JPS6296660A - Sintered iron alloy for valve seat - Google Patents

Abstract

PURPOSE:To improve the wear resistance and to weaken the attacking property to a valve as an opposite member by uniformly dispersing alloy particles contg. prescribed percentages of Cr, W, Mo, etc., in an Fe alloy contg. prescribed percentages of Cr, Mo, V or Mn and C. CONSTITUTION:This sintered Fe alloy is obtd. by uniformly dispersing, by weight, 5-25% alloy particles in the matrix of an Fe alloy consisting of 1-20% one or more among Cr, Mo, V and Mn, 0.5-2% C and the balance Fe. The alloy particles consist of 10-70% Cr, 5-20% W, 5-20% Mo, 0.5-3% C, <=20% Fe and the balance Co.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sintered alloy for valve seats of internal combustion engines,
More specifically, the present invention relates to an iron-based sintered alloy that has improved wear resistance and is less aggressive against mating valves.

[Conventional technology]

In recent years, internal combustion engines for automobiles have been designed to have higher leakage power, higher rotation speeds, and lower fuel consumption, and there has been a trend to take measures against exhaust gases. For this reason, valves and valve seat components are being exposed to more severe conditions than ever before.

This valve seat has a
Iron-based sintered alloys to which alloying elements such as Cr, Ni, Co, and Mo are added are increasingly being used.

[Problem that the invention seeks to solve]

By the way, the valve seat is required to improve its own wear resistance and reduce its aggressiveness to the pulp it is attached to, and the selection of the material for the valve seat should be determined in relation to the pulp it is attached to. If this selection is incorrect, it will not only weaken the wear resistance of the valve itself, but also increase its aggressiveness towards the mating member, which will have an undesirable effect on the entire valve mechanism. Therefore, if a conventional valve seat, for example, which has extremely high wear resistance by simply adding an intermetallic compound such as ferromolybdenum or a composite carbide, is used as it is, the wear of the engine valve will increase.

Even when the present invention is applied to a general-purpose engine valve whose wear resistance is not particularly enhanced (for example, JIS NFC751 crack), it does not wear out the other material or significantly increase its own wear. This is what we are trying to do.

[Means to solve the problem]

The iron-based sintered alloy for valve seats of the present invention has one or more elements selected from the group consisting of chromium (Cr), molybdenum (Mo), vanadium (V), and manganese (Mn) in terms of weight ratio. 1 to 20%, carbon (C) 0.
Based on an iron-based alloy containing 5-2%, optionally (Ni) 1-10% and unavoidable impurities, chromium (Cr) 10-10%.
70%, tungsten (W) 5-20%, molybdenum (
5 to 25 alloy particles consisting of 5 to 20% Mo), 5 to 3% carbon (C) II, 20% or less iron (Fe), and the balance Cobalt (Co) are uniformly dispersed in the base. It is characterized by

1. The present invention is characterized in that the sintered alloy is infiltrated with 1 to 20% of lead (Pb).

Incidentally, in the present invention, unless otherwise specified, ``chi'' indicates heavy ``chi''.

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

First, each component element of the alloy particles added as hard particles will be explained.

Cr (chromium) in the alloy particles combines with C (carbon) to form carbides, and a portion also forms an alloy with CO, which has the effect of improving the hardness of the alloy particles. If it is less than 70%, the above effect is insufficient, and if it exceeds 70%, the diffusion of Cr will proceed too much to the surrounding bases, creating voids inside and at the periphery of the alloy particles, making the alloy particles brittle. Therefore, Cr Vil was limited to 0 to 70%. However, 40-70% is more preferred.

W (tungsten) combines with C to form a double carbide of MC-type hard carbide and CO and improves the hardness of the alloy particles, but if W is less than 5 inches, this effect is not exhibited, and 2
If the WFi exceeds 0%, the alloy particles become too hard and the aggressiveness towards the mating material, the valve, increases, so the WFi was set at 5 to 20%.

Mo (molybdenum) combines with C to form hard carbides and increases the hardness of the alloy particles, but if MO is less than 5%, this effect will not appear, and if it exceeds 20%, the alloy particles will become too hard Since it attacks the parts, it was set at 5 to 20%.

CId Cr% combines with Mo and W to form carbides,
C improves the hardness of the alloy particles, but if it is less than 0.5 inches, its effect will not be exhibited, and if it exceeds 3 inches, the amount of carbides will be too large and it will become brittle. Therefore, C was set to 0.5 to 3 inches.

