JP2011177723A - Resistance welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a sufficient electric current to a planned weld zone, in performing resistance welding by bringing a pair of electrodes into contact together with one metallic plate. <P>SOLUTION: A pair of electrodes 30, 40 are arranged, with the pair in contact with an upper metallic plate 10, in a manner that the route length of the shortest energization route L1 through the upper metallic plate 10 is made longer than the route length of the shortest energization route L2 through the lower metallic plate 20. With an electric current made to flow between the electrodes 30, 40 in this state, a lot of electric current flows by the shortest energization route L2 through the lower metallic plate 20, so that an excellent weld zone can be formed by making sufficient electric current flow to the weld zone (planned weld zone Q') of the metallic plates 10, 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to resistance welding for joining two metal plates by bringing a pair of electrodes into contact with two superimposed metal plates and passing a current between the pair of electrodes, and in particular, a pair of electrodes. The present invention relates to a resistance welding method in which both are brought into contact with one metal plate.

  For example, as shown in FIG. 5, when a current is passed in a state where a pair of electrodes 130 and 140 are in contact with the upper metal plate 110 of the two stacked metal plates 110 and 120, the electrodes 130 and 140 are disposed. Is formed on the surface of the upper metal plate 110, so that the largest amount of current flows through the shortest energization path L1 '. For this reason, there is a possibility that the current flowing through the portion to be joined Q ″ between the upper metal plate 110 and the lower metal plate 120 is reduced, resulting in a poor bonding state. When the value of the current flowing between the electrodes 130 and 140 is increased for reliable welding, an excessive current flows through the shortest energization path L1 ′, and the contact portion of the electrode 140 of the upper metal plate 110 is locally melted. There is a risk of causing problems such as spatter.

  In order to avoid such a problem, for example, as shown in FIG. 6, there is a method of bringing the conductive plate 150 into contact with the lower surface of the lower metal plate 120. In this case, by forming the conductive plate 150 with a material having a low resistance value, a current flowing between the electrodes 130 and 140 is guided to the energization path L2 ′ via the conductive plate 150, and thereby the planned joining portion Q ″. Sufficient current can flow. However, this method requires the cost of the conductive plate 150 itself and the time and effort required to place the conductive plate 150 in an appropriate position each time welding is performed, and is applicable to a workpiece having a shape in which the conductive plate 150 cannot be disposed. Can not do it.

  For example, in Patent Document 1, the tip of the electrode is formed into a spherical surface, and a metal plate with which the electrode is brought into contact is formed in advance, and the electrode is pressed and contacted so as to crush the seat surface. A spherical portion is formed on the metal plate. By making this spherical surface point-contact with the lower metal plate, the current density is increased even with a small current to enhance the heating effect.

JP 2002-239742 A

  However, as shown in Patent Document 1, even when a one-step higher seating surface is formed on the metal plate, the shortest energization path connecting the electrodes is formed on the upper metal plate, so that the current flowing in the planned joining portion Cannot solve the problem of reducing

  The problem to be solved by the present invention is to form a good welded portion by supplying a sufficient current to the joining portion in a resistance welding method in which a pair of electrodes are brought into contact with one metal plate. is there.

  In order to solve the above-described problem, the present invention provides a method in which a pair of electrodes are brought into contact with one of the two stacked metal plates, and a current is passed between the pair of electrodes. A resistance welding method of welding a metal plate of a current path, wherein a current path that connects a pair of electrodes through one metal plate in the shortest direction is a current path that connects a pair of electrodes through the other metal plate in a minimum length A resistance welding method is provided in which a pair of electrodes are arranged so as to be longer.

  Thus, in the resistance welding method of the present invention, the shortest energization path (indicated by L1 in FIG. 1) through one metal plate is the shortest energization path (indicated by L2 in FIG. 1) through the other metal plate. Longer than shown). When a current is passed between the pair of electrodes in this state, a large amount of current flows through the shortest energization path (L2) through the other metal plate. As a result, a sufficient current can be supplied to the joint portion (indicated by Q ′ in FIG. 1) between one metal plate and the other metal plate, so that the joint portion is sufficiently melted and a good welded portion is obtained. Can be formed.

  For example, if the current-carrying inhibition part is provided on the shortest path between the contact parts of a pair of electrodes in one metal plate, the shortest current-carrying path through one metal plate bypasses the current-carrying inhibition part. Therefore, the path length becomes long. Thereby, the shortest energization path through one metal plate can be made longer than the shortest energization path through the other metal plate.

  As described above, according to the resistance welding method of the present invention, a sufficient weld can be formed by supplying a sufficient current to the portion to be joined.

