JPH03155450A - Manufacture of composite sliding member - Google Patents

Abstract

PURPOSE:To manufacture a composite sliding member having high sliding performance by executing hot press sintering to the specific quantities of SiC whisker, graphite powder and Al alloy powder, preheating the composite base material obtd. by executing hot working forming to the sintered body at the specific temp. and inserting this with the specific temp. of molten Al alloy as internal chill. CONSTITUTION:Mixed material containing 15 - 30vol.% SiC whisker, 2 - 10vol.% graphite powder having <=10mum the max. particle diameter and the balance Al alloy powder having <=50mum the max. particle diameter, is heated under vacuum, and after executing degassing treatment, the hot press sintering is executed. The sintered body is hot-worked to form the prescribed shape of composite base material. This is preheated at 400 - 550 deg.C under non-oxidizing atmosphere and set to the position in a mold corresponding to the sliding posi tion. Successively, the molten Al alloy at 600 - 800 deg.C is cast under pressurizing to insert the composite base material as internal chill. As the Al alloy powder, the material having alloy composition containing <=10wt.% Si component, is used. By this method, the sliding member used under high temp. and severe conditions can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a composite sliding member in which the sliding portion is composed of a composite base material consisting of SiC whiskers, fine graphite powder, and 11 alloy.

[Conventional technology]

Attempts have been made for a long time to manufacture sliding members with excellent wear resistance by combining SiC whiskers with Al alloys, and many development proposals have been made so far. Many of these prior art techniques are aimed at reducing or adjusting the wear resistance phenomenon of the mating member due to composite SiC whiskers, and those that specify the combination with the mating member (JP-A-59-70734, JP-A-59-70734, JP-A-59-70734; -70735 publication)
, those using reinforcing materials mixed with solid lubricants (Japanese Unexamined Patent Publication No. 6
3-103033, 64-52032, etc.) have been proposed.

However, in this type of conventional technology, the composite means is generally carried out by a pressure casting method (molten m-forging method) in which a reinforced material molded body is impregnated with an Al-based matrix metal under high pressure.

For example, in Japanese Patent Application Laid-open No. 64-52032, a fibrous porous body made by molding solid lubricant powder such as graphite, Mobt, or BN into a predetermined shape and non-aluminum short fibers containing SiC whiskers is added to an Al-based matrix. A method is disclosed in which molten metal is impregnated and solidified under pressure, and it is stated that powder metallurgy requires a complicated manufacturing process and cannot produce a sliding member with low wear resistance and low attack on mating materials.

[Problem to be solved by the invention]

However, when forming composites using the pressure casting method, the reinforcing material preform is often damaged by external forces during casting, and in cases where only sliding parts are locally strengthened, the reinforcing material preform becomes porous and weak. Powder metallurgy is more practical in terms of operability, since it is difficult to fix it in a predetermined position in a mold due to the density.

From this perspective, the present inventor has conducted extensive research on a method for manufacturing composite sliding members using a three-component powder metallurgy method using SiC whiskers, graphite powder, and Al powder, and has clarified the most appropriate conditions. This led to the present invention.

[Means to solve the problem]

That is, the method for manufacturing a composite sliding member according to the present invention includes S
iC whisker 15-30vol%, maximum particle size 10μ
A mixture consisting of 2 to 10 vol% of fine graphite powder of 2 to 10 vol. The composite base material molded into a predetermined shape is preheated to 400 to 550°C in a non-oxidizing atmosphere, set at the mold position corresponding to the sliding part, and then heated to a temperature of 600 to 800"C.
A structural feature is that the composite base material is cast by pressure casting the molten L alloy.

The blending ratio of SiC whiskers, which serve as reinforcing materials, is 15 to 30.
The reason for limiting the volX range is that if it is less than 15 volχ, sufficient wear resistance will not be imparted, and if it exceeds 30 volχ, a sintered body with a good structure cannot be obtained and the cost will be high.

The fine graphite powder is a lubricant component, and preferably has a content of 20
Those with developed graphite crystals that have been graphitized in a high temperature range exceeding 00°C are selected and used. It is preferable that the fine graphite powder has a particle size as small as possible; if the maximum particle size exceeds 10 μm, a sintered body with a homogeneous structure cannot be obtained. In addition, it is important to set this blending ratio to 2 to 10 volχ, and if it is less than 2 vol χ, lubricity will not be imparted, and 1 o vol χ will not provide lubricity.
If the amount exceeds lχ, the material strength and wear resistance of the composite base material will decrease.

