JP2553664B2 - High temperature wear resistant iron-based sintered alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to a sintered alloy having high wear resistance, which is mainly developed for studying an internal combustion engine.

<< Conventional Technology >> The operating conditions of automobile engines are becoming more and more severe. In a diesel engine valve seat, since the surface pressure applied to the seat surface is high and the temperature is as high as 400 to 550 ° C, strength and wear resistance which are not easily deformed even at high temperatures are required.

The present applicant has also developed a high-temperature wear-resistant sintered alloy intended for such applications, and has already disclosed it in JP-A-62-10245.

This alloy has C0.6-1.2%, Ni0.5-3%, Mo0.5-3
%, Co5.5-7.5% and Fe balance in the base, Si1.5-2.5
%, Cr7 to 9%, Mo26 to 30%, and Co residual hard phase; or Si4 to 12%, Mo33 to 36%, and Co residual hard phase either 5 to 25%. is there.

Further, the performance is improved by densifying the sintered alloy, quenching and tempering, or infiltrating lead into the pores.

<Problems to be solved by the invention> By the way, the above-mentioned lead-containing sintered material was excellent in wear resistance and strength at high temperatures as compared with the conventional example, but with the increase in output of the engine that continues thereafter, There is a problem that the valve seat is exposed to a temperature of 400 to 550 ℃, which exceeds the melting point of lead, and due to high compression, lead does not work effectively.

An object of the present invention is to develop a sintered alloy having wear resistance at a temperature of 400 ° C. or higher by making improvements based on the conventional iron-based sintered alloy.

<< Means for Solving the Problems >> The present invention is based on conventional experience in designing materials, and strengthens the matrix by dispersing a hard phase composed of an intermetallic compound in the matrix of the heat-resistant alloy steel, and also has a high degree of oxidation resistance. The aim was to create a structure in which materials were dispersed to prevent wear and abrasion.

That is, C0.6-1.2%, Ni0.5-3%, Mo0.5-3
%, Co5.5-7.5%, and Fe balance in the base, Si1.5-
2.5%, Cr7-9%, Mo26-30%, and hard phase of the balance Co, or Si4-12%, Mo33-36%, and hard phase of the balance Co, or both, total 5-25% dispersion In addition, a Cu alloy phase containing 30 to 50% of Pb exhibits a structure in which 10 to 20% of the Cu alloy phase is dispersed, and the sintered alloy is characterized by achieving the initial object.

<< Action >> In the structure of the present invention, the matrix is a basic element responsible for strength and wear resistance, the hard phase has the function of strengthening the matrix and improving the wear resistance at high temperatures, and the Cu-Pb alloy phase is mainly used. It is responsible for improving thermal conductivity, material strength, and lubrication.

First, in the base, Ni and Mo mainly contribute to the improvement of strength, but if less than 0.5% is insufficient, while if added in an amount of 3% or more, the effect is small for the cost. Further, if Mo is used excessively, the oxidation resistance decreases. If Co is less than 5.5%, the high temperature hardness is insufficient and wear tends to occur. On the other hand, if Co is more than 7.5%, the raw material powder becomes hard and compression molding becomes difficult. 0.6 to 1.2% is suitable for C in terms of control of the sintering process and stable quality.

When blending these components, it is conceivable to blend plain ones, but it is preferable to use iron alloy powder containing all components other than carbon. As a result, a desired alloy can be obtained in which segregation at the time of compounding is prevented and the mutual diffusion of the matrix and the hard phase is small.

Commercially available ternary or quaternary intermetallic compounds are suitable for the hard phase. That is, it is a Co-based heat-resistant alloy whose composition is Si
Two types are 1.5 to 2.5%, Cr7 to 9%, Mo26 to 30% and Co balance, or Si4 to 12%, Mo33 to 36%, and Co balance. The composition ranges of these are specified in the manufacturer's standards.

Either one of the above hard phases is used, or a mixture of both is used.

When the hard phase is added to the matrix material, the radial crushing strength decreases as the content increases, but the wear resistance sharply improves up to a content of 5%, then slowly increases around 20%, and hardly changes thereafter. . Therefore, the content of the hard phase has a lower limit of 5% in order to avoid variations in abrasion resistance, is most preferably about 15%, and has an upper limit of 25% at which practical strength is acceptable.

