JPS5940217B2 - Fe-based sintered alloy with wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has excellent wear resistance and can be used to form the butt surface of a valve arm of an internal combustion engine or to manufacture tappets, etc. The present invention relates to an Fe-based sintered alloy that is not damaged and exhibits excellent wear resistance.

Generally, for example, the butt surface of a valve rocker arm in an internal combustion engine is subject to strong impact loads and high-speed sliding, so the material forming the butt surface must have wear resistance and properties that will not damage the camshaft, which is the mating member. is required.

Conventionally, the manufacturing of mechanical parts that are subjected to such loads and sliding has been done using (a) cast iron whose parts that are subjected to loading and sliding are chilled during casting, and (b) hard particles made of tungsten carbide, molybdenum carbide, etc. Materials such as sintered alloys, which are dispersed to improve hardness, have been used, but the above materials (a) do not exhibit satisfactory wear resistance, and the above materials (b) themselves have very poor wear resistance. Because it is hard, it causes damage to the mating part,
Furthermore, the degree of wear increases as the amount of dispersed hard particles increases and the particle size increases.Conversely, if the amount of dispersed hard particles is reduced and the particle size is made finer, This is undesirable because it reduces its own wear resistance, and furthermore, since this (b) material is manufactured by a normal sintering method, it usually has a low density, which results in a lack of toughness. However, there are problems such as matrix destruction progressing.

From the above-mentioned viewpoints, the present inventors conducted research to obtain an alloy that has excellent wear resistance and toughness and causes almost no wear on mating parts. ), C: 1 to 3%.

Contains Cr: 10.1-20%, Nb: 0.2-5fO1, and if necessary, one of the following: Ni: 0.5-10%, Co: 0.5-10%, or In an Fe-based sintered alloy having a composition containing two kinds of carbide and the remainder consisting of Fe and unavoidable impurities, (ma) wear resistance is improved by hard carbide particles uniformly dispersed in the IJ lux, and The average particle diameter of the particles is relatively fine, 3 to 50 μm, because the acicular carbide is reduced by the action of the Nb component.
In the early stages of use, the I-IJ lux, which is softer than carbide particles, wears out and forms a smooth worn surface at an early stage, resulting in extremely good compatibility with the mating member, and
Since the surface pressure on the friction surface is uniformly dispersed in the fine carbide particles, it improves not only the wear itself but also the wear of the mating member, and the inclusion of Nb further improves the sinterability. However, since the alloy has a dense structure with a theoretical density ratio of 90% or more, it has extremely high toughness, and as a result, there is no mal-'J-lux fracture due to lack of toughness, and the required It was found that the Ni and Co components contained in the steel sheet further strengthened the IJTx and also significantly improved the conformability.

Next, in the Fe-based sintered alloy of the present invention, the reason why the component composition range, theoretical density ratio, and average particle size of carbide particles are numerically limited as described above will be explained.

(a) C The C component combines with Cr and Nb to form carbides and has the effect of improving the wear resistance of the alloy, but if its content is less than 1%, the amount of carbide precipitation is too small. On the other hand, if the content exceeds 3, the amount of carbide precipitated becomes too large, resulting in significant wear of the mating member and a decrease in toughness. Therefore, the content was determined to be 1 to 3.

(b) Cr The Cr component has a Vickers hardness of 1000 when combined with C.
It has the effect of precipitating high hardness Cr carbide with a hardness of ~1800 and further improving the wear resistance of the alloy, and also forming a solid solution in the Mar-IJ lux and significantly improving its heat resistance. If the content is less than 101%, the desired effect cannot be obtained, while if the content exceeds 20%, the wear of the mating member becomes severe and alloy embrittlement occurs. The amount was determined to be 10.1-20%.

(c) Nb The Nb component has a Vickers hardness of 23 when combined with the C component.
In addition to forming high-hardness carbides with a hardness of 00 to 3300 to improve the wear resistance of the alloy, as mentioned above, the formation of acicular carbides is suppressed to make the carbides finer, thereby improving conformability and improving the sinterability. It has the effect of improving concretion and densifying the structure, but if its content is less than 0.2%, this effect is insufficient, that is, the average particle size of carbide particles cannot be reduced to 50 μm or less. It is difficult to make the structure dense, and on the other hand, if the content exceeds 5, the average particle size becomes 3.
Since a large amount of hard and fine carbide particles of less than .mu.m are formed and cause significant wear on the mating member, the content thereof is determined to be 0.2 to 5.

