JPS61291954A - Sintering material having wear resistance and corrosion resistance at high temperature and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a sintering material particularly improved in wear resistance at high temp. by allowing hard grains A of steel having a prescribed composition to be dispersedly retained in a specific weight ratio by a steel matrix B having a composition other than of the above steel and also to exist in the matrix B in a state unentered into solid solution. CONSTITUTION:The hard gains A consisting of, by weight, 1.1-3.95% C, 2.0-8.0% Cr, 20.0-35.0% (W+2Mo), 1.0-8.0% V and the balance essentially Fe are retained dispersedly by the matrix B consisting of, by weight, 0.3-2.5% C, 0.1-2.0% Si, 0.1-1.0% Mn, 2.5-14.0% Cr, 0.3-3.0 Mo, 0.5-1.5% V, 0.3-5.0% Ni and the balance essentially Fe. Further, as essential requirements, the hard grains A are dispersedly retained by the matrix B in the ratio satisfying (hard grains A)/(hard grains A + matrix B)(weight ratio)=5.0-25.0 and are allowed to exist in the state unentered into solid solution in the matrix B. The resulting sintering material material excellent in resistance to corrosion and wear at high temp. can be most suitably used for valve seats which is used under severe service conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-temperature wear-resistant and corrosion-resistant sintered material particularly suitable as a material for valve seats of internal combustion engines, and a method for producing the same.

[Conventional technology]

In recent years, there has been an increasing demand for high performance not only for unleaded gasoline but also for internal combustion engines, and as a result, the conditions required for valve seats are becoming increasingly severe.

Regarding the material of the valve seat, Cr-Mo cast iron is used for the intake side of gasoline engines, and 5KD1 is used for diesel engines.
In recent years, most of the materials have been made into sintered alloys, except for the use of high grade ingot materials.

A wide variety of sintered alloy materials have been developed for this purpose, but they can be roughly divided into approximately 2% Ni by weight.
A material in which 10-15% of C-Cr-W-Go alloy powder, usually called stellite, is dispersed as hard particles in a Fe matrix containing 1.2% of C (Japanese Patent Publication No. 57-45298)
), based on the same idea, a material in which Fe-Mo particles are dispersed (
JI
Materials in which powder particles of a component equivalent to S 5KH9 are dispersed (Japanese Patent Publication No. 55-29142), materials in which Ni-Mo particles are dispersed (Japanese Patent Publication No. 58-10460), materials in which high carbon Cr alloys are dispersed (Japanese Patent Publication No. 52-43167), etc. There is a group of materials represented by

These materials are provided with corrosion resistance and heat resistance by appropriately adding NLCo, Cr, MO, etc. to the base metal.

Abrasion resistance is basically obtained by dispersing hard particles. However, with regard to wear resistance, dispersion of hard particles alone is not necessarily sufficient, and many methods have been disclosed in which an interfacial lubricant is added.

For example, by impregnating PB into the residual pores (Special Publication Publication No. 55-36
242), adding low melting point glass (Japanese Patent Publication No. 55-30
063).

It has been proposed to disperse sulfides (Japanese Patent Publication No. 58-18342), and to improve oxidation resistance by appropriately oxidizing the remaining pores in addition to adding these lubricating substances.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a material with particularly improved high-temperature wear resistance among these materials.

[Means to solve the problem]

In the present invention, in weight ratio, C1,1-3,95%, Cr
2.0-8.0%, W+2Mo 20. (1-35.
0%, V 1.0-8.0%, Go 1°0-15.0
%, the balance is Fe and the hard particles A consisting of unavoidable impurities are
By weight, CO, 3-2.5%, Si 0.1-2.0
%, Mn 0.1-1.0%, Cr 2.5-14.
0%, Mo 0.3-3.0%.

The weight ratio of hard particles A to substrate B is 5.0 to 25. A high-temperature wear-resistant and corrosion-resistant sintered material characterized by being dispersed and maintained at a ratio of 0% and existing in a substantially unsolid solution state in the substrate B, and the raw materials that will become the hard particles A and the substrate B, This is a method for producing a high-temperature wear-resistant and corrosion-resistant sintered material, which is characterized in that the pre-alloyed powder materials are mixed in the above proportions, pressure-molded, and then sintered at 1100°C or higher. . In addition, in order to provide further wear resistance, p
B or Pb gold alloy or Cu or Cu alloy is infiltrated.

