JPH0733287B2 - Silicon carbide composite sliding member - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silicon carbide composite sliding member, particularly a silicon carbide composite sliding member that is used as a submerged bearing used in a fluid pump or the like and exhibits good performance. It is about.

[Prior Art] Conventionally, a carbon material has been used as a submerged bearing used as a bearing for a fluid pump or various flow meters, for example.
Since this product has a defect that abnormal wear occurs due to the inclusion of foreign matter such as earth and sand or slurry on the sliding surface, a silicon carbide sintered body has recently been used. The silicon carbide sintered body as a submerged bearing exhibits excellent sliding characteristics under low load conditions, but has the disadvantage that the friction coefficient increases and wear increases under high load conditions. Is usually
Machining into a desired shape with a grinder, but if the depth of cut is large during processing, chattering will occur and it will be difficult to obtain a good finished surface.Therefore, the depth of cut must be reduced during processing. There is a problem of workability such as not being.

Furthermore, the submerged bearing of a fluid pump is used under so-called dry or boundary friction conditions in which the liquid that acts as a lubricant does not sufficiently spread on the sliding surface due to idling at the time of pump startup or operation error. There was something. Under dry or boundary friction conditions, the bearing made of the above-mentioned silicon carbide sintered body has an increased friction coefficient and an increased amount of wear. Therefore, a complete liquid lubrication film is formed on the sliding surface. It had the drawback of being limited to use in.

As means for solving the above-mentioned drawbacks of the bearing made of a silicon carbide sintered body, for example, JP-A-60-141676 (hereinafter referred to as "prior art I") and JP-B-62-46508 (hereinafter referred to as "prior art II"). ) Is proposed.

This prior art I consists of 1 to 48% by weight of graphite elemental carbon, an effective amount of sintering aid and the remaining amount of silicon carbide, by adding 1 to 48% by weight of graphite elemental carbon. It can be used under dry or boundary friction conditions. Further, Prior Art II relates to a coke-silicon carbide composite sintered body, in which the oxidation resistance of the sintered body is improved.

[Problems to be Solved by the Invention] However, the above-described silicon carbide composite sintered body according to the conventional technique I exhibits excellent sliding characteristics under dry or boundary friction conditions, but has low mechanical strength and a small amount. There is a problem in handling such that the impact will cause the sintered body to crack.

Further, when the coke-silicon carbide composite sintered body according to Conventional Technique II is applied to a sliding member, it is particularly inferior in abrasive resistance and cannot be used as a bearing for a submersible pump in which inflow of earth and sand is forced. There is a drawback of wanting.

INDUSTRIAL APPLICABILITY The present invention solves the above-mentioned problems and exhibits excellent sliding characteristics even under dry or boundary friction conditions or high load conditions at the time of starting a pump, and exhibits high mechanical strength, and is particularly applied to a submerged bearing. The object is to obtain a suitable silicon carbide composite sliding member.

[Means for Solving the Problems] As a result of various studies conducted by the present inventors in order to achieve the above object, the coke having a residual volatile content of 4% by weight or more, 25 to 45% by weight, boron or a boron compound, 0.5 to 5% by weight. , 2-4% by weight of carbon or 2-4% by weight of carbon content after carbonization
The silicon carbide composite sintered body obtained by sintering a mixed powder of 6 to 10% by weight of a carbonizable organic material and the balance silicon carbide is not only under liquid lubrication conditions but also under dry or boundary lubrication conditions. Moreover, they have found that they also exhibit excellent sliding characteristics and high mechanical strength under high load conditions, and have completed the present invention based on this finding.

The silicon carbide powder which is the main component in the present invention can be used in either α type or β type, and powder having an average particle size of 5 μm or less is used.

The coke used in the present invention is a so-called raw coke having a volatile content, and may be any of petroleum-based, coal-based, and resin-based coke, but in order to obtain a particularly high strength product, a residual volatile content of 4% by weight or more is used. It is preferable to include.

