JPH0193468A - Sliding member - Google Patents

Abstract

PURPOSE:To obtain a sliding member having sufficient mechanical strength and free from adhesion at the sliding surface, by constructing sliding surfaces with sintered silicon carbides each having respective specific density. CONSTITUTION:The objective sliding member has sintered silicon carbides on both sliding surfaces. One of the sintered silicon carbides has a density of 2.85-3.05g/cm<3> and the other has a density of >3.05. Although the low- density sintered silicon carbide may be used either the mobile side or the stationary side of the sliding member, it is preferable to use a low-density one at the easily changeable side because a low-density silicon carbide is liable to abrade. The density of the low-density silicon carbide is selected within 2.85-3.05g/cm<3> since a silicon carbide having a density of 2.85g/cm<3> has poor strength and is liable to cause chipping phenomenon which causes scuffing on the sliding face. When the density exceeds 3.05g/cm<3>, the pore content decreases to increase the contacting area, the sliding surfaces are closely contacted with each other owing to high finishing degree of the surfaces to necessitate large force for operation and, in the case of using in a liquid, the lubricity is lowered by the decrease in the amount of liquid retained on the sliding surface because of the absence of pores.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sliding member whose sliding surfaces are made of silicon carbide sintered bodies, and more specifically, by making one of the sintered bodies low in density, The present invention relates to a sliding member that can contain liquid in its pores, thereby improving sliding characteristics.

[Prior Art] Silicon carbide sintered bodies are known to be excellent materials for mechanical seals, sliding members such as bearings, etc. because of their excellent corrosion resistance and high hardness.

In this case, the silicon carbide sintered body generally has a high density of more than 3.05 sr/- from the viewpoint of mechanical strength and surface smoothness.

[Problems to be Solved by the Invention] Sliding members generally have particularly smooth surfaces to reduce frictional resistance during sliding and to prevent scratches on the sliding surfaces. However, when the surface of high-density silicon carbide sintered body is finished, it has a very smooth mirror surface, and the sliding surface is dense and has the disadvantage that it is difficult to slide under light force, which is especially a problem at the beginning of sliding. be.

Furthermore, in the case of silicon carbide sintered bodies having a low density, there is a problem in strength, and since the lapped surfaces are rough on both sides, chips are likely to occur and the life is short.

An object of the present invention is to provide a sliding member made of a silicon carbide sintered body that has no problems in terms of mechanical strength and does not cause adhesion on the sliding surface.

[Means for Solving the Problems] As a result of various studies to solve the above object, the inventors have found that:
The density of one side of the silicon carbide sintered body is low, 2.85 to 3.0
5g/cffl, and the other density is high, 3.05g/cffl.
It has been discovered that a sliding member configured to exceed - is good, and the present invention has been achieved.

Generally, one side of a sliding member is a movable side and the other side is a fixed side, but in mechanical seals, bearings, etc., sliding members are often used in water or other liquids.

In the sliding member of the present invention, either the movable side or the fixed side may be made of low-density silicon carbide sintered body, but it is preferable to use a low-density silicon carbide sintered body for easy replacement, since a low-density one is more likely to wear out. .

The density of low density silicon carbide is 2.85 to 3.05 g/Cl1
The reason why it is set as 1 is because if it is less than 2.85y/c++1, the strength will be low, chipping will occur easily, and it will cause galling on the sliding surface, and if it exceeds 3.05g/-, the pores will decrease, The contact area is large and the surface finish is good, so they stick together and require a large force to operate.Furthermore, even when used in liquid, there are almost no pores, so liquid does not accumulate on the sliding surface. This is because the lubricity decreases and the lubricity also decreases.

When the low-density silicon carbide sintered body is in a liquid, the liquid accumulates in its pores, improving sliding properties. Furthermore, the contact area with the high-density silicon carbide sintered body on the sliding surface becomes smaller, and the adhesion becomes weaker.

A silicon carbide sintered body is manufactured by adding known sintering aids such as carbon, boron, aluminum, etc. to fine powder of silicon carbide, followed by molding and sintering. At this time, by changing the amount of sintering aid, sintering conditions, etc., it is possible to produce sintered bodies ranging from low density to high density.

Silicon carbide has an α type and a β type, and in the present invention, both types and a mixture thereof can also be used.

The silicon carbide sintered body is machined into the intended sliding member and the surface is finished. For example, surface finishing is performed as follows.

First, both sides are ground using a grinder. After that, the sliding surface side is wrapped with diamond. For lapping, coarse diamonds are used at first, and the diameter is gradually reduced. For example, first use a 30μm diamond, then gradually reduce the diameter until the final diameter is 1μm.
Finished with diamonds.

[Example] To 100 parts by weight of silicon carbide powder with an average particle size of 0.45 μm, 0.8 parts by weight of boron carbide powder, 2.5 parts by weight of carbon black powder, 2.5 parts by weight of polyvinyl alcohol, and water were added. and mixed in a ball mill for 10 hours until 40%
A concentrated slurry was made and granulated using a spray dryer.

The granules were filled into a mold and press-molded at a pressure of 1500 kg/cm to obtain a green body.

Next, this formed body was sintered in an argon gas atmosphere at 2050°C to obtain a low-density sintered body having a density of 2.9 g/cI11, an average pore diameter of 5 μm, and a strength of 35 kg/−.

On the other hand, the granules were pressure-molded at a pressure of 2000 kg/cd to obtain a green body.

Next, this formed body was sintered in an argon gas atmosphere at 2130°C to have a density of 3.15 g/cd and a strength of 45 kg/cd.
A high-density sintered body of IIJ was obtained.

The above two sintered bodies were ground to an outer diameter of 3'h+ms, an inner diameter of 24mm, and a thickness of 8IIm, and one side of each was lapped to obtain a mechanical seal member with a surface roughness of 0.05 μm.

This mechanical seal is inserted into the ring-on disk (S) under water.
The friction coefficient was measured by placing a ring of SIC sintered body on a disk of IC sintered body and rotating it around the central axis of the ring. The density of the disc at this time is 3.15g
It was /-.

As a result, the friction coefficient of a mechanical seal with a density of 2.9 g/c+TI is a surface pressure of 1-8 kg/cd and a peripheral speed of 0.5 m/cd.
It was recognized that the s.

[Effects] As mentioned above, by making one side of the sliding member of the present invention low-density silicon carbide, the sliding properties are improved, and it is extremely excellent for applications such as mechanical seals and bearings used in liquids. This makes it possible to improve durability and reliability, making it extremely useful industrially.

Claims (1)

[Claims] In a sliding member whose sliding surfaces are made of silicon carbide sintered bodies, one silicon carbide sintered body has a density of 2.85 to 3.05 g.
/cm^3, and the other has a density exceeding 3.05.