JPS6144152A - Manufacture of wear resistant sintered alloy - Google Patents

Abstract

PURPOSE:To obtain the titled alloy in which wear of opposing material is decreased even in high surface pressure, by arranging a Cu infiltration material on the surface of a prescribed shape body obtained by molding powder mixture of Cr, C and >=one kind of P, Si, B, and heating said body to liquid phase generating temp. or above and m.p. of Cu infiltration material or above. CONSTITUTION:Fe base alloy powder contg. Cr and powder contg. >=one kind of P, Si, B are mixed to prepare the powder mixture contg. by weight, 0.1-4%, especially 0.1-2% of >=one kind of P, Si, B, 1-20%, especially 1-3% Cr. Next, said mixture is molded to a prescribed shape, then Cu infiltration material is arranged on the surface of said molded body generally by <=about 20% thereof. Said body under the state is heated to liquid phase generating temp. (about 950 deg.C) or above and Cu m.p. (about 1,070 deg.C) or above. In the sintered alloy obtd. as the result, wear of opposing material is decreased even in usage requiring wear resistance under high surface pressure such as rocker arm tip, distortion or harmful strain, etc. of sintered parts are less due to small size variation ratio during sintering.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing wear-resistant sintered alloys. The present invention relates to a method for manufacturing a sintered alloy used in applications requiring excellent wear resistance, such as sliding members such as tips of engine lower car arms.

(Prior art) Conventionally, sliding members such as rocker arms for internal combustion engines have high C.
It was made of cast steel, alloyed cast iron, etc. At this time, since the wear resistance and scuff resistance of high Cr cast steel materials themselves are insufficient, the sliding surfaces are hardened by quenching, chilling, carburizing, etc. to add wear resistance and scuff resistance. .

Furthermore, in recent years, emphasis has been placed on reducing the weight of internal combustion engines.
Aluminum rocker arms are manufactured instead of cast steel, cast iron, etc. However, aluminum does not have the wear resistance required for the cam contact part of a rocker arm, and on the other hand, with the high loads and high output of internal combustion engines in recent years, even conventional cast steel and cast iron materials have less wear resistance in the cam contact part. Since the wear resistance is insufficient, only the cam contact part of the aluminum rocker arm is made of high-density sintered material with excellent wear resistance and scuff resistance. A composite rocker arm that is fixed to the casting is manufactured.

Here, the high-density sintered material includes P and B in iron-based powder.

It is easy to generate a liquid phase by adding and mixing powders such as Si and C, and the generation of a liquid phase during sintering can significantly reduce the pores of the sintered body, and further add Cr and Mo as necessary.

It is a sintered material that has excellent wear resistance, scuff resistance, and pitting resistance by forming carbides such as (2) in the sintered body. Such sintered materials are, for example,
It is described in Japanese Patent Application Laid-Open No. 58-210103. However, since conventional high-density sintered materials generate a liquid phase to increase their density, they have a disadvantage that they have a larger dimensional change rate than general in-phase sintered materials, making it difficult to achieve dimensional accuracy. In addition, if Cr, etc. added for the purpose of improving wear resistance, etc., is added in a small amount, carbide precipitation will be small and the wear resistance will not be sufficient.If it is added in a large amount, the wear resistance of the material itself will be affected, but it will not be used in the other material! ? A tendency to increase wear and tear appears. In addition, in a member that operates a valve, such as a rocker arm, if the wear of the mating material increases, the valve opening/closing timing will be out of order, which is extremely undesirable, especially in recent high-performance engines such as 3-valve or 4-valve engines.

(Problems to be Solved by the Invention) When sliding members used in conventional rocker arms, rocker arm tips, vanes, etc. are manufactured by the liquid phase sintering method, the rate of dimensional change becomes large, so the accuracy of the member is become insufficient. As a result, the rocker arm requires modification to match the valve opening/closing timing, and because the wear resistance of the rocker arm and the mating material are poor, the valve opening/closing cycle is interrupted during engine use. I had a problem with it going crazy. In addition, in the case of vanes, the seal between the housing and the vanes becomes insufficient, resulting in problems such as a decrease in compressor performance.

As a result of research on conventional liquid phase sintering methods, the present inventors found that in conventional methods, it is difficult to select additive components for generating a liquid phase, control the sintering temperature, and ultimately the amount of liquid phase generated.
We focused on the fact that when the amount of liquid phase generated is small, pores remain and the desired hardness and density cannot be obtained, and when the amount of liquid phase generated is too large, there are problems such as distortion of the shape of the product.