The Al alloy powder constitutes the matrix material, and from the viewpoint of wear resistance as a material, it is rated as, for example, JIS: AC8A.
It is desirable to select an Al alloy having a composition containing 10 wt% or more of Si component, such as AC9A. Also,
Components such as Cu, MgNi, and Mn are added as necessary. It is important to use the Al alloy powder in a fine powder state with a maximum particle size of 50 μm or less; if the maximum particle size exceeds 50 μm, the homogeneous structure of the sintered body will be impaired.

These raw material components are sufficiently stirred and mixed in water or an appropriate organic solvent, and then dried.

Next, the mixture is heated under vacuum to be degassed and then sintered under hot pressure. At this time, the preferred conditions for the degassing treatment are a temperature of about 500°C and a vacuum of about 10 Torr, and the sintering conditions are a temperature of about 500°C and a pressure of 1 to 1.5 ton/cm.
It is preferable to set it to .

The sintered body obtained in the sintering process is subsequently subjected to hot working such as extrusion and molding to form it into a predetermined shape. During this process, the sintered body transforms into an extremely strong structure.

Next, the composite base material after hot processing is preheated and then set at a position corresponding to the sliding position in the mold of the final shape.
The composite base material is cast by pressure casting the molten alloy. It is preferable that the composition of the Affi alloy used is the same as that of the Al alloy that is a component of the composite base material.

Preheating of the composite substrate in this step must be carried out under a non-oxidizing atmosphere such as Ar in order to prevent oxidation of the constituent components. Temperature conditions include preheating the composite base material to 400~400℃.
The molten metal temperature of the Al alloy is set at 550°C and within the range of 600 to 800°C. If these temperatures exceed the above-mentioned lower limit, poor contact between the casting materials will occur, and if the temperature exceeds the upper limit, the composite base material will melt.

Through the above steps, a composite sliding member whose sliding portion is reinforced with a composite base material is manufactured.

[For production]

According to the present invention, SiC whiskers, graphite fine powder, AI
! The process of mixing composite components consisting of alloy powder with appropriate particle size and blending ratio and sintering this gives properties such as wear resistance, sliding properties, and low abrasion resistance, and at the same time, it can be used as a sliding material. Necessary properties such as suitable strength, hardness, heat resistance, and corrosion resistance are taken into consideration. Next, in the process of hot working the sintered body into a predetermined shape! The dispersion of the SiC whiskers and fine graphite powder into the alloy matrix and the dust further progresses to form a uniform structure, and the above-mentioned performances are further improved.

Furthermore, by controlling the method and conditions of hot working, the orientation of the SiC whiskers can be adjusted as appropriate, so that the sliding performance can be improved from this perspective.

Through the following actions, it becomes possible to form a composite base material of a sliding member by powder metallurgy techniques.

The formed composite base material is completely cast in 11 alloy through a pressure casting process under the following specified conditions, and manufactured as a composite sliding member with an integral structure in which the sliding part is locally reinforced. Ru.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

Example 1 SiC whiskers with an average diameter of 0.5 μI and an average length of 15 μm, an average particle size of 1 μm graphitized at 3000°C,
Fine graphite powder with a maximum particle size of 2 μm and a maximum particle size of 44 μm
Nohe 2 alloy powder (JIS AC8A) was mixed with wet stirring in ethanol at various blending ratios, and dried to form a homogeneous mixture.

This mixture was filled into a mold with an inner diameter of 80 ann to produce 3 tons/
c11! After preforming at a pressure of 52
Degassing was performed by vacuum heating for 12 hours at 0°C, 1 vacuum degree, 5 x 10□' Torr, and then the atmosphere was changed to Ar gas, and the heat and pressure conditions were sintered at a temperature of 500'C, and a pressure of 1.5 ton/cm''. Figure 1 shows the relationship between the SiC whisker blending ratio and the sintered body filling rate at each blending ratio of graphite fine powder in this case.When the SiC whisker blending ratio exceeds 30volχ, the sintered body fills This tendency became remarkable when the blending ratio of fine graphite powder exceeded 10 vol.chi., and a good sintered body could not be obtained.

Next, each sintered body was heated to a temperature of 450 ”C with an outer diameter of 60 m +
m.

A composite base material was prepared by hot extrusion processing into a tubular shape with an inner diameter of 55 mm. At this time, the blending ratio of SiC whiskers is 30vo
lχ and the blending ratio of fine graphite powder is 20v.

In the case of a sintered body with a diameter exceeding 1χ, the surface became a hangnail state and the composite structure deteriorated.

Cut the above composite base material into lengths of 20 mm and have an outer diameter of 70 mm.
.

It is attached to a tubular jig with an inner diameter of 60-1, preheated to a temperature of soo'c in an Ar gas atmosphere, and set in a mold. After that, molten Al alloy (JIS AC8A) at 700 °C is injected and pressure cast. and allowed to solidify.

For each composite sliding member obtained, bearing ill (SU
A wear test was carried out under the conditions of a load of 100 kgf, a circumferential rotational speed of 1, and 0 s/s using a mating material (J2, square timber) in contact with the composite base material part. As a result, the relationship between the SiC whisker blending ratio and the wear amount of the composite sliding member at each blending ratio of fine graphite powder is shown in Figure 2, and similarly
The relationship between the blending ratio of whiskers and the amount of wear of the mating material is
Shown in the figure. From the results shown in Figure 2.3, the wear amount of both the composite sliding member and the mating material decreased under the conditions that the blending ratio of SiC whiskers was 15 to 30 volχ and the blending ratio of fine graphite powder was less than loVOIX (excluding Ovo12). It was confirmed that the material exhibited good sliding performance.

Example 1 20 vol% of the same SiC whiskers as in Example 1, 5 vol% of graphite fine powder with different particle sizes, and Al alloy powder (
JIS AC8A) 15vo12 and Example 1
A composite base material was created under the same conditions as described above. Subsequently, in the same manner as in Example 1, an aluminum alloy casting treatment was performed by pressure casting to obtain a composite sliding member.

In this case, the tensile strength (extrusion direction) of the composite base material and the wear age of the composite sliding member and the mating material in the sliding test were measured,
The results are shown in Table 1.

Table 1 From Table 1, RLIN No. outside the particle size range of the present invention,
It is found that in all Examples 2 to 5, the strength characteristics and relative sliding performance are deteriorated compared to RUN No. 1.

Example 3 Using the composite base material of RUN No. 1 of Example 2, sewing and packaging integration treatment was performed by changing the pressure casting conditions.

The tensile strength of the joint interface portion of each composite sliding member obtained was measured, and the results are shown in Table 2 in comparison with the pressure casting conditions.

Table 2 Table note: (1) Composite base material dissolves (2) Deformation of composite base material Among the examples in Table 2, the example that satisfies the conditions of the present invention is RLIN N.

1, 5, examples that deviate from the requirements are 2, 3, and 4.6. As is clear from comparing these two examples, the example of the present invention had a strong integrally joined structure without causing any damage or deformation to the composite base material.

〔Effect of the invention〕

As described above, according to the present invention, a sintered composite base material made of an appropriate combination of SiC whiskers, fine graphite powder, and Al alloy powder is used, and the sliding part is locally strengthened to provide high sliding performance. Composite sliding members can be manufactured.

Therefore, stable performance over a long period of time is guaranteed as various sliding members used under high temperature and harsh conditions.

FIG. 3 is a diagram showing the relationship between the SiC whisker blending ratio and the wear amount of the mating material.

Claims (1)

[Claims] 1. A mixture consisting of 15 to 30 vol% of SiC whiskers, 2 to 10 vol% of fine graphite powder with a maximum particle size of 10 μm or less, and the balance of Al alloy powder with a maximum particle size of 50 μm or less is vacuum heated to remove the mixture. After gas treatment, heat-pressure sintering is performed, and the sintered body is hot-processed to form a predetermined shape. A composite base material is preheated to 400 to 550°C in a non-oxidizing atmosphere to form a sliding part. Set it in the mold position, then heat it to 600-800℃
A method for manufacturing a composite sliding member, characterized in that the composite base material is cast by pressure casting a molten Al alloy. 2. The method for manufacturing a composite sliding member according to claim 1, wherein the Al alloy powder has an alloy composition containing 10 wt% or more of Si component.