JPH03225008A - Valve seat made of fe-based sintered alloy having superior abrasion resistance - Google Patents

Abstract

PURPOSE:To improve the abrasion resistance by dispersing hard particles of a specific composition, CaF2 and MnS about Fe-base alloy material of a specific composition and structure. CONSTITUTION:The abrasion resistance of a valve seat is improved by using the Fe-base sintered alloy basic material which is formed by dispersing the hard particles A having the composition containing Cr 25-45%, each of W, Co 20-30%, C 1-3%, each of Si, Nb 0.2-2%, and the rest Fe and inevitable impurities and the hard particles B having the composition containing Co 55-65%, Cr 25-32%, Mo 7-10%, Si 1.5-3.5%, and the rest Fe and inevitable impurities, into the Fe-base alloy material which has the composition containing Cr 1-3%, each of Mo, Ni 0.5-3%, Co 2-8%, C 0.6-1.5%, Nb 0.2-1%, and the rest Fe and inevitable impurities and has the structure of pearlite phase and bainite phase as main body, so that the sum of the hard particles A and B becomes 10-25%, and one or two kinds between CaF2 and MnS is 0.2-5wt.% or more.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to an engine that has excellent wear resistance and is particularly suitable for high-output internal combustion engines such as diesel engines and gasoline engines. The present invention relates to a valve seat made of a smoked alloy containing a small amount of Fe-based material.

C. Prior Art] Conventionally, as described in Japanese Unexamined Patent Publication No. 58-178073, Mo
: 0.1-0.9%, NI: o, 5-2
．． 5%.

Co: 4.5-7.5%, Cr: 3-6
．． 5%.

C: 0.5-1.7%, W: 1-2.7%.

2 to 3%, and 15% to 15% Co.

W: 15-25%, Fe: 1-8%.

Cr-based alloy particles having a composition with the remainder consisting of C and inevitable impurities, and Fe-Mo alloy particles: 8 to I2
A valve seat made of a copper-impregnated Fe-based sintered alloy is known, which is obtained by infiltrating Cu into an Fe-based sintered alloy substrate having a structure in which % by volume is dispersed and a porosity of 6 to 14 % by volume.

[Problem to be solved by the invention]

However, recent internal combustion engines have been designed to achieve higher output through the use of superchargers, multiple valves, and higher rotation speeds, resulting in an increasing thermal and mechanical load. When equipped with the above-mentioned conventional copper-impregnated Fe-based sintered alloy valve seat, the Cr-based alloy particles and Fe-Mo alloy particles dispersed in the Fe-based alloy substrate have poor adhesion to the Fe-based alloy substrate, although they are hard. , Cr-based alloy particles and F dispersed in the Fe-based alloy matrix during operation of the internal combustion engine.
There is a problem in that the e-Mo alloy particles oxidize and fall off, causing the valve seat itself to wear out, and furthermore, the falling alloy particles also wear out the valve, which is a mating member.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a valve seat that has even better wear resistance and can sufficiently withstand the increased output of the internal combustion engine. Results: Cr: 0.5-3%, Mo
: 0.5-3%.

Ni: 0.5-396. Co: 2-8
%.

c: 0.6-1.5%, Nb: 0.2-1%
.

Cr: 25 to 45%, Cr: 25 to 45%,
W: 20-30%.

Co: 20-30%, C: 1-3%.

Sl: 0.2-2%, Nb: 0.2-2%.

hard particles A having a composition containing Fe and unavoidable impurities, co = 55 to 65%, Cr: 25 to 32%
.

Mo: 7-10%, Si: 1.5-3
．． 5%.

and hard particles B having a composition with the remainder consisting of Fe and unavoidable impurities, the total of hard particles A and hard particles B is 10 to 25%, CaF
2. One or two types of MnS: 0.2 to 5 (1,
, S, F which combines the dispersed structures so that (the weight is 06)
It has been found that a valve seat made of an Fe-based sintered alloy having an e-based sintered alloy base can fully satisfy the above requirements.

The present invention was made based on this knowledge, and the present invention is directed to a copper-impregnated Fe base formed by further infiltrating 5 to 20% by weight of Cu into an Fe-based sintered alloy base having the above-mentioned structure. A valve seat made of an Fe-based sintered alloy made of a sintered alloy or a Fe-based smoldered alloy made of a lead-impregnated Fe-based sintered alloy made by infiltrating 5 to 20% by weight of Pb. Valve seat included.

Next, in the valve seat of the present invention, the reason why the composition of the Fe-based sintered alloy base constituting the valve seat is limited as described above will be explained.

