JP2017131916A - Manufacturing method of vehicle body part and its manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a vehicle body part which can obtain a vehicle body part in which the generation of a local stress concentration is suppressed at the surroundings of a portion in which a nugget is formed even if spot welding is used, and its manufacturing device.SOLUTION: Two processes of an electric conduction heating process and a spot welding process are performed for spot-welding an overlapped part 13 which is formed by overlapping flanges 14, 15 of a first member and a second member on each other. In the electric conduction heating process, a softened part 18 which is tempered by heating using an electric conduction heating device 21 is formed at a periphery of a nugget formation portion 17 except for a portion in which a nugget is formed by the spot welding in the spot welding process in a state that the softened part possesses extensity. In the succeeding spot welding process, welding electrodes 32, 33 of a spot welding device 31 are made to abut on the nugget formation part 17, and spot welding is performed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a vehicle body part and a manufacturing apparatus therefor.

  As vehicle body parts such as vehicle frame parts and reinforcing parts, there are cases in which a plurality of metal members are formed into a predetermined shape. In this case, at least a part of the plurality of metal members is overlapped, and the plurality of metal members are joined to each other by welding at the overlapped portion. As the welding method, spot welding is often used (for example, refer to Patent Document 1 for reinforcing parts).

Japanese Patent Laid-Open No. 2003-2058

  By the way, when joining metal members by spot welding, a nugget (melting part) is formed between metal members which form plate shape, and members are joined by the nugget. However, when the metal member is made of a high-strength steel plate having a tensile strength exceeding 1000 MPa, the periphery of the portion where the nugget is formed is tempered by heating during spot welding, and the portion is softened.

  FIG. 6 is a graph showing the hardness distribution around the portion where the nugget is formed by spot welding. As shown in FIG. 6, a softening peak portion P is formed around the nugget formation portion where the nugget is formed by spot welding. In such a state, when an external force is applied to the vehicle body part, there is a concern that stress concentrates on the softening peak portion P and breaks easily.

  Therefore, the present invention provides a method of manufacturing a vehicle body part capable of obtaining a vehicle body part in which the occurrence of local stress concentration is suppressed around the portion where the nugget is formed even in the joining using spot welding. And it aims at providing the manufacturing apparatus.

  In order to achieve the above object, the first invention is a vehicle body part manufactured by superimposing plate-like parts that are at least a part of a plurality of metal members and spot welding the superposed superposed parts. In the manufacturing method, a spot welding process in which spot welding is performed by applying an electrode of a spot welding apparatus to a portion where the nugget is formed by spot welding in the overlapped portion, and the periphery of the portion is tempered by heating. And a heating step for forming the softened portion so as to have a spread along the plate surface of the overlapped portion.

  In a second aspect based on the first aspect, in the heating step, the softening portion is formed by energization heating using an energization heating device, and the energization heating device abuts on the overlapping portion and A pair of energizing electrodes sandwiching the overlapping portion is provided.

  According to a third aspect of the present invention, in the second aspect of the present invention, a hole that matches the size of the portion is formed on a contact surface of the energizing electrode that contacts the overlapping portion. .

  According to a fourth aspect, in the third aspect, the diameter of the hole is not less than the diameter of the portion and not more than a value obtained by adding 2 mm to the diameter of the portion.

  According to a fifth aspect, in the third or fourth aspect, the contact surface of the energizing electrode is an annular shape having a certain width.

  In a sixth aspect of the invention, in the body part manufacturing apparatus for manufacturing the body part by superimposing the plate-like parts that are at least part of the plurality of metal members and spot-welding the superimposed part, A spot welding apparatus that performs spot welding by applying an electrode to a portion where nugget is formed by spot welding in the overlapping portion, and a softened portion tempered by heating around the portion. An energization heating device formed so as to extend along the plate surface, and the energization heating device has a pair of energization electrodes that are in contact with the overlapping portion and sandwich the overlapping portion, and the energization electrode In the contact surface to the overlapping portion, the hole portion is formed in accordance with the size of the portion.

  According to the first aspect of the invention, in the spot welding process, spot welding is performed at the nugget forming portion (nugget forming portion), and the metal members are joined to each other by the formed nugget. In the heating step, the softened portion tempered by heating is formed around the portion in a state of spreading along the plate surface of the overlapping portion. In a vehicle body part welded by a manufacturing method that passes through these two steps, a softened part having a spread is formed around the part where the nugget is formed, so that the local stress concentration is suppressed. Can be obtained.