Fe (iron) does not need to be added, but if there is no problem with the strength required for the valve seat, it can be used in any amount of 20% or less in place of the expensive CO. Moreover, when Cr%W%Mo is used as a raw material for an alloy not as a single substance but as a ferroalloy, it is added.

Alloy particles are used because they are effective in improving wear resistance. The particle size is preferably 30 to 150 μm, and a part of the Co in the alloy diffuses into the matrix to form a diffusion layer around the particles, increasing the bonding force between the particles and the matrix.
The particles are prevented from falling off. If the alloy particles are less than 5%, the wear-resistant effect of the resulting sintered alloy will not be exhibited, and if it exceeds 25%, the formability, compressibility and machinability will decrease, and the mating material, the valve, will be attacked. In order to increase the number of alloy particles, the number of alloy particles was limited to 5 to 25 particles.

Next, I will explain the base.

By using one or more types of iron-based alloys containing one or more of Cr%Mo, V (vanadium), and Mn (77 cancer), the heat resistance, corrosion resistance, and properties of the iron base can be improved. can be done. In particular, Cr1-5%, Mo
iron-based alloy containing 0.1-1% and v0.1-1%,
Cr0.5-2%, MOo, 1-1% and Mnα1-1
It is preferable to use an iron-based alloy containing Cr or an iron-based alloy containing Cr6-18. Cr included in the upper railway foundation fee
%Mo%V%Mn or 2ft1 or more and less than #'i14 has no effect on improving the heat resistance and corrosion resistance of the iron base, and even if it exceeds 20%, no further effect can be obtained.
It was set as 1 to 20 inches.

C diffuses into the above-mentioned iron-based alloy to promote sintering and has the effect of strengthening the matrix, and unreacted free graphite is
When C is present in the base to some extent, it exhibits a lubricating effect, but if it is less than 15%, it has no effect.
If it exceeds 0%, cementite will precipitate and the base will become brittle, and the strength of the base will decrease due to too much free graphite, so the C content was set at 0-5 to 2 inches.

Ni (nickel) is a solid solution in the Fe base] 7 and is useful for improving the strength of the base, so it is added when further strength is required, but if Ni is less than 1 inch, the effect will not be exhibited, If it exceeds 10 inches, the base becomes soft and the wear resistance decreases, so the Ni content was set at 1 to 10%.

Infiltration of sintered alloys with PB (lead) is carried out in the case of valve seats used under more severe conditions. The infiltrated PB acts as a lubricant by forming a Pb & compound layer at the contact area between the valve and the valve seat, improving the mutual wear resistance of the valve and the valve seat. If it is less than 1%, the effect of PB infiltration will not be exhibited, and if it exceeds 20%, the skeleton of the sintered alloy will be weakened and wear will increase.

〔Example〕

The present invention will be explained by examples.

Example 1 (ylO%, V2O4, Mo10%, Fe 10%, c
Alloy atomized powder (-1
00 meth) 15%, graphite powder (-350 meth)
1.5%, carbonyl Ni powder (10μm or less) 5%
, and the powder composition for sintering is an alloy atomized iron powder (-100 mesh) consisting of 12% Cr and the balance Fe, and 1r stearic acid as a lubricant! After mixing copper powder α8%, this mixed powder was filled into a mold and molded at a molding pressure of 7 t/ctA to obtain a powder molded body having a rough shape of a valve seat.

This powder compact was heated to 115% in an ammonia decomposition gas atmosphere.
A sintered body was obtained by sintering at a temperature of 0° C. for 60 minutes. The density of the sintered body is ZO/7° The obtained sintered body is processed into the shape of an exhaust valve seat and the exhaust f20
It was installed in a 4-cylinder diesel engine and subjected to a bench durability test under full load for 200 hours, and the amount of increase in surface width per valve seat and the amount of valve wear were measured. JIS NFC751 was used for the p-, 8-hand valve.

Examples 2 to 4 Each material was mixed in the respective composition ratios shown in Tables 1 and 2 in the same manner as in Example 1, with -, to obtain each sintered body. In addition, in Examples 3 and 4, the obtained sintered body was brought into contact with a PB lump and heated again at a temperature of 1050 ° C. for 50 minutes in an ammonia decomposition gas atmosphere to infiltrate PB into the sintered body. It is.

Each of the obtained sintered bodies was processed into a valve seat shape, and the increase in surface width per valve seat and the amount of valve wear were tested and measured in the same manner as in Example 1.

