JPH0233784B2 - TAIMAMOSEIOJUSURUFEKISHOKETSUGOKIN - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention has excellent wear resistance, and when used, for example, for forming the part surface of a valve locker arm of an internal combustion engine or manufacturing a tappet, it will not damage the camshaft, which is a mating member. The present invention relates to an Fe-based sintered alloy that itself exhibits excellent wear resistance without any damage. [Prior art and its problems] In general, for example, the part surface of a valve locker arm of an internal combustion engine is subjected to strong impact loads and high-speed sliding. It is required that the camshaft, which is a member, not be damaged. 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 that are dispersed to improve hardness have been used, but materials (a) above do not exhibit satisfactory wear resistance, and materials (b) above do not exhibit sufficient wear resistance. Because it is extremely hard, it causes damage to the mating member, and the degree of this wear increases as the amount of dispersed hard particles increases and the particle size increases. If the particle size is made finer, the wear resistance of itself will decrease, which is undesirable.
(b) Since the material is manufactured by a normal sintering method, it usually has a low density, which results in problems such as insufficient toughness and progression of matrix fracture. There is. [Purpose of the research and findings based on the research] From the above-mentioned viewpoints, the present inventors conducted research in order to obtain an alloy that has excellent wear resistance and toughness and causes almost no wear on mating parts. As a result, it contained, in weight% (hereinafter % indicates weight%), C: 1 to 3%, Cr: 10.1 to 20%, Nb: 0.2 to 5%, and further Mo: 0.5 to 10. %, W: 0.5-10%, V: 0.2-5%, Ta: 0.2-5%, containing one or more of the following (but
Total amount of carbide-forming components consisting of Mo, W, V, and Ta: 20% or less), and if necessary, one or two of the following: Ni: 0.5 to 10%, Co: 0.5 to 10%. In the Fe-based sintered alloy, which has a composition of Fe and unavoidable impurities, the wear resistance is improved by the hard carbide particles uniformly dispersed in the matrix.
In addition, the average particle size of the carbide particles is 3 to 3, since acicular carbides are reduced by the action of the Nb component.
Since it is relatively fine at 50 μm, the matrix, which is softer than the carbide particles, wears out in the early stages of use, forming a smooth worn surface at an early stage, resulting in extremely good compatibility with the mating part, 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 improves sinterability. As the alloy is further improved and 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 matrix fracture due to lack of toughness. Ni and Co contained
They discovered that the matrix can be further strengthened and its compatibility can be significantly improved depending on the ingredients. [Components of the invention] Therefore, this invention was made based on the above knowledge, and contains C: 1 to 3%, Cr: 10.1 to 20%, and Nb: 0.2 to 5%. , Mo: 0.5-10%, W: 0.5-10%, V: 0.2-5%, Ta: 0.2-5%, containing one or more of the following (however,
Total amount of carbide-forming components consisting of Mo, W, V, and Ta: 20% or less), and if necessary, one or two of the following: Ni: 0.5 to 10%, Co: 0.5 to 10%. The remainder is Fe and unavoidable impurities (wt%), and the theoretical density ratio is 90% or more, and carbide particles with an average particle size of 3 to 50 μm are uniformly distributed in the matrix. This is a Fe-based sintered alloy with a dispersed structure. [Reason for technical limitation] 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) The C component contains Cr and Nb components, and further combines with the above carbide-forming components to form carbide,
It has the effect of improving the wear resistance of the alloy, but if its content is less than 1%, the amount of carbide precipitated is too small to ensure the desired excellent wear resistance, while if it exceeds 3%. When it is included,
If the amount of carbide precipitated becomes too large, it will cause significant wear on the mating member and also cause a decrease in toughness, so the content should be reduced to 1 to 3.
%. (b) Cr The Cr component combines with C to precipitate high-hardness Cr carbide with a Vickers hardness of 1000 to 1800, which further improves the wear resistance of the alloy, and also forms a solid solution in the matrix. , has the effect of significantly improving its heat resistance, but its content is
If the content is less than 10.1%, the desired effect cannot be obtained, while if the content exceeds 20%, the wear of the mating member becomes severe and alloy embrittlement occurs. 10.1~
It was set at 20%. (c) Nb The Nb component combines with the C component to form a high hardness carbide with a Vickers hardness of 2300 to 3300 to improve the wear resistance of the alloy. It has the effect of suppressing the formation of carbides and making them finer, thereby improving conformability, as well as improving sinterability and densifying the structure, but if the content is less than 0.2%, the above effects are insufficient. In other words, the average particle size of carbide particles is 50 μm.
Not only is it impossible to reduce the content to less than 5%, but it is also difficult to make the structure dense, and on the other hand, if the content exceeds 5%, a large amount of hard and fine carbide particles with an average particle size of less than 3 μm will be formed. This will result in significant wear and tear on the mating parts.
Its content was set at 0.2-5%. (d) Carbide-forming components These components include, in combination with the C component, W and Mo are composite carbides having a Bitkers hardness of 1000 to 3000, and V and Ta are MC having a Bitkers hardness of 2300 to 3300. In addition to forming type carbides and improving the wear resistance of the mote alloy,
It dissolves in the matrix and has the effect of improving heat resistance, but the content is
%, W: less than 0.5%, V: less than 0.2%, and Ta: less than 0.2%, the desired effect cannot be obtained, while Mo: 10%, W: 10%, V: 5
If the content exceeds Mo: 0.5% and Ta: 5%, not only will the degree of wear on the mating member increase, but also the grindability will deteriorate.
-10%, W: 0.5-10%, V: 0.2-5%, and Ta: 0.2-5%. In addition, if the total amount of these carbide-forming components exceeds 20%, the amount of precipitated carbides will similarly become too large and cause significant wear on the mating component, so the total amount of these carbide-forming components should be reduced to 20% or less. It was determined that (e) Ni and Co As mentioned above, Ni and Co components are selectively included in order to further strengthen the matrix and improve compatibility, but if their content is less than 0.5% each, the desired addition content is reduced. No effect was obtained, and on the other hand, no further improvement was observed even if the content exceeded 10% of each, so the upper limit was set at 10% in consideration of economic efficiency. (f) Theoretical density ratio of the alloy When the theoretical density ratio is less than 90%, the strength of the matrix is low and voids are present, and the crack propagation is promoted by the notch effect of the voids. Therefore, the matrix on the friction surface is extensively destroyed, resulting in significant wear, so it must have a theoretical density ratio of 90% or more. (g) Average particle size of carbide particles If the average particle size is less than 3 μm, it is too fine to ensure the desired excellent wear resistance, whereas if the average particle size is larger than 50 μm, the carbide particles The average particle size was set at 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. [Examples and Confirmation of Effects] Next, the Fe-based sintered alloy of the present invention will be explained using Examples and in comparison 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 form an alloy powder. from alloy powder
After forming a green compact at a pressure of 5 ton/cm ² , this green compact is sintered in a vacuum at a predetermined temperature within the range of 1120 to 1180°C, each having the component composition shown in Table 1. A sintered body is manufactured, and then this sintered body is
Temperature: After heating to 1000℃ and quenching, temperature:
Alloys 1 to 23 of the present invention and Comparative Alloys 1 to 6 were produced by heat treatment maintained at 540 to 560°C for 1 hour. In addition, for Comparative Alloys 1 to 6, one of the constituent components (components marked with * in Table 1) was

