JPS6164855A - Iron compound sintered alloy for valve seat - Google Patents

Abstract

PURPOSE:To develop an Fe sintered alloy for valve seat which is excellent in heat resisting property, corrosion resistance and wear resistance by mixing an Fe alloy powder containing a hard carbide, and powder of Co, C, Fe-Mo, etc. by a specified percentage, in an Fe powder, and pressing, forming and sintering them. CONSTITUTION:In a powdery Fe, 0.3-2wt% carbon powder, 3-15wt% Co powder, 3-15wt% Fe-Mo whose Mo content is 60-70%, 5-40wt% one kind or two kinds or more among Cr, Mo, W, Co and Si containing a carbide whose hardness Hv is 800-1,880 for crystalizing or depositing one kind or two kinds or more of elements selected from a group of Cr, Mo, W and V after sintering, and 3-20wt% one kind or two kinds or more of an Fe alloy which contains 0.5-2wt% C, whose balance consists of Fe, and whose hardness after sintering becomes Hv300-900 are mixed, formed and sintered, and also 1-20wt% Pb is infiltrated as necessary.

Description

[Detailed Description of the Invention] [Field of Industrial Application] Various materials have been proposed for valve seats for internal combustion engines, particularly for valve seats for automobile internal combustion engines, in order to prevent pulse reset due to the use of lead-free Ganlin fuel. ing. Examples include iron-based sintered alloys containing FeMo, Co, and C and having good wear resistance.

[Problem that the invention seeks to solve]

However, in recent years, demands on valve seats have become stricter due to demands for higher performance in internal combustion engines, and further improvements in heat resistance, corrosion resistance, abrasion resistance, etc. are desired. In order to meet these demands, it is conceivable to use a large amount of expensive materials, but this will result in high costs.

An object of the present invention is to provide an iron-based sintered alloy for valve seats that has excellent heat resistance, corrosion resistance, wear resistance, etc.

[Means for solving problems]

The iron-based sintered alloy for valve seats of the present invention has a) Fe as a base material, b) Cα 3-2%, C) ＼Co 5-15%, d) Mo 60-60%. FeMo containing 70% by weight 5~
15%, and e) Cr, M containing a carbide with a hardness Hv of 800 to 1800 that crystallizes or precipitates one or more elements selected from the group consisting of Cr, Mo, W, and V after sintering.
One or more of o, W, Co, and Si5
The hardness after sintering is Hv 30, consisting of Fe containing ~40% by weight, Ca, ~2% by weight S, and the remainder unavoidable impurities.
One or more types of iron-based alloys having a value of 0 to 900, 3 to 20
%, FeMo, and iron-based alloy are uniformly dispersed in the sintered alloy.

Hereinafter, in the present invention, unless otherwise specified, CH indicates weight %.

In the present invention, as the iron-based alloy, Moα5-6CH, C
r6~18%, V(L1~1%, Si[11~
Iron-based alloy consisting of Fe containing 1%, Ca 5-2% and the balance unavoidable impurities, Mo 1-10%, Cr 1-1
0%, ■15~6chi, Siα1~1%, W1~10%
, C0.5-2% and the remainder containing unavoidable impurities
Iron-based alloy consisting of e, Mo15-6%, Crα5-6%
, Vα5-6%, Siα1-1ch, W 5-15'i
It is preferable to use at least one type of iron-based alloy consisting of Fe containing 5 to 15% of Co, 5 to 2% of Ca, and the remainder unavoidable impurities.

Furthermore, if necessary, it is also preferable to infiltrate 1 to 20 pieces of Pb into the above sintered alloy.

The reason for limiting each component element used in the present invention will be explained below.

C (carbon) is a solid solution and diffuses into the iron base during sintering, promotes sintering, and strengthens the iron base, and the addition of C less than α3 has no effect. If it is added in excess of 2%, the amount of C remaining in the matrix as free graphite becomes too large and the strength of the matrix decreases.
It was limited to 13-2%.