  Further, in the heating step, the softened portion is formed in a portion excluding the portion where the nugget is formed. As long as the nugget is formed by spot welding, it is not necessary to soften the part where the nugget is formed. Therefore, it is possible to increase the production efficiency by avoiding the formation of the softened portion even in unnecessary portions.

  According to the second aspect of the invention, the pair of energizing electrodes of the energization heating device are in contact with the overlapped portion so as to sandwich the overlapped portion, and the softened portion is formed by energization heating. Temporarily, in the case of heating using a high frequency or a laser, the heating range is difficult to control because it is heated in a non-contact manner, unlike the heating in which the current-carrying electrode is in contact with the overlapping portion and heated. There is a possibility that a softened portion is formed by heating. On the other hand, in the electrification heating that energizes and heats between the electrodes that are in contact with the overlapped portion, a desired heating range can be obtained by setting the size of the contact surface of the energized electrode, so only the necessary range is softened. The part can be formed.

  According to the third invention, since the hole portion corresponding to the size of the nugget formation portion is formed on the contact surface of the energization electrode, the softened portion excluding the nugget formation portion can be easily formed. .

  According to the fourth invention, since the diameter of the hole is not less than the diameter of the part and not more than a value obtained by adding 2 mm to the diameter of the part, there is a region that is not electrically heated on the outer peripheral side of the nugget formation part. It can suppress forming. Thereby, it can suppress that the peak part of softening generate | occur | produces around a nugget by the heating at the time of spot welding.

  According to the fifth aspect, since the contact surface of the energizing electrode is an annular shape having a certain width, the overlapping portion is formed with an annular softened portion. As a result, a uniform softened region is formed over the entire circumference around the nugget formation portion, and stress concentration around the nugget can be further suppressed.

  According to the sixth aspect of the invention, it is possible to suitably realize a method for manufacturing a vehicle body part that can obtain the effects of the first to third aspects of the invention using a spot welding device and an electric heating device.

The perspective view which shows a part of vehicle body components spot-welded. Explanatory drawing which shows the welding process in manufacturing vehicle body components. Sectional drawing which shows the electricity supply electrode of an electricity heating apparatus. It is explanatory drawing which shows the state after electric heating, (a) is a top view, (b) is a graph which shows distribution of hardness. It is explanatory drawing which shows the state of a spot weld part, (a) is a top view, (b) is a graph which shows distribution of hardness. The graph which shows the hardness distribution after the conventional spot welding.

  Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings.

  A vehicle body part 10 shown in FIG. 1 is an example of a skeletal part or a reinforcing part that constitutes the body of a vehicle such as an automobile, and a part thereof is shown in FIG. Specifically, the vehicle body part 10 is a pillar, a cross member, a side member, or the like.

  The vehicle body part 10 shown in FIG. 1 has a first member 11, a second member 12, and an overlapping portion 13 in which both members 11 and 12 are overlapped. The first member 11 and the second member 12 as metal members are each made of a high-strength metal material having a tensile strength exceeding 1000 MPa, such as steel, and formed into a groove shape by hot pressing (hot stamping). Has been.

  The overlapping portion 13 is a portion formed by overlapping the flanges 14 and 15 that the members 11 and 12 respectively have. The flanges 14 and 15 are provided so as to extend outward from the side walls 11a and 12a of the members 11 and 12 at both ends in a direction orthogonal to the direction in which the vehicle body part 10 extends. The flanges 14 and 15 correspond to plate-like portions. Then, spot welding is performed at the overlapping portion 13, and both the members 11 and 12 are joined. A large number of spot welded portions 16 that are spot-welded are provided along the direction in which the vehicle body part 10 extends.

  As shown in FIG. 2, the welding process for forming the spot welded portion 16 goes through two processes: an energization heating process that is a heating process and a spot welding process. These two steps may be carried out continuously for each spot where spot welding is planned, or a method of carrying out the energization heating process at every place or every plurality of places and then carrying out the spot welding process. It may be adopted.

  The electric heating process is a process in which electric heating is performed at a place where the spot welded portion 16 is planned to be provided in the overlapping portion 13 of the first member 11 and the second member 12. In this step, a portion where the nugget (melting portion) N is formed by spot welding, that is, the nugget forming portion 17 (see FIG. 4) is excluded, and the periphery of the nugget forming portion 17 extends over the entire plate thickness direction of the overlapping portion 13. It is energized and heated. As a result, the energized and heated portion is tempered and softened, and the softened portion 18 is formed in the portion with a spread along the plate surface of the overlapping portion 13. The subsequent spot welding process is a process of spot welding the nugget formation portion 17. Hereinafter, each step will be described in more detail.