A. Reasons for limiting the components of the Fe-based alloy base (a) C The C component combines with Mo and Cr to form carbides and has the effect of improving hardness, and it also has the effect of improving the hardness of the base, which is mainly composed of pearlite and bainite. When the content is less than 0.5%, the desired effect cannot be obtained; on the other hand, when the content exceeds 1.5%, Since the hardness of the base increases and the opponent's aggressiveness increases, its content is increased to 0.6 to 1.
．． It was set at 5%.

(b) CrC component has the effect of improving heat resistance by forming a solid solution in the base material, and also has the effect of forming carbide to improve wear resistance, but if its content is less than 1%, the above-mentioned On the other hand, if the content exceeds 3%, the desired effect cannot be obtained.
Since the sinterability deteriorates and it becomes difficult to ensure high strength, the content was set at 1 to 3%.

(c) M.

The MO acid component forms a carbide in the base material and has the effect of improving wear resistance, but if its content is less than 0.5%, the desired effect cannot be obtained; If the content exceeds 3%, the strength of the material decreases.
Its content was set at 0.5-3%.

(d) Ni The Ni component has the effect of forming a solid solution in the base material and strengthening it, but if its content is less than 0.5%, the desired effect cannot be obtained from the above effect; Even if the content exceeds 3%, the above-mentioned effect will only be saturated and it is uneconomical, so the content was set at 0.5 to 3%.

(e) C.

The Co component has the effect of solidly dissolving in the base material and strengthening it, but if the content is less than 2%, the desired effect cannot be obtained from the above effect, while on the other hand, if the content exceeds 8% Even if it is contained, the above-mentioned effect is only saturated and it is uneconomical, so its content is set at 2 to 8%.

(f) Nb The Nb component of the base material has the effect of forming Cr-Nb-based fine carbides and dispersing them in the base material to improve wear resistance, but if the content is less than 0.2%, the desired level of wear resistance cannot be achieved. On the other hand, even if the content exceeds 1%, the above effect will be saturated, and the effect of improving the - layer will not appear, so the content should be reduced to 0.2 to 1%. %.

B. Reason for limiting the components of hard particles A (g) C The C component has the effect of forming carbides and strengthening the hard particles A, but if its content is less than 1%, the desired effect will not be achieved. On the other hand, if the content exceeds 3%, the hardness becomes too high and the aggressiveness of the opponent increases, so the content was set at 1 to 3%.

(h) Cr The Cr component has the effect of improving heat resistance by forming a solid solution in the matrix of hard particles A, and also has the effect of forming carbides and intermetallic compounds to improve wear resistance. amount is 2
If it is less than 5%, the desired effect cannot be obtained in the above action; on the other hand,
If the content exceeds 45%, the hardness will increase and the opponent's aggressiveness will increase, so the content should be reduced to 25-45%.
%.

(i) W The W component has the effect of forming carbides and intermetallic compounds in the matrix of hard particles A to improve wear resistance.
If the content is less than 20%, the desired effect will not be obtained in the above action, while if the content exceeds 30%, the hardness will increase and the aggressiveness of the opponent will increase. was set at 20-30%.

(j) Nb The Nb component has the effect of forming carbides in the matrix of the hard particles A to improve the wear resistance of the hard particles A and the effect of strengthening the adhesion of the hard particles A to the matrix. If the content is less than 0.2%, the desired effect cannot be obtained in the above action, while if the content exceeds 2%, the above action is only saturated, and the wettability during powder atomization decreases. Therefore, the content should be reduced to 0.2 to 2.
%.

(k)　C.

The Co component has the effect of solidly dissolving in the matrix of hard particles A to strengthen it and improve heat resistance, but if its content is less than 20%, the desired effect cannot be obtained from the above effects. ,
On the other hand, if the content exceeds 30%, the above effect will only be saturated and it is uneconomical, so the content is set at 20 to 30%.

The (+) 5I Si component has the effect of forming carbides and improving the wear resistance of the hard particles A, but if its content is less than 0.2%, the desired effect cannot be obtained, On the other hand, if the content exceeds 2%, it will only weaken the hard particles A, so the content was set at 0.2 to 2%.

C1 Reason for limiting the components of hard particles B (m) Cr The Cr component has the effect of forming carbides and intermetallic compounds that improve the heat resistance of hard particles B and improving the wear resistance of hard particles B. If B has the effect of strengthening the adhesion to the substrate, if its content is less than 25%, the desired effect cannot be obtained, whereas if the content exceeds 32%, the above effect is saturated. The content was determined to be 25 to 32% since the powder content was determined to be 25% to 32% since the wettability during powder atomization decreased.

(n) M.

The Mo component has the effect of forming a solid solution in the matrix of the hard particles B to form a carbide and improving wear resistance, but if the content is less than 7%, the desired effect cannot be obtained from the above effect. On the other hand, if the content exceeds 10%, the strength of the material decreases, so the content was set at 7 to 10%.

