JPS58157951A - Sintered alloy for sliding member - Google Patents

Abstract

PURPOSE:To prevent deterioration in the characteristics of a sintered Fe alloy contg. dispersed graphite and increases in the extent of wear and the coefft. of friction in accordance with use, by forming hardened Fe-Cu layers between the matrix of the alloy and the graphite particles. CONSTITUTION:Hardened Fe-Cu layers 4 having 3-10mum thickness are formed around graphite particles 2 in a sintered alloy having a structure contg. 1-5wt% free graphite 2 dispersed in the ion matrix 1 contg. <=1.2wt% solubilized carbon. In the figure, each symbol 3 is a pore. The solid lubricity of the alloy is shown by the exposed heads of graphite particles 2 at the surface sliding along its opposite member. The open parts of pores 3 are narrowed during use by the plastic flow 1' of the matrix, yet the layers 4 hinder the graphite particles 2 from flowing in the exposed part of the matrix. As a result, a low coefft. of friction is maintained, and the extent of wear is reduced. The layer 4 are formed by allowing copper plated on the particles 2 with iron as the matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is adapted to operate under relatively high loads or thrust loads;
(This relates to a sintered alloy that can withstand sliding under conditions where the lubricating effect of stored oil is insufficient.

Conventionally, 1~
Sintered alloys with a structure in which 5% free graphite is dispersed generally exhibit excellent sliding properties, and in order to leave the graphite as free graphite without dispersing it in the graphite matrix blended with the raw material powder, it is necessary to It is known that it is sufficient to apply sea bream plating in advance.

However, although conventional materials of the same type are initially good, their properties often deteriorate as they are used, resulting in an increase in the amount of wear and coefficient of friction. The inventors' research results regarding the cause of this problem can be briefly described as follows.

Figure 1 and iF! Figure 2 schematically shows the changes in the cross section of the counterfeit member before and after use. It is dragged away by the sliding movement with the mating member.

In this alloy, the outcrop of graphite particles on the sliding surface exerts a solid lubricating effect, so that maintaining the state before use as shown in FIG. 1 is a necessary condition for maintaining the properties.

However, in reality, graphite particles may peel off from the base during Nlll1, or as shown in Figure 2, graphite particles may peel off from the base during Nlll1.
I! A phenomenon such as the soft base plastically flowing and covering the graphite dew 11 (1') may occur, resulting in an exposed area of graphite, but this method is undesirable as it may promote wear of the mating member.

This invention was made in view of the above-mentioned circumstances, and is based on the idea of forming a hardened steel layer between the base and the graphite particles to prevent the black ship from falling off and being damaged by the base. We have discovered and completed the appropriate range of the thickness of the hardened layer, as well as manufacturing conditions to achieve this (C, the relationship between the thickness of copper plating applied to graphite particles and the sintering temperature, etc.).

The gist is that the thickness of the cured layer is 3 to 10 microns.

The effects of plating thickness and sintering temperature on the thickness of the iron-hardened layer formed by the reaction between the copper coating the graphite and the base iron will be analyzed using first-order factors.

1IIK1 Table Inventive material 1% 2.5% 4.0 voices 1000℃
Comparative material 1'##900℃ Comparative material 2'# I 1100'
C Comparison Material 511 15μ 1000℃ Example First, natural graphite powder and copper-plated graphite powder with three layers of plating layer thicknesses of 15μ, 4μ, and 11μ were prepared as the additive base, and these were shown in Table 1. It is blended into atomized iron powder according to a predetermined ratio and combination, and further iI
i: Add 0.3% to zinc stearate 1 as a lubricant and mix it, then apply a pressure of 2.5t/aII to a size of 71m1X
A large number of rectangular parallelepipeds of 10al x 10tm were made in the tfM shape.

Next, these molded bodies were hammered into the YIII surface and sintered at a temperature of 90°C.
Stratified into 3 groups: 0℃, 1000℃, and 1100℃,
Five types of samples were prepared by sintering in a sintering furnace in a reducing atmosphere for 20 minutes at each predetermined humidity. These samples have a copper plating thickness of 4 μm and a sintering temperature of 1000°C (invention material)
This and Comparative Materials 1 and 2 show the effect of sintering temperature, and Comparative Materials 3 and 4 show the effect of plating thickness.

