JPH06145916A - Iron-based sintered alloy and its production - Google Patents

Abstract

PURPOSE:To remarkably improve the machinability and wear resistance of an iron-based sintered alloy by forming its structural state into one in which a specified amt. of specified MnS grains are uniformly dispersed. CONSTITUTION:The structural state of the iron-based sintered alloy is formed into one in which MnS grains consisting of 5 to 50wt.% grains with <=10mum grain size and 50 to 95wt.% grains with 10 to 100mum grain size are uniformly dispersed by 0.1 to 5.0wt.%. An iron-based raw material is uniformly mixed with MnS grains consisting of 5 to 50wt.% grains with <=10mum grain size and 50 to 95wt.% grains with 10 to 100mum grain size by 0.1 to 5.0wt.% into the iron-based sintered raw material. The raw material is compacted and sintered to produce the iron-based sintered alloy. Thus, the service life of a valve seat and a valve can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based sintered alloy having excellent machinability and wear resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Sintered parts obtained by powder metallurgy are characterized in that they are mass-produced in a short manufacturing process in which raw material powders are formed into product shapes all at once. However, some of them require cutting after sintering because of the shape or dimensional accuracy of parts. Sintered parts usually have high hardness, but in the case of such parts, good machinability is a condition. Further, sintered parts are often used for sliding parts, and in that case, abrasion resistance is required.

Sintered alloys are often used for engine valve seats. Sintered valve seats have good wear resistance, but because of the holes that are unique to sintered parts, intermittent cutting results in poor machinability. To improve the machinability, the following 2
There are two ways. That is, since the iron-based sintered material has many holes, it is subjected to the action of fine interrupted cutting during cutting,
Cutting tool life is a problem.

Therefore, in the prior art, a method of sealing pores with water glass, resin or the like. A method of adding FeS to a sintering raw material as a solid lubricant. Have been adopted. However, in the conventional sealing treatment, the effect of improving the machinability cannot be expected so much, and it may not be used in applications such as oil-impregnated bearings that utilize the pores of the sintered body. Further, FeS has a low melting point (642 ° C.) and is decomposed during the sintering process, which is not an effective method for improving the machinability.

Japanese Unexamined Patent Publication (Kokai) No. 61-147801 has already disclosed a technique in which the machinability is improved by adding MnS having a particle size of 10 μm or less, but it is not so effective in improving the wear resistance. It is the result. As described above, the sintered material used for the sliding portion is required to have wear resistance as well as machinability, and therefore it is necessary to satisfy these two characteristics at the same time.

[0006]

The present invention has been made in order to solve the above-mentioned conventional problems, and in an iron-based sintered alloy, machinability is maintained without changing the original characteristics of the sintered part. It is intended to improve wear resistance and wear resistance.

[0007]

As a result of intensive studies on the influence of the grain size of MnS, the present inventors have found that as for machinability, MnS with a fine grain size of 10 μm or less is effective, and wear resistance. Is a large particle size of 10 to 1
We have found that 00 μm MnS is effective. Therefore, in the present invention, these two types of particle sizes are mixed together at an appropriate compounding ratio, and F having both machinability and wear resistance is provided.
It is an e-based sintered material.

That is, in the present invention, 5 to 50% by weight of particles having a particle size of 10 μm or less and 5 particles having a particle size of 10 to 100 μm are used.
The present invention is an iron-based sintered alloy characterized by having a structure in which MnS particles of 0 to 95% by weight are uniformly dispersed in an amount of 0.1 to 5.0% by weight. Particles 5 to 50% by weight, particles 10 to 100 μm in particle size 50 to 50
95% by weight of MnS particles as an iron-based sintering raw material
It is a method for producing an iron-based sintered alloy, which comprises uniformly mixing, shaping and sintering.

[0009]

With respect to machinability, MnS suppresses the wear of the cutting tool on the cutting surface with the cutting edge during machining and prolongs the cutting life, but the finer the particle size is 10 μm or less, the more chance of contacting the cutting tool. To increase the effect. If the particle size of 10 μm or less is less than 5% of all MnS particles, the effect is small, and if it exceeds 50%, the effect is not changed.
The ratio of MnS particles of m or less to all MnS particles is 5 to
50%.

As a result of the inventors' earnest research on wear resistance, MnS particles have a solid lubricating action, and at the Fe-based sliding portion, not only the wear resistance of the MnS particles is improved, but also the aggressiveness of the mating material. It was discovered that it also had the effect of softening. This effect is M
It is better that the nS particle size is large to some extent, that is, 10 to 1
If the particle size of 00 μm is good and the ratio of the total MnS particles is less than 50%, the effect is small, and if it exceeds 95%, the effect is not changed.