Next, when the Cu—Pb alloy phase is dispersed in the mottled structure, the high temperature wear resistance is significantly improved. Cu has good oxidation resistance and thermal conductivity at high temperatures, and a part of it forms a solid solution in the matrix to increase the material strength and improve heat dissipation. Pb acts as a solid lubricant and prevents cohesive wear.

Cu and Pb are added in the form of Kelmet alloy. When the Pb content of the Cu-Pb alloy is up to 30%, the high temperature wear resistance rapidly improves,
30 to 50% Pb is the best, and when it exceeds 50%, the wear amount approaches 100% Pb. In addition, the material strength is highest in the case of Cu alone, becomes slower up to 50% Pb, and drops sharply above that. Therefore, the composition of Pb 30 to 50% -Cu residue was selected. On the other hand Cu
If the content of the -Pb alloy phase is less than 10% or more than 20% in both strength and wear resistance, the properties become poor.

When the above composition is represented by the overall composition, the first invention using the hard phase containing Cr has C0.3 to 1%, Si0.06 to 0.56%, and Cr0.
3-2%, Ni0.3-2.6%, Mo1.4-8.8%, Co6.5-20%,
Cu5-14%, Pb3-10%, and the balance of Fe, the second invention using a Cr-free hard phase is C0.3-1%, Si0.16-
2.7%, Ni0.3-2.6%, Mo1.7-10%, Co6.3-19%, Cu5
-14%, Pb3-10%, and the balance of Fe, and the third invention using both hard phases is C0.3-1%, Si0.0
6-2.7%, Cr2% or less, Ni0.3-2.6%, Mo1.4-10%,
Co 6.3 to 20%, Cu 5 to 14%, Pb 3 to 10%, and the balance of Fe.

<< Example >> First, an alloy powder having a composition in which carbon is removed from the composition of the base,
That is, prepare an atomized alloy iron powder with a particle size of 100% mesh or less containing 1.5% Ni, 1.5% Mo, and 6.5% Co as the main raw material, and for the hard material to be dispersed in the matrix Mo28%, Cr8 %, Si2% and Co62% intermetallic compound powders were prepared.

The sample was prepared by adding 15 parts of intermetallic compound powder to the above alloy iron powder.
%, Graphite powder 1% and zinc stearate as a lubricant 0.
After mixing 8% and molding into various shapes with various densities of 6.4 to 7.0 g / cm ³ , the temperature is 1200 in an ammonia decomposition gas furnace.
Sintering was performed at 20 ° C. for 20 minutes.

Next, pure copper and various Kelmet materials of 30% Pb, 50% Pb and 70% Pb were prepared, placed on sintered bodies of various densities, and infiltrated at 1140 ° C in the same furnace. Also, a sample impregnated with lead at a temperature of 550 ° C. and 8 atm was prepared in the same manner as the conventional material.

The radial crushing strength of each sample thus obtained at a temperature of 500 ° C. was measured. The results are shown in FIG.

This graph has been rewritten into contour lines at every 5% content based on the results of quantitative analysis of various infiltrant components of the sample whose strength was measured.

Looking at the type of material, it drops sharply when Pb exceeds 50%. Further, the content of 10 to 20% shows high strength.

Next, the amount of wear of the valve seat by each sample was compared using the simulated engine tester. This tester is a mechanism that drives the cam shaft with a motor while heating the valve and valve seat to a predetermined temperature with LPG combustion gas.The temperature, rotation speed, spring pressure of the valve, etc. can be set arbitrarily, and it can be severe in a short time. Various tests can be performed. The valve material is heat resistant steel 21-4N.

With this tester, set the valve seat temperature to 500 ° C and rotate at 520 rpm.
The result of continuous operation at 0 rpm for 50 hours is shown in FIG. The content of the infiltrated material is represented by contour lines as in the case of FIG.

The wear of the Cu alloy containing 30 to 50% Pb is less than that of pure copper. The content shows the same tendency as in the case of radial crushing strength.

