JP3187975B2 - Sintered alloy for sliding members with excellent scuffing and wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member for an internal combustion engine, in particular, a cam follower member or a compressor.
The present invention relates to an iron-based sintered alloy suitable for a material of a sliding member which slides under a high surface pressure such as a vane of a part and requires excellent scuffing resistance and wear resistance.

[Prior art]

At present, as the material for the tip of a cam follower member (tappet, rocker arm), the materials described in Japanese Patent Publication No. 1-40101 and Japanese Patent Publication No. 60-16101 are usually used. . In the case where the material of the camshaft, which is a mating member of these cam follower members, is chill cast iron, it has been put to practical use in a favorable situation. May be subjected to a surface treatment such as nitriding. On the other hand, when the mating camshaft is made of alloy steel,
Since the above-mentioned tip material has insufficient scuffing resistance, it is not actually applied to an alloy steel camshaft.

For this reason, as a tip material for a cam follower having a camshaft made of an alloy steel as a mating member, particularly when used in an engine for high surface pressure, for example, Japanese Patent Laid-Open No. 62-1
Although a cemented carbide as described in Japanese Patent No. 82407 is used, the production cost is high and there remains an economic problem.

JP-A-59-16952 discloses an iron-based sintered alloy suitable as a material for structural members of construction machines and mining machines exposed to earth and sand wear and mud sand wear. This publication states that the sintered alloy is Mo, W, Nb,
Contains 20% or less in total of Ti, V and Zr, and these elements partially form a solid solution in a matrix and partially form carbides to improve wear resistance. Is described as not being usable. However, there is no suggestion that the sintered alloy is used as a sliding member of an internal combustion engine or a sliding member of a compressor that slides under a high surface pressure.

[Problems to be solved by the invention]

The material of the present invention improves the scuffing resistance, wear resistance and toughness of conventional iron-based materials. For example, when it is used as a cam follower member, it can be applied to a mating camshaft of any material. It was made possible. Also, Japanese Patent Application Laid-Open No. 62-182407 currently used for high surface pressure engines using a cam shaft made of alloy steel.
The high cost is a major problem with the tappets described in Japanese Patent Application Laid-Open Publication No. H11-157, and the short life and low durability are problems with the cast iron tappets used in low surface pressure engines.

The present invention solves all of these problems. (1) The sintered alloy has a C content of 1.5 to 4.0% and a Cr content of 5.0.
１５15.0%, one or more elements selected from the group consisting of P, B and Si 0.1 to 5.0%, Ni,
One or more elements selected from the group consisting of Cu, Co and Mn 0.5 to 10.0%, W, Mo, N
b, Ti, V and Ta have a composition of 22.0 to 40.0% of one or more elements selected from the group consisting of Ta, the balance of Fe and unavoidable impurities, and a theoretical density of 90% or more. It has something.

(2) The sliding surface of the sintered alloy of (1) is super-finished, and the surface roughness is reduced to 0.3 μm by a polishing method.
mRz or less, as a result of lowering the friction coefficient during sliding,
The scuffing resistance is further improved. (3) The sliding surface of the sintered alloy of (2) is further subjected to steam treatment to form an oxide film on the sliding surface, thereby enhancing the initial lubricating action and further improving the scuffing resistance. It is a thing.

The steam treatment used in the present invention is a well-known steam treatment method described in, for example, Japanese Patent Publication No. 61-2739.
Treat with 0.3 to 0.8 kg / cm ² of superheated steam for 1 to 3 hours, and do not perform finishing after the steam treatment.

[0009]

Means for Solving the Problems Conventional iron-based sintered alloy members have a high hardness, in order to improve scuffing resistance.
M with high melting point and effective in scuffing (seizing) resistance
Elements that form C-type and M ₆ C-type carbides (W, Mo, N
b, Ti, V, Ta, etc.) to control the carbide precipitation form and the precipitation amount within a certain range.

[0010] According to this method, a plate-like and easily coarsened Fe
-Since the precipitation amount of the Cr composite carbide can be suppressed,
Compared to conventional iron-based sintered alloys, the resulting alloy has improved scuffing resistance and wear resistance by several steps, and can be combined with alloy steel camshafts that have not been adopted so far. It becomes.

Further, the scuffing resistance is improved by superfinishing the cam contact surface to 0.3 μmRz or less, and the scuffing resistance is further improved by performing a steam treatment thereon to form an oxide film. improves.

