JPS6296659A - 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., and prescribed Fe alloy particles in the pearlite-base matrix of iron. CONSTITUTION:This sintered Fe alloy is obtd. by uniformly dispersing, by weight, 5-25% alloy particles and 1-10% Fe alloy particles in a pearlite-base matrix consisting of 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. The Fe alloy particles are made of FeMo contg. 60-70% Mo, FeW contg. 70-80% W or a mixture of them.

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 of the alloy itself and is less aggressive to mating pulp.

[Conventional technology]

In recent years, internal combustion engines for automobiles have been designed to have higher output, higher rotation speed, and lower fuel consumption, and there has been a trend toward measures against exhaust gas. For this reason, valves and valve seat parts are being exposed to more severe conditions than ever before.

This valve seat has a
Iron-based sintered alloys containing alloying elements such as cr, Ni%Co, and M are increasingly being used.

[Problem that the invention seeks to solve]

By the way, valve seats are required to improve their own abrasion resistance and reduce their aggressiveness to the partner pulp, and the selection of the material for the valve seat is determined based on the relationship with the partner pulp. If the selection is incorrect, it will either weaken the abrasion resistance of the pulp itself or increase its aggressiveness towards the mating member, giving an undesirable effect on the pulp mechanism as a whole. Therefore, unlike conventional pulps, for example, intermetallic compounds or composite carbides are simply added to make the abrasion resistance extremely high.

Continued use of the sheet results in increased wear of the engine pulp.

The present invention provides a valve that does not wear out the mating material or significantly increase its own wear even when used with general-purpose engine pulp that does not have particularly high wear resistance (for example, JIS NFC751). The present invention aims to provide a ferrous sintered alloy for sheets.

[Means for solving problems]

The iron-based sintered alloy for valve seats of the present invention has a weight ratio of 2: chromium (Cr): 10-70%, tungsten%: 5-20%.
%, Molybde 7 (Mo) 5-20%, Carbon (q
(5 to 25 alloy particles consisting of L5 to 3%, iron (Fe) 20 ah or less and the balance cobalt (CO), and ferromolybdenum (FeMo) containing 60 to 70 pieces of molybdenum (Mo) or tungsten ( 5) from 70
1 out of 80 ferrotungsten (FeW) containing
Carbon (qas~2
It is characterized in that it is uniformly dispersed in a base mainly composed of barlite, which is composed of iron (Fe) and the balance iron (Fe) and unavoidable impurities.

Further, the iron-based sintered alloy of the present invention has nickel (N 1 to 1
The present invention is characterized in that Ochi is contained in the above-mentioned barite-based base. Furthermore, one aspect of the present invention is that lead (P) is added to the sintered alloy.
b) Characterized by infiltration of 1 to 20%.

Note that in the present invention, the weight indicates the weight ratio unless otherwise specified. The preferable iron-based sintered alloy of the present invention has a weight ratio of 1.
(Cr)40~709b%=r hak) (Co
) 5-30%.

Tungsten 5~20 yen, molybdenum (Mo) 5~2
0 width, 5 to 25 pieces of alloy particles consisting of iron (Fe) of 20 pieces or less and carbon (qα5 to 3) are dispersed in the base together with Fe alloy particles. 〇Limitations of each component element used in the present invention Let me explain the reason.

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, but when Or is 10 If the temperature 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, and the 1 alloy particles will become brittle and begin to crack or fall off. Becomes extremely susceptible to deterioration. Therefore, among the alloy particles of the present invention, in which Cr is limited to 10 to 70%, those containing 40 to 70% Cr and 5 to 50% Co are preferable in terms of hardness and brittleness. (Tungsten) combines with C to form MC-type hard carbides and double carbides with Co, improving the hardness of 1 alloy particles, but this effect is not exhibited when W is less than 591, and 20-chip If W exceeds 5 to 2, the alloy particles become too hard and become more aggressive towards pulp, which is the mating material.
It was set to 0.

Mo (molybdenum) combines with C to form hard carbides and increases the hardness of the alloy particles, but if Mo is less than 54, this effect will not appear, and if it exceeds 2.0, the alloy particles will not be too hard. Since C attacks the mating member, it is set at 5 to 20% @C combines with Cr, Mo and W to form carbide.

It improves the hardness of alloy particles, but if C is less than α5, the effect will not be exhibited, and if it exceeds 5, the amount of carbides will be too large and it will become brittle.Therefore, O Fe (with C of α5 to 3) There is no need to add iron), provided there are no problems with the strength required for the valve seat.

It can be used in place of expensive CO in any range of 20 or less. Further, Cr, W, and Mo are added when they are used as raw materials for an alloy not as single substances but as a ferroalloy.

CO forms an alloy with other components to improve the heat resistance of the alloy particles, and at the same time, a part of it diffuses into the base, improving the bondability between the alloy particles and the base.

For example, in alloy particles containing 40 to 70% Cr.

If the amount of CO is less than 5%, the effect of improving heat resistance and bondability is not exhibited, and if it exceeds 30%, the effect becomes almost constant. Therefore, it is preferable that the content of Co is 5 to 60%. When the particle size of the alloy particles is less than 20 μm, the wear resistance is insufficiently weak, and when the particle size exceeds 2Q (1), the formability and compressibility decrease and the wear resistance becomes low. Therefore, it is preferable that the grain size of the alloy particles is 20 to 200 microns, particularly 30 to 150 microns.

In addition, if the hardness of 1 alloy particle is less than Hv1000, 1
It is preferable that the hardness is HvIQGO or higher, since the wear of the particles tends to progress and the wear resistance decreases. Since the alloy particles are effective in improving the wear resistance, the Co content in the alloy used is A part of the particles diffuses into the base and forms a diffusion layer around the particles, increasing the bonding force between each particle and the base and preventing the particles from falling off. The wear resistance effect of the sintered alloy is not exhibited.

If it exceeds 25 yen, the moldability, compressibility, and rigidity will decrease, and the aggressiveness to pulp, which is the mating material, will increase, so the alloy particles were limited to 5 to 25%.

Ferromolybdenum (FeMo) added as hard particles
contains 60-70% Mo and has a particle size of 50-150μ
m, and hardness Hv800-1300.

However, tungsten (FeW), which is also a hard particle, contains 70 to aol of W, and is effective in improving wear resistance like FeMo. FeM.

Or, if the total content of FeW is less than 1 ton, the effect is not effective (
, 1096, the moldability and stiffness deteriorate,
1 to 10% 〇The base will be explained next.O C dissolves in the Fe of the base to form a complete barlite structure, improves the strength and hardness of the sintered alloy, and also improves the strength and hardness of the sintered alloy. Combines with Cr, Mo and W to form a hard carbide5
It has the effect of further improving the hardness of the alloy particles, and also because some unreacted free graphite remains in the matrix.

A lubricating effect is exerted, but if C is less than 15%, it is not effective, and if it exceeds 2%, the cementite becomes coarse and there is too much free graphite, making the base brittle. did.

N1 (-Tsukeru) is solid dissolved in the Fe base and helps improve the strength of the base, so it is added when further strength is required, but if Nt is less than 10, its effect will not be exhibited. If it exceeds 10%, the base becomes soft and the wear resistance decreases, so the Ni content was set to 1 to 10%.

The infiltration of PB (lead) into the sintered alloy is carried out in the case of valve seats used under very severe conditions. By forming an oxide layer, it acts as a lubricant and improves the wear resistance between the pulp and the valve seat, but if the amount of Pb infiltrated is less than one layer, the effect of Pb infiltration is not exhibited.

If infiltration exceeds 20%, the skeleton of the sintered alloy will weaken and wear will increase, so it was set at 1 to 20%.

〔Example〕

The present invention will be explained by way of examples.

