JPS62297267A - Manufacture of sliding material for sliding seal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a method for producing a silicon carbide sliding material for mechanical seals with good corrosion resistance by a reaction sintering method. Sliding materials for mechanical seals used as shaft seal devices for technical pumps and the like are focused on properties such as wear resistance, friction coefficient, heat resistance, corrosion resistance, and strength. Therefore, as sliding materials for mechanical seals, a combination of self-lubricating carbonaceous materials and wear-resistant hard materials such as hardened steel, ceramics, and cemented carbide has traditionally been used. In recent years, sintering methods using silicon carbide as the main component have come into use. This is because the silicon carbide sintering method has extremely high hardness, excellent heat resistance and corrosion resistance, and also high thermal shock resistance, which is unusual for ceramics.

Typical methods for producing silicon carbide sintered bodies include hot press sintering of silicon carbide with the addition of a special sintering aid (e.g., Japanese Patent Application Laid-open No. 5O-34608);
A method of sintering without pressure (e.g., JP-A-50-78609) J3 and a method of infiltrating silicon melt or steam from the outside into a mixed powder compact of silicon carbide and carbon to convert carbon particles into silicon carbide. Reaction sintering method to convert
No. 061), but it is well known that each has its advantages and disadvantages.

Looking at this with respect to the reaction sintering method, the reaction sintering method has very little dimensional shrinkage during the sintering process, so the dimensional accuracy of the product is good, and there is little variation in physical properties such as strength and strength, and it has excellent heat resistance and durability. It has the advantage of producing products with excellent wear resistance, but in terms of corrosion resistance, it is only slightly inferior to silicon carbide sintered bodies produced by Ike's manufacturing methods, such as pressureless sintering. The problem is that the finger is +Xl.

That is, silicon carbide sintered bodies produced by the reaction sintering method exhibit somewhat insufficient corrosion resistance when used as sliding materials for mechanical seals used under severe conditions in which they come into contact with strong chemical solutions such as acids and alkalis. This is because about 10 to 30% of unreacted silicon remains in the product.

Therefore, it is clear that corrosion resistance can be improved by selecting manufacturing conditions such that the amount of unreacted silicon is reduced, but this is by no means easy. For example, the method of making the molded object subjected to silicon infiltration treatment more dense to prevent an excessive amount of silicon from penetrating makes it difficult to uniformly penetrate the silicon melt to the core of the molded object, resulting in product strength. This tends to lead to a decrease in

2. Problems to be Solved by Meiji The present invention solves the above-mentioned problems when producing silicon carbide sliding materials for mechanical seals by the reaction sintering method, and is comparable to that produced by Ike's method in terms of corrosion resistance. The purpose of the present invention is to provide a method for manufacturing a sliding material that has the following properties.

Means for Solving the Problems The method of manufacturing a silicon carbide sliding material for mechanical seals according to the present invention involves forming a molded body from silicon carbide powder and carbon powder into a molded body having a density that allows silicon melt to penetrate to the core. The surface layer of the molded product is impregnated with a thermosetting resin, and then fired in a non-oxidizing atmosphere to carbonize the thermosetting resin. Remove the parts of the material other than those that will be in contact with the liquid (not all of them), then infiltrate silicon melt into the molded body and react with the carbon in the molded body to produce silicon carbide. It is characterized by allowing

Below, the surface (area from position X to Y) on the outer peripheral side of the sliding surface 1 has a cross-sectional shape as shown in FIG.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings regarding a specific example of manufacturing a sliding material for mechanical seals having a circular ring shape.

First, silicon carbide powder and carbon powder are molded using a suitable amount of a binder (for example, a thermosetting resin such as a phenolic resin) according to a conventional reaction sintering method. The blending ratio of each component is approximately 60 to 90% by weight of silicon carbide powder, 10 to 40% by weight of carbon powder, and 5 to 40% by weight of organic binder. Too much carbon powder and organic binder will increase the amount of unreacted carbon in the sintered body, and too little will increase the amount of unreacted silicon in the sintered body, both of which are undesirable.