Example 5 Cr43%, W16%, MO17%, Fe8%, C1,
Alloy atomized powder (-100
mesh) 15%, i-lead powder (-350 mesh) 1.1%, carbonyl Ni powder (10Pm or less) 4%
, and the balance of the powder is alloy atomized iron powder (-100 mesh) consisting of 12% Cr and the balance Fe, and 18% zinc stearate powder as a lubricant.
After mixing, this mixed powder was filled into a mold and molded at a molding pressure of 7 t/cd to obtain a powder molded body in the rough shape of a valve seat.

This powder compact was heated to 115% in an ammonia decomposition gas atmosphere.
A sintered body was obtained by sintering at a temperature of 0° C. for 60 minutes. The density of the sintered body is &85)/aA 0 The obtained sintered body was processed into the shape of an exhaust valve seat and installed in a diesel engine with a displacement of 2000 (E4 cylinders), and a bench durability test was conducted for 200 hours at full load. The increase in surface width per valve seat and the amount of pulp wear were measured.The mating valve was JIS NPC75.
1 was used.

Examples 6 to 8 Each material was blended in the respective composition ratios shown in Tables 1 and 2, and the same procedure as in Example 1 was carried out to obtain each sintered body. In addition,
In Examples 7 and 8, the obtained sintered body was brought into contact with a Pb lump and heated again at a temperature of 1050°C for 30 minutes in an ammonia decomposition gas atmosphere to infiltrate Pbtl into the sintered body. .

Each of the obtained sintered bodies was processed into a valve seat shape, and the increase in surface width per valve seat and the amount of valve wear were tested and measured in the same manner as in Example 1.

Comparative Examples 1 and 2 Comparative Example 1 is JISFC30 cast iron, Comparative Example 2 is JISFC30 cast iron.
IS heat-resistant steel material SUM 4B was processed into the shape of a valve seat, and these were tested in the same manner as in Example 1 to measure the amount of valve wear.

The above measurement results are summarized in Table 1.

Table 2 As can be seen from Table 1, the amount of increase in surface width per valve seat in Examples 1 to 8 was α1 to 12. , which shows a considerably smaller value compared to 1.2 and 1.4 M in Comparative Examples 1 and 2,
The sintered alloys of Examples 1 to 8 have excellent wear resistance as valve seat materials for diesel engines used under severe conditions. In addition, the amount of pulp abrasion in Examples 1 to 8 was 2 to 7.
The sintered alloys of Examples 1 to 8 have low aggressiveness against pulp as the mating material, which is considerably smaller than the 30 and 40 μm of Comparative Examples 1 and 2.

〔Effect of the invention〕

As mentioned above, the iron-based sintered alloy for valve seats of the present invention has alloy particles uniformly dispersed in the iron-based alloy matrix containing one of Cr, Mo%V%Mn, or two or more types of Fi, so it has excellent wear resistance. It has excellent properties and low aggressiveness towards pulp, which is the mating material, making it ideal as a sintered alloy for valve seats.

Patent applicant: Toyota Motor Corporation Agent Patent Attorney Yumi Sakai [゛ (1 piece?-1,?)) 1,.

Claims (20)

