JPH0116296B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has excellent wear resistance and self-lubricating properties, and is particularly useful for sliding members that are subjected to high surface pressure and are exposed to usage conditions where it is not possible to form a sufficient lubrication state at the start of operation, such as The present invention relates to an Fe-based sintered alloy suitable for use in manufacturing sliding members such as rocker arm sliding parts, cams, valve seats, valve guides, and sleeves in internal combustion engines. In recent years, with the increase in speed, efficiency, and output of vehicles, the sliding of internal combustion engine valve mechanism members, especially rocker arm part surfaces, cams, valve seats, valve guides, and sleeves, which are subject to high surface pressure, has become increasingly important. For moving parts, the usage conditions tend to become more severe, for example, as it becomes difficult to form a stable lubricant film, and there is therefore a strong desire to develop materials that can withstand these harsh usage conditions. . However, at present, no material has yet been proposed that fully satisfies these requirements. Therefore, from the above-mentioned viewpoint, the present inventors conducted research in order to obtain a material suitable for manufacturing sliding members that are particularly subjected to high surface pressure and are exposed to usage conditions with insufficient lubrication. As a result, the sliding member contained, in weight%, C: 2 to 8%, Si: 0.1 to 5%,
Contains Cr: 4 to 30%, one or two of P and B (in total): 0.02 to 5%, calcium fluoride (hereinafter referred to as _CaF2 ): 0.05 to 5%, and additionally necessary Depending on the amount, one or both of Mo and Nb (in total amount): 0.1-10% and Mn: 0.1-10%
When composed of an Fe-based sintered alloy containing either or both of the following, with the remainder consisting of Fe and unavoidable impurities, this Fe-based sintered alloy
Free graphite and CaF ₂ uniformly dispersed in the base material ensure excellent self-lubricating properties, and the base material also ensures excellent wear resistance.
It was discovered that this sliding member exhibits excellent performance over an extremely long period of time without damaging the mating member, even under conditions of high surface pressure and insufficient lubrication. . This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below. (a) C For the C component, solid solution is added to the base material to strengthen it.
In addition to combining with carbide-forming components such as Cr to improve the wear resistance of the alloy, the remaining C
is precipitated in the matrix as free graphite and has the effect of improving the self-lubricating properties of the alloy, but if its content is 2.
If the content is less than 8%, the desired effect of improving the above action cannot be obtained, while if the content exceeds 8%, the fluidity of the mixed powder becomes extremely poor during alloy production, making it impossible to form a green compact. undesirable;
From this point of view, the content was determined to be 2 to 8%. (b) Si The Si component has the effect of forming a solid solution in the matrix, strengthening it, generating a liquid phase during sintering, activating sintering, and densifying the sintered body. ,
It has the effect of accelerating the precipitation of graphite, but if the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 5%, the embrittlement of the alloy becomes significant. Its content is 0.1~5%
It was determined that (c) Cr The Cr component has solid solution in the base material to strengthen it.
In addition, as mentioned above, Cr has the effect of forming Cr carbides with high hardness and improving the wear resistance of the alloy, but if the content is less than 4%, the desired excellent wear resistance cannot be achieved. On the other hand, if the content exceeds 30%, the alloy will become brittle, and as a result, its aggressiveness will increase, so the content was set at 4 to 30%. (d) P and B These components have the effect of forming a solid solution in the base material, strengthening it, increasing its hardness and improving the wear resistance of the alloy, and also suppressing the liquid phase during sintering. When the content is less than 0.02%, the desired effect cannot be obtained; On the other hand, if the content exceeds 5%, the toughness of the alloy will be significantly impaired, so the content was set at 0.02 to 5%. (e) CaF ₂ The CaF ₂ component has the effect of dispersing itself into the substrate and improving self-lubricating properties, and also has the effect of contributing to the spheroidization and stabilization of precipitated free graphite, but when the content is 0.05 If the content is less than 5%, the desired effect cannot be obtained, while if the content exceeds 5%, the alloy will become brittle.
It was set at 0.05-5%. (f) Mo and Nb These components have the effect of forming a solid solution in the base material, strengthening it, and combining with C to form carbides, thereby improving the wear resistance of the alloy. It is included as necessary especially when higher wear resistance is required, but the content is 0.1%.
If the content is less than 10%, the desired effect of improving wear resistance cannot be obtained, whereas if the content exceeds 10%, the damage to the mating member becomes significant. Therefore, the content was set at 0.1 to 10%. (g) Mn The Mn component has the effect of further improving the alloy strength by forming a solid solution in the base material, so it is included as necessary when particularly high strength is required, but the content is 0.1 If the content is less than 10%, the desired strength improvement effect cannot be obtained, and on the other hand, if the content exceeds 10%, no further improvement effect will be obtained. Established. The Fe-based sintered alloy of the present invention preferably has a theoretical density ratio of 90% or more, because if the theoretical density ratio is less than 90%, the strength of the base material will be low.
This is because large pores are present, and the notch effect of these pores makes the substrate more likely to be destroyed and pitting wear to occur. Next, the Fe-based sintered alloy of the present invention will be specifically explained with reference to Examples. Example Raw material powders include flaky graphite powder with a particle size of -200mesh, atomized Fe-Cr alloy powder (containing Cr: 12.5%) with a particle size of -100mesh, and high carbon powder with a particle size of -100mesh.
Fe-Cr alloy powder (Cr: 60% content), -200mesh
Fe-Si alloy powder (Si: 17% content),
350mesh Fe-P alloy powder (P: 17% content), -250mesh Fe-P alloy powder (P: 25.7% content),
-200mesh Fe-B alloy powder (B: 20% content), -200mesh CaF ₂ powder, -350mesh
Mo powder, -200 mesh Fe-Nb alloy powder (Nb: 15% content), Mn powder with average particle size: 5 μm,
and -100mesh Fe powder were prepared, and these raw material powders were blended into the composition shown in Table 1, and zinc stearate was added as a lubricant.
After adding 0.5% and mixing with a V-type mixer,
Formed into a green compact under a pressure of 5ton/ ^cm2 , then sintered in a vacuum at a predetermined temperature within the temperature range of 1050 to 1200℃ for 60 minutes, and after sintering. ,
By immediately performing forced cooling quenching at a temperature of 1000°C, Fe-based sintered alloys 1 to 28 of the present invention having substantially the same composition as the blended composition and comparative
Fe-based sintered alloys 1 to 9 were produced, respectively. In addition,
Comparative Fe-based sintered alloys 1 to 9 all have the following content of one of the constituent components (those marked with * in Table 1).