[Effect]

In the present invention, the hard particles A contain a large amount of carbide having high heat resistance and high hardness, and provide high temperature wear resistance. In addition, substrate B itself has strength and toughness.

It has excellent oxidation resistance and heat resistance, and firmly holds hard particles A. In particular, when A and B are obtained from prealloyed powder materials, high-temperature wear resistance is improved due to the microstructure effect during powder production.

The reason for limiting each alloy component of A and B will be described below.

First, regarding A particles, C is an element essential for forming carbides with high heat resistance and high hardness by combining with carbide forming elements. This C and each carbide forming element Cr, W, Mo, V
Between, Ctheo=0, 06 Cr+0.03
3W+0.063Mo+0.2V (7) It is desirable that the relationship holds true. This is because C combines with carbide-forming elements and Cr2. Cs, Fe4V/zC or W, C,
It defines the amount of C required to stoichiometrically generate carbides such as Fe4Mo2C, MozC, v4c, etc.

Difference between Ctheo and actual C content (Cact), C
When act-Ctheo is +0.4 or more, the hard particles become brittle and crack and fall off more often under repeated impact stress.
Conversely, if it is -0,4 or less, the hardness tends to decrease and the effect of imparting wear resistance tends to be insufficient.

Or is an element necessary to maintain the corrosion resistance and hardenability of hard particles A. If it is less than 2.0%, these properties will be insufficient, but if it is added in excess of 8.0%, These properties improvement effects are small and have no industrial significance.

The amount of W + 2 Mo added is an important factor that determines the amount of M and C type carbides produced, and this carbide has Hv130
It has a hardness of 0 to 2300 and provides wear resistance.

The absolute value of the hardness of carbide is determined by the ratio of W/(2Mo), and the larger the W/(2Mo) ratio, the higher the hardness of the carbide particles. Usually, this ratio is set to 0.5 to 0.9, and Hv1
It is desirable to set it as the range of 500-2000.

When W + 2 Mo is less than 20%, the amount of carbides produced is insufficient and the effect of imparting wear resistance is reduced, and when it exceeds 35%, the amount of carbides produced is excessive and embrittlement becomes severe.

■ is Hv250 (very hard v4C1 from 1 to 3200)
Or it is an element that produces VC carbide and has a large effect of imparting wear resistance. If ■ is less than 1%, this effect is small and 8%
Exceeding this will impair grindability and increase wear on valves, etc., which are contacting materials.

CO mainly dissolves in solid solution in the matrix of hard particles A to improve heat resistance and oxidation resistance, and some CO dissolves in solid solution in matrix particles B during sintering to improve the heat resistance and oxidation resistance of the particles. improve. Go
If it is less than 1%, these effects will be insufficient, and if it exceeds 15%, no effect commensurate with the amount added will be obtained.

Hard particles A containing the above elements are prepared in the form of pre-alloyed powder, uniformly mixed with the substrate B described below in a weight ratio of 5 to 25%, and sintered, and substantially remaining after sintering. They are present in the material in the form of particles and act primarily as wear resistance imparting particles. If the proportion of hard particles A is less than brocade, the wear resistance will decrease, and if it exceeds 25%, embrittlement will increase.

Next, the substrate material B basically needs to have a coefficient of thermal expansion similar to that of the cylinder head, and this value should be set to 12 to 15.
X 10-'', thereby preventing combustion gas from blowing through. Furthermore, this material is required to have strength, toughness, oxidation resistance, heat resistance, etc.

The substrate material of the material of the present invention contains 2.5 to 14.0% Cr.
The matrix contains M, C3, M2. C, type primary Cr
It has a structure in which carbides are dispersed. If water atomized or gas atomized powder is used as the material for the substrate B layer, the primary carbides will be extremely finely dispersed within each grain, providing toughness. This substrate material B has a heat-treated condition of lRc35 to 50
It has hardness, wear resistance, heat resistance, and particularly toughness, and firmly holds hard particles, improving overall wear resistance retention.

If C is less than 0.3%, the hardness after heat treatment decreases, and 2
．． If it exceeds 5%, it will cause embrittlement.