Example 1 Cr45%, wio 俤, Mo17%, Fe9%, C10
% and Co1B14 alloy particle powder (particle size 65p
g, -80 mesh, hardness Hv1380n15.

FeMo (-10 mesh'/z) 2%, graphite powder (-550 mesh 31.2%, carbonyl Ni powder (10 μm or less) 3 parts, and the balance atomized iron powder (-1
00 mesh) was mixed with α8 g of zinc stearate as a lubricant, and this mixed powder was filled into a mold and molded at a molding pressure of 7 t/- to obtain a powder molded body in the rough shape of a valve seat.

This powder compact was heated to 114 mL 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 was 6. ．． 8t/ctA, its hardness is lv220
Met.

The obtained sintered body is processed into the shape of an exhaust valve seat and exhaust ii2
D 00c, c, was installed in a 4-cylinder diesel engine, and a bench durability test was conducted for 300 hours at full load, and the amount of increase in surface width per valve seat and the amount of pulp wear were measured.

Note that JIS NFC751 was used as the mating pulp.

Examples 2 to 4 Each material was blended in the composition ratio shown in the following table and the same procedure as in Example 1 was carried out to obtain each sintered body. Examples 5 and 4
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 Pb into the sintered body. In addition, in Example 2, FeW was applied as the Fe alloy particles, and in Example 3, FeMo and FeW were applied as the same particles. - Face width increase and pulp abrasion were measured after testing in the same manner as in Example 1 〇Example 5 Cr 30%, W 10%, Mo 10%, Fe
10%, C2,0 and balance, Co alloy atomized powder (-100 mesh) 15%, FeMo
5% graphite powder (-450 mesh), 1.2% carbonyl Ni powder (10 μm or less), and the balance reduced iron powder (-100 mesh) were mixed with 8% zinc stearate α as a lubricant. The powder was filled into a mold and molded at a molding pressure of 7 t/- 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 was 7.0f/-0.The obtained sintered body was processed into the shape of an exhaust valve seat, and the displacement was 2000c. c. Installed on a 4-cylinder diesel engine and conducted a 200-hour bench durability test under full load to determine the amount of increase in valve seat surface width and pulp wear t.
In addition, the mating valve is JIS NFC75.
1 was used.

Examples 5 to 8 Each material was mixed in the composition ratio shown in the following table and the same procedure as in Example 5 was carried out to obtain each sintered body. In addition, Example 7
and 8 are those obtained by bringing the obtained sintered body into contact with a Pb lump and heating it again at a temperature of 1050°C for 30 minutes in an ammonia decomposition gas atmosphere to infiltrate Pb into the sintered body. Each sintered body was processed into a valve seat shape, and the amount of increase in surface width per valve seat and the amount of pulp abrasion were tested and measured in the same manner as in Example 5. Comparative Examples 1 and 2 Comparative Example 1 was JIS I"C50. Cast iron and JIS heat-resistant steel S UH4B as Comparative Example 2 were processed into valve seat shapes, and these were tested in the same manner as in Example 1 to measure the amount of increase in surface width per valve seat and 1 ton of pulp wear.

The above measurement results are summarized in the following table.

As can be seen from the table, the increase amount of the surface width per valve seat in Examples 1 to 8 was 0.1 to cL5fi, and Comparative Examples 1 and 2
The sintered alloys of Examples 1 to 8 have wear resistance as valve seat materials for diesel engines used under severe conditions. Excellent. Also.

The amount of pulp abrasion in Examples 1 to 8 was 3 to 7 μm.

It is considerably smaller than the 30 and 40 μm of Comparative Examples 1 and 2, and the sintered alloys of Example 1+IJ 1 to 8 have low sheet weight relative to the pulp that is the mating material.

〔Effect of the invention〕

As mentioned above, the iron-based sintered alloy for valve seats of the present invention has alloy particles and Fe alloy particles as hard particles uniformly dispersed in an iron base mainly composed of barlite, so it has excellent wear resistance and It has low aggressiveness against pulp, which is the mating material, and is ideal as a sintered alloy for valve seats.

