heated. . That is, the joining portion can give sufficient heat to the joining portion without excessively irradiating the laser beam as compared with the conventional flat joint. Therefore, according to the joint for laser welding according to the present embodiment, when a joined body such as the railway vehicle structure 80 is formed by laser welding or laser / arc hybrid welding, it is due to excessive heat input to the member to be joined by the laser beam. It is possible to improve the quality by preventing the occurrence of distortion.

By the way, in the said embodiment, although the joint of the extrusion hollow shape material was demonstrated, even if it is another to-be-joined member, the joint joint for laser welding is formed similarly. 3 and 4 are views showing other embodiments of the laser-welded joint joint.
FIG. 3 is a view showing a laser-welded joint when joining the flat plates 21A and 21B. In the present embodiment, convex portions 25 and 26 are formed on the joining end surfaces 23 and 24 to be abutted. The convex portions 25 and 26 are provided so as to project on the laser irradiation surface side in the vertical direction of the drawing, and are continuously formed in the longitudinal direction of the extruded hollow members 21A and 21B penetrating the drawing. Therefore, this laser welding joint is also a joint in which the laser irradiated portion is raised from the other surface.

Furthermore, a welding groove 27 is formed on the surface of the convex portions 25 and 26, and the welding groove 27 is half the size of the above embodiment. That is, an inclined surface is formed on the laser irradiation surface side only on one convex portion 25 side, and the other convex portion 26 has a rectangular shape. As described above, the weld grooves are not necessarily symmetrical.
Therefore, also in this embodiment, when the convex portions 25 and 26 are irradiated with the laser beam, the convex portions 25 and 26 are intensively heated, and heat is efficiently transmitted in the depth direction of the joint portion. And since a laser beam repeats reflection by the welding groove 27, a junction part can be heated efficiently. Therefore, even when a joined body is formed by laser welding or the like, it is possible to improve the quality by preventing the occurrence of distortion due to excessive heat input to the members to be joined.

  FIG. 4 is a view showing a laser-welded joint when joining the flat plates 31A and 31B. In the present embodiment, a thick portion 32 is provided at the joint end portion, and the convex portion 35 is formed on the joint end surfaces 33 and 34 to be abutted. The convex portion 35 protrudes on the laser irradiation surface side in the vertical direction of the drawing, and is formed continuously in the longitudinal direction of the extruded hollow members 31A and 31B penetrating the drawing. Therefore, this laser welding joint is a joint having a shape in which the laser irradiation portion is raised from the other surface. Further, a welding groove 36 is formed on the surface of the convex portion 35, and the welding groove 26 is formed with an inclined surface on the laser irradiation surface side of the convex portion 35 and has a V-shaped cross section.

  Therefore, also in this embodiment, when the laser beam is irradiated to the welding groove 36 of the convex portion 35, the convex portion 35 is intensively heated, and heat is efficiently transmitted in the depth direction of the joint portion. And since a laser beam repeats reflection by the welding groove 36, a junction part can be heated efficiently. Therefore, even when a joined body is formed by laser welding or the like, it is possible to improve the quality by preventing the occurrence of distortion due to excessive heat input to the members to be joined.

  By the way, since it welds by forming the welding groove 36, there exists a problem which an underfill produces in the welding part. That is, when a dent is generated on the surface, stress concentration occurs there, which may cause cracks. In this regard, in this embodiment, since the thick portion 32 is provided, the thickening portion 32 is cut and flattened after joining. Thereby, even if a dent arises, since it is made into a flat finished surface by a simple grinding operation, the appearance is excellent, and in addition, stress concentration in the welded portion can be avoided.

  As mentioned above, although one embodiment of the joint for laser welding and the joined body concerning the present invention was described, the present invention is not limited to this but can be variously changed within the range which does not deviate from the meaning.

It is the figure which showed the joint joint for laser welding of an extrusion hollow shape material. It is the figure which expanded the junction part of the joint joint for laser welding. It is the figure which showed the joint joint for laser welding of a flat plate. It is the figure which showed the joining joint for flat plate laser welding which considered the underfill. It is the figure which showed the railway vehicle structure comprised by the to-be-joined member using the joining joint for laser welding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B Extrusion hollow shape material 2 Upper surface board 3 Lower surface board 5,6 End rib 11,12 Joining protrusion 13,14 Joining end surface 15 Convex part 16 Welding groove 80 Railroad vehicle structure

Claims (5)

In order to join the joint portion where the joining end faces of the members to be joined are joined by laser welding or laser-arc hybrid welding, in the joint for laser welding formed on the member to be joined,
The joining end portion of the member to be joined is formed with a convex portion protruding on the laser irradiation surface side so that the joining end surface is continuous, and a welding groove is formed on the laser irradiation surface side of the convex portion. A welded joint for laser welding, characterized in that: In the laser-welded joint according to claim 1,
The welded joint for laser welding, wherein the weld groove has a V-shaped cross section by an inclined surface formed on the laser irradiation surface side of the convex portion. In the joint for laser welding according to claim 1 or claim 2,
The welded joint for laser welding, wherein the member to be joined is made of aluminum or an aluminum alloy material. In a joined body composed of a member to be joined provided with a welded joint for laser welding that joins a joined portion where the joining end faces are butted together by laser welding or laser / arc hybrid welding,
In the joint for laser welding, a convex portion projecting on the laser irradiation surface side is formed at the joint end portion of the member to be joined so that the joint end surface is continuous, and welding is performed on the laser irradiation surface side of the convex portion. A joined body in which a groove is formed. In the joined body according to claim 4,
The joined member is made of aluminum or an aluminum alloy material.

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