JPH02225376A - Electroconductive sialon sintered product, its production and dice for wire elongation - Google Patents

Abstract

PURPOSE:To obtain electroconductive sialon sintered product having high flexural strength and special and complicated shapes by sintering formed products from a sintering auxiliary-containing starting substances for beta-type sialon and Ti or a nitride and Si under specific conditions. CONSTITUTION:Starting substances for beta-type sialon containing a sintering auxiliary is mixed with 25 to 60vol.% of at least one selected from Ti and Zr nitride, 0.2 to 3.5vol.% of Si and the mixture is formed. The formed products are kept at 1,550 to 1,850 deg.C for 1 or more hours in a nitrogen atmosphere at normal or elevated pressure, then sintered at 1,700 to 1840 deg.C over 2 hours to give the subject sintered products. The use of Ti or Zr nitride is due to their high electroconductivities and high melting points with reduced adverse effects on sialon sintering. Si is readily wettable with the melt formed in sialon sintering to give a texture of higher homogeneity and reduced defects. Thus. the product gives a high strength matching those in hot press or HIP processing.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sialon sintered body, a method for manufacturing the same, and a wire drawing die.
The present invention relates to a conductive sintered body mainly composed of β-type sialon represented by 6-zI4izOzNe-2).

(Conventional technology) β-type sialon sintered bodies have advantages such as being relatively resistant to adhesion of metals such as iron, having excellent high-temperature strength and oxidation resistance, and having a small coefficient of thermal expansion and high thermal shock resistance. Therefore, in recent years, attempts have been made to apply it in various fields.

On the other hand, β-type sialon sintered bodies have difficulties in workability, and currently they are generally processed using diamond grinding wheels, but the grinding wheels tend to become clogged with processing debris.
There is a problem that processing time and cost become extremely large. For this reason.

Recently, it has been proposed to add oxides, nitrides, and carbides of IVa, Va, and Vla group elements to β-type sialon to impart electrical conductivity to obtain a sialon sintered body that can be processed by electric discharge machining (particularly 1982-285177), electric discharge machining allows special and complex shapes to be machined in a relatively short time and at low cost. Therefore, even a shape with a combination of tapered and curved surfaces, such as a die for wire drawing, can be processed relatively easily.

(Issue 8 to be solved by the invention) The present inventor has conducted an experimental study to apply the conductive sialon sintered body according to the above-mentioned known technology to metal processing tools such as dies and bits, and has found that it is practical. concluded that a sintered body with higher bonding strength between ceramic particles is desirable.

That is, when the bonding force between particles is weak, high stress generated when a metal such as iron is plastically deformed causes one particle to separate and wear progresses. In order to suppress this wear and extend tool life, it is necessary to increase the bonding force between particles, that is, to increase the bending strength. As a method for increasing the bending strength, physical methods such as hot pressing and HIP have been proposed (Japanese Patent Laid-Open No. 53-207881).

However, when sintering by hot pressing,
Although a sintered body with a relatively simple shape can be obtained, it is difficult to obtain a sintered body with a complicated shape.

Furthermore, when HIP is used, it is possible to obtain a sintered body with a complicated shape, but sintering is required in the previous step, which increases the number of manufacturing steps.

In view of the above circumstances, it is an object of the present invention to provide a conductive sialon sintered body having higher flexural strength and a special/complicated shape without increasing the number of manufacturing steps. Furthermore, it is an object of the present invention to provide a die with a long life by applying one sintered body to a die for wire drawing.

(Means for Solving the Problems) In order to achieve the above object, the first invention is a β-type sialon (S i &-ZMZ 0zNs) containing a sintering aid.
A sintered body consisting of 25 to 60% by volume of one or more of the nitrides of Zr) and nitrides of Zr and 0.2 to 3.5% of Si to the total volume. be.

The reason why Ti and Zr nitrides are used as constituent components is that these are compounds with conductivity and a high melting point, and have little adverse effect on the sintering of Sialon. The amount of these compounds added is 25% to 60% by volume.
If it is less than 60% by volume, there are few contact points between the conductive compound particles and the conductivity required for electrical discharge machining cannot be obtained.
This is because it is difficult to adhere and the high strength and high toughness are impaired. The amount of nitride added is more preferably 30 to 50% by volume.

Sl easily wets with the melt produced during Sialon sintering. Therefore, in the absence of Si as shown in Fig. 1 (A), the melt is mixed between ceramic particles such as β-type Sialon and nitrides of Ti and Zr. It may be difficult to ensure that it spreads sufficiently, but when there is Sl as shown in Figure 1 (B), the melt actively wets the surfaces of these heavy particles, and at the same time! Since the surface of the particles in the A area is also wetted, the melt can spread between the particles every minute,
This results in a more homogeneous structure with fewer defects. the result,
It has high strength comparable to hot press and HIP.

The amount of Si added is 0.2 to 3.5% by volume.

This is because if it is less than 0.2% by volume, it is insufficient to improve the wetting of the melt and the particles, and if it exceeds 3.5% by volume, the effect that the particles themselves become a starting point for destruction becomes more pronounced. Si
The amount added is more preferably 1.0 to 2.5% by volume.