Co (cobalt) dissolves into the iron base during sintering and strengthens it, improving heat resistance and maintaining high-temperature strength, but this effect is not seen when less than 3% of CO is added. ,
On the other hand, even if more than 15 inches of CO is added, no further effect will be obtained; on the contrary, the substrate will become softer and wear will increase, and since CO is expensive, it is not economical to add a large amount of Co. The number was limited to 3 to 15 inches because it was disadvantageous.

FeMo (ferromolybdenum) has Mo of 60 to 70
%, Vickers hardness Hv600-1300
It has a hardness of If it is too small, the effect of wear resistance will not be exhibited, and on the other hand, if FeMo is added in excess of 15%, the wear-resistant component will be too large, damaging the mating member and making cutting difficult. It was limited to 15%.

Iron-based alloys partially diffuse into the iron base to strengthen the base and increase heat resistance, and exhibit wear resistance due to finely dispersed carbides.If the addition of iron-based alloys is less than 3%, the above-mentioned It has little effect, and on the other hand, if it is added in excess of 20%, the strength of the base material decreases.

PbO infiltration is performed under more severe usage conditions, and
is present at the contact area between the valve and the valve seat, and acts as a lubricant by forming a Pb oxide layer to improve mutual wear resistance between the pulp and the valve seat.
If the Pb infiltration is less than 1%, the effect of Pb infiltration will not appear;
Pb infiltration exceeding 0% weakens the skeleton of the sintered body and increases wear, so it was limited to 1 to 20%.

The compacting pressure when compacting the mixed powder for producing a sintered body is preferably 6 to 7 t/-.

In addition, the sintering of the molded body is performed in a reducing atmosphere with a
, 250° C. for 30 to 60 minutes. When Pb is infiltrated, the sintered body is preferably brought into contact with Pb and heat-treated again at a temperature of 1.000 to 1.100° C. for 30 to 60 minutes in a reducing atmosphere.

[For production]

In the present invention, the addition of 6 to 2% carbon α strengthens the substrate, the roughening of 3 to 15% Co is effective in maintaining heat resistance, and the addition of FeMo 3 to 15 containing 60 to 70% Mo
The addition of Cr, Mo
, W, V, one or more strains of Cr, Mo, W, V, Co, Si having a carbide with a Vickers hardness of Hv 800 to 1800 that crystallizes or precipitates. Hardness after sintering is Hv50, consisting of Fe containing 5-40%, Cα5-2%, and the remainder unavoidable impurities.
One of the iron-based alloys having a value of 0 to 900 or Fi23i or more of 3 to 900
The 20% addition acts to strengthen the matrix and improve heat and abrasion resistance. Also, if necessary, add 1 to 2 Pb.
0% infiltration can improve wear resistance and lubricity.

〔Example〕

The present invention will be explained below using examples.

Example Fe powder (-100 mesh), FeMo powder (-20 mesh)
0 mesh), Co powder (-100 mesh), C powder (-325 mesh), and iron-based alloy powder shown in Table 1 (-
100 mesh) according to the composition shown in Table 2, further add 15 to 1 piece of zinc stearate, mix, and mold at a molding pressure of 7 tons to produce a molded body.Then, this molded body is decomposed with ammonia. Sintering was carried out at a temperature of 1.150° C. for 45 minutes in a gas atmosphere.

In addition, for sample numbers 6.7 and 10, the obtained sintered bodies were re-coupled with Pb lumps in an ammonia decomposition gas atmosphere.
Pb was infiltrated by heating at a temperature of 0° C. for 30 minutes.

Using the valve seat described in JP-A No. 48-90907 as a comparison material, the wear amount, radial crushing strength, overall hardness, and hardness of the iron-based alloy of each of these materials were measured, and the results are presented. Shown in 3. To measure the wear amount, as shown in Fig. 1, the test piece 1 was pressed against the a-plate 2 made of 545C quenched and tempered material with a spring 3, the rotor 2 was rotated, and the sliding speed (15 m/sec, abrasion) was measured. Distance: 100m.

The test was carried out under the conditions of a final load of 2.1 KP, and the friction width 4 and the wear amount of the test piece 1 shown in FIG. 2 were set.

Table 1 Iron-based alloy composition table 2 Example composition table 3 Example results As can be seen from the results shown in Table 3, FeMo, Co,
The wear amount of the invented materials with C compositions of 5, 5, and 1.0%, respectively, was 1.81 to 1.93 m, which was 2.00 m smaller than that of the corresponding comparative material, and FeN1o * Co *
The wear i of the invented materials with C compositions of 10, 10, and 1.0%, respectively, is 1.65 and 1.70! IIm was 1.77 mm smaller than the corresponding comparative material, and the invented material had excellent wear resistance. In addition, the wear resistance of the Pbtl-infiltrated material was superior to that of the comparative material at the same Pb infiltration rate as the comparative material, and was superior to that of the non-infiltrated material even when the Pb infiltration rate was low. .

The radial crushing strength of the invented materials was comparable to that of the comparative materials in some cases, but depending on the component composition, the radial crushing strength of the invented materials was significantly higher than that of the comparative materials.

〔Effect of the invention〕

The present invention makes it possible to obtain an iron-based sintered alloy for valve seats that has excellent heat resistance, corrosion resistance, and wear resistance by having the above-mentioned component composition.

Furthermore, by adjusting the component composition, a valve seat with considerably superior radial crushing strength than conventional valve seats can be obtained.

Further, by using the iron-based alloy of the present invention, a valve seat with excellent wear resistance can be obtained without using large quantities of expensive materials such as Co and Mo.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a wear test conducted in an embodiment of the present invention, and FIG. 2 is a diagram showing the amount of wear of the test piece shown in FIG. 1. In the figure, 1... Test piece 2... Rotor 3... Pressing spring 4... Wear width Patent applicant: Toyota Motor Corporation, Japan Powder Alloy Co., Ltd., agent, patent attorney, Yumi Kaede, and one other person 1 Figure 1 - Tsume, Shunkata 2... Rotor 3... 1 Insert size, Tar, Fang 2 Figure

Claims (2)

[Claims] (1) FeMo3-1 which is made of Fe as a base material and contains b), C0.3-2%, c), Co3-15%, d), Mo 60-70% by weight in total weight ratio.
5%, and e) Cr, Mo, containing a carbide with a hardness of Hv 800 to 1800 that crystallizes or precipitates one or more elements selected from the group consisting of Cr, Mo, W and V after sintering. One or two of W, Co and Si
One or more iron-based alloys having a hardness after sintering of 300 to 900 Hv, consisting of Fe containing 5 to 40% by weight of seeds, 0.5 to 2% of C, and the remainder unavoidable impurities. An iron-based sintered alloy for valve seats, characterized in that FeMo and an iron-based alloy are uniformly dispersed in the sintered alloy. (2) a), FeMo3-1 which is made of Fe and contains b), C0.3-2%, c), Co3-15%, and d), Mo 60-70% by weight in total weight ratio.
5%, and e) Cr, Mo, containing a carbide with a hardness of Hv 800 to 1800 that crystallizes or precipitates one or more elements selected from the group consisting of Cr, Mo, W and V after sintering. One or two of W, Co and Si
One or two or more iron-based alloys having a hardness after sintering of 300 to 900 Hv, consisting of Fe containing 5 to 40% by weight of seeds, 0.5 to 2% by weight of C, and the balance unavoidable impurities. An iron-based sintered alloy for a valve seat, characterized in that the sintered alloy is made of a sintered alloy in which FeMo and an iron-based alloy are uniformly dispersed in the sintered alloy, and is infiltrated with 1 to 20% by weight of Pb. Money.