  First, the electric heating process will be described with reference to FIGS. 3 and 4 in addition to FIG. As shown in FIG. 2, an energization heating device 21 is used in this energization heating process. The energization heating device 21 has a pair of energization electrodes 22 and 23. As shown in FIG. 3, the energizing electrodes 22 and 23 have contact surfaces 24 and 25 that contact the plate surfaces of the flanges 14 and 15 constituting the overlapping portion 13. The outer shape of each contact surface 24, 25 is circular. In this case, for example, if the diameter (nugget diameter) of the nugget N formed by spot welding is 6 mm, the diameters of the contact surfaces 24 and 25 are set to 20 mm.

  In the case where electric heating is performed using the electric heating device 21, the contact surfaces 24 and 25 of the pair of electric current electrodes 22 and 23 are connected to the flanges at locations where spot welding is planned in the overlapping portion 13. 14 and 15 are brought into contact with the respective plate surfaces. By energizing between the energizing electrodes 22 and 23 in this abutting state, the portion sandwiched between the abutting surfaces 24 of the energizing electrodes 22 and 23 is heated to a predetermined temperature (for example, about 600 ° C.).

  Here, the contact surfaces 24 and 25 of the respective energizing electrodes 22 and 23 are provided with holes 26 and 27 at the center thereof. Each of the holes 26 and 27 is provided in a state of being recessed from the contact surfaces 24 and 25, and has a circular shape in a cross section parallel to the contact surfaces 24 and 25. The diameter is set to be the same as the nugget diameter, that is, the diameter of the nugget forming portion 17. It is optimal that the diameters of the holes 26 and 27 are the same as the nugget diameter, but a slightly larger diameter is acceptable. For example, when the nugget diameter is 6 mm, the allowable range is 2 mm or less (diameter 6 to 8 mm of the holes 26 and 27), and more preferably 1 mm or less (diameter 6 to 7 mm of the holes 26 and 27). .

  Thus, since each energizing electrode 22 and 23 is provided with holes 26 and 27 corresponding to the nugget diameter, a portion heated by both energizing electrodes 22 and 23, that is, each contact surface 24 and 25 is provided. The abutting portion has an annular shape. As shown in the plan view of FIG. 4A, the portion that is tempered and softened by heating has an annular shape in the planar shape, and the portion is the softened portion 18.

  FIG. 4B is a graph showing the softened state at the softened portion 18. As shown in FIG. 4B, in the softened portion 18, the hardness of each member 11, 12 is lower than the other portions. For example, when a steel plate having a tensile strength of 1500 MPa is used as the first member 11 and the second member 12, the hardness decreases to 780 MPa by tempering by heating at about 600 ° C.

  On the other hand, the central portion of the softened portion 18 having an annular shape is not energized and heated because the abutting surfaces 24 and 25 of the energizing electrodes 22 and 23 do not abut due to the presence of the holes 26 and 27. Therefore, tempering and softening are suppressed at that portion, and the original hardness of the metal material constituting each of the members 11 and 12 is maintained. This part is a nugget forming portion 17 for forming the nugget N by spot welding.

  Next, the spot welding process will be described with reference to FIG. 6 in addition to FIG. First, as shown in FIG. 2, a spot welding apparatus 31 is used in this spot welding process. The spot welding apparatus 31 and the energization heating apparatus 21 that performs the above-described energization heating process constitute a manufacturing apparatus for the vehicle body part 10. The spot welding apparatus 31 has a pair of welding electrodes 32 and 33. The outer shapes of the welding surfaces 34 and 35 of the welding electrodes 32 and 33 are circular.

  As described above, the softened portion 18 having an annular shape has already been formed in the overlapping portion 13 where spot welding is planned. In this state, the welding surfaces 34 and 35 of the pair of welding electrodes 32 and 33 are brought into contact with the nugget forming portion 17 at the center of the softened portion 18 to perform spot welding. Thereby, in the nugget forming portion 17, a nugget N is formed between the flange 14 of the first member 11 and the flange 15 of the second member 12. With the nugget N, the flanges 14 and 15 of the first member 11 and the second member 12 are joined to each other at the overlapping portion 13.

