JPH0360876A - Spot welding method for materials to be welded having insulating coating - Google Patents

Abstract

PURPOSE:To perform spot welding with a low current without providing a bypass circuit by superposing the material sides or coating sides of materials to be welded having insulating coating on each other, interposing metallic superfine powder between the joining faces and energizing and pressurizing these from the outside surfaces of both materials to be welded to perform spot welding. CONSTITUTION:The Ni superfine powder 3 is applied in proper quantity on the material side to be the joining face of a cold rolled steel sheet 1a having organic resin coating 2a. The material side of a cold rolled steel sheet 1b having organic resin coating 2b is then fitted thereon and chromium-copper electrodes 4 are arranged in opposition respectively on the outside surfaces of both cold rolled steel sheets 1a and 1b and pressurization 6 is applied thereon and welding is started while applying an electric current from a power source 5. In an initial pressurized state, the cold rolled steel sheets 1a and 1b and the Ni superfine powder 3 are then subjected to solid phase joining together to some extent and dielectric breakdown resistance is reduced by further, applying the current, hence the current 7 between the electrodes is carried via the cold rolled steel sheet 1b and the Ni superfine powder 3 from the electrodes 4. Afterwards, when the low current is applied in a short time, a nugget 8 is formed and spot welding is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for spot welding materials to be welded having an insulating coating.

[Conventional technology]

The conventional method for welding insulation-coated steel plates by spot welding is explained with reference to the schematic diagram in Figure 2 and the diagram in Figure 3.
In 1), a cold rolled steel sheet 1a having organic resin waves i2a, 2b.

lbs are stacked with their raw material sides aligned or, conversely, their coated sides aligned, as shown in the figure, and for spot welding, chromium copper electrodes 4 are placed facing the outer surfaces of the cold rolled steel plates la and lb, respectively. The cold rolled steel plates 1a and 1b are resistively heated by applying electricity from the power source 5 to utilize their conductivity, and at the same time, pressure 6 is applied to weld them.In this case, an organic resin wave ff12a is applied to the current path.

Since it is difficult to conduct electricity at the initial current stage due to the presence of the insulator part 2b, the organic resin waves 13j2a, 2b
A conductive bypass circuit 9 is connected between the electrodes 4 and 4, and a small bypass current (0) as shown in region (1) in FIG. 3 is applied to start welding.
．． When the dielectric breakdown resistance between electrodes 4 and 4 becomes smaller, an interelectrode current 7 begins to flow as shown in FIG. 2(n), and a large welding current as shown in the region (If) of FIG.
Once the current begins to flow, resistance heats up in the cold rolled steel sheets 1a and 1b, and welding progresses, and by applying a blood pressure 6 to the electrode 4 accordingly, the cold rolled steel sheets 1 are heated as shown in FIG. 2 (III).
A nugget 8 is formed on the bonding surfaces of a and lb, and the bonding is completed.

However, such a method has the following drawbacks.

(1) It is complicated to provide a bypass circuit, and depending on the shape of the workpiece, the bypass circuit may not be properly arranged and joining may not be possible.

(2) Voltage if the insulation coating has high insulation.

The current needs to be considerably large, which necessitates an increase in power supply capacity.

(3) In order to increase the amount of heat generated by the resistor, it is necessary to set the energization time to be long and to increase the pressing force, which causes the problem of deformation of the workpiece.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
It is possible to perform spot welding with a small current without installing a bypass circuit, and it is also possible to obtain sound joint strength with a simple welding operation, which in turn reduces construction costs and man-hours and improves welding quality. It is an object of the present invention to provide a method for spot welding materials to be welded having an insulating coating.

[Means to solve the problem]

To this end, the present invention provides spot welding of materials to be welded that have insulating coatings to be joined by overlapping the material sides or coating sides, by interposing ultrafine metal powder between the joint surfaces to It is characterized by spot welding by applying current and applying pressure.

