JPS6024174B2 - Fe-based sintered alloy for valve seats - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a Fe-based bran having excellent heat resistance, wear resistance, machinability, and self-lubricating properties, and which is particularly suitable for use in manufacturing valve seats in internal combustion engines. It concerns bond money.

Conventionally, for example, leaded gasoline has been used as a fuel for driving an internal combustion engine, and when the gasoline is burned, inorganic lead is produced from the alkyl lead contained in the gasoline, and part of the produced inorganic lead is Since the part adheres to the valve and valve seat, it improves the oxidation resistance, self-lubricating property, and
The effects of lead in gasoline were significant, such as significantly improving wear resistance.

However, in the current situation where it is becoming difficult to use leaded gasoline due to exhaust gas regulations, it is difficult to expect the lead effect in leaded gasoline to suppress oxidation and wear of valves and valve seats, and provide self-lubricating properties. Therefore, the current trend is to try to solve these problems by improving the material of the valve seat itself.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research in terms of materials in order to obtain a valve seat for an internal combustion engine that fully performs its functions even when unleaded gasoline is used.As a result, C: 0.5-3%, Cr: 1-20%, S: 0.05
~2%, Mo: 0.1~5%, B: 0.005~1%, and optionally P: 0.1~2% and Si: 0.
．． Ni: 0.1-5% and Co: 0.1-5% as necessary.
5%, and the rest is Fe and unavoidable impurities. The sulfide phase, which has good adhesion and self-lubricating properties, has a uniformly dispersed structure at the grain boundaries of the substrate, so when it is used in the manufacture of valve seats for internal combustion engines, it is suitable for use with unleaded gasoline, diesel oil, and L. P. They discovered that it has useful properties such as excellent heat resistance, wear resistance, and self-lubricating properties when used as a fuel such as G, and also exhibits excellent machinability when manufacturing valve seats.

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 The C component has the effect of not only strengthening the alloy base by forming a solid solution in the base but also forming carbides and improving the wear resistance of the alloy, but if its content is less than 0.5%, the above-mentioned On the other hand, if the content exceeds 3%, the alloy will become stiff and the hardness will increase significantly, increasing the aggressiveness of the valve as a mating material. Its content was determined to be 0.5 to 3%.

[b} Cr The Cr component not only reacts with C to form carbides and thereby improves the wear resistance of the alloy, but also has the effect of forming a solid solution in the base material and improving its heat resistance. If the content is less than 1%, the desired effect cannot be obtained, while if the content exceeds 20%, the alloy strength will rapidly decrease and the hardness will increase, which will significantly accelerate valve damage. The amount was determined to be 1-2o%.

'c'S The S component reacts with the Fe component to form sulfides that provide self-lubricating properties and free-cutting properties, but the content is 0.
If the content is less than 0.05%, the desired self-lubricating properties and free machinability cannot be imparted to the alloy, while if the content exceeds 2%, the alloy strength will decrease. It was set at .05 to 2%.

'dl Mo Like the Cr component, the Mo component not only solidifies into the base material and improves the heat resistance of the base material, but also reacts with C to form carbides to improve the wear resistance of the alloy. However, if the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 5%, the alloy strength will decrease. , its content was determined to be 0.1 to 5%.

[e'B The B component has the effect of generating a liquid phase during competition and activating the bran cord, making it possible to generate stable carbides and increase the density, but its content is 0.005%. If the content is less than 1%, the desired effect cannot be obtained; on the other hand, if the content exceeds 1%,
Since the alloy arms become remarkable, its content is reduced to 0.005.
It was set at ~1%.

'f' P and Si These components have an equal effect of activating coagulation in coexistence with B, but P:
When the content is 0.1% and Si: less than 0.05%,
No improvement effect was obtained by containing these components, while P:2
% and Si: If the content exceeds 2%, the formation of arms in the alloy will become significant.
2%, and Si: 0.05 to 2%.

(g) Ni and CONNi and Co have the uniform effect of melting into the alloy base and increasing its strength and heat resistance, so they are included especially when it is necessary to strengthen the alloy base. If the content is less than 0.1% each, the desired effect of improving the above-mentioned action will not appear, while if the content exceeds 5% each, no further improvement effect will be seen and it is not economical. The content was determined to be 0.1 to 5%, respectively.