The present invention was made to eliminate the above-mentioned drawbacks of the prior art, and its goals are: (1) to improve the wear resistance and scuff resistance of the wear-resistant member itself; To provide a method for producing a wear-resistant sintered alloy that not only reduces wear of the mating material, but also improves dimensional accuracy after sintering by reducing the rate of dimensional change. It is in.

(Means for solving the problem - Part 1) As a result of various experiments, the present inventors have found that the conventional high-density sintered material (liquid phase sintered material) can be used under appropriate conditions. By infiltrating Cu into the material, a material that achieves the above objective was created.

The present invention uses Fe-based alloy powder containing Cr, P, and Si.
, B, and a powder containing one or more of Tilt or more, and one or more of P, Si, and B is 0
．． 1 to 4% by weight, 1 to 20% by weight of Cr, and 1 to 3% of C
A mixed powder having a heavy weight is prepared, the mixed powder is molded into a predetermined shape, a copper infiltration material is placed on the surface of the molded product, and the temperature is higher than the liquid phase generation temperature of the molded product and copper is infiltrated. It is characterized by heating the infiltrating material to a melting temperature of 78 or higher.

Next, the reasons for the limitations of the present invention will be described. P, B, and Si are necessary in the same way as conventional liquid phase sintering materials to generate a liquid phase in the molded body and densify the sintered body, but P, B, and S
If the total amount of one or more types of i is less than 0.1%, the amount of liquid phase generated is small, and if it exceeds 4%, the amount of liquid phase generated is excessive, and the pores infiltrated with Cu are Since the amount is insufficient and the rate of dimensional change becomes large, the desired sintered body cannot be obtained. The preferred amounts of P, B, and Si are 2% or less. Cr forms a solid solution in the matrix of the sintered alloy and combines with C to form Cr carbide, improving hardness and wear resistance. If it is less than 1%, the amount of carbide produced is small and hardness and desired properties are improved. We cannot wait for 1υ1 to improve wear resistance. On the other hand, even if the amount of Cr exceeds 20%, the degree of improvement in the wear resistance of the sintered alloy is small and the cost of the sintered alloy increases, so the amount of Cr added is set at 1 to 20%. In addition, in the present invention, since the development of old carbides of Cr is hindered by Cu that invades into the molded body as the U'L bond progresses, it is possible to use as much as 20% Cr.

C binds Cr to form carbide, but if it is less than 1%, the amount of carbide precipitated is small and desired hardness and wear resistance cannot be obtained.

Moreover, if C is added in excess of 3%, the carbide becomes coarse and the material becomes concave, which increases the wear of the mating material, which is not preferable, so the C content is limited to 1 to 3%.

Note that Cr and C can be added together as ferrochrome separately from the Fe-based alloy powder, or by incorporating a predetermined amount of Cr into the Fe-based alloy and adding the insufficient amount of C as graphite. It is.

By the way, is it made of copper? 88 immersion is determined by the pores (2) of the green compact, and is therefore not an essential requirement in the present invention. However, the copper infiltration rate is about 20% or less compared to the voids in the generally obtained green compact.

The heating temperature of the molded body must be higher than its liquid phase generation temperature and copper? 8
The temperature above the melting temperature of the immersion material is due to liquid phase sintering and 1.
This is because copper infiltration is performed in both cases by heat treatment twice.

(Function) In the present invention, although it is not fully elucidated metallurgically, solid phase sintering occurs during the process in which the molded body is heated to the temperature at which the liquid phase occurs. It is thought that the skeleton is sufficiently strengthened, and then, in the process of generating and crystallizing a liquid phase, the infiltrant Cu is melted and penetrates into the sintered body that is being sintered. . According to one typical sintering process, the maximum heating temperature is 1070~
When the temperature is 1100'C, a liquid phase is generated in the molded body at about 950°C, and the liquid phase crystallizes between about 950-960°C. On the other hand, from about 1070°C to copper? 8 Soaking begins.

Further, the liquid phase is thought to have a eutectic composition such as Fe-P-C1, and Cr is enriched in this liquid phase to precipitate Cr carbide, thereby improving i1f wear resistance. Due to the generation and crystallization of such a liquid phase, the pores within the skeleton are partially filled by the liquid phase and the powder particles are further bound by the crystals.

The copper further penetrates into the remaining pores and further binds the 4'I) non-particles. Here, it is believed that the liquid phase preferentially fills the small pores, while the copper fills the large pores.

