JPH04157138A - Sintered alloy for valve seat - Google Patents

Abstract

PURPOSE:To improve the material strength at a high temp. and machinability of a sintered alloy by dispersing a hard phase constituted of Cr, Mo, Si and Co into its matrix in which C, Ni, Mo, Co and Fe are specified and dispersing lubricating substance into its grain boundaries each by a prescribed amt. CONSTITUTION:This sintered alloy for a valve seat is formed of a compsn. constituted of, by weight, 0.4 to 1.2% C, 0.3 to 2.9% Ni, 0.3 to 2.3% Cr, 1.7 to 9.8% Mo, 8 to 22% Co, 0.1 to 0.7% Si, 0.5 to 2% lubricating substance and the balance Fe. The above lubricating substance is constituted of an Mg metasilicate series mineral or, together with this, an Mg orthosilicate series mineral or of an Mg metasilicate series mineral and/or an Mg orthosilicate series mineral and B nitride and/or Mn sulfide. Then, this alloy has a structure in which 5 to 25% hard phase is dispersed into its matrix and 0.5 to 2% lubricating substance is dispersed into its grain boundaries.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a sintered alloy for a valve seat of an internal combustion engine that has excellent wear resistance under high temperatures and excellent machinability.

<Conventional technology> In recent years, the types of fuel used in automobile engines have become more diverse, and with the trend toward higher performance, engines that can be used with any type of fuel and are more durable Certain valve seats are required, and various sintered alloys for use in such parts have been proposed.

In order to meet these needs, the present applicant and others have previously demonstrated uniformly excellent wear resistance in the range from low-temperature to high-temperature regions, and have demonstrated that there are no restrictions on the characteristics of the engine or the type of fuel. As a sintered alloy that is not
We have developed a sintered alloy as described in Publication No. 244.

This sintered alloy has a weight ratio of C066 to 1.2%.

Ni0.5-3%+, Mo 0. 5-3%.
In the base of Co 5°5~7.5% and the balance of Fe, Cr
7-9-%, Mo26-30%, S i 1. 5
~2. Hard 1 which is an intermetallic compound of 5% and the balance Co
It is characterized by a 5 to 25% dispersion of 0s.
In addition, there has also been proposed a fuel in which lead is infiltrated into the pores to make it suitable for LPG fuel.

<Problem to be solved by the invention> However, among the conventional materials mentioned above, the trA material, which does not infiltrate lead, exhibits excellent wear resistance especially when used in areas subject to high temperatures; There has been a demand for this type of sintered material that overcomes the drawback of being difficult to cut and has good machinability.

On the other hand, conventional fuel infiltrated with lead and suitable for LPG fuel has a good resistance to 1? However, at higher temperatures, the strength of the material tends to decrease, and it does not exhibit as much wear resistance as expected, so further improvements have been desired.

This invention has been made in view of the above circumstances, and aims to obtain a sintered alloy for a valve seat that has high material strength at high temperatures and has good machinability.

Means for Solving the Problems> In order to achieve the object as stated in item 1, the present invention has an overall composition of 0.4 to 1.2% by weight of C and 0.3 to 2% of Ni.
．． 9%, Cr0. 3-2. 3%lMo1.7
~9.8%, co8~22%, Sin.

1-0.7%, lubricant 0.5-2% and Fe remaining;
and C0%~1.2%, Ni0.5~3%, Mo0.5
~3%, Co5. 5-7. '5% and Fe balance base, Cr7~9%, Mo26~30%, Si
1.5-2.5% and Co balance hard phase is 5-25%
It exhibits a structure in which 0.5 to 2% of a lubricating substance is dispersed in the ↑-°l world, and the -1, written li' is a magnesium metasilicate-based mineral, or a magnesila metasilicate-based mineral and orthogonal. It is characterized in that at least one of a magnesium silicate mineral, a magnesium metasilicate mineral, or a magnesium orthosilicate mineral and at least one of boron nitride or manganese sulfide are dispersed therein.

In addition, the overall composition is C064 to 1.2% by weight.

Ni 0.3-2.9%, Cr 0.3-2.3%.

Mo1.7-9.8%, 008-22%, Sin.

1-0.7%, Pb 3% or less, lubricant 0.5-2% and Fe balance, and C006-1.2%.

Ni 0.5-3%, hlo 0. 5-3i'6.
1 in the base of Co 5°5-7.5% and the balance Fe.
Cr7-9%, Mo26-30%, Si1.5-2.
5% and 5% to 25% hard phase with the remainder of Co, 3% or less of Pb in the grain boundaries or in the pores, and 0.5 to 2% of lubricating material at the grain boundaries.
-1- The lubricant described is a magnesium metasilicate mineral, or a magnesium metasilicate mineral and a magnesium orthosilicate mineral, or a magnesium metasilicate mineral or a magnesium orthosilicate mineral. The magnesium metasilicate mineral powder is enstatite powder.