(o) The 5I Si component has the effect of forming an intermetallic compound to improve the wear resistance of the hard particles B, or its content is 1.5
If the content is less than 3.5%, the desired effect cannot be obtained. On the other hand, if the content exceeds 3.5%, the aggressiveness of hard particles B increases, so the content should be reduced to 1.5%. 5-3
, set at 5%.

(p)　C.

The CO component has the effect of solidly dissolving in the matrix of hard particles B to strengthen it and improve heat resistance, but if its content is less than 55%, the desired effect cannot be obtained from the above effects. ,
On the other hand, even if the content exceeds 65%, the content will be saturated, so in consideration of economic efficiency, the content was set at 55 to 65%.

D. Reason for simultaneously dispersing hard particles A and hard particles B into the substrate Hard particles A are inexpensive and have excellent hardness, but they are easily oxidized, and when oxidized, they fall off from the substrate and do not have sufficient wear resistance. I can't get it. On the other hand, hard particles B have excellent oxidation resistance and are less likely to attack others, but are expensive and lack hardness. Therefore, if the above-mentioned hard particles A and hard particles B are simultaneously dispersed in the base material, the presence of hard particles B prevents the hard particles A from falling off due to oxidation, improves the wear resistance, and also reduces the aggressiveness of the opponent. be. However, if the total amount of hard particles A and hard particles B is less than 100% of the base material, the desired effect cannot be obtained, whereas if the total amount exceeds 25%, the strength of the valve seat will be reduced. Therefore, the total of hard particles A and hard particles B is 10 to 2
It was set at 5%.

In order to impart wear resistance to E, CaF2, MnS materials, it is necessary to disperse hard particles in a heat-resistant matrix, but by making the matrix highly alloyed and dense, the face Since oxides are difficult to form on the outermost surface of the part, it is necessary to disperse the solid lubricant and give the material itself a self-lubricating effect.The solid lubricant dispersed in the Fe-based sintered alloy of this invention , CaF2 powder, M
nS powder is preferred, but CaF2 powder, M
If the amount of one or two of the nS powders added is less than 0.2%, the desired effect will not be obtained in the above action, while if it is added in excess of 5%, the strength of the material will decrease. The amount added was determined to be 0.2 to 5%.

F, Cu infiltration amount The valve seat of the present invention can improve heat resistance by infiltrating copper into the pores of the Fe-based sintered alloy base, strengthening the base material by sealing the pores, and improving thermal conductivity. However, if the amount of infiltration is less than 5%, the desired effect cannot be obtained from the above action. Since increasing the porosity of the Fe-based sintered alloy substrate reduces the strength of the obtained valve seat, the amount of Cu infiltration was
It was set at ~20%.

Amount of G, Pb infiltration Further, in the valve seat of the present invention, lead is infiltrated into the pores of the Fe-based sintered alloy base, and the valve aggressiveness is reduced by strengthening the base material by sealing the pores and by self-lubricating property of lead. However, if the amount of infiltration is less than 596, the desired effect cannot be obtained in the above action.On the other hand, in order to infiltrate with the amount of infiltration exceeding 20%, the The amount of Pb infiltration was set at 5 to 20% because increasing the porosity of the Fe-based sintered alloy substrate would reduce the strength of the obtained valve seat.

In addition, when producing the Fe-based sintered alloy halbunto with excellent wear resistance of the present invention, after molding, the
The alloy was held at ℃ for 30 minutes to remove oil, and after forming, it was pre-sintered in vacuum or reducing gas at a temperature of 700 to 900℃, and then pressurized again at a pressure of 5 to 8 Tons/cd to improve density. For the alloy, sintering was carried out in a vacuum or reducing gas atmosphere at a temperature of 1,100 to 1,250°C for 1 hour; Cu infiltration was carried out in a reducing gas atmosphere at a temperature of 1,090 to 1,000°C.
Conditions of holding at 150°C for 20 minutes, Pb infiltration in neutral gas atmosphere, temperature: 550 to 700°C for 1 hour, forging in methane metamorphic gas atmosphere, temperature: 1000 to 1
It is preferable to carry out the heat treatment at 100°C, and if necessary, heat treatment at a temperature of 550 to 750°C for 1 hour.

〔Example〕

Next, the present invention will be specifically explained based on examples.