The mixing ratio of coke is 25 to 45% by weight, preferably 25 to 40% by weight, based on the total amount of the mixed powder.

When it is less than 25% by weight, it is difficult to obtain good sliding characteristics under high load conditions even under dry or boundary friction conditions or liquid lubrication conditions, and when it is more than 45% by weight. However, the mechanical strength of the sintered body decreases, which is not preferable.

Boron or a boron compound such as boron carbide or boron nitride plays a role as a sintering aid of the mixed powder and a function of promoting graphitization at the time of sintering of the coke described above, and the mixing ratio thereof is the total amount of the mixed powder. With respect to 0.5 to 5% by weight.

Carbon, like the boron or the boron compound, plays a role of a sintering aid for the mixed powder, and examples thereof include carbon black. Further, in the present invention, a carbonizable organic material can be used instead of the above carbon. Examples of the carbonizable organic material include phenol resin and coal tar pitch. Phenol resin is particularly preferably used. The mixing ratio is 2 to 4% by weight when carbon is used and 6 to 10% by weight when carbonizable organic material is used, based on the total amount of the mixed powder. Carbon obtained by carbonizing the organic material The amount is 2 with respect to the total amount of mixed powder
It is used in an amount of about 4% by weight.

In some cases, it is also effective to add a temporary binder such as polyvinyl alcohol to the mixed powder having the above component composition. At this time, the amount of the temporary binder added is preferably about 3 parts by weight with respect to 100 parts by weight of the mixed powder.

Next, the manufacturing method of the present invention will be described.

First, coke powder and boron or a boron compound are added to silicon carbide powder, and further a carbon or carbonizable organic material and, if necessary, a temporary binder are added and mixed to obtain a mixture, and then the mixture is dried. , Crush into powder. The powder is loaded into a mold and pressure-molded at a pressure of 1000 to 2000 Kg / cm ² to obtain a molded body. Then, the above-mentioned molded body is sintered at a temperature of 1900 to 2100 degrees for 0.5 to 2 hours in a non-pressurized state to obtain a sintered body.

Hereinafter, the present invention will be described in detail with reference to Examples.

[Examples 1 to 3 and Comparative Examples 1 to 6] α-type silicon carbide powder (trade name: DU · A-1, manufactured by Showa Denko KK) having an average particle size of 0.5 micron in the proportions shown in Table 1, residual Coke powder having a volatile content of 11%, boron powder, phenol resin and 50 cc of acetone were mixed by using a ball mill for 10 hours, and then the mixture was dried and pulverized to obtain powder classified into 100 mesh under.

The mixed powder was loaded into a mold and pressure-molded at a pressure of 2000 Kg / cm ² to obtain a molded body.

This compact was fired for 1 hour in a heating furnace (argon gas atmosphere) heated to a temperature of 2050 ° C. to obtain a sintered body. This sintered body was machined to obtain a bending strength test piece having a length of 37 mm, a width of 4 mm, and a thickness of 3 mm, and a thrust test piece having a length and width of 32 mm and a thickness of 7 mm.

[Comparative Example 7] α-type silicon carbide powder (trade name: DU / A-1, manufactured by Showa Denko KK) having an average particle size of 0.5 micron in the proportions shown in Table 1, carbon black powder, boron powder, phenol resin , 50 cc of acetone and 3 parts by weight of polyvinyl alcohol were mixed in a ball mill for 10 hours, and then the mixture was dried,
The powder was crushed to obtain 100 mesh undersized powder.

The mixed powder was loaded into a mold and pressure-molded at a pressure of 2000 Kg / cm ² to obtain a molded body.

This compact was fired for 1 hour in a heating furnace (argon gas atmosphere) heated to a temperature of 2050 ° C. to obtain a sintered body. The sintered body was machined to obtain a bending test piece having a length of 37 mm, a width of 4 mm and a thickness of 3 mm and a thrust test piece having a length and width of 32 mm and a thickness of 7 mm.