Next, FIG. 3 shows the test results when the temperature of the valve seat is changed by the above simulated engine tester.

The conventional material in the figure is a sintered body with a density of 6.9 g / cm ³ impregnated with lead. The first invention material (1) has the same sintered body with a Pb content of 50.
% Of Kelmet is infiltrated with 15% of the total composition.
The second invention material (2) is the one in which the kind of the intermetallic compound powder which becomes the hard phase in the production of the sample is replaced by the alloy powder of Mo34%, Si7% and 59% Co, and the density is 6.9 g / cm. ^This is a sample in which Kelkemet of 30% Pb was infiltrated into the sintered body of No. 3 by 15% in the total composition. In addition, the third invention material (3) is a density produced by adding two kinds of intermetallic compound powders in 7.5% by 15% for each convenience.
30% Pb kelmet in 6.9g / cm ³ combustor
% Infiltrated sample.

As is clear from the figure, each of the inventive materials according to the present invention shows good results at both normal temperature and 550 ° C.

<Effect> As described in detail above, the material according to the present invention exhibits excellent body wear properties from a low temperature to a high temperature. The effect can be obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the mechanical properties of a sintered alloy containing the invented material according to the present invention at high temperature, and FIG. 2 is a graph showing the relationship between the additive and the wear amount of a Cu—Pb alloy by a simulated engine tester. FIG. 3 is a graph showing the relationship between the valve seat temperature and the wear amount by the simulated engine tester.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Ikenoue 3-26-3 Tokiwadai, Matsudo City, Chiba Prefecture (72) Inventor Tokoma Aoki 727-25 Minamimasuo, Kashiwa City, Chiba Prefecture (56) Reference Japanese Patent Laid-Open No. Sho 62 -10244 (JP, A) JP 61-179857 (JP, A) JP 60-215748 (JP, A) JP 61-19766 (JP, A) JP 55-36242 (JP, B2) )

Claims (3)

(57) [Claims] 1. The total composition by weight ratio is C 0.3-1%, Si 0.06-0.56%, Cr 0.3-2%, Ni 0.3-2.6%, Mo 1.4-8.8%, Co 6.5- 20%, Cu5-14%, Pb3-10%, and Fe balance, and C0.6-1.2%, Ni0.5-3%, Mo0.5-3%, Co5.5-7.5%, and Fe balance Si 1.5-2.5%, Cr 7-9%, Mo 26-30%, and Co residual hard phase 5-25% are dispersed in the matrix,
Furthermore, a high temperature wear-resistant iron-based sintered alloy having a structure in which a Cu alloy phase containing 30 to 50% Pb is dispersed in 10 to 20%. 2. The weight ratio of the entire composition is C 0.3-1%, Si 0.16-2.7%, Ni 0.3-2.6%, Mo 1.7-10%, Co 6.3-19%, Cu 5-14% , Pb3-10%, and the balance of Fe, and C0.6-1.2%, Ni0.5-3%, Mo0.5-3%, Co5.5-7.5%, and Si4-12% in the base of the balance of Fe. , Mo33-36%, and the remaining hard phase of Co is 5-25% dispersed, and Pb30
A high-temperature wear-resistant iron-based sintered alloy having a structure in which a Cu alloy phase containing -50% is dispersed in 10-20%. 3. The weight ratio of the entire composition is C 0.3 to 1%, Si 0.06 to 2.7%, Cr 2% or less, Ni 0.3 to 2.6%, Mo 1.4 to 10%, Co 6.3 to 20%, Cu5 to 14%, Pb3 to 10%, and the balance of Fe, and C 0.6 to 1.2%, Ni 0.5 to 3%, Mo 0.5 to 3%, Co 5.5 to 7.5%, and the balance of Fe in the base. Si1.5-2.5%, Cr7-9%, Mo26-30% and hard phase of Co balance and Si4-12%, Mo33-3
Disperse 5 to 25% of the hard phase in the balance of 6 and Co.
A high-temperature wear-resistant iron-based sintered alloy having a structure in which a Cu alloy phase containing -50% is dispersed in 10-20%.