The powder is characterized in that it is at least one of clinoenstatite powder, enstenite powder, hyperstenite powder, etc., and the orthosilicate magnesilla L and mineral powder is at least one of forsterite powder, chrysolite powder, etc.

The base phase has the same composition as the sintered alloy described in Japanese Patent Publication No. 55-36242, with Ni and Mo elements mainly contributing to strength, CO contributing to high-temperature hardness, and C is added in the form of graphite powder and alloyed during sintering. The hardness of the base phase is about HV300 to 380.

The hard particles are alloys described in JP-A-62-10244, but among the disclosed intermetallic compounds, MO33
~36% Si, 4-12% cobalt alloys are suitable.

In particular, LPG-fueled engines have dry valve and valve seat bows, which can easily cause abrasion wear (mechanical destructive wear) that occurs when materials come into contact with each other [2], but this Co-based alloy hard particle reduces this. It is effective.

Moreover, the base structure has a structure in which the above-mentioned intermetallic compound is dispersed, and its hardness is about MHV800 to 970.

The amount of Co-based alloy hard particles added is preferably 10 to 20% because wear resistance is stabilized when the amount is 5% or more, but addition of more than 25% is not cost effective.

Co-based alloy hard particles are dispersed in the iron base as described above,
Further addition of lead to this material improves wear resistance and machinability when the fuel, such as LPG, does not contain anti-friction components. do.

However, lead-added H-A material has a temperature higher than the melting point of lead.
℃ or higher and the lead content is high, the strength of the key material decreases, so it is desirable to keep the lead content below 3%.

Lead can be added by infiltration or in the form of lead powder into a mixed powder, but when the pores are filled with lead by ordinary infiltration, the density of the sintered body is 7.2 g/cm3. Since the amount of lead is about 10%, the thorough infiltration is controlled by the lead infiltration temperature, pressure, and infiltration time.

Lead reduces high-temperature strength, which is presumed to be related to the volumetric expansion of molten lead.

The decrease in strength is caused by the fact that the temperature of each part of the valve seat is usually not uniform and tends to change, resulting in a decrease in airtightness, resulting in a decrease in output and uneven wear.

When the lead content is 3% or less, the high temperature strength meets the requirements.

On the other hand, machinability becomes a problem when the amount of lead is kept at zero or below 3%, but by adding specific amounts of magnesium metasilicate minerals, magnesium orthosilicate minerals, boron nitride, and manganese sulfide, Without lowering the high-temperature material strength, machinability equivalent to that obtained by adding a large amount of lead is not achieved.

Magnesium silicate is a solid lubricant interposed in the 11γ field of the base, and magnesium metasilicate (magnesiu
m meLasilicaLe) is Mg S t 03
It is said that there are several types with different crystal structures, but the orthorhombic enstatite l-(ensL
aLiLe, clinopyroxene), monoclinic clinoenstatite (cl 1noenstaLiLe, clinopyroxene)
corresponds to

In addition, those made from natural ores are generally in the form of a solid solution of Mg silicate and Fe silicate, or a solid solution of this solid solution and Mg silicate.
Fe) S i 03, and examples of this type include enstenite (ensLeniLe) and hypersthen (hydropyroxene).

In this invention, magnesium metasilicate and silicates containing the same as described in item 1 are referred to as magnesium metasilicate minerals.

On the other hand, magnesium orthosilicate
or Lhosi I 1cate) is M g 2 S
It is expressed as tO4 and is industrially known as forsterite (r
orsLeriLe, bitter f-JJiJr! It is an ore called stone. Also, 1. Similar to the above, it is in the form of a solid solution with silicate of Mg and Fe.
There is jJ [R stone].

Chrysolite is forsterite (Mg2
S t 04 ) and f'ayaliL
e, Fe5iO4), or even Tefroid (L
ephr.

iLe, Mn　5i04) in a solid solution containing (Mg.

Fe) 2S t O4 or (Mg, Fe
, Mn) 2S i04.

In this invention, the above-described magnesium orthosilicate and silicate containing the same are referred to as magnesium orthosilicate minerals.

As for the lubricating effect, it is effective when added at 0.5% by weight or less, and the effect increases when the amount added is increased, but when more than 2% is added, the volume of the solid lubricant increases. Therefore, the strength of the sintered body decreases, which is not preferable.