Then, M of the above-mentioned particle size with respect to the iron-based raw material powder
Regarding the amount of nS to be added, if MnS is less than 0.1%, machinability cannot be obtained, and if it exceeds 5.0%, sintering is affected and hardness and strength after sintering are reduced. To do. Therefore M
The amount of nS added was in the range of 0.1 to 5.0%. The MnS powder as described above is mixed with the iron-based raw material powder, and further mixed with usual additives such as graphite, lubricant, and Cu powder to obtain a sintering raw material. Normal molding and sintering conditions may be used without being affected.

[0012]

EXAMPLES The present invention will be described below based on examples. A gasoline engine valve seat was selected as the target part. There are two types of valve seats, an exhaust side valve seat used at a relatively high temperature and an intake side valve seat used at a relatively low temperature side. Both of them were tested.

1.0 wt% C as intake side valve seat
-2.5 wt% Cu-0.5 wt% Mo-The balance of the raw material of Fe, and 0.5 wt% of MnS were added to the raw material with a grain size of 10
Addition of MnS having a particle ratio of particles having a particle size of 10 μm or less to particles having a particle size of 10 to 100 μm (Table 1) and MnS having a particle composition of 10% or less and 30% and 70% and 10 to 100 μm, respectively. Various amounts (Table 2) were used.

1.5 wt% for the exhaust side valve seat
C-2.0 wt% Ni-10.0 wt% Cr-0.5w
t% Mo-8.0 wt% Co-3.0 wt% W-balance F
The raw material of the composition of e and 1 wt% of MnS are added to this, and the particle size is 1
Addition by changing the ratio of particles having a particle size of 0 μm or less and particles having a particle size of 10 to 100 μm (Table 3) and addition of MnS having a particle composition of 15% of particle size of 10 μm or less and 85% of particle size of 10 to 100 μm. Various amounts (Table 4) were used.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

The molding / sintering conditions were as follows: press molding at a surface pressure of 6 ton / cm ² and sintering in an ammonia decomposition gas sintering furnace at 1130 ° C. for 30 minutes. The sheet shape was a donut shape with an outer diameter of 30, an inner diameter of 20 and a thickness of 7 mm, and the outer circumference was cut under the following cutting conditions, and the flank wear amount of the chip after 100 pieces was measured.

The cutting conditions are as follows: work speed 560 rpm, depth of cut 0.5 mm, feed 0.15 mm / rev, tip cemented carbide results are shown in FIG. According to FIG. 1, MnS is not added,
It can be seen that the chip flank wear amount is smaller in the embodiment of the present invention than in the case where the particle size is 10 μm or less and the case where the particle size is 10 μm or less exceeds 50%.

The test apparatus shown in FIG. 3 was used for the abrasion resistance test. The valve seat 2 of the test material was fixed as shown in the figure, and the valve 1 heated by the heat source 3 was slid on it.
The conditions of the abrasion resistance test are as follows. Repeating speed 3000 rpm Mating valve material SVH35 Temperature: Intake side valve seat 200 ° C. Exhaust side valve seat 300 ° C. time 9 hours Lift load 60 kgf The results are shown in FIG. According to FIG. 2, MnS is not added,
It can be seen that the embodiment of the present invention is superior in both seat wear and valve wear as compared to the case where the particle size is 10 μm or less only and the case where the particle size is 10 μm or less exceeds 50%. It is noteworthy that the amount of wear of the mating valve is small.

[0022]

Since MnS has a self-lubricating action, it is effective not only in machinability but also in abrasion resistance. In fact, MnS
By adopting the grain size constitution of the present invention as in the present invention, the machinability and the wear resistance were greatly improved. Also, the amount of wear of the valve, which is the material of the wear, was reduced. According to the present invention, not only can the cutting efficiency and the basic unit be improved as described above, but also the life of the valve seat and the valve can be extended.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the results of abrasion test of cutting tips.

FIG. 2 is a characteristic diagram showing the results of wear test of valves and blu seats.

FIG. 3 is an explanatory front view of a valve seat abrasion tester.

[Explanation of symbols]

 1 valve 2 valve seat 3 heat source

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koji Umezawa 1111 Nogi, Nogi-cho, Toga-gun, Tochigi Prefecture Japan Piston Ring Co., Ltd. Tochigi factory

Claims (2)

[Claims] 1. MnS particles having a particle size of 10 μm or less in an amount of 5 to 50% by weight and particles having a particle size of 10 to 100 μm in an amount of 50 to 95% by weight are uniformly dispersed in an amount of 0.1 to 5.0% by weight. An iron-based sintered alloy characterized by having a textured state. 2. MnS particles consisting of 5 to 50% by weight of particles having a particle size of 10 μm or less and 50 to 95% by weight of particles of 10 to 100 μm are uniformly mixed with iron-based powder raw material in an amount of 0.1 to 5.0% by weight. A method for producing an iron-based sintered alloy, which comprises forming and sintering an iron-based sintering material as a raw material.