JPH0616940B2 - Spot welding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a MIG or TIG spot welding method for a lining structure such as a seawater desalination apparatus and a chemical machine.

[Conventional technology]

The conventional MIG spot welding method will be described with reference to FIG. That is, the thickness of the base material 1 such as carbon steel is 2 to 3
2 mm of stainless steel or copper alloy, etc.
The welding torch 4 is brought into contact with the lining material 2, the welding wire 6 is fed into the power feed tip 5, and the inert gas 7 is flown into the welding torch 4, while the welding time setting timer 8
A voltage is applied between the base material 1 and the power feed tip 5 by the welding power source 9 provided with to generate an arc 10 at the tip of the welding wire 6 to form the weld metal 3 and the base material 1 and the lining material 2. Is to be welded.

[Problems to be solved by the invention]

In the conventional spot welding method, the arc is concentrated in one place for welding, so as shown in Fig. 5, the penetration depth is deep, it is difficult to guarantee the components, and the thermal stress becomes large, resulting in a weld boundary. There is a drawback that high temperature cracks 11 are likely to occur in the crater portion and the crater portion. Therefore, the conventional spot welding method cannot be used for important welded structures.

Therefore, there is a method of forming a hole in the lining material 2 and plug-welding the hole portion by a normal welding method. However, although this method can obtain a weld of good quality, it has a drawback of being very inefficient because it requires a large number of man-hours.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a MIG or TIG spot welding method capable of obtaining a high quality welded portion.

[Means for solving problems]

In the spot welding method of the present invention, in spot welding a plate material to the surface of the base material, a plurality of pairs of exciting coils are provided around the tip of the torch so as to face each other, and alternating currents having different phases are passed through the exciting coils of each pair. It is characterized by welding while.

The exciting coil is provided, for example, with 4 to 6 poles around the arc generating portion at the tip of the torch, and a single-phase or three-phase alternating-current exciting current is passed through this.

[Action]

According to such a spot welding method, a welding current in a substantially vertical direction from the welding wire (tungsten electrode) and a magnetic field in a substantially horizontal direction generated by the exciting coil cause a direction perpendicular to the magnetic field in the same plane as the magnetic field. An electromagnetic force (Lorentzka) is generated in the magnetic field, and the magnetic field rotates according to the phase of the alternating current, so that the arc rotates by receiving the electromagnetic force. Therefore, the arc is not concentrated in one place, a uniform penetration shape is obtained, and hot cracking does not occur.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, the same members as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1 and FIG. 2, a 6-pole iron core 21 and an exciting coil 22 are arranged around the arc generating portion at the tip of the welding torch 4, and these exciting coils 22 are supplied from an exciting power source 23, 5 A, and 3 phases of 60 Hz. Exciting current is applied.

Here, the three pairs of exciting coils 22 facing each other are shown in FIG.
And the phase of the current flowing through each exciting coil 22 changes as shown in FIG. 3 (b). In this case, the welding current flows from the welding wire 6 in a substantially vertical direction, whereas the magnetic field generated by passing the current through the exciting coil 22 corresponds to the phases at time ˜ and ′ shown in FIG. 3 (b). As shown by → in Fig. 3 (c), it rotates substantially in the horizontal plane. In response to this, the electromagnetic force (Lorentzka) in the direction perpendicular to the magnetic field in the same plane as the magnetic field generated by the welding current and the magnetic field rotates as shown in FIG. 3 (c). Welding is performed while the arc 10 is rotated by receiving this electromagnetic force. Therefore, the arc is not concentrated in one place, a uniform penetration shape is obtained, the components of the weld metal can be assured, the thermal stress is reduced, and the occurrence of hot cracking can be prevented.

Actually, the conventional method and the method of the present invention were used to examine the shape of the weld metal and the occurrence of cracks when a seawater desalination apparatus was manufactured. The base material is carbon steel SM50, and the lining material is austenitic stainless steel SUS316.
Using L, the welding conditions were welding current of 200 A, welding voltage of 28 V, and arc time of 5 seconds in both the conventional method and the method of the present invention. Further, in the method of the present invention, as described above, the 6-pole exciting coil 22 is provided, and 60 seconds H
A three-phase excitation current of z and 5 A was applied.

As a result, the penetration depth of the weld metal 3 was deep in the conventional method and hot cracking occurred, but in the method of the present invention, the weld metal 3'having a uniform penetration was obtained as shown in FIG. 1 and hot cracking also occurred. I didn't.

〔effect〕

As described in detail above, according to the method of the present invention, a uniform penetration shape can be obtained, the components of the weld metal can be guaranteed, and the occurrence of hot cracking can be prevented, and high efficiency and high quality MIG or TIG spot welding becomes possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a spot welding apparatus in an embodiment of the present invention, FIG. 2 is a plan view showing an arrangement of exciting coils of the spot welding apparatus, and FIG. 3 (a) is a wiring diagram of the exciting coils. (B) is a waveform diagram of the current passed through the exciting coil, (c) is an explanatory diagram showing changes in the generated electromagnetic force, FIG. 4 is a configuration diagram of a conventional spot welding apparatus, and FIG. It is explanatory drawing which shows the fault of the method. 1 ... Base material, 2 ... Lining material, 3 3 '... Welding metal, 4 ... Welding torch, 5 ... Feeding tip, 6 ... Welding wire, 7 ... Inert gas, 8 ... Welding Power supply, 9 ... Welding time setting timer, 10 ... Arc, 11 ... High temperature crack, 21 ... Iron core, 22 ... Excitation coil, 23 ... Excitation power supply.

Claims (1)

[Claims] 1. When spot welding a plate material to the surface of a base material, a plurality of pairs of exciting coils are provided around the tip of the torch so as to face each other, and welding is performed while passing alternating currents of different phases to the exciting coils of each pair. Spot welding method characterized in that.