The molding pressure is approximately 4 to 2 G g/c + n'', which is the density force of the molded body obtained by pre-firing after molding, so that the silicon melt can penetrate into the core of the molded body in the subsequent silicon infiltration step. (This density range is the same as that in the conventional reaction sintering method).

The molded shape should almost match the shape of the sliding material of the mechanical seal m to be manufactured, but in the parts that will be removed later, prepare a cutting allowance 3 (second leap state).
.

After molding, it is pre-fired at about 800 to 1000'C to carbonize the binder and form a molded body that can withstand cutting. Next, the part of the mechanical seal sliding material that will become the liquid contact part 2 is cut to adjust its shape to the state shown in Figure 3 (however, the shape of this part has already been finished at the molding stage). 7.-1 The surface layer of the obtained molded product is coated with thermosetting 13 (
It is impregnated with fat, but the resin is 7 el resin, 7
Materials with a high carbonization yield, such as orchid resins and epoxy resins, are suitable. The impregnation treatment can be performed, for example, by degassing in a vacuum using a vacuum impregnation device and then impregnating. (It is necessary to apply fat impregnation only to the surface layer of the molded body, preferably to a depth of about 0.5 to 3 cm from the surface. (This resin-impregnated layer should ultimately reduce the unreacted silicon content.) Since it becomes a layer with low and high corrosion resistance, it is necessary to have a thickness of about 0.5 mm or more to achieve a sufficient effect.However, even if it is impregnated too deeply, the carbide will react with the silicon melt. Not only is it difficult to do so, but it also results in unnecessary removal of more parts of the sliding material for mechanical seals than those that will be in contact with liquid.
The upper limit is usually about 3n+n+. ).

The impregnated molded body (Fig. 4) is fired in a non-oxidizing atmosphere at a temperature of 800 to 160 ml until carbonization of the thermosetting resin is completed.
i) By heating to 0'C. As a result, the thermosetting resin carbide exists in the surface layer t of the molded body at a higher rate than in the pond portion, and as a result, the surface layer t has a denser structure than other portions.

After this, the surface layer 4 of the portion 5 that will become the rotating shaft insertion hole among the parts of the molded body other than the part that will become the liquid contacting part 2 is removed.

In addition to this cutting for deletion, finishing machining of the shape of the portion other than the portion to be the liquid contact portion 2 is performed to obtain the state shown in FIG. 5.

The treatment of infiltrating the silicon melt into the molded body after the above treatment may be carried out according to the conventional reaction sintering method. That is, the molded body is heated in vacuum or in an inert gas for about 1450 min.
The molded body is heated to ~2100°C and the entire surface of the molded body is brought into contact with the silicon melt. Argon, helium, hydrogen, etc. can be used as the inert gas. The silicon melt that permeates into the molded body through this treatment reacts with carbon in the molded body to produce silicon carbide. The reacting carbon includes raw material carbon,
Carbon generated by carbonization of organic binder and thermosetting impregnated in the surface layer? , 4 (There are three types of carbon produced by carbonization of fat, but the last of these is the undeleted surface layer l[, which has a higher carbon ratio and is denser than the pond part, so it is difficult to react. The amount of excess silicon remaining without oxidation is reduced and usually remains below 10% by weight.In the pond section 6, the silicon melt penetrates from the area where the surface layer has been removed and is then subjected to conventional reaction sintering. A sintered body is formed there as in the conventional method.

In the manner described above, a sliding material is obtained in which the liquid contact portion 2 including the sliding surface 1 is covered with a sintered body layer having a low silicon content and having a high degree of corrosion resistance.

Below, the present invention will be further explained with reference to Examples and Comparative Examples.

In the manufacturing method of the sliding material for mechanical seals described with reference to the drawings, the forming raw materials include 70% by weight of α-type silicon carbide powder with an average particle size of 7 μm, 25% by weight of artificial graphite powder with an average particle size of 6 μm, and phenol. Using a material consisting of 5% by weight of resin and 1% by weight of paraffin, methanol was added and mixed, and after drying, it was transferred to a mold and 1, S Lon/
The molded body was press-molded at a pressure of 1.5 mm.Then, it was pre-fired at a temperature of -1200°C in a non-oxidizing atmosphere. It has undergone some plastic surgery.

Thereafter, the molded body was placed in a vacuum impregnating device, vacuum degassed, and then impregnated with liquid furan resin. The average thickness of the resin-impregnated layer was 201,111 mm. Next, the resin is heated to 1200'C in a non-oxidizing atmosphere to carbonize the resin, and then a part of the molded body surface layer 4 where the thermosetting fat carbide is present (a part of the rotary yuzu insertion hole 5 that does not come into contact with the sealing fluid) (part) was deleted. This was followed by contact with a silicon melt at 1600'C to cause reactive sintering.

Table 1 shows the average composition and density of the surface layer 4 (up to a depth of 2++ on) and core 6 in the liquid contact area 2 of the silicon carbide sliding material obtained. there were.

First surface layer core 5iC (weight%) 90 82Si (weight%) 8 16C (weight%) 22 Density (g/cm) 3.08
2.99 Comparative Example 7 Same as Example except that orchid resin impregnation was not performed.
A sliding material for mechanical seals was manufactured. The surface layer of the obtained sliding material had 5iC81% by weight, S: 17% by weight, C2% by weight, and a density of 2.98 g/c+++.

Next, the corrosion resistance of the liquid contact parts 2 of the sliding materials according to the above two examples was investigated by the following method. The results are shown in Table 2.

Test method: The part of the example product that does not have the low silicon content surface layer 4 is covered with a corrosion-resistant jig and immersed in a corrosive test liquid at 70°C for 100 hours. The same applies to comparative products.

Attach it and perform a similar immersion test. Measure the weight of the sample before and after immersion, and evaluate the corrosion resistance based on the weight loss rate.
Determine.

Table 2 Immersion test weight loss rate (%) Test liquid Example bright brown - Comparative example product 50% Na
OH00f) 32 0.7150%KOHO,0
41f), 78 8N○3 (20%) Dou II' (5%) 1,133
12.9 Effects of the Invention According to the manufacturing method of the present invention, not only the corrosion resistance of the wetted parts is improved compared to the conventional reaction sintering method, but also mechanical resistance is improved by making the surface layer of the wetted parts denser. This has the effect of increasing strength. Therefore, according to the present invention, it is possible to manufacture sliding materials used under severe conditions in contact with highly corrosive sealed fluids such as high-temperature acids and alkalis by the reaction sintering method. The advantages of the sintering method can now be utilized in a wider range than before.

[Brief explanation of drawings]

Figures 1 to 5 2 Detailed explanatory diagrams (cross-sectional views) of the present invention 1
:Sliding surface 2:Wetted part Fig. 1 Fig. 5

Claims (2)

[Claims] (1) A molded body having a density that allows the silicon melt to penetrate to the core is manufactured from silicon carbide powder and carbon powder, the surface layer of which is impregnated with a thermosetting resin, and then fired in a non-oxidizing atmosphere. The thermosetting resin is carbonized, and the surface layer of the molded object where the thermosetting resin carbide is present is removed except for the part that will be in contact with the sliding material for mechanical seals, and then silicon melt is added into the molded object. A method for producing a silicon carbide sliding material for mechanical seals by a reactive sintering method, which comprises permeating a liquid and reacting with carbon in a molded body to produce silicon carbide. (2) A molded body manufactured from silicon carbide powder and carbon powder has a silicon carbide content of 60 to 90% by weight and a density of 1.4.
~2.6g/cm^3 Claim 1
Manufacturing method described in section.