JP3246212B2 - Abrasion-resistant free graphite-precipitated iron-based sintered material with excellent seizure resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent seizure resistance and, for example, free graphite-precipitated iron which exhibits excellent wear resistance over a long period of time when applied as a sliding part of various driving devices. It relates to a system-based sintered material.

[0002]

2. Description of the Related Art Conventionally, as described in, for example, JP-A-57-16148 and JP-B-57-8860, free graphite iron-based sintering having a structure in which free graphite is dispersed and distributed in a ferrite base material. Materials are known, and it is also known that they are applied as sliding parts of various driving devices such as piston cylinders of oil pumps and various bearings. Further, the free graphite iron-based sintered material described above, a green compact formed from a mixed powder having a predetermined compounding composition, in a reducing atmosphere, at a low temperature at which the graphite powder blended as the raw material powder does not form a solid solution, That is, it is also known that it is manufactured by sintering at a predetermined temperature in the range of 900 to 1000 ° C.

[0003]

On the other hand, in recent years, various types of driving devices have been remarkably increased in output and reduced in weight, and accordingly, the use conditions of the above-mentioned sliding parts, which are structural members thereof, have become more severe. Despite the situation, the conventional free graphite iron-based sintered material having a structure in which relatively coarse unreacted residual free graphite is dispersed and distributed in the above-described base material is liable to be baked when used under severe conditions. Under such circumstances, at present, satisfactory wear resistance is not always exhibited.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above viewpoints, research was conducted to develop a free graphite iron-based sintered material having excellent seizure resistance. As a result, Fe-BS alloy powder, graphite powder and C
u powder was blended into a predetermined blending composition, and a green compact formed from a mixed powder obtained by mixing was mixed in a reducing atmosphere in a relatively high sintering temperature of 1100 to 1250 ° C.
The graphite powder is heated to a predetermined temperature in the range of
-S alloy powder and solid solution of Cu powder, and then sintering from this state, preferably at a cooling rate of 40 ° C./min. It has a structure in which fine free graphite is precipitated on a ferrite matrix, because it suppresses the solid solution graphite from precipitating as cementite, while it acts to significantly promote the precipitation as free graphite. Iron-based sintered materials can now be obtained, and the resulting free graphite-precipitated iron-based sintered materials exhibit excellent seizure resistance, making them suitable for use under severe conditions when used as sliding parts. The research results show that the steels also exhibit excellent wear resistance over a long period of time.

[0005] The present invention has been made based on the above-mentioned research results, and is expressed in terms of% by weight (hereinafter,% indicates% by weight), C: 0.4 to 1%, S: 0.02 to 0.5%, B: 0.01 to 0.5%, Cu: 0.5 to 4%, and, if necessary, P: 0.05 to 0.6%. The rest is characterized by a wear-resistant free graphite-precipitated iron-based sintered material with excellent seizure resistance, having a composition of Fe and inevitable impurities, and a structure in which fine free graphite is precipitated on a ferrite base. .

Next, the reason why the component composition of the free graphite-precipitated iron-based sintered material of the present invention is limited as described above will be described. (A) C The C component has the effect of precipitating as fine free graphite in the base material by the coexistence of B and S to improve the strength and seizure resistance and, as a result, exhibiting excellent wear resistance. However, if the content is less than 0.4%, the precipitation of free graphite is insufficient and the above effect cannot be obtained, while if the content exceeds 1%, pearlite is formed on the base material. Therefore, the seizure resistance tends to decrease, so the content is set to 0.4 to 1%. Desirably 0.5 to
0.8% is preferred.

(B) S and B These components coexist to suppress the graphite dissolved as a solid solution in the matrix from precipitating as cementite in the cooling process, while promoting the precipitation as fine free graphite. In this case, in order to sufficiently exert the above-mentioned effect, it is desirable to use Fe-BS alloy powder formed by atomization from a molten metal containing B and S in a predetermined amount in Fe as a raw material powder. Therefore, if the content of either S or B is S: less than 0.02% and B:
If the content is less than 0.01%, the desired effect cannot be obtained, and if the content exceeds any of S: 0.5% and B: 0.5%, the sinterability is impaired, and the strength is reduced. Is reduced, the content is S: 0.02 to
0.5%, B: 0.01 to 0.5%. Preferably, the content is 0.1 to 0.3% and B: 0.05 to 0.2%.