As mentioned above, Ni and Co components are selectively included in order to further strengthen the matrix and improve conformability, but if their content is less than 0.5% each, the desired addition effect cannot be obtained. On the other hand, even if each content exceeds 10%, no further improvement effect was observed, and the upper limit was set at 10% in consideration of economic efficiency.

(d) Theoretical density ratio of the alloy When the theoretical density ratio is less than 90%, the strength of the matrix is low and pores are present, and crack propagation is promoted by the notch effect of the pores. Since the mud IJs on the friction surface are extensively destroyed, resulting in significant wear, it is necessary to have a theoretical density ratio of 90% or more.

(e) Average particle size of carbide particles When the average particle size is less than 3 μm, it is too fine to ensure the desired excellent wear resistance, while on the other hand, when the average particle size is larger than 50 μm, the carbide particles The average particle diameter was determined to be 3 to 50 μm because cleavage and peeling occur, and if this continues, not only will the matrix be destroyed, but the mating member will also be significantly worn out.

Next, the Fe-based sintered alloy of the present invention will be explained using examples and comparing with comparative examples.

First, iron oxide powder is used as the main raw material, and a predetermined amount of metal oxide powder and carbon powder of each component are blended into it, and then hydrogen reduction (co-reduction method using carbon and hydrogen) is performed to obtain an alloy powder.
Next, a green compact is formed from this alloy powder at a pressure of 5 tons/i, and then this green compact is heated to 1120 to 1180
The sintered bodies are sintered at a predetermined temperature within the range of 'C to produce sintered bodies having the component compositions shown in Table 1, and the sintered bodies are then heated to a temperature of 100°C. Invention alloys 1 to 14 and comparative alloys 1 to 6 were manufactured by performing heat treatment at a temperature of 540 to 560°C for 1 hour after quenching.

In Comparative Alloys 1 to 6, one of the constituent components (components marked with * in Table 1) has a composition outside the scope of the present invention.

Next, the average grain size, theoretical density ratio, Vickers hardness, and transverse rupture strength of the carbide particles were measured for the resulting alloys of the present invention 1 to 14 and comparative alloys 1 to 6. A wear test was carried out using the bat surface of the bat for 100 hours (spring load: 90 kg), and the wear amount and the wear amount of the mating member cam were measured.

These results are also shown in Table 1. Table 1 also shows the results of a wear test under the same conditions for conventional material, cast iron whose bat surface was chilled.

From the results shown in Table 1, alloys 1 to 14 of the present invention all have significantly superior wear resistance compared to conventional materials, and the wear of the mating member is also extremely small.
As seen in Comparative Alloys 1 to 6, when the content of C and Cr components is low and outside the range of the present invention, sufficient wear resistance cannot be obtained; on the other hand, when the content of C and Cr components is high, If the Nb content is too low, the wear of the mating member will be relatively severe, and if the content of the Nb component is too low, it will not be possible to achieve the desired refinement of the carbide particles and densification of the structure. The average particle size of the material becomes larger than 50 μm, which not only causes significant wear on the mating member, but also causes severe wear on the material itself as the theoretical density ratio becomes less than 90%.On the other hand, the Nb content exceeds the factor 5. It is clear that since a large amount of fine carbide particles with an average particle diameter of 1 μm are present, the wear of the mating member becomes significant.

As mentioned above, the Fe-based sintered alloy of the present invention has excellent wear resistance and extremely low wear and tear on the mating member.

Claims (1)

[Scope of Claims] 1 A composition containing C: 1 to 3 parts, Cr: 10.1 to 20%, Nb: 0.2 to 5%, and the remainder consisting of Fe and unavoidable impurities (the above weight parts) A wear-resistant Fe-based sintered material having a theoretical density ratio of 90 or more and a structure in which carbide particles with an average particle size of 3 to 50 μm are uniformly dispersed in the matrix. Combined gold. 2 Contains C: 1 to 3%, Cr: 10.1 to 20%, Nb: 0.2 to 5 parts, and furthermore, Ni: 0.5 to 10 parts, CO: 0.5 to 10%. , containing one or two of the following, with the remainder consisting of Fe and unavoidable impurities (filling soil weight%), and having a theoretical density ratio of 90% or more, and having an average particle size in the matrix. :3
An Fe-based sintered alloy having wear resistance characterized by having a structure in which carbide particles of ~50 μm are uniformly dispersed.