[Effect]

With the above configuration, spot welding can be performed with a small current without providing a bypass circuit, and a healthy joint strength can be obtained with a simple welding operation, thereby reducing construction costs.

A spout for welded materials with an insulating coating that can reduce man-hours and improve welding quality.

It is possible to obtain a welding method.

〔Example〕

An example in which the method of the present invention is applied to spot welding cold-rolled steel sheets having an organic resin coating will be explained with reference to the drawings. ) is a cross-sectional view of the workpiece during preparation for welding work, FIG. 2 (II) is a schematic diagram during welding work, and FIG.

First, in FIG. 1(1), an appropriate amount of Ni ultrafine particle powder 3 is applied onto one workpiece, that is, the raw material side that will be the joint surface of the cold-rolled steel sheet 1a having the organic resin coating 2a, and then, as shown in FIG. Then, the raw material side of a cold rolled steel plate 1b having an organic resin coating ri 2b, which is a counterpart workpiece, is applied to this, and chromium steel electrodes 4 are placed facing each other on the outer surfaces of these cold rolled steel plates 1a and lb, respectively, and processed. Welding is started while applying pressure e and applying electricity from the power source 5.

Then, the cold rolled steel sheet 1a is in the initial pressurized state.

lb and the Ni ultrafine particle powder 3 are solid-phase bonded to some extent, and the dielectric breakdown resistance becomes smaller by further energizing.
An interelectrode current 7 flows from the chromium copper electrode 4 through the cold rolled steel Fj, lb and the Ni ultrafine particle powder 3. Thereafter, by applying low current for a short time, a nugget 8 is formed and spot welded as shown in FIG. 1 (■).

Thus, in this method, by interposing the Ni ultrafine particle powder 3 on the joint surfaces of the cold rolled steel plates 1a and 1b, these become solid-phase joined in the initial pressurized state, so that the chromium-copper electrodes 4. The dielectric breakdown resistance becomes small, and after that, the power supply 5 becomes energized and spot welding can be performed without a bypass circuit. In addition, spot welding can be performed even with a small current because resistance heat generation is generated through the NiM fine particle powder 3.

Further, the work is simple by simply applying the ultrafine Ni powder 3 onto the cold-rolled steel sheet la, and the nuggets formed by the small current passing die are also of good quality.

〔Effect of the invention〕

In short, according to the present invention, when spot welding two welded materials having insulating coatings to be joined with their raw material sides or coating sides overlapped, metal B fine particle powder is interposed between the joining surfaces, and the outer surface of both welded materials is By spot welding by applying current and applying pressure from the surface, spot welding is possible without the need for a bypass circuit and with a small current.
The present invention provides a spot welding method for materials to be welded having an insulating coating, which can obtain sound joint strength with a simple welding operation, reduce construction costs and man-hours, and improve welding quality. It is extremely useful for industry.

[Brief explanation of drawings]

Figure 1 shows the implementation procedure in the order of steps for an embodiment of the spot welding method applied to the spot welding of cold-rolled steel sheets having an organic resin coating, and (I) in the same figure shows the procedure during preparation for welding work. Figure (n) is a schematic diagram during welding work, and Figure (1) is a schematic diagram when welding work is completed. FIG. 2 is a schematic diagram showing the conventional spot welding method in the order of steps, and FIG. 3 is a diagram showing the current state in the same. Ia, lb...Cold rolled steel plate, 2a, 2b...Organic resin coating, 3...Ni ultrafine particle powder, 4...Chromium copper electrode, 5...Power source, 6...Pressure, 7... Inter-electrode current, 8... Nugget.

Claims (1)

[Claims] When spot welding the materials to be welded that have insulating coatings to be joined by overlapping the material sides or the coating sides, ultrafine metal powder is interposed between the joint surfaces, and the spot welding is performed by applying current and applying pressure from the outer surfaces of both materials to be welded. A method for spot welding a material to be welded having an insulating coating, characterized in that the material is welded.