(C) Cu The Cu component has a function of improving the strength by forming a solid solution in the base material, but if its content is less than 0.5%, the desired strength improving effect cannot be obtained. If the amount exceeds 4%, no further effect of improving the strength is exhibited, and in addition, the amount of expansion at the time of sintering becomes large and causes a decrease in dimensional accuracy. It was decided. Desirably 1-3%
Is good.

(D) Since the PP component has a function of forming a liquid phase at the time of sintering to improve sinterability and contributing to improvement of strength, it is contained as necessary. If the amount is less than 0.05%, a desired strength improving effect cannot be obtained, while the content is 0.6%.
, The content becomes determined to be 0.05 to 0.6%. Preferably, 0.2
-0.3% is good.

[0010]

EXAMPLE Next, the free graphite-precipitated iron-based sintered material of the present invention will be described in detail with reference to examples. As raw material powder,
Various Fe-BS-alloy powders, copper powders, graphite powders, and Fe-P alloys (P: 27%
Powder), these raw material powders were blended in the composition shown in Tables 1 and 2, zinc stearate: 0.5% was added as a lubricant and mixed in a V-type rotary mixer for 30 minutes. And press-molded into a green compact at a pressure of 6 ton / cm ² ,
Then, in a mesh belt type continuous sintering furnace, after maintaining at a predetermined temperature in the range of 1100 to 1250 ° C. for 25 minutes in an ammonia decomposition gas atmosphere, sintering is performed at a cooling rate of 35 ° C./min. By doing so, a tensile test piece having substantially the same composition as the above-mentioned composition and the base structure shown in Tables 1 and 2 and having the dimensions specified in JIS Z2550 and an outer diameter: 18 mm x an inner diameter: 8 mm X thickness: 1
A free graphite-precipitated iron-based sintered material of the present invention (hereinafter, referred to as “sintered material of the present invention”) 1 to 12 and a comparative free graphite-precipitated iron-based sintered material (hereinafter, referred to as a comparative sintered material) having a shape of 0 mm. ) 1-4 were produced respectively. In addition, the comparative sintered materials 1 to 4 have compositions in which the content of any of the components affecting the precipitation of free graphite is out of the range of the present invention.

[0011]

[Table 1]

[0012]

[Table 2]

Next, various sintered materials obtained as a result are used as bearings, and a shaft made of S45C carbon steel is inserted into the bearings. While rotating at 100 m / min.), The surface pressure was gradually increased, and the surface pressure (seizure load) at the time when seizure occurred on the bearing was measured. The measurement results are shown in Tables 1 and 2. Tables 1 and 2 also show the results of the tensile test.

[0014]

From the results shown in Tables 1 and 2, all of the sintered materials 1 to 12 of the present invention have a structure in which fine free graphite is dispersed and distributed in a ferrite base material, and exhibit excellent seizure resistance. On the other hand, as seen in the comparative sintered materials 1 to 4, the content of any one of C, S, and B (marked with * in Table 1) is out of the scope of the present invention. It is clear that the desired effect of improving the seizure resistance cannot be obtained when the composition is obtained. As described above, the free graphite-precipitated iron-based sintered material of the present invention exhibits excellent seizure resistance even under severe conditions and is excellent over a long period of time, for example, when used as a sliding part for various driving devices. Because of its high wear resistance, it has industrially useful characteristics such as high output and small size.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00 304 B22F 1/02 C22C 33/02 103 C22C 38/60

Claims (2)

(57) [Claims] 1. C .: 0.4 to 1%, S: 0.02 to 0.5%, B: 0.01 to 0.5%, Cu: 0.5 to 4% by weight% Abrasion-resistant free graphite-precipitated iron-based sintered material with excellent seizure resistance, characterized by having a composition comprising Fe and inevitable impurities and a structure in which fine free graphite is precipitated on a ferrite base. . 2. In% by weight, C: 0.4-1%, S: 0.02-0.5%, B: 0.01-0.5%, Cu: 0.5-4%, P: 0.05 to 0.6%, with the balance being Fe and unavoidable impurities, and a structure in which fine free graphite is precipitated on a ferrite base. Abrasion-resistant free graphite precipitated iron-based sintered material with excellent seizure resistance.