The Fe-based competitive alloy of the present invention can be manufactured under normal manufacturing conditions according to normal powder metallurgy methods.
For Fe-S alloy powder containing 0% S, coated Fe powder whose surface is coated with sulfide, and for B,
It is desirable to use Fe-B alloy powder containing 30% B, and Cr, Mo, P, and Si can be used as single powders of these components or ferroalloy powders. Moreover, the Fe-based condensation alloy of this invention is 7.
It is desirable to have a density of 0 m/clump or more, which is 7
．． This is because if the density is less than 0/2, the desired excellent abrasion resistance and strength cannot be ensured.

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

Example raw material powders include Fe powder (diluted with atomized iron powder) with a particle size of 10 mm, natural graphite powder, and a particle size of 120 mm.
Mo powder, Fe-S alloy powder containing 36% S with particle size 110mash, Fe-B alloy powder containing 20% B with particle size 110mash, 26% of particle size 110mash
P-containing Fe-P alloy powder, particle size -100hash, 77% Si-containing Fe-Si alloy powder, particle size -20〃m
Prepare a Co powder of After molding the compacted powder in an ammonia decomposition gas atmosphere at a temperature of 500°C for 30 minutes to remove the lubricant added during mixing. , in vacuum, temperature: 11
50 to 120030 for 6 minutes, then rapidly cooled and soldered, and then heated in the atmosphere at a temperature of 5
Akatsuki alloys 1 to 19 of the present invention and comparative competitive alloys 1 to 8 were manufactured by subjecting them to tempering at 80 qo and holding heat for 60 minutes.

Furthermore, for the purpose of comparison, JIS/SUH, which is a martensitic heat-resistant steel mainly used for manufacturing valve seats, is shown below.
An alloy having a composition corresponding to -4 was manufactured as Comparative Alloy 9, and its composition is shown in Table 1.

Next, the density, hardness (Rockwell hardness C scale), and transverse rupture strength of the resulting sintered alloys 1 to 19 of the present invention and Hisame sintered alloys 1 to 8 and comparative alloy 9 were measured. The measurement results are also shown in Table 1.

Furthermore, for each of the valve seats manufactured from the above-mentioned brick alloys 1 to 19 of the present invention, comparative bran alloys 1 to 8, and comparative alloy 9, a bias-zero cam drive type with automatic temperature control was simulated in a practical test. A valve-valve seat wear test with repeated hot impacts was used; atmosphere: propane gas combustion atmosphere;
Valve material: Austenitic valve steel, valve temperature: 90000
, Valve seat temperature: 35000, Stroke: 6.8 degrees, Operating speed: 300 degrees. p. A wear durability test was conducted under the conditions of 5 hours of operation, and the depth of wear of the valve and valve seat after the test was measured.

The measurement results are also shown in Table 1. From the results shown in Table 1, all of the valve seats manufactured using Akatsuki Metals 1 to 19 of the present invention had extremely little wear, and the wear of the other valves was also low. All of the Hisame Sintered Alloys 1 to 8, which have compositions outside the scope of the present invention, and Comparative Alloy 9, which has been conventionally used for valve seats, had large valve seat wear.

As mentioned above, the Fe-based alloy of the present invention has a structure in which sulfides and carbides, which have good adhesion to the matrix, are uniformly dispersed in the matrix of the tempered martensitic phase containing the retained austenite phase. Therefore, it has excellent heat resistance, wear resistance, self-lubricating property, and machinability.
It exhibits excellent high-temperature wear resistance and is industrially useful, especially when used as valve seats in internal combustion engines that use fuels such as unleaded gasoline, diesel oil, and liquefied propane gas that do not produce valve and valve seat protective compounds. It has the following characteristics.

Claims (1)

[Claims] 1 C: 0.5-3%, Cr: 1-20%, S: 0.0
5-2%, Mo: 0.1-5%, B: 0.005-1%
1. An Fe-based sintered alloy for a valve seat, characterized in that it has a composition (by weight %) with the remainder consisting of Fe and unavoidable impurities. 2 C: 0.5-3%, Cr: 1-20%, S: 0.0
5-2%, Mo: 0.1-5%, B: 0.005-1%
further contains P: 0.1-2% and Si: 0.0
Contains one or two of 5 to 2% Fe, with the remainder being Fe.
An Fe-based sintered alloy for a valve seat, characterized in that it has a composition (the above weight %) consisting of and unavoidable impurities. 3 C: 0.5-3%, Cr: 1-20%, S: 0.0
5-2%, Mo: 0.1-5%, B: 0.005-1%
further contains P: 0.1-2% and Si: 0.0
One or two of 5-2% and Ni: 0.1-5
% and Co: 0.1 to 5, and the remainder is Fe and unavoidable impurities (weight %). .