[Claims] (1) Chromium (Cr), molybdenum (Mo) in weight ratio
, vanadium (V), and manganese (Mn), 1 to 20% of one or more elements selected from the group consisting of , carbon (
C) Based on iron-based alloy containing 0.5-2% and unavoidable impurities, weight ratio: chromium (Cr) 10-70%, tungsten (W) 5-20%, molybdenum (Mo) 5-2
0%, carbon (C) 0.5-3%, iron (Fe) 20% or less, and balance cobalt (Co) 5-25%.
An iron-based sintered alloy for a valve seat, characterized in that: is uniformly dispersed in the base. (2) Chromium (Cr) 1-5%, molybdenum (Mo) 0.1-1% and vanadium (V) 0.1-1% by weight
% of the iron-based sintered alloy for a valve seat according to claim 1. (3) By weight, chromium (Cr) 0.5-2%, molybdenum (Mo) 0.1-1%, and manganese (Mn) 0.1
The iron-based sintered alloy for a valve seat according to claim 1, characterized in that the iron-based alloy contains ~1% of the iron-based sintered alloy. (4) The iron-based sintered alloy for a valve seat according to claim 1, wherein the iron-based alloy contains 6 to 18% of chromium (Cr) by weight. (5) The iron-based sintered alloy for a valve seat according to claim 1, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight. (6) Chromium (Cr), molybdenum (Mo) in weight ratio
, vanadium (V), and manganese (Mn), 1 to 20% of one or more elements selected from the group consisting of , carbon (
C) Based on an iron-based alloy containing 0.5-2% nickel (Ni), 1-10% nickel (Ni), and unavoidable impurities, the weight ratio is 10-70% chromium (Cr) and 5-20% tungsten (W).
%, molybdenum (Mo) 5-20%, carbon (C) 0.5
~3%, less than 20% iron (Fe) and the balance cobalt (Co
1. An iron-based sintered alloy for a valve seat, characterized in that 5 to 25% of alloy particles consisting of ) are uniformly dispersed in the matrix. (7) Chromium (Cr) 1-5%, molybdenum (Mo) 0.1-1% and vanadium (V) 0.1-1% by weight
% of the iron-based sintered alloy for a valve seat according to claim 6. (8) By weight, chromium (Cr) 0.5-2%, molybdenum (Mo) 0.1-1%, and manganese (Mn) 0.1
The iron-based sintered alloy for valve seats according to claim 6, characterized in that the iron-based alloy contains ~1% of the iron-based sintered alloy. (9) The iron-based sintered alloy for a valve seat according to claim 6, characterized in that the iron-based alloy contains 6 to 18% by weight of chromium (Cr). (10) The iron-based sintered alloy for a valve seat according to claim 6, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight. (11) Chromium (Cr), molybdenum (Mo) in weight ratio
), vanadium (V), and manganese (Mn) in an amount of 1 to 20% of one or more elements selected from the group consisting of In terms of weight ratio, chromium (Cr) 10-70%, tungsten (W) 5-20%, molybdenum (Mo) 5-5%.
20%, carbon (C) 0.5 to 3%, iron (Fe) 20% or less, and the balance cobalt (Co).
% of lead (
An iron-based sintered alloy for valve seats, characterized in that it is infiltrated with 1 to 20% Pb). (12) By weight, chromium (Cr) 1-5%, molybdenum (Mo) 0.1-1%, and vanadium (V) 0.1-5%
12. The iron-based sintered alloy for a valve seat according to claim 11, wherein the iron-based sintered alloy contains 1% of the iron-based alloy. (13) By weight, chromium (Cr) 0.5-2%, molybdenum (Mo) 0.1-1%, and manganese (Mn) 0.
12. The iron-based sintered alloy for a valve seat according to claim 11, wherein the iron-based sintered alloy contains 1 to 1% of the iron-based alloy. (14) The iron-based sintered alloy for a valve seat according to claim 11, wherein the iron-based alloy contains 6 to 18% of chromium (Cr) by weight. (15) The iron-based sintered alloy for a valve seat according to claim 11, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight. (16) Chromium (Cr), molybdenum (Mo) in weight ratio
), vanadium (V), and manganese (Mn), 1 to 20% of one or more elements selected from the group consisting of, carbon (C) 0.5 to 2%, nickel (Ni) 1 to 10%, and Based on an iron-based alloy containing unavoidable impurities, the weight ratio is 10 to 70% chromium (Cr) and 5 to 2% tungsten (W).
0%, molybdenum (Mo) 5-20%, carbon (C) 0.
5 to 3%, less than 20% iron (Fe) and the balance cobalt (C
An iron-based sintered alloy for valve seats, characterized in that 1-20% of lead (Pb) is infiltrated into a sintered alloy in which 5-25% of alloy particles consisting of o) are uniformly dispersed in the matrix. . (17) By weight, chromium (Cr) 1-5%, molybdenum (Mo) 0.1-1%, and vanadium (V) 0.1-5%
17. The iron-based sintered alloy for a valve seat according to claim 16, wherein the iron-based sintered alloy contains 1% of the iron-based alloy. (18) By weight, chromium (Cr) 0.5-2%, molybdenum (Mo) 0.1-1%, and manganese (Mn) 0.
17. The iron-based sintered alloy for a valve seat according to claim 16, wherein the iron-based sintered alloy contains 1 to 1% of the iron-based alloy. (19) The iron-based sintered alloy for a valve seat according to claim 16, wherein the iron-based alloy contains 6 to 18% by weight of chromium (Cr). (20) The iron-based sintered alloy for a valve seat according to claim 16, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight.