JPH09150276A - How to start flash welding - Google Patents

Abstract

(57) Abstract: It is an object of the present invention to provide a flash welding start method capable of easily performing flash welding even when there is a scale on an end surface of a member to be welded. SOLUTION: Two members to be welded 1 and 2 are respectively held by two electrodes 3A and 3B which are respectively connected to both output ends on the secondary side of a power supply transformer 5, and end surfaces of the members to be welded 1 and 2 are welded to each other. In the method of flash welding in which an electric current is applied between the electrodes 3A and 3B by contacting with each other, the end surfaces of the two members to be welded 1 and 2 are brought into contact with each other via the conductive contact medium 6 to start energization. Immediately after energization, flash welding is started after performing an initial energization process in which the current value is set to a predetermined current value required for flash welding and then an arc is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting flash welding by confirming the energization state between the end faces of two members to be welded during flash welding.

[0002]

2. Description of the Related Art As is well known, in flash welding, two members to be welded are held by their respective electrodes and the end faces of the members to be welded are brought into pressure contact with each other, and the applied voltage is as low as 7 to 13 V. A large current is passed between the electrodes to generate heat intensively at local contact points on the end faces to melt and disperse a spark, and one electrode is moved toward the other electrode to bring the end faces into close contact with each other. While repeating, contact and sparks are repeated. After the end face is sufficiently heated, it is pressed and thus the entire end face is welded.

The surface of a member to be welded in ordinary flash welding is covered with a scale, an oxide film or the like (hereinafter, simply referred to as scale). Particularly, scale is likely to occur in the high temperature steel material that is the welded member in continuous rolling. These films have a very large resistance value (impedance) as compared with the member to be welded, and cause poor conduction. When the current supply failure occurs, it causes freezing when the current necessary for the generation of the initial flash does not flow, and the time until the generation of the initial flash increases.

Therefore, conventionally, before welding, the end face is ground to obtain a clean surface, and if the flushing is not started, the welding is performed again.

[0005]

In many cases, poor electrical conduction between the electrode and the gripped portion of the member to be welded can be dealt with by re-gripping with the electrode or polishing the gripped portion. However, since the end surface of the member to be welded is difficult to be ground or the like, sufficient measures have not been taken, and the problem of the current flow failure still remains. In particular, when performing flash welding while a member to be welded is running, for example, when flash welding a next member to be welded to a member to be continuously rolled, a complicated device is required for end face polishing, and a large size of the device is required. In some cases, and in some cases, the operating efficiency may be reduced.

The present invention solves such a problem and provides a method capable of simply and inexpensively starting flash welding without requiring a special device.

[0007]

Two members to be welded to be flash-welded are respectively held by two electrodes respectively connected to both output ends on the secondary side of the power feeding transformer.

In the present invention, the end faces of the two members to be welded are brought into contact with each other via a conductive contact medium to start energization, and the current value immediately after energization is set to a predetermined current value required for flash welding. The flash welding is started after the initial energization process for generating an arc from.

When the above-mentioned end faces are brought into contact with each other through a contact medium, even if there is a scale on the end faces, this is broken or peeled off, and even if there are irregularities, the contact area increases,
The electric current required to generate the arc for flash welding comes to flow. Then, flash welding is started and continued under normal conditions.

As the contact medium, for example, metal fibers, particularly steel wool, metal powder (iron powder or the like), metal foil, or the like can be used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings.

In FIG. 1A, reference numerals 1 and 2 denote members to be welded, the ends of which are held by two sets of electrodes 3A, 3B and 4A, 4B. One set of electrodes 3A, 3B
Is connected to the secondary side of the power supply transformer 5. The two sets of electrodes are the electrodes 3A and 4A and the electrodes 3B and 4 that face each other.
B can be brought into and out of contact with the members to be welded 1 and 2 by a clamp mechanism (not shown) so as to grip the members to be welded 1 and 2 at a predetermined time. Further, one of the opposing electrodes, for example, the electrodes 3A and 4A, can be moved axially to a position where it is held in contact with the welded member 2 shown in FIG. 1 while holding the welded member 1 during flash welding. ing.

In this example as shown in FIG. 1 (A), flash welding is started under an initial energization process of the following procedure.
The flowchart is as shown in FIG.

First, as shown in FIG. 1 (A), the members to be welded 1 and 2 whose scale has already been removed at the portion to be gripped are operated by a clamp mechanism (not shown) to move the members to be welded 1 by the electrodes 3A and 4A. Then, the members 2 to be welded are grasped by the electrodes 3B and 4B, and the end faces of the members 1 and 2 to be welded are brought into contact with each other via a conductive contact medium, for example, steel wool 6.

Even if scales are attached to the end surfaces of the members to be welded 1 and 2, the contact medium 6 as shown in FIG.
Ensuring the energization path of the contact area necessary for arc generation,
The scale is broken or peeled off, and a current necessary for arc generation, for example, about 1,000 A flows there. By energizing, the contact medium 6 is heated and melted at the pinching portion.

When the current required for arc generation in the above is obtained and the contact medium 6 is melted, an arc is generated and flash welding is started and continued as it is, as shown in FIG. 1 (C). At that time, since the contact medium is melted and scattered, it is not taken into the welding site, but if possible, the contact medium is preferably made of the same material as the member to be welded.

[0017]

As described above, according to the present invention, in order to perform flash welding, the end surfaces of two members to be welded are brought into contact with each other via a contact medium to destroy or peel off the scale to secure a contact area. Therefore, it is possible to start and continue the flash welding by passing a current necessary for generating the arc of the flash welding of the member to be welded by an extremely simple method. Since the method of the present invention can be carried out by a simple device, it can be easily adopted during flash welding of a member to be welded during traveling.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment for carrying out the method of the present invention.

FIG. 2 is a flowchart showing a procedure for carrying out the method of the present invention.

[Explanation of symbols]

 1, 2 Members to be welded 3A, 3B Electrodes 4A, 4B Electrodes 5 Power transformer 6 Contact medium (Steel wool)

Claims (2)

[Claims] 1. The two electrodes to be welded are respectively held by the two electrodes respectively connected to both output terminals on the secondary side of the power feeding transformer, and the end faces of the members to be welded are brought into contact with each other so that the two electrodes are connected to each other. In the flash welding method in which an electric current is applied, the end faces of two members to be welded are brought into contact with each other via a conductive contact medium to start energization, and immediately after energization, the current value is set to the predetermined current value required for flash welding. The method for starting flash welding is characterized in that flash welding is started after performing an initial energization process for generating an arc. 2. The method for initiating flash welding according to claim 1, wherein the contact medium is steel wool.