JPS62124258A - Wear-resisting ferrous sintered alloy - Google Patents

Abstract

PURPOSE:To improve wear resistance of sintered alloy by subjecting a metal power consisting of particularly large amounts of Cr, specified amounts of Cu, P, and C, and the balance Fe with impurities to sintering to a specific density or above. CONSTITUTION:This ferrous sintered alloy has a composition consisting of, by weight ratio, 15-25% Cr, 1-5% Cu, 0.3-0.8% P, 2-4% C, and the balance Fe with <=2% impurities. An atomized alloy powder of >=about 100 mesh is produced out of the metal powder prepared by removing carbon from the alloy with above-mentioned composition. Subsequently, a natural graphite powder is added as carbon source to the above atomized alloy powder, and the resulting powder mixture is blended by means of a mixer and pressurized in a metal mold so as to compact the atomized alloy powder into a green compact with about 6.2- about 6.4g/cm<3> density, which is heated and sintered to be formed into a sintered alloy of >=7.3g/cm<3> density. Owing to the constitution, this sintered alloy shows high strength and superior wear resistance when applied as machinery component parts to a sliding part used under high surface pressure, so that it can be advantageously, in particular, used for making automobiles, etc., highly efficient.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a wear-resistant iron-based sintered alloy, and more specifically, shows excellent wear resistance in sliding parts used under relatively high surface pressure. This relates to iron-based sintered alloys.

[Conventional technology]

Conventionally, it is difficult to obtain a stable lubricating oil film on sliding parts of one machine component that are used under relatively high blood pressure, and therefore high wear resistance and pitting resistance are required of the component materials. Currently, hardened steel and chilled cast iron with high hardness, or surface treated materials such as hard chromium plating and soft nitrided steel are used as such materials, but these materials are not always sufficient and may cause wear, pitting, etc. On the other hand, in recent years there has been a growing demand for higher performance and longer life for automobile parts, and in particular there is a strong desire to improve the durability of these parts. Iron-based sintered alloys are generally considered to have excellent wear resistance, and they are advantageously used as component materials for parts with relatively low surface pressure.

[Problem that the invention seeks to solve]

However, when applied to high surface pressure parts, since sintered alloys generally have many pores, lubricating oil escapes into the pores of the sintered material, making it impossible to obtain a stable oil film and reducing the material strength. Since it is low, problems such as buckling and caving phenomena due to high blood pressure are likely to occur, and pitching, which is a localized fatigue phenomenon of the surface portion, is likely to occur. For this reason, there have been few examples of using iron-based sintered alloys in high surface pressure areas.

The inventors of the present invention have conducted various studies to improve these drawbacks of iron-based sintered alloys, and as a result, they have developed an iron-based sintered alloy that has high density and high hardness and eliminates all of the above-mentioned drawbacks. Moreover, the shape distribution of precipitated carbides has been improved, and the sintered alloy of the present invention has been completed, which exhibits good effects not only on its own wear resistance and pitting resistance, but also on the wear of the mating material.

[Means for solving problems]

That is, the wear-resistant iron-based sintered alloy of the present invention has a weight ratio of chromium (Cr): 15 to 25% and copper (Cu): 1 to 5%.
%, phosphorus (P): 0.3-0.8%, carbon (C)
: Metal powder consisting of 2.0 to 4.0%, balance iron and impurities of 2% or less is sintered to a density of 7.3 g/Cm' or more.

The purposes of use of each component element in the alloy of the present invention and reasons for limitations will be explained below.

Although P is generally known to promote sintering of Fe-based sintered alloys, P has a remarkable effect in the sintered alloys of the present invention. As shown in the examples below, 1100 to 1200°
A high-density sintered body can be obtained at the general sintering temperature of P.
This is due to the effect of The effect of such P is 0.3
% or more, it is noticeable, but up to 0.8% is sufficient, so 0
．． It was set at 3 to 0.8%.

A part of C combines with C'', (Fe, Cr)7
In the sintered alloy of the present invention, less than 2% of carbides are formed, such as G3, to improve wear resistance, and the remainder exerts its effect as an effective element to increase the hardness and strength of the matrix. With C, the hardness of the material and the amount of carbide are insufficient, so 2 is required to obtain sufficient # wear resistance under high surface pressure.
% or more is required. However, if it exceeds 4%, carbide particles will grow and wear out the mating material, so it is preferably 4% or less.

Cr is partially precipitated as a solid solution in the matrix and strengthens the matrix, but most of the Cr is combined with C to form carbide particles. If it is less than 15%, the carbon content relative to Cri will increase and the carbide particles will become large, which is not preferable, so it is set to 15% or more. In addition, the higher the Cr content, the more effective it is, but if it exceeds 25%, the effect of increasing it will be less, and moreover, the amount of Fe-Cr system γ phase will increase in the raw powder, making powder compaction difficult, so it is less than 25%. And so.