Si is effective in improving oxidation resistance and is added as a deoxidizing agent for molten metal in an amount of 0.1% or more. If it is added in excess of 2.0%, the sinterability will deteriorate, making it unsuitable for use as a sintered material.

Mn is added as a deoxidizing agent for molten metal and as an auxiliary element for hardenability, and is added in an amount of 0.1%, but in the substrate material of the present invention containing Cr, it is added in an amount exceeding 1.0%. That doesn't make much sense.

As mentioned above, Cr is effective in imparting hardenability, and also improves heat resistance and corrosion resistance. If Cr is less than 0.5%, hardenability and corrosion resistance deteriorate, and if it exceeds 14.0%, machinability decreases.

Mo has a great effect on improving heat resistance. If it is less than 0.3%, this effect will be small, and if it exceeds 3.0%, no effect commensurate with the amount added will be obtained.

(2) Forms hard carbides and is effective in improving wear resistance. If it is less than 0.5%, this effect is small, and ■.

If the content exceeds brocade, the sinterability will decrease, similar to the above-mentioned Si.

Ni has a large effect of improving oxidation resistance. If it is less than 0.3%, this effect will be low, and if it exceeds 5.0%, the transformation temperature will decrease and the stiffness will also decrease.

Next, in the method of the present invention, the sintering temperature is 1100°C or higher. In the method of the present invention, a prealloyed powder is used as the A powder. The B powder does not necessarily need to be a prealloyed powder, but if it is atomized from a molten metal whose composition has been adjusted, a powder with a relatively coarse particle size can be used. As the powder B, it is desirable to use an irregularly shaped powder with excellent moldability. The average particle size of the A powder is preferably -60 mesh, and the B powder is preferably -100 mesh if prealloyed by atomization.

The present invention will be explained in detail in Examples below.

(Example) The powders used were produced by water atomization of molten metals having the chemical components shown in Table 1, and all powders were sieved through a lOO mesh sieve.

Table 1 (%1t%) Example 1 Using the A1 and B1 powders in Table 1, A1 powder was blended at 6.12.24% and 36%, respectively, and zinc stearate was added at 0.7% of the total. %, mixed in a V-type mixer, press-molded at a molding pressure of 6 tons/aiT, and sintered at 1170°C. Each sintered body has an approximate outer diameter of 4
The diameter was 4.5 mm, the inner diameter was 37.5 m, and the thickness was 7.5 m, which were almost constant, and the density ratio was also about 94%.

Table 2 A valve seat of a predetermined size was cut out from the test piece, and 1
After quenching at 000°C, tempering was performed at 550°C xih. This test piece was subjected to an engine mounting bench test and a radial crushing strength test. As for the engine.

'JP a Ji 2000cc knob easel engine, the test piece was used for the exhaust valve seat, 4000r,
Evaluation was made based on the amount of valve sinking after full load operation for 150 hours. In addition.

The bulb is made of Stellite N006 welded overlay. The results are shown in Table 2 as a comparative example, in which a powder having almost the same composition as powder B1 was sintered alone (sample No. 100
) and a cast material of the same composition (sample No. 110).

From Table 2, it can be seen that comparative example 100 has slightly improved radial crushing strength and abrasion resistance compared to 110, but the product of the present invention in which hard particles A are blended with comparative example 100 has a hard particle blend. As the ratio increases, the amount of sinking decreases rapidly.
It can be seen that the wear resistance is improved. However, sample No. 1
3 (36% ratio without Al powder).

Some chipping occurred. Sample No. 11 (A1 powder-free ratio: 12%) is considered to be the most excellent in terms of the balance between wear resistance and radial crushing strength.

Example 2 Using A1 powder and B2 powder in Table 1 above, Example 1
A similar test was conducted. The results are shown in Table 3 in comparison with Comparative Example 110 in Table 2 above.

In this example, the strength and toughness of the substrate were improved compared to Example 1.

In addition, in this example, sample No. 23 (Al powder non-blending ratio 3)
6%), some chipping occurred.

Table 3 Example 3 Using A2 powder and B2 powder in Table 1 above, Example 1
A similar test was conducted. The results are shown in Table 4 in comparison with Comparative Example 110 in Table 2 above.