(A) is sectional drawing which shows the resistance welding method concerning one Embodiment of this invention, (b) is a top view of a workpiece | work. It is a front view of an electrode. It is a graph which shows the time change of the electric current value sent between electrodes. (A) is a top view which shows the resistance welding method which concerns on other embodiment, (b) is the same sectional drawing. It is sectional drawing which shows the conventional resistance welding method. It is sectional drawing which shows the conventional resistance welding method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The workpiece W to be welded in the present embodiment is a hollow columnar member used as, for example, a skeleton component (side member or the like) of an automobile, and as shown in FIG. It is formed by welding the metal plate 20. Hereinafter, for the sake of convenience, description will be made using the vertical direction and the horizontal direction shown in FIG. 1A. The metal plate 10 having a cross-sectional hat shape is referred to as an “upper metal plate 10”, and the flat metal plate 20 is referred to as “ Say “lower metal plate 20”.

  Each of the upper metal plate 10 and the lower metal plate 20 is formed of a steel plate, for example, a high-tensile steel plate having a tensile strength of 400 MPa or more, particularly, an ultra-high strength steel plate having a tensile strength of 900 MPa or more. The upper metal plate 10 is formed to be thicker than the lower metal plate 20. For example, in the case of a side member of an automobile, the upper metal plate 10 is about 2 mm and the lower metal plate 20 is about 1 mm. Note that the upper metal plate 10 does not necessarily have to be thicker than the lower metal plate 20, and both metal plates 10 and 20 may have the same thickness.

  The upper metal plate 10 includes a U-shaped portion 11 that opens downward, and flange portions 12 and 13 that protrude left and right from the lower end portion of the U-shaped portion 11. By joining the flange portions 12 and 13 of the upper metal plate 10 and the lower metal plate 20 by welding, the two metal plates 10 and 20 are integrated. For example, after joining one flange portion 12 of the upper metal plate 10 and the lower metal plate 20 by an arbitrary welding method (for example, direct spot welding), the other flange portion 13 of the upper metal plate 10 The lower metal plate 20 is joined by welding. FIG. 1 shows a state in which one flange portion 12 of the upper metal plate 10 and the lower metal plate 20 are joined, and the already joined portion is indicated by P in the drawing. In the state shown in FIG. 1, the other flange portion 13 of the upper metal plate 10 and the lower metal plate 20 are not joined, and a joining scheduled portion is indicated by Q ′ in the drawing.

  The welding apparatus according to the present embodiment includes a pair of electrodes 30 and 40 and a current control unit (not shown) that supplies current to the electrodes 30 and 40. As shown in FIG. 2, the tip portions of the electrodes 30 and 40 each have a truncated cone shape. Specifically, the circular end surfaces 31 and 41 have small diameters, and the diameters increase upward from the end surfaces 31 and 41. Conical surfaces 32, 42. The tip angle α of the conical surfaces 32 and 42 is set within a range of 120 ° to 165 °.

  The resistance welding method according to one embodiment of the present invention is performed as follows. That is, as shown in FIG. 1A, a pair of electrodes 30 and 40 of the welding apparatus are brought into contact with the flange portions 12 and 13 of the upper metal plate 10 from above, and the upper metal plate 10 is contacted by the electrodes 30 and 40. By energizing while pressing, the joint portion Q ′ is welded. Of the pair of electrodes 30, 40, one electrode 30 is brought into contact with the already joined portion P of the one flange portion 12, and the other electrode 40 is brought into contact with the joint portion Q ′ of the other flange portion 13. One electrode 30 functions as a ground electrode, and the other electrode 40 functions as a welding electrode. As a result, welding is not performed at the location where the one electrode 30 is in contact (the already-joined portion P), and only the planned joining portion Q ′ where the other electrode 40 is in contact is welded.

  FIG. 1A shows an energization path between the electrodes 30 and 40. A path L1 indicated by a dotted arrow in the figure is the shortest energization path (hereinafter referred to as an upper energization path L1) via the upper metal plate 10, and a path L2 indicated by a chain line arrow in the figure is a lower metal plate. 20 is the shortest energization path (hereinafter referred to as the lower energization path L2). In the resistance welding method of the present invention, the contact positions of the electrodes 30 and 40 are set so that the upper energization path L1 is longer than the lower energization path L2. In this embodiment, the ground electrode 30 is brought into contact with one flange portion 12 of the upper metal plate 10, and the welding electrode 40 is brought into contact with the other flange portion 13, whereby the U-shape of the upper metal plate 10 is made. An upper energization path L1 having a long path length passing through the shape portion 11 is formed. On the other hand, since the lower energizing path L2 is formed in a straight line except for both ends, the path length is shortened. Thus, the upper energization path L1 has a longer path length than the lower energization path L2, and in the illustrated example, the upper energization path L1 has a path length that is 1.5 times or more that of the lower energization path L2. Accordingly, since a larger amount of current flows through the lower energizing path L2, a sufficient current can be passed through the planned joining portion Q 'formed on the lower energizing path L2 to ensure welding. In particular, when the upper metal plate 10 is formed thicker than the lower metal plate 20 as in the present embodiment, it is difficult to pass a sufficient current through the planned joining portion Q ′. In addition, by making the upper energization path L1 longer than the lower energization path L2, it is possible to allow a sufficient current to flow through the joint portion Q ′ without flowing an excessive current through the upper metal plate 10.