As raw material powder, Fe powder, Fe-Cr powder (Fe1%Cr-0,3
%Mo), Fe-Cr-Nb powder (Fe-1396C
r-5%Nb), Ni powder, CO powder, MO powder, and natural graphite powder, all of which had a particle size of 100
Hard particles A having the composition shown in Table 1 below:
In addition, as a solid lubricant, Ca F 2 powder and MnS powder, both of which have a particle size of 100 mesh or less, are prepared. After blending and mixing the powder, raw material powder for hard particles B, and solid lubricant,
Press molding into a green compact at a pressure of 6 to 6.5 Ton/c-, and hold the green compact at 500°C for 30 minutes to remove oil or heat the green compact in an ammonia decomposition gas at a temperature of 800°C.
After pre-sintering under the condition of time holding, 6~7Ton/
After repressurizing at a pressure of cd to increase the density, sintering was performed in an ammonia decomposition gas at a temperature of 1200°C and held for 1 hour, and this sintered body was sintered in a methane converted gas.
Forged at a temperature of 1050℃, and further in the atmosphere at a temperature of 620℃
, tempering was performed under the condition of holding for 1 hour, and the outer diameter was +34m1.
1. Inner diameter: 27 mm, thickness: 7.2 mm valve seats made of Fe-based sintered alloy of the present invention (hereinafter referred to as the present invention valve seat) 1 to 32 and comparative Fc-based sintered alloy valve seat (hereinafter referred to as the present invention valve seat) , referred to as comparative valve seat)1
-22 were produced.

The above-mentioned valve seats of the present invention) 23.24 and comparative valve seats 20.22 were infiltrated with Cu in a methane converted gas atmosphere at a temperature of 1110°C and held for 20 minutes, and then heated to a temperature of 2620°C in the atmosphere. Further, the valve seats 25, 26 of the present invention and the comparative valve seat 21 were manufactured by tempering under the conditions of holding for 1 hour in a nitrogen gas atmosphere at a temperature of 2650°C and tempering for 1 hour.
It is manufactured by infiltration.

The various valve seats obtained in this way were subjected to wear resistance tests under the following conditions, and the maximum wear depth of the various valve seats was measured to evaluate the wear resistance, and the maximum wear depth of the valve was also measured. The valve aggressiveness was evaluated by measurements and the results are shown in Table 1.

Wear resistance test conditions Valve material: 5UH-36, Valve heating temperature: 900℃, Valve seating frequency 73,000 times/+g1n, Atmosphere:
0.4kg/c-9 propane gas and flow rate 1.5j! /s
combustion gas with oxygen gas, valve seat heating temperature (water cooling): 250-300℃, seating load: 30kg
.

Test time: 100 hours [Effects of the Invention] From the results shown in Table 1, the valve seat of the present invention has less wear and shows lower values for valve aggressiveness and total sinkage, whereas the comparative valve seat As seen in
It is clear that any one of the above characteristics is inferior when the conditions of the present invention are not met, and it is also seen that the amount of wear and total amount of sinkage is smaller than that of the conventional valve seat.

In this example, a valve seat made of an Fe-based sintered alloy obtained by hot forging a sintered body was shown, but the present invention is directed to a valve seat made of an Fe-based sintered alloy obtained by hot forging a sintered body. The valve seat made of Fe-based sintered alloy is not limited, but includes a valve seat made of FQ-based sintered alloy of a general sintered body and a valve seat made of Fe-based smoldered alloy obtained by cold forging.

As mentioned above, the Fe-based sintered alloy valve seat of the present invention has excellent wear resistance and low valve aggressiveness,
Demonstrates outstanding long-term performance as a valve seat for high-output internal combustion engines.

Out wish Man : Mitsubishi Metals Co., Ltd. teenager Reason Man Goods Field sum husband 1 other person

Claims (3)

[Claims] (1) Cr: 1-3%, Mo: 0.5-3%, Ni: 0
．． 5-3%, Co: 2-8%, C: 0.6-1.5%, Nb: 0.2-1%, with the remainder consisting of Fe and inevitable impurities, pearlite phase and bainite. Cr: 25 to 45%, W: 20 to
30%, Co: 20-30%, C: 1-3%, Si: 0.2-2%, Nb: 0.2-2%,
Hard particles A having a composition with the remainder consisting of Fe and unavoidable impurities, Co: 55-65%, Cr: 25-32%, Mo: 7-
10%, Si: 1.5-3.5%, and the rest is F.
Hard particles B having a composition consisting of e and inevitable impurities
and, the total of hard particles A and hard particles B is 10 to 25%, CaF
_2, one or two types of MnS: 0.2 to 5%, Fe having a structure dispersed so that (or more weight %)
A valve seat made of an Fe-based sintered alloy that has excellent wear resistance and is characterized by being made of a sintered-alloy base. (2) The Fe-based sintered alloy substrate according to claim 1 has 5 to 20
A valve seat made of a Fe-based sintered alloy with excellent wear resistance, characterized in that it is made of a copper-impregnated Fe-based sintered alloy formed by infiltrating Cu in the amount of % by weight. (3) The Fe-based sintered alloy substrate according to claim 1 has 5 to 20
A valve seat made of a Fe-based sintered alloy with excellent wear resistance, characterized in that it is made of a lead-impregnated Fe-based sintered alloy formed by infiltrating Pb in an amount of % by weight.