As in Examples 1 and 2, the one in which 36% of hard particles were added caused chipping, but the others all showed good abrasion resistance and radial crushing strength.

Table 4 Example 4 Sample No. 21 produced in Example 2 was heated to 1150°C.
After sintering in vacuum and making the density ratio 86%, it was immersed in molten salt to infiltrate Pb and Cu into the pores.
A similar test was conducted.

Table 5 shows the test results. Infiltration of Pb and Cu had the effect of reducing the amount of wear by half.

As described above, the material of the present invention exhibits superior wear resistance and radial crushing strength as a material for valve seats compared to conventional materials, and no corrosion wear was observed even in the inspection of test pieces after the bench tests in Examples 1 to 4. There wasn't.

Table 5 The material of the present invention was developed as a material for valve seats, but it goes without saying that it can also be used as a material for high temperature wear and corrosion resistance.

〔Effect of the invention〕

As explained above, the material of the present invention is most suitable for valve seats used under severe conditions and is extremely useful industrially.

Claims (1)

[Claims] 1 By weight: C1.1-3.95% Cr2.0-8.0% W+2Mo20.0-35.0% V1.0-8.0% Co1.0-15.0 % The hard particles A consisting of the balance Fe and unavoidable impurities are: C0.3-2.5% Si0.1-2.0% Mn0.1-1.0% Cr2.5-14.0% Mo0 .3 to 3.0% V0.5 to 1.5% Ni 0.3 to 5.0% The balance is Fe and unavoidable impurities, and the weight ratio of the hard particles A to the substrate B is 5. 0-25.
A high-temperature wear-resistant and corrosion-resistant sintered material characterized in that it is dispersed and maintained at a ratio of 0% and exists in the substrate B in a substantially undissolved state. 2 Weight ratio: C1.1-3.95% Cr2.0-8.0% W+2Mo20.0-35.0% V1.0-8.0% Co1.0-15.0% Remaining Fe and unavoidable impurities The prealloyed hard particles A are composed of: C0.3-2.5% Si0.1-2.0% Mn0.1-1.0% Cr2.5-14.0% Mo0. 3 to 3.0% V0.5 to 1.5% Ni 0.3 to 5.0% The balance is Fe and unavoidable impurities, and the weight ratio of the hard particles A to the substrate B is 5.0. ~25.
It is dispersed and held at a ratio of 0%, exists in the substrate B in a substantially undissolved state, and is further infiltrated with an infiltrant material to impart wear resistance. High temperature wear and corrosion resistant sintered material. 3 The infiltrant is Pb or Pb alloy, or Cu or C
The high-temperature wear-resistant and corrosion-resistant sintered material according to claim 2, which is a u-alloy. 4 Weight ratio: C1.1-3.95% Cr2.0-8.0% W+2Mo20.0-35.0% V1.0-8.0% Co1.0-15.0% Remaining Fe and unavoidable impurities Prealloyed hard particles A consisting of: C0.3-2.5% Si0.1-2.0% Mn0.1-1.0% Cr2.5-14.0% Mo0. 3-3.0% V0.5-1.5% Ni 0.3-5.0% The balance is Fe and unavoidable impurities. , 5.0
A method for producing a high-temperature wear-resistant and corrosion-resistant sintered material, which comprises mixing the materials at a ratio of ~25.0%, press-forming, and then sintering at 1100°C or higher. 5 By weight, C1.1-3.95% Cr2.0-8.0% W+2Mo20.0-35.0% V1.0-8.0% Co1.0-15.0% The remainder Fe and inevitable impurities Prealloyed hard particles A consisting of: C0.3-2.5% Si0.1-2.0% Mn0.1-1.0% Cr2.5-14.0% Mo0. 3 to 3.0% V0.5 to 1.5% Ni 0.3 to 5.0% The balance is Fe and unavoidable impurities. , 5.0
A high-temperature wear-resistant product characterized by being mixed at a ratio of ~25.0%, press-formed, sintered at 1100°C or higher, and then further infiltrated with an infiltrant to provide wear resistance. Method for producing corrosion-resistant sintered material. 6 If the infiltrant is Pb or Pb alloy, or Cu or Cu
The high-temperature wear-resistant and corrosion-resistant sintered material according to claim 5, which is an alloy.