In the production of the sintered alloy of the present invention, a tip portion of a sliding member is formed, and this is attached to a predetermined portion of a base material of an alloy steel to form a base material (tappet, rocker).
(Sintering, diffusion bonding) or sintering only the chip separately, and then casting with a tappet, rocker arm and molten aluminum, or chip and tappet, rocker. The end product is obtained by brazing the arm.

[0013]

The reasons for limiting the numerical values of the respective alloy components in the composition of the sintered alloy of the present invention will be described below.

(A) C 1.5 to 4.0% by weight When the C content is less than 1.5% by weight, the amount of carbides generated is small, and scuffing resistance and wear resistance cannot be ensured. If it exceeds 4.0% by weight, the amount of carbide precipitation increases, which coarsens and increases the aggressiveness to the mating cam material, and the alloy becomes brittle.

(B) Cr 5.0-15.0% by weight The component forms a solid solution in the matrix, strengthens it, and combines with C to form an Fe, Cr composite carbide. This has the effect of improving the scuffing resistance and wear resistance of the alloy.

If the Cr content is less than 5.0% by weight, the total amount of carbides decreases and the scuffing resistance and abrasion resistance cannot be satisfied. Conversely, if the Cr content exceeds 15.0% by weight, the Fe-Cr composite carbide becomes coarse. And the concentration of matrix C decreases, so that the hardenability deteriorates.

(C) One or more of P, B and Si are dissolved in a matrix of 0.1 to 5.0% by weight to lower the melting point of the alloy, so that liquid phase sintering becomes easy. Further, there is an even action for densification of the obtained sintered body and stabilization of carbide formation. If the amount is less than 0.1% by weight, the above effect cannot be obtained. If the amount is more than 5.0% by weight, embrittlement of the alloy becomes remarkable.

(D) One or more of Ni, Cu, Co, and Mn 0.5 to 10.0% by weight These components strengthen the matrix and harden the matrix (to form martensite, Bainite). The content is determined as necessary, but the content is 0.5% by weight.
If it is less than 10% by weight, the above-mentioned effects cannot be obtained.

(E) One or more of W, Mo, Nb, Ti, V, and Ta 22.0-40.0% by weight These components are different from Cr in the M ₆ C type and the MC type. And has a higher melting point and a higher melting point than the Fe-Cr composite carbide, and is a fine-grained precipitate, so that it has the effect of further improving scuffing resistance and wear resistance. Further, it has a function of suppressing the coarse growth of the Fe—Cr composite carbide. If it is less than 22% by weight, M ₆ C type, MC
Since the amount of carbide of the mold is insufficient, the scuffing resistance is inferior. If it exceeds 40% by weight, the alloy is significantly embrittled and disadvantageous economically.

The iron-based sintered alloy of the present invention desirably has a theoretical density ratio of 90% or more. At a theoretical density ratio of less than 90%, the base strength decreases and the notch effect of large pores is reduced. This is because pitting wear is likely to occur.

The mating camshaft may be any of chill cast iron, hardened cast iron, hardened steel, and sintered alloy material as well as the above alloy materials, and can be used in combination with these.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Among the constituent elements in the sintered alloy of the present invention, C,
With respect to elements other than Ni, Cu and Co, atomized powder of alloy steel having a predetermined content is prepared, and a predetermined amount of C powder, Ni powder, Cu powder and Co powder are added thereto, and desired A blended powder was obtained. The mixed powder was obtained by mixing by adding 1.0% zinc stearate as a further lubricant powder blended to the composition shown in Table 1 were molded at a pressure of 5 ton / cm ^2,
A green compact was obtained.

[0023]

[Table 1]

This green compact is placed on a tappet-shaped base material (material: SCM415), and placed in a vacuum furnace at 1100 to 12
The temperature was kept at 00 ° C. for 45 minutes to complete the sintering. Thereafter, the sintered base material was carburized and quenched to harden the surface of the base material, and then processed and polished to designated dimensions to finish.