As in the case of ordinary iron-based sintered alloys, Cu precipitates finely in the matrix during cooling after sintering and has the effect of strengthening the alloy. The important effect is that the carbide is made finer and spheroidized. Cu
The preferred range of ff1 is 1 to 5%.

The sintered alloy of the present invention has a hard Vickers hardness of 400
~700. In addition, this alloy has a strong Fe-Cr-
Very hard, finely granular composite carbides such as (Fe, Cr)7G3 are uniformly distributed in a Cu-P-C (α phase + γ phase) matrix. The sintered alloy of the present invention can be obtained as a sintered alloy with high density and high hardness as described above by using almost the same manufacturing method as that for ordinary iron-based sintered alloys, and the results of the wear test are also very good. .

〔Example〕

The invention will be explained in further detail by the following examples. Note that the present invention is not limited to the following examples.

Weight ratio: Cr: 17%, Cu: 2%, P: 0.5
%, G: 2.5%, the balance is Fe, and a sprayed alloy of 100 mesh or more having a composition excluding carbon (C) from an alloy composition consisting of 2% or less of impurities contained in ordinary iron-based sintered alloys. A powder was produced, to which flaky natural graphite powder as a carbon source and zinc stearate powder as a lubricant were added and uniformly mixed using a mixer. after that,
The Tokiyoyoi alloy powder was press-molded in a mold with a pressure of 6.5 jan/cm' to give a density of 6.2 to 8.4 g/cm.
This molded body was heated at 1100 to 1200℃xe in a decomposed ammonia gas atmosphere (82+82).
A sintered alloy according to the present invention was obtained by heating and sintering for 0 minutes in the same manner as a normal iron-based sintered alloy. The density and hardness of the obtained sintered alloy were measured, and an abrasion test was performed on the sintered alloy to determine the amount of butt wear and cam wear. This wear test was performed on the obtained sintered alloy according to the present invention. )1. C
, Displacement 22 with (Over Rad cam) valve mechanism
A rocker arm pad l as shown in Fig. 2 for a 00cc diesel engine is manufactured, and it is brazed to the rocker arm 2 and combined with a cam 3 made of alloyed chilled cast iron (the arrow in the figure indicates the direction of rotation). I ran the actual machine. This actual @ operation was performed with the engine alone, 4.40 Or, p
, mX full load x 50 hours + 2.00Or, p, m X no load x 150 hours cycle pattern total 5 times 1,
Conducted as a 000 hour test, wear I4 is bar 2 bar,
The maximum wear depth was measured for both cams.

Hereinafter, sintered alloys of the present invention and the conventional sintered alloys having different alloy compositions were manufactured in the same manner as in Example 1, and the density and hardness measurements and wear tests were conducted in the same manner. The alloy M1 composition, density and hardness, and wear test results in these examples and comparative examples are as follows:
-) The results of Example 1 mentioned above are also summarized in the table below.

The comparative example is a conventional alloy 5Cr2 which has been quenched and tempered, and the surface thereof is plated with hard chromium.

As can be seen from the results in the table above, since a diesel engine was used in this wear test, fine soot from the combustion gas got mixed into the lubricating oil during the test, making it an extremely severe wear test. Even though the hard chrome plating used caused significant wear, the sintered alloy of the present invention has good performance due to the uniform distribution of fine grained carbides in the matrix consisting of a strong (α + γ) phase. Because it has excellent wear resistance,
Both the bat and cam have shown extremely advantageous results2.
It also has the effect of not abrading the mating material. Regarding density and hardness, the sintered alloy of the present invention has a high density (7.3z/cm
It has high hardness (Vicker hardness of 400 to 700) and has material strength that can withstand high surface pressure.

〔Effect of the invention〕

As described above, the iron-based sintered alloy using the composition according to the present invention has high density, high strength, and wear resistance even when applied to sliding parts used as machine components under relatively high surface pressure. This solves all the conventional problems and works well, so it is very advantageous for the high performance and long life of automobiles, etc., which are desired today. The sintered alloy of the present invention can also be used as a general wear-resistant material, in addition to wear parts that are subject to high surface pressure, such as internal combustion engine cams, rocker arm pads, valve lifters, and valve tips, for which it is particularly suitable. It has a wide range of applications and is extremely valuable industrially.

[Brief explanation of drawings]

Figure 1 is a W4 micrograph (magnification: 400x) of the metal structure of an example of the wear-resistant iron-based sintered alloy of the present invention. Figure 2 is a side view of a part of the equipment for performing the wear test. show. In the diagram, 1...Rocker hat 2...Rocker arm 3
...Cam patent applicant Toyota Motor Corporation (and 2 others)

Claims (1)

[Claims] Chromium (Cr): 15-25%, copper (Cu): by weight ratio
1-5%, phosphorus (P): 0.3-0.8%, carbon (C):
A wear-resistant iron-based sintered alloy characterized by sintering metal powder consisting of 2.0 to 4.0%, the balance iron and impurities of 2% or less to a density of 7.3 g/cm^2 or more.