  As shown in the plan view of FIG. 5A, the spot welded portion 16 after spot welding has a nugget forming portion 19 in which a nugget N is formed between the flanges 14 and 15. . Around the nugget forming portion 19, a softened portion 18 having a spread is formed. FIG. 5B shows the hardness distribution around the spot weld 16 in this state. As shown in FIG. 5B, local softening peaks are not formed by the softening portion 18 around the nugget forming portion 19, and stress concentration due to the presence of such a peak can be avoided. Become.

  The manufacturing method of the vehicle body part 10 in the present embodiment is as described above, and according to this manufacturing method, the following effects can be obtained.

  (1) Since the softening part 18 which spreads around the nugget formation part 19 is formed in the spot welding part 16 as already demonstrated, the vehicle body component 10 with which local stress concentration was suppressed is obtained. Can do. Thereby, even if an external force acts on the vehicle body part 10, it is possible to suppress a decrease in strength due to stress concentration.

  (2) In the electric heating process, the softened portion 18 is formed in a portion excluding the nugget forming portion 17. As long as the nugget N is formed by spot welding, the nugget forming portion 17 does not need to be softened to that portion. Therefore, it is possible to increase the production efficiency by avoiding the softened portion 18 being formed even in unnecessary portions.

  (3) If heating is performed using a high frequency or a laser, the heating is performed in a non-contact manner, so that it is difficult to control the heating range, and a softened part may be formed by heating to an unnecessarily large range. There is. The expansion of the softened portion is a factor that reduces the strength of the vehicle body part 10. In that respect, in the energization heating in which the energization electrodes 22 and 23 abutted against the plate surface of the overlapping portion 13 are energized and heated, a desired heating range can be obtained by setting the size of the abutment surfaces 24 and 25. And the softened portion 18 can be formed only in a necessary range. Moreover, since the heating method using the electric heating device 21 has higher heating efficiency than the heating method using a high frequency or a laser, the manufacturing cost of the vehicle body part 10 can be suppressed.

  (4) Holes 26 and 27 matching the size of the nugget forming portion 17 are formed in the contact surfaces 24 and 25 of the pair of energizing electrodes 22 and 23. The softened portion 18 excluding the nugget forming portion 17 can be easily formed only by using the energizing electrodes 22 and 23. In this case, it is sufficient to replace only the current-carrying electrodes 22 and 23 in the conventional current-carrying heating device 21, so that no significant modification of the device is necessary, and this point also contributes to the reduction of the manufacturing cost.

  (5) Due to the presence of the holes 26 and 27, the areas of the contact surfaces 24 and 25 of the energizing electrodes 22 and 23 are reduced accordingly. Therefore, the amount of current per unit area is increased as compared with the contact surfaces 24 and 25 in which the holes 26 and 27 are not provided, and the heat generation efficiency necessary for heating can be increased accordingly. It is done.

  (6) The diameters of the holes 26 and 27 are set to be equal to or larger than the diameter of the nugget forming portion 17 and not more than a value obtained by adding 2 mm to the diameter of the nugget forming portion 17. Therefore, it is possible to suppress the formation of a region that is not heated by energization and does not become the softened portion 18 on the outer peripheral side of the nugget formation portion 17. Thereby, it can suppress that the peak part of softening generate | occur | produces around the nugget N by the heating at the time of spot welding.

  (7) Since the contact surfaces 24 and 25 of the pair of energizing electrodes 22 and 23 have an annular shape having a certain width, the overlapping portion 13 is formed with a softened portion 18 having an annular shape. . As a result, a uniform softened region is formed over the entire circumference around the nugget formation portion 17, and stress concentration around the nugget N can be further suppressed.

  The present invention is not limited to the above-described embodiment, and for example, the following manufacturing method may be performed.

  (A) In the present embodiment, the energization heating device 21 and the spot welding device 31 are described as separate devices. However, both the energization heating and the spot welding are the same in that an object is energized using electrodes. is there. For this reason, parts other than the electrodes, such as a current generator, may be shared. That is, using one apparatus having the energizing electrodes 22 and 23 and the welding electrodes 32 and 33, the energizing heating process and the spot welding process may be performed while changing the electrodes to be used.