Claims (12)

[Claims] (1) Chromium (Cr) 10-70%, tungsten (W) 5-20%, molybdenum (Mo) 5-20% by weight
%, 5 to 25% of alloy particles consisting of 0.5 to 3% of carbon (C), 20% or less of iron (Fe), and the balance cobalt (Co),
and ferromolybdenum (FeMo) containing 60 to 70% molybdenum (Mo) or tungsten (W).
0 to 80% of ferrotungsten (FeW) containing 1 to 10% of one or more Fe alloy particles, carbon (C) 0
．． An iron-based sintered alloy for a valve seat, characterized in that it is uniformly dispersed in a matrix mainly consisting of barlite, which is composed of 5 to 2% iron (Fe) and inevitable impurities. (2) 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. (3) The iron-based sintered alloy for a valve seat according to claim 1, wherein the alloy particles have a particle size of 20 to 200 μm and a hardness of Hv1000 or more. (4) By weight, chromium (Cr) 10-70%, tungsten (W) 5-20%, molybdenum (Mo) 5-20
%, 5 to 25% of alloy particles consisting of 0.5 to 3% of carbon (C), 20% or less of iron (Fe), and the balance cobalt (Co),
and ferromolybdenum (FeMo) containing 60 to 70% molybdenum (Mo) or tungsten (W).
0 to 80% of ferrotungsten (FeW) containing 1 to 10% of one or more Fe alloy particles, carbon (C) 0
．． 5-2%, nickel (Ni) 1-10% and balance iron (
An iron-based sintered alloy for valve seats, characterized in that it is uniformly dispersed in a matrix mainly consisting of barlite, which is composed of Fe) and inevitable impurities. (5) The iron-based sintered alloy for a valve seat according to claim 4, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight. (6) The iron-based sintered alloy for a valve seat according to claim 4, wherein the alloy particles have a particle size of 20 to 200 μm and a hardness of Hv1000 or more. (7) By weight, chromium (Cr) 10-70%, tungsten (W) 5-20%, molybdenum (Mo) 5-20
%, 5 to 25% of alloy particles consisting of 0.5 to 3% of carbon (C), 20% or less of iron (Fe), and the balance cobalt (Co),
and ferromolybdenum (FeMo) containing 60 to 70% molybdenum (Mo) or tungsten (W).
0 to 80% of ferrotungsten (FeW) containing 1 to 10% of one or more Fe alloy particles, carbon (C) 0
．． It is characterized by infiltrating 1 to 20% of lead (Pb) into a sintered alloy that is uniformly dispersed in a matrix mainly composed of barlite, which consists of 5 to 2% of lead (Pb) and the balance iron (Fe) and unavoidable impurities. Iron-based sintered alloy for valve seats. (8) The iron-based sintered alloy for a valve seat according to claim 7, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight. (9) The iron-based sintered alloy for a valve seat according to claim 7, wherein the alloy particles have a particle size of 20 to 200 μm and a hardness of Hv1000 or more. (10) By weight, 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%.
, and 1 to 10% of ferromolybdenum (FeMo) containing 60 to 70% of molybdenum (Mo), carbon (C)
Lead (Pb) 1 is uniformly dispersed in a sintered alloy consisting of barlite, which consists of 0.5-2% nickel (Ni), 1-10% nickel (Ni), and the balance iron (Fe) and unavoidable impurities.
An iron-based sintered alloy for valve seats, characterized by being infiltrated with ~20%. (11) The iron-based sintered alloy for a valve seat according to claim 10, wherein the content of chromium (Cr) in the alloy particles is 40 to 70% by weight. (12) The iron-based sintered alloy for a valve seat according to claim 10, characterized in that the particle size of the alloy particles is 20 to 200 μm, and the hardness of the alloy particles is Hv1000 or more.