In addition, talc is known as magnesium silicate,
Talc (Mg3S t40., H2O) dehydrates crystal water during sintering, contaminates the sintering furnace gas, and some of it becomes silicon dioxide (S 102 ), causing sliding mating parts +4
This is undesirable as it may cause damage to the data.

Magnesium metasilicate minerals and magnesium orthosilicate minerals have a specific gravity of about 3.2 to 3.9 and have interfold properties, so they act as solid lubricants, improving the free machinability, sliding properties, and
Improves conformability and abrasion resistance.

Note that when comparing magnesium metasilicate minerals and magnesium orthosilicate minerals, the latter is harder and less prone to creases, so it is preferable to use it in combination with magnesium metasilicate minerals.

Powder of the above-mentioned magnesium silicate mineral having such properties is added to metal powder and manufactured by compression molding and sintering, but during powder molding, the friction with the molding die decreases, resulting in poor moldability. Get better.

In addition, it is relatively stable in terms of heat resistance and can be manufactured using normal sintering methods of powder metallurgy.

In order to further improve the machinability and wear resistance of the sintered alloy, in addition to one or both of magnesila metasilicate T3 minerals and magnesium orthosilicate minerals, at least one of boron nitride or manganese sulfide is required. When dispersed in a metal matrix, boron nitride and manganese sulfide act as solid lubricants and improve the wear resistance of sintered parts.

When boron nitride and manganese sulfide are compared, boron nitride is superior in machinability, while manganese sulfide is superior in wear resistance.

Further, the amount added is set to be in the range of 0.1 to 2 weight 26 in total with the magnesium silicate mineral, for the same reason as in the case of the lubricating effect of the magnesium silicate mineral.

Magnesium silicate minerals and a small amount of boron nitride or manganese sulfide (although there are no restrictions on the combination ratio of either one, from a cost perspective, boron nitride and manganese sulfide are about 10 to 30 times more expensive than magnesium silicate minerals) In consideration, it is preferable to reduce the amount by half or less.

<Function> The sintered alloy for valve seats according to the present invention has Ni and Mo added to strengthen the base, and Co added to improve high-temperature hardness.
Then, CO-based alloy hard particles are added to reduce abrasion wear, and magnesium metasilicate minerals, magnesium orthosilicate minerals, boron nitride, manganese sulfide, etc. are dispersed in specific combinations in predetermined amounts at the grain boundaries. By forming the alloy structure, it is possible to obtain a sintered alloy for a valve seat that has high material strength at high temperatures and also has good machinability.

<Example> Examples will be explained below.

The composition and blending ratio are Ii ratios.

In preparing the sample, the following raw material powder was prepared using semi-f11 powder.

(1) Alloy iron powder Fe-1,5%Ni-1,5%Mo-6,5%CO for base formation (2) Cobalt alloy powder Co-2 for hard tr't and final formation
8% MO-8% Cr-2% Si alloy powder (3) Natural graphite powder (4) Lubricating substance a; enstatite powder b; forsterite powder C; boron nitride powder d; manganese sulfide powder (5) zinc stearate Powder comparison A1: ゛Conventional, cobalt alloy powder 1 is added to alloy iron powder for base formation.
5%, natural graphite powder 1% and zinc stearate powder 0.8%
% was compression molded into a ring shape, and then sintered in an ammonia decomposition gas furnace at a temperature of 1200°CCl2O for minutes.

Comparative materials 2 to 6: 10. Comparison trA' 1 is +4 material infiltrated with lead,
Samples with different amounts of lead dipping were prepared by varying the infiltration temperature and time.

Comparative materials 7 to 9 and invention shrines 1 to 7: Enstatite powder, which is an example of a magnesium metasilicate mineral, forsterite, which is an example of a magnesium ortosilicate mineral, and powders of boron nitride and manganese sulfide,
1. Sample f was obtained by adding a predetermined amount to the same mixed powder as in Comparison +fl, molding and sintering.

Invention A8-9: These are samples in which a sintered body containing 1% of the enstatite powder of Invention Shrine 2 was impregnated with lead.

The radial crushing strength, machinability, and wear resistance of these samples at high temperatures were measured.

The radial crushing strength is a value measured at a temperature of 400°C.

In addition, machinability was measured by cutting the outer edge of the sample using a lathe with a cutting allowance of 0.
The cutting resistance value (principal force) when cutting was performed at 5 mm, one feed Q, and 1 mm was measured, and expressed as an index with comparison month 1 as 100.

Wear resistance was determined by cutting each sample according to the specified valve seat method, mounting it on a simulated engine test machine, setting the temperature of the valve seat at 400°C with LPG combustion, and after continuous operation for 30 hours. Expressed as valve seat wear amount.

This testing machine is a JfifM model whose camshaft is driven by a motor, and the temperature, number of rotations, valve spring pressure, etc. can be set arbitrarily, and severe tests can be conducted in a short period of time.

The above measurement results for each sample are shown in the table.

As is clear from this result, comparative months 1 to 6 show the effect of lead, and machinability improves as the lead base increases.
Radial crushing strength and wear resistance are reduced.

Therefore, it can be seen from the radial crushing strength and abrasion test that the lead content is preferably 3% or less.

Comparative materials 7 to 8 and invention materials 1 to 3 show the effect of addition of enstatite powder (♀), and as the amount of enstatite powder added increases, machinability becomes better.

Further, the wear resistance is best when the content is 1 to 2%, but it tends to deteriorate when the content is 3%, and the radial crushing strength is further decreased.

From this, enstatite improves machinability and wear resistance with specific gold, but addition lowers the density of group H and reduces radial crushing strength, and if too much is added, This indicates that wear resistance also deteriorates.

Comparative hole 9 shows the effect of the amount of forsterite powder added, and has inferior machinability compared to enstatite.

Inventive material 4 is a case where enstatite and forsterite coexist, and it can be seen that the machinability is improved.

Invention materials 5 to 7 show the effects of boron nitride and manganese sulfide, and it is clear that boron nitride is particularly effective in improving machinability (1-), and manganese sulfide is particularly effective in improving wear resistance (1-). Ru.

Inventive materials 8 to 9 have good machinability, but are slightly inferior in radial crushing strength and wear resistance because they contain lead.

<Effects of the Invention> As explained above, the sintered alloy for valve seats according to the present invention has Ni and Mo added to strengthen the base, Co added to improve high-temperature hardness, and CO Addition of hard particles of the alloy to reduce abrasion wear, and magnesila metasilicate T and minerals to the grain boundaries.

By creating an alloy structure in which a specific combination of magnesium orthosilicate minerals, boron nitride, manganese sulfide, etc. are dispersed in a predetermined amount, an internal combustion engine with high f-1 strength under high temperatures and good machinability is achieved. A sintered alloy for engine valve seats can be obtained.

Furthermore, since it is relatively stable against heat and does not undergo dehydration and decomposition during sintering, it has the advantage that it can be manufactured at low cost by ordinary sintering means. .

Patent applicant Hitachi Powder Metallurgy Co., Ltd. Nissan Motor Co., Ltd

Claims (1)

[Claims] 1. The overall composition is C0.4-1.2% by weight, Ni0.
3-2.9%, Cr0.3-2.3%, Mo1.7-9
．． 8%, Co 8-22%, Si 0.1-0.7%, lubricant 0.5-2% and Fe remainder, and C 0.6-1.
2%, Ni0.5-3%, Mo0.5-3%, Co5.
7-9% Cr in the base of 5-7.5% and the remainder Fe;
26-30% Mo, 1.5-2.5% Si, 5-25% hard phase with the remainder of Co, and 0.5-2% lubricant at grain boundaries.
has a dispersed structure, and the lubricating substance is composed of at least one of a magnesium metasilicate mineral, a magnesium metasilicate mineral and a magnesium orthosilicate mineral, or a magnesium metasilicate mineral or a magnesium orthosilicate mineral. A sintered alloy for a valve seat, characterized in that at least one of boron nitride and manganese sulfide is dispersed therein. 2. The overall composition is C0.4-1.2% by weight, Ni0.
3-2.9%, Cr0.3-2.3%, Mo1.7-9
．． 8%, Co8-22%, Si0.1-0.7%, Pb
3% or less, lubricating substance 0.5-2% and Fe remainder, and C0.6-1.2%, Ni0.5-3%, Mo0.5-
3%, Co5.5-7.5% and Fe balance base,
Cr7-9%, Mo26-30%, Si1.5-2.5
It exhibits a structure in which the hard phase of % and Co balance is 5 to 25%, Pb is 3% or less in the grain boundaries or pores, and 0.5 to 2% of the lubricating substance is dispersed in the grain boundaries. A magnesium metasilicate mineral, a magnesium metasilicate mineral and a magnesium orthosilicate mineral, or at least one magnesium metasilicate mineral or a magnesium orthosilicate mineral and at least one of boron nitride or manganese sulfide are dispersed. A sintered alloy for valve seats that is characterized by: 3. The magnesium metasilicate mineral powder is at least one of enstatite powder, clinoenstatite powder, enstenite powder, hyperstenite powder, etc., and the magnesium orthosilicate mineral powder is at least one of forsterite powder, chrysolite powder, etc. The sintered alloy for a valve seat according to claim 1 or 2, wherein the sintered alloy is of type 1.