JPS6160138B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a ferrous sintered alloy member having excellent wear resistance, high strength, and high toughness. Generally, for example, the part surface of a valve rocker arm of an internal combustion engine is subjected to high-speed sliding and strong impact loads, so the material forming the part surface is required to have wear resistance, strength, and toughness. . Traditionally, fields subject to this type of sliding and load include:
Sintered parts made of various materials manufactured by powder metallurgy and sintered parts subjected to quenching treatment for the purpose of improving properties are used, but all sintered parts have sufficient wear resistance, Since it lacks strength and toughness, it has only a relatively short service life. In addition, when performing quenching treatment, in the case of ordinary sintered parts, there is a considerable temperature difference between the sintering temperature and the quenching temperature. The procedure is to heat the product to the quenching temperature and then rapidly cool it. Therefore, not only does the manufacturing cost increase due to the need for a heating furnace and heating process to heat the product to the quenching temperature. A decrease in dimensional accuracy was unavoidable due to heating to the quenching temperature. From the above-mentioned viewpoints, the present inventors conducted research to obtain a sintered member having excellent wear resistance, high strength, and high toughness with high dimensional accuracy and at low manufacturing cost. The final component composition of a sintered member manufactured by a normal powder metallurgy method is as follows: C: 0.5 to 3.0%, Cr: 0.5 to 30%, and Mo: 0.5 to 10%. W: 0.5-10%, V: 0.2-5%, Nb: 0.2-5%, Ta: 0.2-5%, Ni: 0.2-10%, Co: 0.5-10%, 1 of the group consisting of Fe and unavoidable impurities: The remainder contains Fe and unavoidable impurities: This sintered member will have a quenching temperature very close to the sintering temperature.
Immediately after sintering is completed, by rapidly cooling the material from a temperature close to the sintering temperature, it becomes possible to obtain a sintered member with the desired hardened structure, which is not achieved by normal hardening treatment. It was possible to avoid an increase in manufacturing costs and a decrease in dimensional accuracy, and it was found that the resulting sintered member has excellent wear resistance, high strength, and high toughness. Therefore, this invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below. (a) C The C component includes Cr, Mo, W, V, Nb, and
It combines with Ta to form carbide, which improves the wear resistance of the component and also dissolves in the matrix to increase strength, but if its content is less than 0.5%, the desired effect is not achieved. Not obtained, on the other hand
If the content exceeds 3.0%, the amount of carbide precipitated becomes too large, resulting in a decrease in toughness, so the content was set at 0.5 to 3.0%. (b) Cr The Cr component has a Vickers hardness H when combined with C.
_V : Precipitates high-hardness Cr carbide with a value of 1000 to 1800, which improves the wear resistance of parts, and also dissolves in the matrix to improve its heat resistance. However, when the content is 0.5 If the content is less than 30%, the desired effect will not be obtained, while if the content exceeds 30%, the member will become brittle, so the content was set at 0.5 to 30%. ₍ c) Mo, W, V, Nb, and Ta. H _V :2300 to 3300 (MC type carbide) is formed to improve the wear resistance of the component, and it has a uniform effect of solid solution in the matrix to improve heat resistance, but its content is Mo: less than 0.5%, W: less than 0.5%, V: less than 0.2%, Nb: 0.2%, respectively.
If Ta: less than 0.2%, the desired effect cannot be obtained; on the other hand, Mo: 10%, W: 10
%, V: 5%, Nb: 5%, and Ta: 5%, respectively, not only the toughness decreases but also the grindability deteriorates, making it more economical. Since this is also disadvantageous, the content ranges of each of the above components were determined as described above. (d) Ni and Co Ni and Co have the effect of further strengthening the matrix and improving compatibility with the mating member during use, but if their content is less than 0.5% each, the desired effect is not achieved. Because the effect of Although it is necessary to contain 5% or more,
On the other hand, even if the content exceeds 10% of each, further improvement effects cannot be obtained, so the upper limit was set at 10% in consideration of economic efficiency. Next, the present invention will be explained with reference to examples. First, iron oxide powder is used as the main raw material, and predetermined amounts of metal oxide powder and carbon powder of each component are blended and mixed, followed by hydrogen reduction (co-reduction with hydrogen and carbon).
By doing so, Fe-based alloy powders having the compositions shown in Table 1 are produced, and then 0.7% by weight of zinc stearate powder is added and mixed as a lubricant to this alloy powder, and the mixture is molded into a mold of a predetermined shape. let me in
After forming a green compact at a pressure of 5ton/ ^cm2 , the green compact is held at a predetermined temperature within the range of 1150 to 1270℃ for 60 minutes in a vacuum of 10 ^-2 torr to complete sintering. Immediately, the sintering furnace is transferred to a cooling chamber installed adjacent to the lower part of the sintering furnace through a gate valve, and in this cooling chamber, _N2 gas is blown to perform a rapid cooling quenching process.
Fe-iron-based sintered alloy members 1 to 12 of the present invention having substantially the same composition as the Fe-iron-based alloy that is the raw material powder
were manufactured respectively.

【table】

[Table] Density, Rockwell hardness (C
scale) and transverse rupture strength were measured, and the measurement results are shown in Table 1. In addition, the first review includes Fe-based sintered alloy members 1 to 12 of the present invention having the above-mentioned quenched structure.
The hardness and transverse rupture strength after being repeatedly subjected to tempering treatment at a predetermined temperature in the range of 520 to 600°C for 1 hour twice are shown for each of them. Next, the resulting Fe-based sintered alloy members 1 to 12 of the present invention after being quenched and tempered were each used on the part surface of a rocker arm, installed in a four-cylinder automobile engine, and subjected to wear test for 100 hours. A test was conducted to measure the maximum wear depth and the average wear depth of the mating member, the cam. The measurement results are also shown in Table 1, and no abnormal wear such as chipping was observed in any of the Fe-based sintered alloy members 1 to 12 of the present invention. From the results shown in Table 1, it can be seen that Fe-based sintered alloy members 1 to 12 of the present invention were all made of chilled castings currently in practical use and had a wear test under the same conditions. Maximum wear depth on surface: 50μm, average wear depth on cam: 70μm
It is clear that the material has excellent wear resistance and the degree of wear on the mating member is extremely small compared to that shown in FIG. As described above, according to the present invention, a high quality iron-based sintered alloy member having excellent wear resistance, high strength, and high toughness can be manufactured at low cost and with high dimensional accuracy. Industrially useful effects are brought about.

Claims (1)

[Claims] 1. According to the usual powder metallurgy method, raw material powders are blended and mixed, a green compact is formed from the mixed powder, and the green compact is molded in a non-oxidizing atmosphere or in a vacuum. A method for manufacturing a sintered member, which comprises manufacturing a sintered member through a basic step of sintering, and then subjecting the sintered member to a heat treatment including a quenching process in which the sintered member is heated to a quenching temperature and then rapidly cooled. In, the above-mentioned sintered member contains C: 0.5 to 3.0%, Cr: 0.5 to 30%, and further contains Mo: 0.5 to 10%, W: 0.5 to 10%, V: 0.2 to 5% by weight. %, Nb: 0.2-5%, Ta: 0.2-5%, Ni: 0.2-10%, Co: 0.5-10%, containing one or more of the following, Fe and unavoidable 1. A method for producing an iron-based sintered alloy member, comprising a composition consisting of impurities: remainder, and quenching is performed by rapidly cooling from a temperature near the sintering temperature immediately after sintering is completed.