JPS5825722B2 - Manufacturing method of sintered mechanical parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing highly wear-resistant sintered mechanical parts.

It is well known that methods of improving the mechanical properties of sintered metal materials include densification, alloying, and heat treatment.

By the way, in general, quenching steel materials has the drawback of causing considerable deformation, so in the case of mechanical parts that require high precision, nitrocarburizing treatment, which hardly causes deformation, is often used.

In addition, the soft-nitrided surface has excellent wear resistance and seizure resistance, and is applied to various sliding parts.

However, when applying this to sintered metal materials, there are the following problems: nitriding progresses to the inside of the material due to the ventilation holes inherent in the sintered material, which affects its mechanical properties.
In particular, it had the disadvantage of decreasing wear resistance.

Regarding this issue, the inventors of the present invention previously filed a patent application filed in 1984-1.
No. 24181 (Japanese Unexamined Patent Publication No. 5647504), by infiltrating the sintered material with copper in advance and then subjecting it to nitriding treatment, it is possible to eliminate the above-mentioned drawbacks, improve mechanical properties, and improve wear resistance. disclosed.

This invention is a further improvement of the earlier invention mentioned above, that is, this invention includes a predetermined amount of MoS in the raw material powder.
2 is blended and molded into a desired shape, and this is sintered at a temperature below 1185°C, which is the melting point of MoS2, and then copper or copper alloy is infiltrated into it, and then it is subjected to soft nitriding treatment. The gist of this is to form a hardened layer on the surface, and as a result, it not only has its own wear resistance but also has excellent properties that do not damage the mating material.

Example First, the specifications and manufacturing conditions of the sample are shown below.

Sample shape: 60φ x 5-inch disc-shaped pressure crab 6.5t/ffl Copper infiltration: 1130°C, 20 minutes Nitriding treatment: 570°C, 2 hours To briefly explain the contents of the above table, A is MoS2 B is the one with M o S2 added to A, C
Although it has the same composition as B, it was sintered at a higher temperature than the melting point of MO82, and the subsequent copper infiltration and nitrocarburizing treatments were performed under the same conditions.

In addition, as comparative samples, A and B without nitriding were designated as A/ and B/, respectively.

Next, the results of the wear test for each of the above-mentioned samples will be explained.

Figure 1 shows the method of the wear test, in which the rotor 3 is slid on the sample 1 held in the lubricating oil 2 under predetermined conditions, and then the wear amount of the sample 1 and the surface roughness of the rotor 3 are measured. This is the reason to investigate.

The sample conditions are as follows. Rotor material: 5UJ-2, hardness HR, C58 Heru2 Lubricating oil viscosity: 5AE20 Sliding speed: 5 m/sec Surface pressure: 50 to 250 ky/i Sliding time: 5 minutes The graph in Figure 2 is as follows: This figure shows a comparison of the wear resistance of each sample based on the results of the above tests.

As is clear from this figure, soft nitriding treatment (sample A) and addition of MoS2 (sample B/) to the base alloy (sample A/) have considerable effects on improving wear resistance, but these When used in combination (sample B), even more remarkable effects can be obtained due to the synergistic action of the two factors.

Next, the graph in Figure 3 shows the surface roughness of the rotor 3, comparing it with sample A which was only subjected to soft nitriding treatment.
It can be seen that the sample in which oS2 was added (sample B) is excellent not only in its own wear resistance but also in not damaging the mating material.

However, sample C, which has the same composition as sample B but whose sintering temperature was raised above the melting point of MoS2, has its own wear resistance unchanged (see figure 2), but as shown in figure 3. This makes it easy to damage the other material.

Therefore, sintering in the present invention must be performed at a temperature below the melting point of MoS2.

The following Figure 4 shows the relationship between the amount of MoS2 added and the amount of wear of the samples.The sintering temperature of each sample was 1130℃,
The test load was a surface pressure of 250 kg/i.

From this, the amount of wear decreases as MoS2 increases.

However, due to the deterioration of moldability, the amount added was limited to about 5%.

As described above, by adding a predetermined amount of MoS2 to the iron-based base material, sintering it below 1185°C, which is the melting point of MoS2, and performing copper infiltration, and then performing soft nitriding treatment,
It has been found that sintered machine parts with excellent wear resistance and less damage to mating materials can be obtained.

In the examples, infiltration of copper was described, but the same effect as that of copper is obtained when a copper alloy is infiltrated.

The present invention can be applied to parts that require both airtightness and abrasion resistance, such as cylinder blanks for pumps for construction machinery.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the wear test, Figure 2 is a graph showing the amount of wear after the test, Figure 3 is a graph showing the surface roughness of the mating roller, and Figure 4 is the relationship between the amount of Mo82 and the amount of wear. It is a graph. 1...Test piece, 2...Lubricating oil, 3...
····rotor.

Claims (1)

[Claims] An iron-based sintered body containing 10.2 to 5% by weight of MoS2 is sintered at a temperature of 1185°C or lower, infiltrated with copper or copper alloy, and then nitrocarburized to form a hardened layer on the surface. A method for manufacturing sintered mechanical parts, characterized by: