JPH05271851A - Production of fe-base sintered alloy member having high strength and high toughness - Google Patents

Abstract

PURPOSE:To improve the strength and toughness of an Fe-base sintered alloy member by subjecting an Fe-base sintered alloy member prepared by means of powder metallurgy to hot forging and then to resintering at specific temp. CONSTITUTION:Fe powder, metal powder for alloy, carbon powder, etc., as raw materials are mixed, and the resulting powder mixture is compacted and then sintered at high temp. The resulting Fe-base alloy sintered member is hot-forged in a nonoxidizing atmosphere, by which the pores in the sintered member are reduced to perform densification. Subsequently, the member is subjected to carburizing, hardening, and tempering in a temp. atmosphere and resintered at a temp. lower than the sintering temp. at the first sintering. By this resintering treatment, the sintered member improved in strength and toughness to a greater extent than convent Fe-base alloy sintered member can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Fe-based sintered alloy member having high strength and high toughness.

[0002]

2. Description of the Related Art Conventionally, in general, a green compact is sintered into a sintered body, which is then hot forged, and then subjected to heat treatments such as carburizing and tempering to form an Fe-based quenching bond. A method for manufacturing a gold member is known, and it is also well known that this method is applied to manufacture mechanical structural members such as various gears and connecting rods.

[0003]

On the other hand, with the recent progress in performance and multifunction of various mechanical devices, there is a strong demand for thinning and miniaturization of these structural members.
At present, the Fe-based sintered alloy member manufactured by the above-mentioned conventional method cannot sufficiently and satisfactorily cope with it due to insufficient strength and toughness.

[0004]

Therefore, the present inventors have
From the above viewpoint, as a result of conducting research to produce an Fe-based sintered alloy member having strength and toughness far superior to the Fe-based sintered alloy member produced by the above-mentioned conventional method, In the production of the Fe-based sintered alloy member by the above-mentioned conventional method, the sintered body after the hot forging is densified by eliminating the pores existing before the hot forging. However, the bond between the crystal grains in the portion where the pores were present is only mechanical bond, and therefore, the sintering process is performed again, that is, the sintering of the green compact (hereinafter referred to as the primary sintering). When the sintering is performed under the condition of exhibiting the same sintering function (hereinafter, referred to as secondary sintering), the crystal grains that mechanically bond with each other become metallurgically bonded to each other. Metallurgical bond by binding is much stronger than mechanical bond. Et al., It is the strength and toughness of the Fe-based sintered alloy member as a result got finding that become significantly improved.

The present invention has been made based on the above-mentioned research results. The green compact is sintered (primarily sintered) into a sintered body, and this sintered body is subjected to hot forging. When the Fe-based sintered alloy member is manufactured by subjecting it to heat treatment such as carburizing and tempering, after the hot forging, the sintering treatment is performed again at a temperature not exceeding the primary sintering temperature (2
This is characterized by a method for producing a Fe-based sintered alloy member which is subjected to the following sintering) to improve strength and toughness.

When carrying out the method of the present invention, (a) carbon powder: 0.2% to 0.7%, Fe-0.1 to 5% by weight (hereinafter,% means% by weight). % Ni-
0.1-2% Mo alloy powder: rest, (b) carbon powder:
0.2-0.7%, Fe: 0.1-3% Cu-0.1
5% Ni-0.1-2% Mo alloy powder: rest, (c)
Carbon powder: 0.2-0.7%, Fe-0.1-2% Mn
-0.1-2% Cr-0.1-2% Mo alloy powder: The rest, (d) Carbon powder: 0.2-0.7%, Fe powder:
Remaining (e) Carbon powder: 0.2 to 0.7%, Cu powder: 0.1 to 5%, Fe powder: Remaining, (f) Carbon powder: 0.2 to 0.7%, Ni powder: 0.1-5%, Fe
Powder: the rest, (g) Carbon powder: 0.2-0.7%, C
u powder: 0.1 to 5%, Ni powder, Fe powder: the rest, and it is desirable to use a powder compact of a mixed powder having any one of the above-mentioned compositional compositions (a) to (g).

