JPS63177975A - Projection welding method - Google Patents

Abstract

PURPOSE:To make the current density of a contact surface constant,and to stabilize the joining strength by forming a projection to a circular ring shape in which the top surface is flat and the center positions of the inner periphery and the outer periphery are different from each other, and welding it by the electric conduction of a current of a specified crest time. CONSTITUTION:While pressing the upper electrode 3a, a current to which crest time is <2mm is brought to an electric conduction to both electrodes 3a, 3b by a power source 9. The current is conducted into a first metal plate material 1a with a ring-like current density distribution by a surface effect and reduced in the part of a ring-shaped projection 13. Also, in this case, the current in conducted in large quantities to the opposite side of a bus bar 8 by electromagnetic force, therefore, by a positioning the thickest part of the ring of the projection 13 at the opposite side of the bus bar 8, the current density becomes uniform in all parts on the contact surface of the ring-shaped projection 13 and a second metal plate material 1b, and the joining state also becomes constant. Therefore, a flow diversion to the part having no relation to a junction is eliminated, and the current brought to an electric conduction is all utilized effectively for the junction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection welding method for joining two metal plates by overlapping them, particularly for welding by applying a current with a wave height of less than 2 milliseconds. It is about the method.

[Conventional technology]

Conventionally, for example, "Resistance welding phenomenon and its applications (■),
"Butt Projection Welding", Welding Society Resistance Welding Committee Wire Mesh, Welding Society Technical Data No. 9. December 1981, as shown on pages 138-144, weld two metal plates by overlapping them via projection. Grojection welding methods are generally known.

Figure 3 shows welding of doors, etc. using this type of conventional projection welding method, and shows a case where a back plate such as a mild steel plate is welded to the front plate to reinforce the front plate made of metal plate material. . In the figure, (1a) is a first metal plate provided with a truncated cone-shaped projection (2), for example, a back plate made of a mild steel plate, and (1b) is a second metal plate on the other side without a projection. For example, a top plate made of mild steel plate, (
3a) is an upper electrode connected to the upper surface of the first metal plate (1a), and (3b) is the second metal plate fixed on the frame (4) in a state insulated from the frame (4). The lower electrode (5) is connected to the lower surface of the plate (1b), and the upper electrode (3a)
) is used to pressurize the soil part electrode (6a) and both metal plates (1a) and (1b) via the n-rod (a) fixed to the upper frame (6). There is. The rod (A) is insulated from the upper electrode (3a), and both electrodes (3a) and (3b) are connected to a power source (9) via a bus bar (8).

As this power supply (9), a capacitor power supply is used.
It is set so that the current peak time is less than 2 milliseconds.

The conventional projection welding method is constructed as described above, in which both metal plates (1a) and (ib) are superimposed, and a power source (9) is used to press both electrodes (3a) while applying a predetermined pressure to the electrodes (3a). ), (3b), the current flows through the first metal plate (1a), the projection (2), and the second
Flow the metal plate material (1b). Then, the current concentrates in the projection (2), generating Joule heat, and both metal plates (
1a) and (1b) are joined.

[Problem that the invention seeks to solve]

In the conventional projection welding method as described above, if the current wave height time is less than 2 milliseconds, the projection (2) has a truncated conical shape, so due to the skin effect of the current and the electromagnetic force accompanying energization, Projection (
There is a problem in 2) that the current density is not uniform at each part of the top surface.

Figure 4 shows a conventional truncated cone-shaped projection (2)
This figure shows the joint state of the joint interface of a welded part obtained by a projection welding method using This shows the part that melted and exploded into holes due to overcurrent density.

As described above, there is a problem in that the bonding state is affected by the non-uniformity of the current density on the contact surface of the projection (2), making it difficult to obtain a healthy bond.

The present invention was made to solve these problems, and an object of the present invention is to provide a projection welding method that can obtain a sound joint state over the entire contact surface of the projection top surface.

[Means for solving problems]

In the projection welding method according to the present invention, the projection has a circular ring shape with a flat top surface and center positions of the inner and outer peripheries that are different from each other, and two metal plates are bonded together.
In addition to pressure contacting through this projection, welding is performed by passing current through both metal plates with a wave height time of less than 2 milliseconds.

[Effect]

In this invention, the projection is a circular ring shape with a flat top surface and different center positions on the inner and outer peripheries. Contact portions are formed between the metal plates according to the distribution. Therefore, the current density at each part of the contact surface is constant, and the bonding state is also uniform. As a result, the bonding strength is stable, there is no melting or explosion due to overcurrent density, and surface distortion of the plate material can be suppressed.

〔Example〕

1 and 2 show an example of the implementation of this invention, and in the figures, the same reference numerals as in FIGS. 3 and 4 indicate the same or corresponding parts. (18) is a ring-shaped projection whose top surface is flat and the center positions of the inner and outer peripheries are different from each other, and the inner and outer peripheries of the top surface are both perfectly circular as shown in FIG. Moreover, the center position of the inner periphery is eccentric toward the bus bar (8) side. Also, this projection α3) has a height of 0. ] Above the wing, the first metal plate (1
The thickness is set to be less than the plate thickness in a).

In the projection welding method configured as described above, in the state shown in FIG.
), (3b) is passed with a current having a peak time of less than 2 milliseconds. Then, the current flows into the first metal plate (1a) with a ring-shaped current density distribution due to the skin effect, and is narrowed down at the ring-shaped projection aa+. Also, at this time, the current flows through the busbar (8) due to electromagnetic force.
), the projection (18
) by positioning the thickest part of the ring on the opposite side of the bus bar (8), the current density at the contact surface between the ring-shaped projection CIBI and the second metal plate (1b) is uniform at all points. Therefore, the bonding state is also constant. For this reason, there is no branching of current to parts unrelated to the bonding, and all the passed current is effectively used for the bonding, making it possible to reduce the passed current. This makes it possible to reduce the thermal influence on the metal plates (1a) and (Ib), and at the same time suppress distortion on the plate surfaces.

〔Effect of the invention〕

As explained above, this invention has a gloziexion,
A circular ring shape with a flat top surface and different center positions on the inner and outer peripheries is used, and two metal plates are pressed together through this projection, and both metal plates are heated with a wave height of less than 2 milliseconds. Since welding is performed by applying current, the above projection forms contact areas between the metal plates in response to the uneven distribution of current density due to the skin effect and electromagnetic force, and welding occurs at each part of the contact surface. There is no current explosion, and the surface distortion of the plate material can be suppressed.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of an apparatus for implementing the projection welding method according to the present invention, Fig. 2 is an explanatory diagram showing the configuration of the projection part, and Fig. 3 is a diagram showing an example of a device for implementing the projection welding method according to the present invention. FIG. 1 is a diagram showing an apparatus for this purpose, and FIG. 4 is an explanatory diagram showing a state of joining at a joining interface by a conventional welding method. (1a): First metal plate (1b): Second metal plate (3
a): Upper electrode (3b): Lower electrode (8) Nib spar (9): Power source α3): Projection In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] (1) The first metal plate and the second metal plate are brought into contact via a projection provided on the first metal plate, and the electrodes connected to each of the metal plates are connected via a bus bar. In a projection welding method in which welding is performed by connecting each to a power source, the projection is formed into a circular ring shape with a flat top surface and different center positions on the inner and outer peripheries, and both metal plates are welded through this projection. At the same time as pressure welding, the wave height time is 2 for both metal plates.
A projection welding method characterized by welding by applying a current of less than milliseconds. (2) The projection welding method according to claim 1, wherein the projection has a height of 0.2 mm or more and less than the thickness of the first metal plate. (8) The projection welding method according to claim 1 or 2, wherein the projection has an inner circumference and an outer circumference of the top surface each having a perfectly circular shape. (4) The center position of the inner periphery of the projection is eccentric to the bus bar side.
The projection welding method according to any one of items 3 to 3.