[Comparative Example 8] α-type silicon carbide powder (trade name: DU / A-1, manufactured by Showa Denko KK) having an average particle size of 0.5 micron in the proportions shown in Table 1, graphite powder, boron powder, phenol resin, And acetone
After mixing 50 cc with a ball mill for 10 hours, the mixture was dried and pulverized to obtain powder classified into 100 mesh under.

The mixed powder was loaded into a mold and pressure-molded at a pressure of 2000 Kg / cm ² to obtain a molded body.

This compact was fired for 1 hour in a heating furnace (argon gas atmosphere) heated to a temperature of 2050 ° C. to obtain a sintered body. The sintered body was machined to obtain a bending test piece having a length of 37 mm, a width of 4 mm and a thickness of 3 mm and a thrust test piece having a length and width of 32 mm and a thickness of 7 mm.

Comparative Example 9 38.9% by weight of α-type silicon carbide powder having an average particle size of 0.5 micron, 51.2% by weight of coke powder having a residual volatile content of 11%, and 9.9% by weight of boron carbide powder were milled and mixed for 5 hours with a raker. The mixed powder thus obtained was loaded into a mold, and 2000
A compact was obtained by pressure molding at a pressure of Kg / cm ² , and then sintered in a heating furnace (argon gas atmosphere) heated to a temperature of 2000 ° C. for 1 hour to obtain a sintered compact. This sintered body was machined to obtain a bending test piece having a length of 37 mm, a width of 4 mm and a thickness of 3 mm and a thrust test piece having a length and width of 32 mm and a thickness of 7 mm.

The above Examples 1 to 3 and Comparative Examples 1 to 9 were subjected to a three-point bending strength test in accordance with JIS R 1601 "Bending strength test of fine ceramics" and an underwater load bearing thrust test under the following conditions. The results are shown in Table 1. In addition, "-" in the table
Indicates that the test was stopped midway because the friction coefficient increased.

Speed: 5m / min Load: 12.5Kg / cm ² accumulated every 0.5hr and finished at 250Kg / cm ² Mating material: SiC (φ12 × φ25 × 17) From the test results, the sintered bodies of Examples 1 to 3 showed stable sliding characteristics over the entire test time. On the other hand, in the sintered bodies of Comparative Examples 1 to 5, the friction coefficient gradually increased with an increase in the load, and a sharp increase in the friction coefficient was observed at a surface pressure of 150 kg / cm ² , so the test was stopped.

Next, the severer underwater thrust test was performed on the sintered bodies of Example 3 and Comparative Example 9 showing good sliding characteristics in the above-mentioned test. The test conditions are as shown below.

Surface pressure: 150Kgf / cm ² Speed: 5m / min Time: 50hr Water: Distilled water 0.1wt% Kanto loam 7 types (JIS Z 8901)
Addition partner material: SiC (φ12 × φ25 × 17) Table 2 shows the above test results.

From the test results, the sintered body of Comparative Example 9 cannot be applied to a bearing such as a submersible pump in which the wear amount is large, the resistance to abrasiveness is poor, and the intrusion of earth and sand is forced.

[Advantages of the Invention] The silicon carbide composite sliding member of the present invention exhibits good sliding characteristics not only under liquid friction conditions but also under dry or boundary friction conditions or under high load conditions, and has high mechanical properties. Since it has high mechanical strength and excellent resistance to abrasiveness, it is suitable as a material for submerged bearings used in water, chemicals, etc.

Claims (1)

[Claims] 1. Coke having a residual volatile content of 4% by weight or more.
25-45% by weight, boron or boron compound 0.5-5% by weight, carbon 2-4% by weight or carbon content after carbonization is 2
A silicon carbide composite sliding member formed by sintering a mixed powder of 6 to 10% by weight of a carbonizable organic material of 4 to 4% by weight and the balance silicon carbide.