Similarly, the primary sintering is maintained at a temperature of 1100 to 1300 ° C. for 30 to 120 minutes in a non-oxidizing atmosphere, and the secondary sintering is performed in a non-oxidizing atmosphere at a temperature of 1000.
It is desirable to carry out the treatment at a temperature of 1150 ° C. for 20 to 60 minutes.

Further, hot forging is performed in a non-oxidizing atmosphere at a temperature of 900 to 1100 ° C. and a forging reduction rate of 5 to 60.
It is better to do it in% condition.

The heat treatment is performed in a carburizing atmosphere at a temperature of 8
It consists of carburizing and quenching under the conditions of holding at 50 to 950 ° C for 0.5 to 3 hours, and tempering treatment under the conditions of holding at temperature of 150 to 500 ° C for 0.5 to 2 hours in the atmosphere or oil.

[0010]

EXAMPLES Next, the method of the present invention will be specifically described by way of Examples. As a raw material powder, an Fe-based alloy powder having the composition of components shown in Table 1 and having a particle size of 100 mesh or less by atomization, an Fe powder having a particle size of 100 mesh or less by atomization, Cu
Powder, Ni powder, and carbon black were prepared, and these raw material powders were blended in the blending composition shown in Tables 1 and 2, and 1% zinc stearate was added thereto and mixed with a V-type mixer, and then 4 The green compacts A to N are formed by press molding at a predetermined pressure within the range of up to 8 ton / cm ² , and these green compacts are then heated to 700 ° C. in a H ₂ gas atmosphere at a temperature of 700 ° C.
After the zinc stearate was removed by sintering under the condition of holding time, primary sintering and hot forging were performed under the conditions shown in Tables 3 and 4, and theoretical density ratios shown in Tables 3 and 4 were also obtained. , And vertical: 10 mm × horizontal: 10 mm × length: 55 mm, forged material was subjected to secondary sintering under the conditions shown in Tables 3 and 4, and subsequently shown in Tables 5 and 6. The Fe-based sintered alloy members were manufactured by carrying out the methods 1 to 14 of the present invention by carrying out heat treatments of carburizing and tempering under the conditions described below.

For comparison purposes, as shown in Tables 1 to 6, the conventional method 1 was used under the same conditions except that secondary sintering was not performed.
~ 14 to produce a Fe-based sintered alloy member.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

[0016]

[Table 5]

[0017]

[Table 6]

[0018]

[Table 7]

[0019]

[Table 8]

Then, with respect to the various Fe-based sintered alloy members obtained as a result, the tensile strength, elongation, and Charpy impact value (without notch) were measured for the purpose of evaluating the strength and toughness, and the surface portion was further measured. With the hard carburized layer removed, the tensile strength, elongation, and Charpy impact value (with notch) were measured. The results are shown in Tables 7 and 8.

From the results shown in Tables 3 to 8, the method 1 of the present invention was used.
Fe-based sintered alloy members manufactured in any of
It is clear that it has high strength and high toughness as compared with the Fe-based sintered alloy members 1 to 14 manufactured by the conventional methods 1 to 14 without subsequent sintering.

As mentioned above, according to the method of the present invention,
It is possible to manufacture an Fe-based sintered alloy member having high strength and high toughness. Therefore, if the resulting Fe-based sintered alloy member is applied, not only can it be made thinner and downsized, but also Industrially useful effects are brought about such as excellent performance in practical use over a long period of time.

Claims (1)

[Claims] 1. A Fe-based sintered alloy member is manufactured by sintering a green compact to form a sintered body, subjecting the sintered body to hot forging, and then subjecting it to carburizing and tempering heat treatments. The method for producing an Fe-based sintered alloy member having high strength and high toughness, which is characterized in that after the hot forging, the sintering treatment is performed again at a temperature not exceeding the sintering temperature.