The sintered density of each sample was 40 g/cd, and the oil content when No. 2 turbine oil tS oil was used was 1p5%.

Next, the cross section of each sample was examined under a microscope to measure the microstructure and the thickness of the iron-copper valence layer formed around the graphite particles. Friction and wear tests were conducted under different conditions, and the friction coefficient, its fluctuations, and the amount of sample wear after a specified period of time were investigated.

Disc: 50M21 hardened material (HIC60) Sliding speed: 40wt/surface Pressure: 25kl! F/a11 Lubrication: Only oil is added to the sample (no oil) Test time:
The results of the 120 minute test are as shown in Table 812.

#J2 table Inventive material 5μ No change 29μ comparative material 1
# After 90 minutes 64 # Comparison material 2
- After 102 minutes 51μ comparison material 3
2p 108 minutes IN 82 voices comparison material 4 1
3μ No change 55According to the results, the material of the present invention with a hardened layer thickness of 5μ shows a stable value of 0.25 in friction coefficient from beginning to end, has the least wear, and is the most excellent.

The thickness of the hardened layer is preferably in the range of 3 to 10 .mu.m, and as the results for Comparative Material 3 show, if it is 2 .mu.m or less, there is no effect. On the other hand 10
If the thickness is greater than β (as shown in the results for comparative material 4), the wear on the material itself will only increase slightly, but it will cause scratches on the mating member, which is not preferable.

3 and 4 are schematic diagrams for explaining the effects of the present invention, and FIG. 3 shows the state of the material of the present invention before the test.
This figure differs from the first figure in that a hardened layer 4 is interposed between the Kurofune particles 2 and the base.

Figure 114 shows the foreshadowing after the sliding test, and the opening of the hole 3 is narrowed by the 1° plastic flow part of the base 1, but the graphite particle 2 is narrowed by the intervening hardened layer. 4 prevents the graphite from flowing to the exposed graphite portion of the base. This is low l! This is thought to be the cause of the persistence of the friction coefficient, reduction of the amount of Jlk, and other effects of the present invention.

Now, since the iron-copper valence layer 4 is formed by alloying the copper plated on the Kurofune particles with the base iron, one of the factors that influences its thickness t is the thickness of the plating layer. , is determined to be slightly thinner than the desired thickness of the cured layer, in the range of 2 to 9 μm.

Another factor, the sintering temperature, is between 950°C and 1050°C.
If the sintering temperature is lower than this, the bond between the hardened layer and the base will be insufficient, and the graphite particles will easily fall off during sliding. This fact is considered to indicate Y.

In addition, if the sintering temperature is 1050°C or higher, the copper coating on graphite 1 will diffuse into the base, and as shown in the results for comparative material 2, the desired hardened layer will not be formed. The properties of the component deteriorate.

Although chemical plating is commonly used to coat graphite particles with copper, other methods such as K with a particle size of 20μ or less*
**A granulation method using powder or other appropriate means can be used. In addition, dispersing 1 to 5% free graphite and adding 12% or less carbon to the base both belong to the prior art, but the former has no solid lubrication effect if it is less than 1%. If it exceeds the above, the strength of the part will decrease.The latter is a base structure of ferrite and silica, and the amount of addition should be determined depending on the material of the mating member or the load conditions. At 12%, almost the entire area becomes pearlite.

[Brief explanation of drawings]

Figure 1111 is a schematic diagram showing the cross-sectional shape i1Y of a conventional graphite-dispersed iron-based sintered sliding member before the sliding test, and Figure 2 is a schematic diagram showing the cross-sectional shape st- of the same member after the test. and FIG. 4 are schematic diagrams showing the cross-sectional states of the sliding member according to the heather invention before and after the test, respectively. 1... Base 2... Graphite particles Cl1i11 graphite)
3... Void 4... Iron-copper hardening layer agent Kunihiko Masubuchi Figure 2, Figure 4

Claims (1)

[Claims] 1. A sintered alloy odor having a structure in which 1 to 5% of free graphite is dispersed in an iron base having a solid solute carbon vt of 12% or less by weight, and a thickness around the free graphite. A sintered alloy for a sliding member, characterized in that an iron-copper valence layer having a diameter of 3 to 10μ is formed.