  By the way, if the upper metal plate 10 and the lower metal plate 20 are not in contact with each other at the point P directly below the ground electrode 30, the point P cannot be energized. It is formed by detouring. In this case, the path length of the lower energization path L2 becomes longer and the difference from the upper energization path L1 becomes smaller. In the worst case, the path length of the lower energization path L2 is longer than the path length of the upper energization path L1. There is a fear. In the present embodiment, by setting the point P directly below the ground electrode 30 as the already-joined portion, the metal plates 10 and 20 can be reliably brought into contact with each other at the point P to enable energization. It can be avoided reliably.

  In the present embodiment, the current flowing between the electrodes 30 and 40 is controlled by the current control unit, and welding is performed with an energization pattern (see FIG. 3) including a plurality of sections having different current values. Specifically, the first energization section A1 energized with a current value I1 that softens the upper metal plate 10 and the non-welding current value that is smaller than the current value I1 of the first energization section A1 and is not welded. A second energizing section A2 energized at I2, a third energizing section A3 energized at a welding current value I3 larger than the current value I1 of the first energizing section A1 and capable of welding the metal plates 10 and 20, and a third energizing. It consists of 4th electricity supply area A4 which supplies with electricity with the electric current value I4 (this embodiment is the same value as I2) smaller than the welding current value I3 of area A3. In the first and second energization sections A1 and A2, the upper metal plate 10 is softened and the electrode 40 bites into the upper surface of the flange portion 12, thereby ensuring a sufficient contact area between the electrode 40 and the metal plate 10. Therefore, generation of spatter due to local melting can be prevented. In the third energization section A3, the current is rapidly increased from the non-welding current value I2 to the welding current value I3, whereby the metal plates 10 and 20 of the planned joining portion Q ′ are partially melted, By solidifying, a welded portion Q (not shown) that joins both the metal plates 10 and 20 is formed.

  The present invention is not limited to the above embodiment. In the above embodiment, the upper energization path L1 is provided by bypassing the U-shaped portion 11 of the upper metal plate 10, thereby making the path length of the upper energization path L1 longer than the path length of the lower energization path L2. However, it is not limited to this. For example, as illustrated in FIG. 4, the upper metal plate 10 may be provided with an energization inhibiting portion to increase the length of the upper energization path L <b> 1. In the illustrated example, the upper metal plate 10 is energized on a path that connects the contact portions with the electrodes 30 and 40 (positions of the already-joined portion P and the planned joining portion Q ′ in FIG. 4A) at the shortest. For example, the slit 50 is formed as the inhibition portion. Accordingly, the upper energization path L1 is provided around the slit 50, and thus the path length becomes long. On the other hand, since the lower metal plate 20 is formed in a flat plate shape, the lower energization path L2 is formed in a straight line except for both ends, and the path length is shortened. Thereby, the path length of the upper energization path L1 can be made longer than the path length of the lower energization path L2.

  Further, the shape of the tip portions of the electrodes 30 and 40 is not limited to the truncated cone shape as shown in FIG. 2. For example, one or both tip portions of the electrodes 30 and 40 have a convex spherical shape, or the ground-side electrode 30. It is also possible to make the tip of the flat surface.

  In the above embodiment, one electrode 30 is a ground electrode, and the other electrode 40 is a welding electrode. However, the present invention is not limited to this. For example, both electrodes 30 and 40 are welding electrodes. Two welds may be formed simultaneously.

  Moreover, in said embodiment, after joining one flange part 12 and the lower metal plate 20 of the upper metal plate 10 by direct spot welding etc., and forming the already joined part P, the upper metal plate 10 The other flange portion 13 and the lower metal plate 20 are joined by the method shown in FIG. 1 to form the welded portion Q. However, the pre-joined portion P is necessarily formed prior to the formation of the welded portion Q. There is no need.

  In the above-described embodiment, the electrodes 30 and 40 are energized by the energization pattern (so-called four-stage energization, see FIG. 3) including four energization sections A1 to A4 having different current values. Absent. For example, an energization pattern (so-called two-stage energization, not shown) consisting of only two energizing sections, a second energizing section A2 having a non-welding current value I2 and a third energizing section A3 having a welding current value I3, is formed between the electrodes 30, 40 It may be energized.

10 Upper metal plate (hat shape)
20 Lower metal plate (flat plate)
30 electrodes (earth electrode)
40 electrodes (welding electrodes)
50 Slits L1, L2 Current path P Existing joint Q '

Claims (2)

This is a resistance welding method in which a pair of electrodes is brought into contact with one of the two stacked metal plates and an electric current is passed between the pair of electrodes to weld the two metal plates. And
The energization path (L1) connecting the pair of electrodes through the shortest through one metal plate is longer than the energization path (L2) connecting the pair of electrodes through the other metal plate in the shortest. A resistance welding method characterized by disposing electrodes.   The resistance welding method according to claim 1, wherein an energization inhibiting portion is provided on a path connecting the contact portions with the pair of electrodes in the shortest of the one metal plate.

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