JPH07113137B2 - Manufacturing method of sintered high speed steel members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] This invention uses a normal powder metallurgy method without using means such as hot forging or hot isostatic pressing (hereinafter referred to as HIP). The present invention relates to a method for producing a sintered high speed steel member having high strength and high toughness.

[Conventional technology]

Generally, a sintered high-speed steel member uses a high-speed steel powder formed by a water atomizing method as a raw material powder to obtain a sintered body by an ordinary powder metallurgy method, and quenching and sintering the sintered body. It is well known that it is manufactured by performing a heat treatment for tempering.

[Problems to be solved by the invention]

However, in the production of the above-mentioned conventional sintered high speed steel member, a relatively coarse high speed steel powder having a particle size of 100 mesh or less, generally having an average particle size of about 60 to 100 μm is used as a raw material powder. In addition, the sinterability is inferior, and as a result, it is not only difficult to produce a high-strength and high-toughness sintered high-speed steel member, but also the appropriate sintering temperature range becomes extremely narrow. The liquid phase appearance temperature (T) of the high-speed powder is from about several degrees to about 10 ° C. As a result, there is a problem that extremely strict temperature control is required in mass production.

[Means for solving problems]

Therefore, the inventors of the present invention have conducted research from the above viewpoints to solve the problems of the conventional method for producing a sintered high-speed steel member, and as a result, as the raw material powder, have an average particle diameter of 5 to 5. 40μ
m high-speed steel powder is used, with an oxygen content of 300 to 1
In the case of 000 ppm, the high-speed steel powder alone, while when the oxygen content is more than 1000 ~ 3000 ppm, 0.01-0.3 wt% carbon powder is mixed with the high-speed steel powder for the purpose of deoxidation. Then, it is made into a sintered body by an ordinary powder metallurgy method, and in this case, the sinterability is good, and the sintering temperature is set to a relatively wide range of the liquid phase appearance temperature (T) to T + 30 ° C. of the high speed steel powder. Finally, when the sintered body is subjected to heat treatment of quenching and tempering under normal conditions, the average grain size of the carbide is 1 to 10
It has been found that a sintered high-speed steel member having a structure in which carbides having a grain size of 20 μm or more are substantially absent and having high strength and high toughness can be obtained by making it to be μm. .

The present invention has been made based on the above findings, in which a high-speed steel powder is used as a raw material powder, a sintered body is formed by an ordinary powder metallurgy method, and this sintered body is heat treated for quenching and tempering. When producing a sintered high-speed steel member, the raw material powder is (a) having an average particle size of 5 to 40 μm and an oxygen content of 30.
Water atomized high-speed steel powder of 0 to 1000 ppm, or (b) an average particle size of 5 to 40 μm and an oxygen content of 10
More than 00 to 3000ppm of water atomized high speed steel powder, 0.01 to
By using a mixed powder in which 0.3% by weight of carbon powder is mixed and by sintering at a predetermined temperature within the range of the liquid phase appearance temperature (hereinafter referred to as T) to T + 30 ° C. of the high-speed steel powder, Characterized by a method for producing a high-strength and high-toughness sintered high-speed steel member having a structure in which the average grain size of carbides is 1 to 10 μm and carbides having a grain size of 20 μm or more are substantially absent. is there.

Next, the reason why the manufacturing conditions are limited as described above in the method of the present invention will be described.

(A) Average particle size of high-speed steel powder If the average particle size is less than 5 μm, the oxygen content is 3000 ppm
The following powder is extremely difficult to produce and the fluidity is lowered, and it becomes difficult to form a homogeneous green compact as a density difference locally occurs during press molding of the green compact, On the other hand, if the average particle size exceeds 40 μm, the proper sintering temperature range becomes narrow as described above, and it is not possible to secure a wide proper sintering temperature range of T to T + 30 ° C. Average particle size of carbides in
Carbides with a grain size of more than 20 μm and more than 20 μm appear, which also acts as a starting point of fracture and cannot secure desired high strength and high toughness. Was determined to be 5 to 50 μm.

(B) Sintering temperature If the sintering temperature is lower than T ° C, sufficient sintering cannot be performed. On the other hand, if the sintering temperature exceeds T + 30 ° C, the carbide of the member partially coarsens and exceeds 20 μm. Further, since carbides will appear and the carbides will develop into a mesh shape, and in any case, it will cause a decrease in strength and toughness, so the sintering temperature was set to T to T + 30 ° C.

