JPH06346181A - Valve guide member made of fe-base sintered alloy excellent in wear resistance - Google Patents

Abstract

PURPOSE:To produce a valve guide member made of Fe-base sintered alloy, excellent in wear resistance. CONSTITUTION:The valve guide member for internal combustion engine is composed of an Fe-base sintered alloy having a composition consisting of, by weight, 1-4% C, 1.5-6% Cu, 0.1-0.8% P, 0.1-4% Cr, 0.05-2% Mo, and the balance Fe with inevitable impurities and further containing, if necessary, 0.2-4% Mn and 0.05-1% S and also having a structure in which hard Fe-C-P compound, carbide, and free graphite and further, if necessary, MnS are dispersed and distributed in a matrix composed essentially of pearlite. Moreover, the theoretical density ratio at the end on one side or at the ends on both sides is regulated to 87-97%, and further, the theoretical density ratio in the part on the other side or in the central part is regulated to 79-85%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe-based sintered alloy valve guide member for an internal combustion engine that exhibits excellent wear resistance.

[0002]

2. Description of the Related Art It is well known that many Fe-based sintered alloys have been conventionally applied to the manufacture of valve guide members for internal combustion engines.

[0003]

On the other hand, in recent years, the high output and high speed of internal combustion engines have been remarkable, and along with this,
The conditions of use of these structural members become even more severe, and especially for valve guide members that undergo severe sliding wear with the valve that is inserted into the center hole and reciprocates, the wear resistance is further improved. Although many conventional Fe-based sintered alloy valve guide members do not exhibit sufficient wear resistance to meet these requirements, the development of valve guide members that exhibit excellent wear resistance in a stable manner is required. Is desired.

[0004]

Therefore, the present inventors have
From the above viewpoints, as a result of research to develop a valve guide member made of an Fe-based sintered alloy having excellent wear resistance, the valve guide member of an internal combustion engine is expressed in weight% (hereinafter,
% Represents% by weight), C: 1 to 4%, Cu:
1.5-6%, P: 0.1-0.8%, Cr: 0.1
.About.4%, Mo: 0.05-2%, and, if necessary, Mn: 0.2-4%, S: 0.05-1.
%, With the balance consisting of Fe and unavoidable impurities, and a base body mainly composed of pearlite, and hard Fe.
Fe-based sintered alloy having a structure in which a C—P compound, a carbide, and free graphite are dispersed and distributed, and when Mn and S are additionally contained, manganese sulfide (hereinafter referred to as MnS) is dispersed and distributed. And one side end portion or both side end portions, preferably one side end portion (that is, only the valve seat side), 1/5 to 5% of the total length
1/2, 1/5 to 1 of the total length for both ends
/ 3 length has a theoretical density ratio of 87-97%, and the other side or center has a low theoretical density ratio of 79-85%. Then, the resulting Fe-based sintered alloy valve guide member has a hardness due to the hard Fe—C—P-based compound and carbide dispersed in the base material and the high density portion formed at one end or both ends. The improvement, free graphite that is also dispersed in the matrix, and the improvement of self-lubricating property by MnS, and the improvement of the oil retention effect by the low density part formed on the other side part or the center part are combined. We obtained the results of research that demonstrated excellent wear resistance in practical use.

The present invention has been made based on the above-mentioned research results. C: 1 to 4%, C
u: 1.5-6%, P: 0.1-0.8%, Cr:
0.1 to 4%, Mo: 0.05 to 2%, and, if necessary, Mn: 0.2 to 4%, S: 0.0
5 to 1%, the balance consisting of Fe and unavoidable impurities, and a matrix mainly composed of pearlite, fine Fe-C-P-based compounds, carbides, and free graphite, and optionally MnS. Fe having a dispersed distribution of
It is made of a base sintered alloy and has a theoretical density ratio of 87 to 97% at one end or both ends and a theoretical density ratio of the other side or central part of 79 to 85%, which is excellent in wear resistance. It is characterized by the valve guide member.

Next, the reason why the composition and the theoretical density ratio of the Fe-based sintered alloy constituting the valve guide member of the present invention are limited as described above will be explained. A. Composition (a) In the CC component, pearlite of the base material is formed and strengthened, and a hard Fe-CP compound and a carbide are formed to improve hardness, and also as free graphite. It has a function of improving the self-lubricating property by being distributed to the base material, and thus improving the wear resistance of the member, but if its content is less than 1%, the desired improving effect on the above function cannot be obtained, while its content When it exceeds 4%, the content becomes brittle and the desired strength cannot be obtained. Therefore, the content is defined as 1 to 4%.

(B) Cu The Cu component has a function of forming a solid solution in the matrix to strengthen it and stabilize the pearlite matrix, but if the content thereof is less than 1.5%, it is desirable for the above-mentioned effect. However, even if the content exceeds 6%, no further improvement effect is obtained due to the above-mentioned action, and rather the material becomes brittle, so the content is 1.5-6. Defined as%.

(C) The P P component not only improves the sinterability and contributes to the strength improvement, but also has the action of forming a Fe--C--P compound as described above to improve the wear resistance. , Its content is 0.1
If the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 0.8%, the base material is excessively hardened and coarse Fe-C-P compounds tend to precipitate. Since the machinability is significantly deteriorated, its content is set to 0.1
It was set at 0.8%.

(D) Cr The Cr component has the function of forming a solid solution in the matrix to improve the heat resistance and also forming a carbide to improve the hardness.
If the content is less than 0.1%, the desired improvement effect on the above-mentioned action cannot be obtained, while if the content exceeds 4%, the toughness is rapidly reduced, so the content is set to 0.
It was set at 1 to 4%.

(E) Mo Mo The Mo component is solid-solved in the base material to strengthen it, and
Although it has an effect of forming carbides to improve hardness, if the content is less than 0.05%, the desired improving effect on the above function cannot be obtained, while if the content exceeds 2%, machinability is increased. The content of 0.05-
It was set at 2%.

(F) Mn and S Both of these components are present mainly as MnS dispersedly distributed in the base material to enhance self-lubricating property, thereby contributing to the improvement of wear resistance of the member and the action of improving machinability. However, if the content of Mn is less than 0.2% and the content of S is less than 0.05%, a slight solid solution in the matrix is unavoidable. Of less than 0.2%, the desired effect cannot be obtained in the above-mentioned action, while the content of each is Mn: 4%.
If the content of S and S exceeds 1%, the distribution ratio of MnS becomes too large, and as a result, the strength of the member decreases. Therefore, the content of Mn is 0.2 to 4% and S:
It was set at 0.05 to 1%.

B. Theoretical Density Ratio By increasing the density of one end or both ends of the valve guide member, the hardness of this part is further increased, while at the same time, the oil-retaining effect is sufficiently exhibited in the low-density part, and therefore the wear resistance is improved. Although it is possible to contribute to the improvement, if the theoretical density ratio of the high density portion is less than 87%, sufficient hardness cannot be improved. On the other hand, in order to increase it to more than 97%, the compacting pressure of the green compact is increased. It is necessary to increase the sintering temperature as well as the sintering temperature, which shortens the service life of the molding die and reduces the dimensional accuracy after sintering. When the ratio is less than 79%, the strength of the valve guide member decreases, and cracks are likely to occur during press-fitting and mounting to the cylinder head, while when the theoretical density ratio exceeds 85%, the desired oil retaining effect is obtained. Is not possible and wear progress is promoted. Therefore, the theoretical density ratio of the high density portion is 87 to 97% and that of the low density portion is 79%.
~ 85%.

[0013]

EXAMPLES Next, the valve guide member of the present invention will be specifically described by way of examples. As raw material powder, particle size:-
80mesh Fe powder, same-150mesh carbon powder, same-
Cu powder of 100 mesh, Fe-27% of -150 mesh
P alloy powder, Cu-8% P alloy powder of the same -200 mesh,
All of them have a particle size of -100 mesh and various atomized Fe-Cr- with various contents of Cr and Mo.
Mo alloy powder and MnS powder with the same -150 mesh were prepared, and these raw material powders were blended in a predetermined blending ratio to obtain 1%.
Zinc stearate of No. 1 was added and mixed in a V-type mixer for 30 minutes, and then these mixed powders were placed in the center hole of the die 1 and downward in the center hole as shown in the schematic longitudinal sectional view in FIG. The upper surface of the lower punch 2 fitted from above, and the lower punch 2
In the case of inserting into the cavity formed by the outer peripheral surface of the core rod 3 inserted into the die 1 through the center hole of, and then forming a high density portion at one end, As shown, while adjusting the pressure within the range of 5 to 7 ton / cm ² and adjusting the stroke, the upper punch 4 is pressed into the center hole of the die 1 and high density parts are formed at both ends. In this case, the lower punch 2 is fixed, the upper punch 4, the die 1 and the core rod 3 are adjusted while adjusting the pressure and stroke as shown in FIG.
Each with a predetermined stroke to lower the powder compact S,
S'is press-molded, and these green compacts are degreased by holding them at a temperature of 650 ° C for 20 minutes in an atmosphere of decomposition gas of natural gas, and then heated to a predetermined temperature within a range of 1050 to 1150 ° C. And hold at this temperature for 60 minutes to sinter,
While having the composition of components shown in Tables 1 and 2 by performing a finishing process after sintering, a hard Fe-C-P-based compound, a carbide, and free graphite are dispersed and distributed in a matrix mainly composed of pearlite, If necessary, in addition to this, add M
It is composed of a Fe-based sintered alloy having a structure in which nS is dispersed and distributed, and one end portion or both end portions has a theoretical density ratio shown in Tables 3 and 4, and further, length: 50 mm x outer diameter: 1
2 mm × inner diameter: Fe-based sintered alloy valve guide member of the present invention having a size of 6.6 mm (hereinafter, referred to as the present invention sintered bubble guide) 1 to 17 and containing any one of alloy constituents Comparative Fe-based sintered alloy valve guide members (hereinafter referred to as comparative sintered valve guides) 1 to 7 whose amounts, or theoretical density ratios at one end or both ends, were out of the range of the present invention were manufactured. .

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

Then, the various sintered valve guides obtained as a result are press-fitted by locating the high density portion on the valve seat side on the exhaust side of the Al cast cylinder head of a 2000 cc DOHC engine. Then, using the unleaded gasoline as the fuel with the finished inner diameter, the actual machine test was conducted at 400 rpm for 6 hours, and the inner diameter at the inner surface position of 5 mm from the edge on the valve seat side. Was measured, and the change in inner diameter after the test with respect to the inner diameter before the test was measured as the wear amount. The results of these measurements are shown in Tables 3 and 4.

[0019]

From the results shown in Tables 1 to 4, the sintered valve guides 1 to 17 of the present invention all show excellent wear resistance in spite of extremely high speed continuous operation for a long time. As can be seen in Comparative Sintered Valve Guides 1 to 7, if any of the component composition and the theoretical density ratio of the Fe-based sintered alloy constituting the same is out of the range of the present invention, the desired excellent resistance can be obtained. It is clear that the wear resistance cannot be ensured. As described above, Fe of the present invention
A valve guide member made of a base sintered alloy exhibits excellent wear resistance even when used under severe conditions, and has characteristics capable of sufficiently responding to high performance and high speed of an internal combustion engine.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing a press forming process of a green compact.

Claims (4)

[Claims] 1. By weight%, C: 1-4%, Cu: 1.5-6%, P: 0.1-0.8%, Cr: 0.1-4%, Mo: 0.05 Fe having a composition in which a hard Fe—C—P-based compound, a carbide, and free graphite are dispersed and distributed in a base material mainly containing pearlite Fe group having excellent wear resistance, which is made of a base sintered alloy and has a theoretical density ratio of one end portion of 87 to 97% and a theoretical density ratio of the other end portion of 79 to 85%. Sintered alloy valve guide member. 2. By weight%, C: 1 to 4%, Cu: 1.5 to 6%, P: 0.1 to 0.8%, Cr: 0.1 to 4%, Mo: 0.05. Fe having a composition in which a hard Fe—C—P-based compound, a carbide, and free graphite are dispersed and distributed in a base material mainly containing pearlite Made of a base sintered alloy, and the theoretical density ratio of both end portions is 87 to 97%,
A valve guide member made of an Fe-based sintered alloy having excellent wear resistance, characterized in that the theoretical density ratio of the central portion is 79 to 85%. 3. By weight%, C: 1 to 4%, Cu: 1.5 to 6%, P: 0.1 to 0.8%, Cr: 0.1 to 4%, Mo: 0.05. ˜2%, Mn: 0.2 to 4%, S: 0.05 to 1%, and the balance of Fe and unavoidable impurities, and a base material mainly composed of pearlite. , A hard Fe-C-P-based compound, a carbide, free graphite, and a Fe-based sintered alloy having a structure in which manganese sulfide is dispersed and distributed, and the theoretical density ratio of one side end is 87 to 97%, A Fe-based sintered alloy valve guide member having excellent wear resistance, characterized in that the theoretical density ratio of the other side portion is 79 to 85%. 4. By weight%, C: 1-4%, Cu: 1.5-6%, P: 0.1-8%, Cr: 0.1-4%, Mo: 0.05-2. %, And further, Mn: 0.2 to 4%, S: 0.05 to 1%, and the balance consisting of Fe and inevitable impurities, and a base body mainly composed of pearlite, Fe-C-P-based compound, carbide, free graphite, and Fe-based sintered alloy having a structure in which manganese sulfide is dispersed and distributed, and the theoretical density ratio of both end portions is 87 to 97%, A valve guide member made of an Fe-based sintered alloy having excellent wear resistance, which has a theoretical density ratio of 79 to 85%.