【table】

It has a composition outside the scope of the invention shown in [Table]. Next, the average grain size, theoretical density ratio, Vickers hardness, and transverse rupture strength of the carbide particles were measured for the resulting invention alloys 1 to 23 and comparative alloys 1 to 6. A wear test was conducted on the pad surface for 100 hours of operation (spring load: 110 kg), and the amount of wear and the amount of wear on the cam, which is the mating member, was 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 part surface was chilled. From the results shown in Table 1, the invention alloys 1 to 23
All of these alloys have significantly superior wear resistance compared to conventional materials, and the wear of mating parts is also extremely small. However, as seen in Comparative Alloys 1 to 6, If the content is low and outside the range of the present invention, sufficient wear resistance cannot be obtained, while if the content of C and Cr components is high, the wear of the mating member becomes relatively severe, and If the content of Nb component deviates to the lower side,
Since it is not possible to achieve the desired refinement of the carbide particles and densification of the structure, the average grain size of the carbide particles becomes larger than 50 μm, which not only causes significant wear on the mating member but also reduces the theoretical density to 90 μm.
If the Nb content is less than 5%, the wear of the mating member will be severe, while if the Nb content exceeds 5%, there will be a large amount of fine carbide particles with an average particle size of 1 μm, which will cause wear and tear on the mating member. It is clear that the As mentioned above, the Fe-based sintered alloy of this invention is
It has excellent wear resistance and minimal wear and tear on the mating member.

Claims (1)

[Claims] 1 Contains C: 1 to 3%, Cr: 10.1 to 20%, Nb: 0.2 to 5%, and further contains Mo: 0.5 to 10%, W: 0.5 to 10%, V: Contains one or more of the following: 0.2-5%, Ta: 0.2-5% (but
The total amount of carbide-forming components consisting of Mo, W, V, and Ta: 20% or less), the remainder consisting of Fe and unavoidable impurities (weight% or more), and the theoretical density ratio: 90% or more In addition, the average particle size in the matrix:
A wear-resistant Fe-based sintered alloy characterized by a structure in which carbide particles of 3 to 50 μm are uniformly dispersed. 2 Contains C: 1-3%, Cr: 10.1-20%, Nb: 0.2-5%, Mo: 0.5-10%, W: 0.5-10%, V: 0.2-5%, Ta: 0.2 ~5%, containing one or more of the following (but
The total amount of carbide-forming components consisting of Mo, W, V, and Ta: 20% or less), Ni: 0.5 to 10%, Co: 0.5 to 10%, and one or two of the following. has a composition (weight%) consisting of Fe and unavoidable impurities, has a theoretical density ratio of 90% or more, and has a structure in which carbide particles with an average particle size of 3 to 50 μm are uniformly dispersed in the matrix. Fe-based sintered alloy with wear resistance.