JPS6033183B2 - Fe-based sintered alloy for valve seats - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has excellent corrosion resistance, heat resistance, wear resistance, and machinability, and is particularly suitable for use in manufacturing valve seats for internal combustion engines that use high lead gasoline as fuel. Suitably, it relates to Fe-based alloys.

Generally, when ferrous gasoline is used to drive internal combustion engines such as automobiles, lead oxide (hereinafter referred to as POO) is contained in the exhaust gas.
In Japan, the United States, and other countries, unleaded gasoline is the mainstream gasoline used to drive internal combustion engines, as lead-free gasoline has become the mainstream gasoline used to drive internal combustion engines in countries such as Japan and the United States. on the other hand,
Even today, in many foreign countries, the usefulness of leaded gasoline,
That is, P is generated from the alkyl lead mixed in gasoline during combustion, and a portion of the generated Pbo adheres to the valve and valve seat, giving the valve and valve seat excellent oxidation resistance and resistance. The focus is on the fact that it has abrasive properties and self-lubricating properties, and in fact, many countries are using high-leaded gasoline that contains even more Pb than regular leaded gasoline. It is.

However, when leaded or highly leaded gasoline is used in this way, the conventional valve seat corrosion material suffers from significant corrosion due to Pb0, which increases the amount of valve seat wear, resulting in a relatively short service life and failure. there were.

Therefore, from the above-mentioned viewpoint, the present inventors have demonstrated excellent corrosion resistance not only when using unleaded gasoline but also when using leaded and highly leaded gasoline as gasoline for driving internal combustion engines. As a result of research to develop alloys for valve seats, C: 0.4-2%, Cn: 0.5-5%,
Ni: 0.5-5%, Cr: 0.5-5%, B: 0.0
05 to 0.5%, and further contains calcium fluoride (hereinafter referred to as CaF2) and barium fluoride (hereinafter referred to as B) as necessary.
aF2), and boron nitride (hereinafter referred to as BN)
One or more of the following: 0.2 to 5%,
The remainder consists of Fe and unavoidable impurities (more than % by weight,
All % indications below mean weight %)
Basic alloys exhibit excellent corrosion resistance, heat resistance, and wear resistance in lead-free as well as lead-containing combustion atmospheres, and therefore exhibit excellent long-term performance when used as valve seats in internal combustion engines. 100% performance during the period, especially CaF
2, mother F2, and BN. In this case, these components become finely dispersed in the grain boundaries of the base material, resulting in a structure with even better self-lubricating properties and excellent machinability, making it easy to apply to the valve seat. They discovered that it has useful properties such as ease of cutting.

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) CC The C component dissolves in the base material and has the effect of strengthening it, but if its content is less than 0.4%, the desired strength and wear resistance cannot be secured; If the content exceeds 2%, the alloy becomes noticeably warped, so the content was set at 0.4 to 2%.

'bl Cu The Cu component has the effect of promoting sintering during alloy production and improving the wear resistance and oxidation resistance of the alloy, but if its content is less than 0.5%, this effect is impaired. On the other hand, if the content exceeds 5%, not only will the alloy itself become noticeably vertical, but when exposed to a combustion atmosphere containing a high lead content, the reaction between Cu and Pb○ will increase. This is due to the increased strength and the amount of wear.
Its content was determined to be 0.5 to 5%.

'c} Ni The Ni component has the effect of improving the strength, heat resistance, and abrasion resistance of the substrate by solid bathing it, as well as improving the resistance to corrosion by Pb0 (hereinafter referred to as Pbo corrosion resistance). However, if the content is less than 0.5%, the desired effect cannot be obtained in the above-mentioned action, and on the other hand, if the content exceeds 5%, no further improvement in wear resistance will be achieved.
Considering economic efficiency, the content was determined to be 0.5 to 5%.

{d) CrCr component reacts with C to form carbide,
It has the effect of improving the wear resistance of the alloy and the corrosion resistance of P, but if the content is less than 0.5%, the desired effect cannot be obtained; on the other hand, if the content exceeds 5% If it is contained, the strength and machinability will deteriorate, so the content was set at 0.5 to 5%.

[c1 B The B component has the effect of activating the coagulation reaction during alloy production and significantly improving the wear resistance and strength of the alloy, but if its content is less than 0.005%, the desired effect may not be achieved. No effect can be obtained, and if the content exceeds 0.5%, the sulfidation of the alloy itself becomes significant, so the content was set at 0.005 to 0.5%.

[f- CaF2, BaF2, and BN These components are finely dispersed in the grain boundaries of the alloy matrix and have the uniform effect of improving the self-lubricating properties of the alloy, thereby improving wear resistance. It is contained as necessary when particularly excellent wear resistance and self-lubricating properties are required, but if the content is less than 0.2%, the desired effect of improving the above effects cannot be obtained; If the content exceeds 0.2 to 0.2, the alloy strength will decrease.
It was set at 5%.