(C) Mixing amount of carbon powder The lower the oxygen content in the high-speed steel powder as the raw material powder, the better, but the oxygen content is 300 to 1000 ppm.
In the case of (high-speed steel powder with an oxygen content of less than 300 ppm is difficult to manufacture in the normal reduction process after water atomization), there is no problem because it does not have any adverse effect on the characteristics of the member, but the oxygen content is low. If the amount exceeds 1000 ppm, it will affect the characteristics of the member, so in this case it is advisable to mix carbon powder for the purpose of deoxidation, usually over 1000 ~ 3000
Proportional mixing in the range of 0.01 to 0.3% by weight with respect to the oxygen content of ppm should be performed. In this case, if it exceeds 0.3%, it causes local coarsening and network growth of carbide of the member. Therefore, the mixing amount was set to 0.01 to 0.3% by weight. When the oxygen content of the powder exceeds 3000 ppm, vacancies are likely to occur when the amount of carbon added is 0.3% by weight or less, and when it exceeds 0.3% by weight, coarse carbides are locally formed.

〔Example〕

Next, the method of the present invention will be specifically described by way of Examples.

Prepare high-speed steel powders having the composition and average particle size shown in Table 1, respectively, and carbon powder with an average particle size of 2 μm. These high-speed steel powders alone or in addition to them are shown in Table 1. In the state of mixing the carbon powder in the ratio shown below, according to the usual powder metallurgy method, it is pressed into a green compact at a pressure of 5 ton / cm ² , and this green compact is in a vacuum atmosphere (or in a non-oxidizing atmosphere) ) In the same manner as above, the same temperature as shown in Table 1 was maintained for 2 hours, and after sintering, in vacuum, the
After holding at a predetermined temperature in the range of 1240 ° C for 1 hour, quenching with N ₂ gas
According to the method of the present invention, by applying a heat treatment consisting of tempering for holding time. 1 to 10 and Comparative Methods 1 to 4 were carried out to manufacture sintered high speed steel members.

In Comparative Methods 1 to 4, any of the manufacturing conditions (the conditions marked with * in Table 1) are out of the scope of the present invention.

Next, for various sintered high-speed steel members obtained as a result, the average grain size of carbides is measured, and the presence or absence of coarse carbides with a grain size of 20 μm or more is observed to further evaluate strength and toughness. Then, the tensile strength and the transverse rupture strength were measured, and the Rockwell hardness (C scale) was also measured. The results are shown in Table 1.

〔The invention's effect〕

From the results shown in Table 1, all of the sintered high-speed steel members produced by the methods 1 to 10 of the present invention have a structure in which carbides are fine and coarse carbides do not exist, and accordingly, have high strength. While exhibiting high toughness, as seen in Comparative Methods 1 to 4, when any of the manufacturing conditions deviates from the scope of the present invention, the sintering high speed satisfying the above characteristics is provided. It is clear that steel parts cannot be manufactured.

As described above, according to the method of the present invention, in a relatively wide proper sintering temperature range, good sinterability, high strength and high toughness,
Further, it is possible to manufacture a sintered high speed steel member having high hardness.

Claims (2)

[Claims] 1. A high-speed steel powder is used as a raw material powder to obtain a sintered body by an ordinary powder metallurgy method, and the sintered body is subjected to heat treatments of quenching and tempering to produce a sintered high-speed steel member. In doing so, as the raw material powder, water atomized high speed steel powder having an average particle size of 5 to 40 μm and an oxygen content of 300 to 1000 ppm is used, and the liquid phase appearance temperature (T) to T + of the high speed steel powder is used.
Manufacture a sintered high-speed steel member having a structure in which the average grain size of carbides is set to 1 to 10 μm by sintering at a predetermined temperature within the range of 30 ° C. and carbides having a grain size of 20 μm or more are substantially absent. A method for producing a sintered high speed steel member having high strength and high toughness, which is characterized by: 2. A high-speed steel powder is used as a raw material powder to obtain a sintered body by a normal powder metallurgy method, and the sintered body is subjected to heat treatments of quenching and tempering to produce a sintered high-speed steel member. In doing so, as the raw material powder, the average particle size is 5 to 40 μm, the oxygen content is water atomized high-speed steel powder of more than 1000 to 3000 ppm, using a mixed powder of 0.01 to 0.3% by weight of carbon powder, And liquid phase appearance temperature (T) to T of the high-speed steel powder
Manufacture a sintered high-speed steel member having a structure in which the average grain size of carbides is 1 to 10 μm by sintering at a predetermined temperature within a range of + 30 ° C. and substantially no carbides having a grain size of 20 μm or more are present. A method for producing a sintered high-speed steel member having high strength and high toughness, characterized by: