JPS62127183A - Welding jig - Google Patents

Abstract

PURPOSE:To improve positioning accuracy and to make a positioning jig usable for a long period of time by forming said jig of silicon nitride ceramics. CONSTITUTION:The positioning jig 1 for spot welding is produced by adding an org. binder to a powder mixture composed of silicon nitride, several % of yttrium oxide as a sintering assistant and alumina, mixing the powder, molding the mixture to a prescribed shape and degreasing the molding then sintering the molding under an atm. pressure. Two steel members 4, 5 are positioned by the jig 1 and are then welded via upper and lower electrodes 2, 3 in the stage of subjecting said members to spot welding. Since the jig 1 has excellent wear resistance, the positional accuracy is improved. Since the jig has an excellent electrical insulating characteristic and thermal impact resistance, the jig is usable for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a welding jig for positioning two members to be welded in spot welding or the like.

[Technical background of the invention and its problems] For example, in assembling gears for automobiles, there are cases where two steel members must be welded at a predetermined position. The two are positioned through a welding jig and spot welded in this state.

This welding method θ will be explained in detail as shown in FIGS. 2 and 3. That is, the welding jig 1 has its lower part fitted into a lower electrode 2 made of, for example, a copper alloy, and its bottle-shaped upper part protrudes above the lower electrode 2. When performing welding, the steel member 4 having the hole 4a is placed on the lower mold 141 by passing the jig 1 through the hole 4a, and then the other steel member 5 to be welded is inserted into the hole formed in the steel member 5. Pass the jig 1 through 5a and place it on the steel material 4. Next, as shown in FIG. 3, the upper electrode 3 is lowered to separate the lower electrode 2 and the upper electrode 3.
The steel members 4 and 5 are fixed together by spot welding.

The jigs used for spot welding as described above are used under harsh thermal and mechanical conditions, so they must have wear resistance and thermal shock resistance, as well as electrical insulation to prevent electrical conduction. It is also required to have a To meet these requirements, one type of welding jig that has traditionally been used is one that uses a steel material such as stainless steel as a base material and has ceramics such as alumina sprayed on the surface to provide insulation properties. .

However, in the case of such 41 Fl, the coated insulation material peels off during use of the jig, making it unusable, or even if it does not peel off, the contact area between the workpiece and the jig wears out due to repeated use. However, there were problems such as the inability to perform the positioning function.

Also, jigs made of a single ceramic such as alumina are known, but they have a drawback in that their thermal shock resistance is low, ranging from room temperature to 200°C, and the jigs may be damaged by the heat generated during welding.

[Objective of the Invention 1] The present invention was made to solve the conventional problems as described above, and provides a welding jig that has electrical insulation, wear resistance, and thermal shock resistance, and can be used for a long period of time. The purpose is to provide

[Summary of the Invention] 1. The welding jig of the present invention is characterized in that it is made of silicon nitride ceramics.

The welding jig according to the present invention may have any shape, such as the shape shown in FIG. 1.

The welding jig of the present invention can be manufactured, for example, as follows.

Silicon nitride powder and, if necessary, a sintering aid such as yttrium oxide are mixed to form a mixed powder, a binder is added to this, molded into a predetermined shape, degreased, and then fired.
Manufactured by polishing. The firing method can be either the pressureless sintering method or the hot pressing method, but although manufacturing using the hot pressing method is more expensive, it is denser with fewer bores, has excellent mechanical strength, and has good thermal shock resistance. is preferable because it is (;1).

[Embodiments of the invention] Next, the present invention will be explained by examples.

Example An organic binder was added to a mixed powder consisting of silicon nitride and a few percent of yttrium oxide and alumina as sintering aids, the mixture was formed into the shape shown in Figure 1, degreased, and then sintered under pressure. A welding jig was manufactured by firing using a binding method.

The welding jig thus obtained had excellent electrical insulation, abrasion resistance of 1500° Vickers hardness, and thermal shock resistance of 700°C.

On the other hand, as a conventional example, a welding jig with a stainless steel base and alumina sprayed on the surface was manufactured.

The electrical insulation properties of this welding jig were good at the initial stage of use, but after repeated use, the insulating coating peeled off and the jig became defective. Further, the abrasion resistance was 1000 or less in terms of Vickers hardness, and the thermal shock resistance was from room temperature to 1000°C. Further, the life of this welding jig was about 1/3 of the life of the welding jig manufactured according to the above-mentioned embodiment of the present invention.

[Effects of the Invention] As explained above, the welding jig of the present invention has excellent wear resistance, so it is possible to prevent the workpiece from shifting due to wear of the jig, and to improve positioning. Accuracy can be improved.

In addition, the thermal shock resistance, which was a drawback of conventional Reramix jigs, has been improved, and the electrical insulation properties are also improved, so it can be used for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a front view of a welding jig showing one embodiment of the present invention;
FIGS. 2 and 3 are diagrams for explaining spot welding using a welding jig. 1...Welding jig 2...
・・・・・・・・・・・・Lower electrode 3・・・・・・・・・
......Top electrode 4.5......Steel members 4a, 5a...holes

Claims (1)

[Claims] (1) A welding jig characterized by being made of silicon nitride ceramics.