【table】

It has a composition outside the scope of the invention shown in [Table]. Next, the theoretical density ratio, maximum hardness of the substrate (Vickers hardness), and transverse rupture strength were measured for the resulting Fe-based sintered alloys 1 to 28 of the present invention and comparative Fe-based sintered alloys 1 to 9. At the same time, we cut out a chip piece that fits the part surface of the car engine's rocker arm, and cast it in when casting the rocker arm.The resulting rocker arm was assembled into a 4-cylinder OHC engine, using oil: Diamond 20W.
(trade name), a wear resistance test was conducted under the conditions of rotation speed: 850 rpm, and operating time: 200 hours, and the wear depth of the rocker arm pad surface and the mating member cam was measured. These measurement results are also shown in Table 1. From the results shown in Table 1, Fe-based sintered alloys 1 to 28 of the present invention all have excellent wear resistance and self-lubricating properties, so the amount of wear on the rocker arm part surface and mating cam is extremely small. ,
The worn surface was also extremely smooth.
On the other hand, as seen in Comparative Fe-based sintered alloys 1 to 9, when the content of any one of the constituent components falls outside the range of the present invention, the desired wear resistance and self-lubricating properties are lost. As a result, the amount of wear on at least one of the two members has increased, and scuffing and pitting have been observed on the worn surface. As mentioned above, the Fe-based sintered alloy of this invention is
It has excellent wear resistance and self-lubricating properties, so when used in the manufacture of valve train parts for internal combustion engines that are subject to high surface pressure and are not well lubricated at the start of operation, they hardly damage the mating parts. It has industrially useful properties such as being able to stably exhibit excellent performance over a long period of time without causing any damage.

Claims (1)

[Claims] 1 C: 2 to 8%, Si: 0.1 to 5%, Cr: 4 to 30%, one or two of P and B (total amount): 0.02 to 5%, Contains calcium fluoride: 0.05 to 5%, with the remainder consisting of Fe and unavoidable impurities (weight percent), and has a structure in which free graphite and calcium fluoride are uniformly dispersed in the matrix. A wear-resistant Fe-based sintered alloy with self-lubricating properties. 2 C: 2-8%, Si: 0.1-5%, Cr: 4-30%, One or two of P and B (total amount): 0.02-5%, Calcium fluoride: 0.05- 5%, and further contains one or two of Mo and Nb (total amount): 0.1 to 10%, and the remainder is Fe and unavoidable impurities (in weight %). A wear-resistant Fe-based sintered alloy having self-lubricating properties and having a structure in which free graphite and calcium fluoride are uniformly dispersed in the matrix. 3 C: 2-8%, Si: 0.1-5%, Cr: 4-30%, One or two of P and B (total amount): 0.02-5%, Calcium fluoride: 0.05- 5%, further contains Mn: 0.1 to 10%, and the remainder is Fe and unavoidable impurities (weight%), and free graphite and calcium fluoride are uniform in the matrix. A wear-resistant Fe-based sintered alloy with self-lubricating properties characterized by having a dispersed structure. 4 C: 2-8%, Si: 0.1-5%, Cr: 4-30%, One or two of P and B (total amount): 0.02-5%, Calcium fluoride: 0.05- 5%, and further contains one or two of Mo and Nb (total amount): 0.1 to 10%, Mn: 0.1 to 10%, and the remainder consists of Fe and inevitable impurities. A wear-resistant Fe-based sintered alloy with self-lubricating properties, which has a composition (weight% or more) and has a structure in which free graphite and calcium fluoride are uniformly dispersed in the matrix.