The Fe-based alloy of the present invention can be produced by a normal powder metallurgy method under normal manufacturing conditions, but with respect to the raw material powder, especially the B component, B: 5 to 30%.
Containing Fe-B alloy powder, Cr component: Cr:1
It is preferable to use Fe-Cr alloy powder containing 0 to 70%.

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

Examples of raw material powders include Fe powder, natural graphite powder, electrolytic Cu powder, and three types of Fe powder each having a particle size of -10 esh.
Cr alloy (Cr: 13%, 45%, and 60%, respectively)
% containing) powder, Fe-B alloy (B: 20% containing) powder,
CaF2 powder, base F2 powder, BN powder, and particle size -2
Prepare Ni powder of 0.0 hessh, blend these raw powders so that they have the final component composition shown in Table 1, mix them, mold them into a compact at a pressure of n/flow, and then This green compact is heated in a neutral or reducing atmosphere at a temperature of 1100.
Sintered alloys 1 to 21 of the present invention and Bisame sintered alloys 1 to 10 having the component compositions substantially shown in Table 1 were manufactured by competitively maintaining the temperature at ~1150°C for 1 hour, respectively. did.

It should be noted that all of the Hisame Sintered Alloys 1 to 10 have a composition in which one of the constituent components (indicated by * in Table 1) is outside the scope of the present invention. Furthermore, the conventional casting alloys having the compositions shown in Table 1 are martensitic heat-resistant steels (mainly used in the manufacture of valve seats).
SUH-4) and is separately prepared. Furthermore, Table 1 shows the densities and hardnesses (Rockwell hardness B scale, but conventionally cast The hardness of the alloy was C scale), and the strength was high. Next, valve seats were manufactured from the above-mentioned phosphorus alloys 1 to 21 of the present invention, Bisame sintered alloys 1 to 10, and conventional casting alloys, and each valve seat was subjected to a practical test using a bias D with automatic temperature control. Using a cam-driven valve-valve seat wear tester that performs hot repeated impact, atmosphere: propane gas combustion atmosphere, valve material: austenitic valve steel, valve temperature: 800oo, valve seat temperature: 350qo, stroke: 6
．． 8 ribs, operating speed: 300 ratio. p. m. ,operating time:
A wear durability test was conducted under the condition of 5 addition times, and the depth of wear of the valve seat and the mating material (valve) after the test was measured.

The measurement results are also shown in Table 1. In addition, each of the valve seats manufactured from the above-mentioned sintered alloys 1 to 21 of the present invention, Hisame sintered alloys 1 to 10, and conventional cast alloys was placed in a Pbo solution heated and melted at a temperature of 800 qC in the atmosphere. A Pb○ corrosion test was conducted on the 30-minute immersion test, and the depth of corrosion was measured.

The measurement results are also shown in Table 1. From the results shown in Table 1, the valve seats manufactured with Comparative Sintered Alloys 1 to 10 and the secondary cast alloy have excellent wear resistance (valve seat wear depth) and mating aggressiveness (valve wear depth). , and corrosion resistance of P (
At least one of the properties (in Table 1*
Valve seats manufactured using the sintered alloys 1 to 21 of the present invention all exhibit excellent wear resistance and corrosion resistance of P, as well as poor attack resistance (indicated by marks). It is clear that it exhibits excellent performance over a long period of time.

Further, among the various alloys mentioned above, especially the condensed alloys 1 to 1 of the present invention
No. 21 showed extremely good machinability when manufacturing valve seats. As mentioned above, the Fe-based sintered alloy of the present invention has excellent corrosion resistance, heat resistance, wear resistance, and machinability, especially P corrosion resistance, so it is particularly suitable for use as valve seats in internal combustion engines. When using a variety of fuels, from unleaded gasoline to high-lead gasoline, it exhibits excellent high-temperature durability, and also has excellent machinability, making it easy to cut valve seats. It has many useful properties.

Claims (1)

[Claims] 1 C: 0.4-2%, Cu: 0.5-5%, Ni: 0
．． 5-5%, Cr: 0.5-5%, B: 0.005-0
．． 5% of Fe for valve seats, with the remainder consisting of Fe and unavoidable impurities (weight %)
Base sintered alloy. 2 C: 0.4-2%, Cu: 0.5-5%, Ni: 0
．． 5-5%, Cr: 0.5-5%, B: 0.005-0
．． 5%, and further contains 0.2 to 5% of one or more of calcium fluoride, barium fluoride, and boron nitride finely dispersed in the grain boundaries of the alloy matrix,
Composition with the remainder consisting of Fe and unavoidable impurities (more than % by weight)
An Fe-based sintered alloy for a valve seat, characterized by having the following.