  (B) In the present embodiment, the softened portion 18 is formed in an annular planar shape, but the planar shape of the softened portion 18 may be other shapes such as an oval shape, a rectangular shape, and a polygonal shape. You may make it form. In this case, what is necessary is just to change the shape of the contact surfaces 24 and 25 of each energizing electrode 22 and 23 according to the external shape of the softening part 18. FIG.

  (C) In the present embodiment, the vehicle body part 10 constituted by the two members of the first member 11 and the second member 12 is taken as an example, but the vehicle body part 10 is constituted by a plurality of three or more members. It may be.

  (D) In this embodiment, the flanges 14 and 15 included in the members 11 and 12 are examples of plate-like portions, and a portion where the flanges 14 and 15 are overlapped is referred to as an overlapping portion 13. Instead of this, the plate-like portion to be overlapped may be any part of the members 11 and 12, such as the side walls 11a and 12a being plate-like portions, or the members 11 and 12 are entirely overlapped. Also good.

  (E) In the present embodiment, the vehicle body part 10 is constituted by the first member 11 and the second member 12 that are molded into a groove shape, but the shape of the metal member that constitutes the vehicle body part 10 is the vehicle body part. The shape varies depending on the ten types, and is not limited to a specific shape.

  (F) In the present embodiment, the softened portion 18 is formed by energization heating in the heating process, but a heating method using a high frequency or a laser may be employed. However, since heating using a high frequency or a laser has the above-described problems, it is preferable to employ energization heating as in this embodiment in that the softened portion 18 can be formed only in a necessary range.

  (G) In the present embodiment, as a manufacturing method of the vehicle body part 10, the nugget formation portion 17 is formed by the spot welding process after the nugget formation portion 17 is energized and heated around the nugget formation portion 17 by the current heating step. Spot welding was performed. Alternatively, the steps may be performed in the reverse order. That is, an energization heating process in which a spot welding process for spot welding is performed on the nugget formation portion 17 and a nugget N is formed on the nugget formation portion 17 and then a softened portion 18 is formed around the nugget formation portion 17 by energization heating. May be implemented.

  DESCRIPTION OF SYMBOLS 10 ... Body part, 11 ... 1st member (metallic member), 12 ... 2nd member (metallic member), 13 ... Overlapping part, 14, 15 ... Flange (plate-shaped part), 17 ... Nugget formation part, DESCRIPTION OF SYMBOLS 18 ... Softening part, 21 ... Current heating apparatus, 22, 23 ... Current supply electrode, 24, 25 ... Contact surface, 26, 27 ... Hole part, 31 ... Spot welding apparatus, N ... Nugget.

Claims (6)

In a method for manufacturing a vehicle body part manufactured by stacking plate-shaped parts that are at least a part of a plurality of metal members and spot-welding the stacked overlapping parts,
A spot welding process in which spot welding is performed by applying an electrode of a spot welding apparatus to a portion where the nugget is formed by spot welding in the overlapped portion,
A heating step of forming a softened portion tempered by heating around the portion so as to have a spread along the plate surface of the overlapping portion;
A method of manufacturing a vehicle body part, comprising: In the heating step, the softening portion is formed by energization heating using an energization heating device,
The method of manufacturing a vehicle body part according to claim 1, wherein the energization heating device includes a pair of energization electrodes that are in contact with the overlapping portion and sandwich the overlapping portion.   3. The method of manufacturing a vehicle body part according to claim 2, wherein a hole that matches the size of the portion is formed in a contact surface of the energizing electrode that contacts the overlapping portion.   The method of manufacturing a vehicle body part according to claim 3, wherein the diameter of the hole is equal to or larger than the diameter of the portion and equal to or smaller than a value obtained by adding 2 mm to the diameter of the portion.   5. The method of manufacturing a vehicle body part according to claim 3, wherein the contact surface of the energizing electrode is an annular shape having a certain width. In a vehicle body part manufacturing apparatus that manufactures a vehicle body part by superimposing plate-like parts that are at least a part of a plurality of metal members and spot-welding the overlapped overlapping part,
A spot welding apparatus that performs spot welding by applying an electrode to a portion where the nugget is formed by spot welding in the overlapped portion,
An energizing heating device that forms a softened portion tempered by heating around the portion so as to have a spread along the plate surface of the overlapping portion;
With
The energization heating device has a pair of energization electrodes that abut on the overlapped portion and sandwich the overlapped portion, and the contact surface of the energization electrode on the overlapped portion has a size of the portion. An apparatus for manufacturing a vehicle body part, characterized in that a hole is formed in accordance with the above.

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