The tappets of the present invention are shown in Table 2 below.
A rig test was performed under the following conditions to evaluate scuffing resistance and wear resistance. Note that the cam surface roughness is 1.0 μm Rz of a general finish, and the roughness of the surface of the tappet material per cam is an important factor that affects the characteristics.
It was unified to mRz. On the other hand, in order to confirm the difference in tappet surface roughness and the effect of the steam treatment, 0.1% of the general finish was used.
8μmRz, super-finished 0.2μmRz
, And a tappet having a superfinished roughness of 0.2 μmRz and then subjected to steam treatment.
For the rig test, a cam tappet testing machine for a diesel in-line 6 cylinder was used.

[0026]

[Table 2]

The test results are shown in FIGS. In FIG. 1, the bar graph shows the scuffing load generated when the test was performed according to the scuffing resistance test method shown in Table 2 above. As is clear from FIG. 1, it can be understood that the sintered alloys D to K of the present invention have much better scuffing resistance than the conventional sintered alloys A to C.

FIG. 3 shows the results of a scuffing resistance test method carried out in the same manner as in FIG. 1 by using a test piece of the material D of the present invention in which the surface roughness and surface properties were changed, and the scuffing load at that time was measured. is there.

As is clear from FIG. 3, in the material D of the present invention, the test piece subjected to the general finish of 0.8 μm Rz is inferior in scuffing resistance to the test piece subjected to the super finish of 0.2 μm Rz. The effect of superfinishing is remarkable for improving the scuffing property. Further, it was confirmed that the test piece subjected to the steam treatment after the superfinishing of 0.2 μmRz was further improved in the scuffing resistance.

The bar graph on the right side in FIG. 2 shows the test results obtained by performing a wear test on the tappet manufactured from the sintered alloy according to the wear test method shown in Table 2, and shows the results of the sintered alloys DK of the present invention.
Resistance of tappets manufactured by the conventional sintered alloys A to C
It is understood that the tappet is very excellent as compared with the tappet manufactured in the above.

Further, the bar graph on the left side of FIG. 2 shows a camshaft formed when a camshaft made of S48C steel is induction-hardened as a mating member, and the tappets A to K are used in combination. Is the result of measurement of the wear amount of the camshaft. When the sintered alloy of the tappet that is the mating member of the camshaft is DK of the present application, the camshaft wear is extremely small, while the camshaft is connected to the conventional sintered joint. Gold A
It can be understood that the camshaft is greatly worn when the tappets made in -C are used in combination.

[0032]

As described above, when the sintered alloy of the present invention is used as a member that slides under a high surface pressure, it exhibits extremely excellent scuffing resistance and wear resistance. It is particularly suitable as a material for sliding members and compressor parts.

[Brief description of the drawings]

FIG. 1 shows a tappet manufactured by using the sintered alloy of the present invention and each of the conventional sintered alloys, and in a rig test in which the tappet is combined with a surface-hardened camshaft of S48C steel, a scuffing resistance of each sintered alloy is obtained. It is a bar graph which shows sex.

FIG. 2 is a bar graph showing a wear amount of each sintered alloy tappet and camshaft of each combination in the present invention.

FIG. 3 is a bar graph in which a rig test was performed in the same manner as in FIG. 1 using tappet test pieces of the material D of the present invention having different surface roughness and surface properties, and a scuffing load at that time was measured.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-277905 (JP, A) JP-A-1-212737 (JP, A) JP-A-62-5047 (JP, A) JP-A-61- 69946 (JP, A) JP-A-58-3951 (JP, A) JP-A-63-65056 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 C22C 38 / 18

Claims (3)

(57) [Claims] 1. 1.5 to 4.0% by weight of C, 5.0 to 1.0% of Cr
15.0% by weight, 0.1 to 5.0% by weight of one or more elements selected from the group consisting of P, B and Si,
1 selected from the group consisting of Ni, Cu, Co and Mn
Species or two or more elements 0.5-10.0% by weight, W,
It has a composition comprising 22.0 to 40.0% of one or more elements selected from the group consisting of Mo, Nb, Ti, V and Ta, the balance being Fe and inevitable impurities, and 9
A sintered alloy for sliding members with a theoretical density of 0% or more and excellent scuffing resistance and wear resistance. 2. The sintered alloy for a sliding member according to claim 1, wherein the surface roughness of the sliding surface of the sintered alloy for a sliding member is 0.3 μmRz or less. 3. The sintered alloy for a sliding member according to claim 2, wherein an oxide film is formed on a sliding surface of the sintered alloy for a sliding member by a steam treatment.