As the sintering aid, known ones can be used.

The amount of Sialon is more preferably 30 to 50% by volume.

Furthermore, the method for manufacturing the conductive sialon sintered body, which is the invention of the youngest brother 2, is as follows. That is, as a raw material for β-sialon, Si! Nn, AR
A mixture or compound of M, A203, and β
As type SiAlON, Z has a predetermined value, and Y2O
3.
A mixture in which i is 0.2 to 3.5% by volume based on the total volume is molded, and this molded body is held at 1550 to 1850°C for 1 hour or more in a normal pressure or pressurized nitrogen gas atmosphere, and then 1
By holding and sintering at 700-1840''C for 2 hours or more, the conductive sialon sintered body of the present invention can be obtained.

Note that the reason why the temperature is maintained at 1550 to 1850°C is to uniformly distribute the melt at the grain boundaries. If the temperature is lower than 1550°C, the distribution of the melt will be insufficient. Also, Si! Once N4 is dissolved in the melt, it precipitates and grows into columnar crystals, and when these columnar crystals grow sufficiently and intertwine with each other to become dense, β-sialon exhibits high strength. However, at 1850 to 1700°C, the growth of columnar crystals is insufficient and densification is not achieved.Therefore, the dissolution of 5ixNa must be suppressed while the melt is uniformly distributed at the grain boundaries. The temperature needs to be below 1B50°C.

Next, the reason for holding it at 1700-1840℃ is 1
If the sintering temperature is less than 700°C, densification will not proceed sufficiently for the reasons mentioned above, and if the temperature exceeds 1840°C, the decomposition of 5iJ4 cannot be suppressed unless it is in a nitrogen gas of 100 atmospheres or more. At such high pressures, it is necessary to eliminate open pores in the molded body in advance, which increases the number of manufacturing steps. In addition, when sintering in a pressurized nitrogen gas atmosphere, the nitrogen gas pressure is preferably 1.1 to 30 atm.

Furthermore, the invention of this section 3 is to apply the above-mentioned sintered compact or the sintered compact manufactured by the above-mentioned manufacturing method to the nib in a wire drawing die having a nib and a die case.

(Function) According to the present invention as described above, by sintering in a normal pressure or pressurized nitrogen atmosphere without hot pressing, the bonding force between particles is stronger than that of conventional conductive sialon sintered bodies. Therefore, it has become possible to easily obtain a sintered body with high bending strength. Furthermore, in a wire drawing die having a nib and a die case, when the above-mentioned conductive sialon sintered body was applied to the nib and a metal wire was drawn, the life of the die was improved compared to conventional materials. This is because the wear of the linib, which makes it difficult for particles to peel off, is suppressed by improving the interparticle bonding strength of the material that makes up the nib.

(Examples) Hereinafter, the present invention will be described in more detail based on Examples.

Example 1 5i3Ni powder (average particle size 0.5l, gelatinization rate 87% or more), Al2O3 powder (average particle size 0.2l), M
ll polytype powder (crystal type 21R1 average particle size 3JJ,
Z of β-sialon in a sintered body using Z = 0.
45, and further added Y2O3 as a sintering aid.
Powder (average particle size 0.6 Kawagiri) was blended so that (Y203/β-type Sialon+Y20x)X100 = 7.3% by weight. On the other hand, TiM, ZrH (both have an average particle size of 2) and Si (average particle size 2)
were added in the proportions shown in Table 1. After mixing and forming these, the mixture was held at 1600°C for 2 hours in a nitrogen gas atmosphere at normal pressure, then sintered at 1750°C for 5 hours, and slowly cooled to room temperature. Table 1 shows the room temperature bending strength and electrical resistivity of the sintered body thus obtained.

Example 2 Some of the sintered bodies of the present invention shown in Example 1 were applied to the nib of a wire drawing die and subjected to a wire drawing test. The results are shown in Table 2.

(The following is a blank space) (Effects of the Invention) The present invention has made it possible to manufacture a β-type sialon sintered body that has higher bending strength than conventional ones and is capable of electrical discharge machining.

Furthermore, by applying the Sialon of the present invention to wire drawing dies, it is possible to extend the life of the dies. It can also be applied to

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the meaning of melt and ceramic particles. 1ass ceramic particles, 2. molten liquid, 3...S
i particle.

Claims (3)

[Claims] (1) β-type sialon (Si_6_-_
zAl_zO_zN_8_-__z) and one or more of Ti and Zr nitrides account for 25 to 60% by volume of the total capacity.
, a conductive sialon sintered body characterized in that Si is comprised of 0.2 to 3.5% by volume based on the total capacity. (2) β-type sialon raw material containing a sintering aid, Ti,
One or more types of Zr nitrides account for 25-6% of the total capacity.
0 volume%, Si is 0.2 to 3.5 volume% of the total capacity
The molded body is held at 1550 to 1850°C for 1 hour or more in a normal pressure or pressurized nitrogen gas atmosphere, and then held at 1700 to 1840°C for 2 hours or more to sinter. A method for manufacturing a conductive sialon sintered body. (3) A wire drawing die having a nib and a die case, wherein the nib is made of the conductive sialon sintered body according to claim 1.