JPS6061180A - Chip cover for welding - Google Patents

Abstract

PURPOSE:To improve mechanical strength and heat shock resistance by connecting the plane part and circular conical part of a ceramic chip cover of which the cylindrical part having a large diameter and the small diameter plane part at the top end are connected by the circular conical part by a curved surface having a specific radius of curvature or above. CONSTITUTION:The boundary part between the plane part 3 and circular conical part 4 of a chip cover for welding which consists of a cylindrical part 1 having a large diameter, the plane part 3 at the tip having a small diameter and having a guide hole 2 for a welding material 5 and the convergent circular conical part 4 and is formed of a ceramics consisting essentially of silicon nitride is formed to a curved surface having >=0.5mm. radius R of curvature. The ceramics consisting essentially of silicon nitride is constituted of 70-97wt% silicon nitride of an alpha layer, 0.1-10wt% of >=1 kind among molybdenum, niobium, halfnium, tantalum, tungsten and the carbide, silicide and boride thereof and 2-20wt% a grain boundary layer consisting of Si-Y-Al-O-N.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a tip cover made of ceramic containing silicon nitride as a main component and suitable for welding, particularly for MIG welding.

[Technical background of the invention and its problems] Conventionally, in a robot welding machine, a part of the power supply section that is affected by the arc has a guide hole for welding material in order to prevent the power supply section from being damaged by the arc. A chip cover made of ceramic such as alumina is fitted.

However, although such a tip cover is less likely to be damaged by arcing, it has the disadvantage that the flat part at the tip and the conical part following it are very easily destroyed by heat shock due to the rapid exposure to high temperatures during welding.

[Object of the Invention] The present inventor has completed the present invention by adopting silicon nitride, which is particularly resistant to heat shock among ceramics, and conducting repeated research to make effective use of this excellent property.

Among ceramics, silicon nitride is known as a material that is particularly resistant to heat shock, as mentioned above, but depending on the application, even a chip cover made of silicon nitride may be heated rapidly to, for example, 100°C. , If the cycle of holding for 10 minutes and then quenching is repeated,
Cracks may appear after about 20 cycles, and there has been a strong desire to improve this problem, especially in robot welding machines that require unmanned operation.

[Object of the Invention] The present inventor has carried out intensive research in order to resolve such conventional difficulties, and in particular, has developed a flat part at the tip having a guide hole for the welding material that directly receives the arc, and a conical part following this flat part. It has been found that the heat shock resistance can be significantly improved by connecting the boundaries between the two with a curved surface having a radius of curvature of a certain value or more.

The present invention was made based on this knowledge, and an object of the present invention is to provide a welding tip cover with excellent heat shock resistance.

[Summary of the Invention] That is, the welding tip cover of the present invention includes a large diameter cylindrical portion, a flat portion at the tip of a smaller diameter having a welding material guide hole, and a tapered portion connecting the cylindrical portion and the flat portion. In a welding tip cover formed of a ceramic whose main component is silicon nitride, the boundary between the flat part and the conical part is formed into a curved surface with a radius of curvature of 0.5 or more. It is a feature.

The ceramic containing silicon nitride as a main component used in the present invention is particularly selected from silicon nitride (70 to 97% by weight), molybdenum, niobium, hafnium, tantalum, tungsten, and their carbides, silicides, and borides. 0.1 to 10% by weight of one or more types and Si-Y-AA
A grain boundary layer composed of 2 to 20% by weight of -0-N is suitable.

Silicon nitride is known to have an α layer and a β layer, but the β layer is suitable as the silicon nitride in the present invention.

In the present invention, if the amount of silicon nitride cord is greater than the above range, problems tend to occur in terms of sinterability, and conversely, if the amount is less than the above range, the mechanical strength and heat resistance of the sintered body will be insufficient.

Furthermore, molybdenum is a component that improves the hardness, abrasion resistance, and bending strength of the sintered body, and its effect is sufficient when the amount exceeds 0.1% by weight, and this effect is noticeable up to 10% by weight. If this range is exceeded, the fracture toughness value begins to decrease and the mechanical strength tends to decrease. The grain boundary layer consisting of Si-Y-An-0-N may be composed of Y2O3-Aβ203 glass or crystalline compound when Y203 A℃203 etc. are used as a sintering aid. The grain boundary layer exhibits excellent sinterability when it is 2% by weight or more, and this effect is greater than 20% by weight.
It is noticeable up to the weight of %. If it exceeds this range, the mechanical strength and heat shock resistance of the resulting chip cover tend to decrease, so it is set within the above range.

In addition to these components, Ti 02 may be present in order to make the resulting chip cover more dense. In this case, the amount of Ti 02 is suitably in the range of 0.1 to 5% by weight.

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

Example 5 is N4 85% by weight, Y2O 35% by weight, 8β20
34 wt%, TiO23 wt% and MO2C3 wt%
After pulverizing and mixing in a ball mill and adding 7% by weight of paraffin to the resulting mixed powder, a large diameter cylindrical part 1 and a guide hole 2 were formed at room temperature under a molding pressure of 700 kg/cl. flat part 3 having
A hollow molded body having a conical portion 4 connecting the cylindrical portion 1 and the flat portion 3 was molded. This molded body was heated to 700°C to degrease it, and then sintered by heating at 1750°C for 120 minutes in nitrogen gas.

The dimensions of each part of the obtained tip cover for MIG welding are as follows: cylindrical part 1 has an outer diameter of 10 mm, an inner diameter of 5 mm, and a length of 7.5 mm.
mm, the diameter of the flat part 3 was 7mm, the diameter of the guide hole 2 was 1mm, the length of the conical part 4 was 7.5mm, and the thickness was 2.5mm.

Note that the reference numeral 5 shown by a dotted line in the figure represents an iron wire as a welding material, 6 a fixing nut, and 7 a power supply member.

Regarding the chip covers obtained in this way, the connecting portion between the flat part 3 and the conical part 4 has a different radius of curvature R.
A heat cycle of rapid heating to 0.degree. C., holding for 10 minutes, and rapid cooling (immersion in water) was performed to measure the number of times until cracks appeared. The measurement results are as follows.

(Left below) Radius of curvature (R) Times to life 0.03i+u 20 times or less 0.5im 85 times 1 in 150 times or more 2 dragons 150 times or more [Effects of the invention] As is clear from the above examples, The welding tip cover of the present invention has excellent heat shock resistance and is particularly suitable for unmanned operation equipment such as robot welding machines.

[Brief explanation of drawings]

The drawing is a sectional view of one embodiment of the present invention. 1・・・・・・・・・・・・Cylindrical part ３・・・・・・・・・・・・Flat area 4・・・・・・・・・・・・Conical part Representative Patent Attorney Noriyuki Chika (1 idiot) 7- (-<go ddl -

Claims (1)

[Claims] (1) It consists of a large diameter cylindrical part, a flat part at the tip of a smaller diameter having a guide hole for the welding material, and a tapered conical part connecting the cylindrical part and the flat part, and the main component is silicon nitride. A chip cover for erosion made of ceramic, wherein the boundary between the flat part and the conical part has a radius of curvature of 0.
A welding tip cover characterized by being formed into a curved surface of 5n or more.