According to the present invention, melt conditioning force <? In order to transmit light, and unlike conventional liquid phase sintered materials, the dimensional change rate of the molded body is high.

(Means for solving the problem - Part 2) In the present invention, in addition to the addition or containing component of one or more of P, Si, B and Cr, one or more of Mo, V and Ni is added to the Fe group. It may be added or contained in the dressing. Among these added components, Mo and V, in particular, form carbides together with Cr and also improve top hardenability, which is useful for strengthening the matrix. Also, N
i dissolves in the matrix and improves hardenability.

In addition, in the present invention, the dimensional change rate of the molded body after sintering is 3
At least one heel of P, Si, and B should be within 0.8%.
~1.2%, sintering temperature 1120-1150°C2 Holding time at sintering temperature 2O-1IO minutes, average boundary from room temperature to sintering temperature 11! ! Preferably, the rate is 5-8°C/min.

In addition, if the cooling after sintering is performed rapidly, the matrix of the sintered alloy becomes martensite, which is desirable for wear resistance when the mating material is a hard material such as ceramic, chilled cast iron, quenched cast iron, or quenched steel. A bonded metal can be obtained from a bond having properties. On the other hand, if cooling after sintering is performed by slow cooling, martensite becomes pearlite, and desired wear resistance can be obtained when the mating material is VIM cast iron, SP1, or a nonferrous metal with a uniform ratio of soft material.

(Example) As the Cr-containing powder, 60% Cr-containing ferrochrome was used, and as the P, B, and Si-containing powders, ferroalloys containing 26% P, to% B, and 75% Si were used, and A mixed powder having the composition shown in Table 1 was prepared using the following. 6ton/crA of this mixed powder
It was compression molded at a pressure of On top of this, Cu-Fe-Mn-Zn based infiltration material was placed at 17% by weight based on the molding weight, and after being heated at 930°C for 30 minutes in ammonia decomposition gas, the temperature was 100-1150°C. The temperature was raised to °C and held for 30 minutes. Further, the sintered body was air cooled from a temperature of 950°C.

As a comparative material, 8 rounds of sintered material without immersion were produced.

From the above table, it can be seen that according to the present invention, the dimensional change rate is extremely small.

FIG. 1A and FIG. 1B show the microscopic structures of the present invention material and No. 6. The magnification of Figure 1A and Figure 1B is 100 each.
and 400 times.

In FIGS. 1A and 1B, the white phase is chromium carbide, the gray phase is infiltration cavities, and the black phase is martensite matrix. From these figures, it can be seen that in the alloy of the present invention, the bore is infiltrated and disappeared with copper, resulting in not only an 8II dense alloy, but also less wear on the mating material.

On the other hand, it can be seen that the chromium carbide is more finely and uniformly dispersed than the copper phase. Such chromium carbide has a remarkable effect on improving wear resistance, and also causes less wear on the mating material.

Each of the above alloys and chrome-plated (hardness Hv950) cast iron were subjected to wear tests under the following conditions.

Test engine - Water-cooled in-line 4-cylinder OHC diesel l
Engine Engine speed - 100 Orpm Oil temperature - 60°C 1rx1 'fft Oil - 130 diesel engine oil (degraded oil) Test time - 508r Compatible material - C3,24yo (ffiiff 1%, same below) Si 1.96% Mo 0.66%, PO, 03%
, Cr 0.45%, NiO, 46%, CuO037
A camshaft made of cast iron with a hardness of HRC49-55 by chilling the sliding surface with the test material mouth 7 car arm arm knob with a chilled metal.

The test results are shown in Fig. 2.As shown in Fig. 2, the liquid phase sintered materials (failures 1 to 4), which are conventional parts, are particularly difficult to use when the Cr content exceeds 5% (N12.4). There is a lot of wear and tear. In addition, the cam wear of the Cr metal plate (5) is also significant. In contrast, the material of the present invention not only has excellent wear resistance, but also
It is clear that cam wear is also reduced. In the product of the present invention, cam wear does not increase even when CO exceeds 5%.

(Effects) The material of the present invention has the advantage of reducing wear on mating materials, not only in ronocar armches and knobs, but also in applications that require wear resistance under high surface pressure.

Furthermore, since the material of the present invention has a small dimensional change rate during sintering, there is less distortion or harmful distortion of sintered parts.

[Brief explanation of the drawing]

FIGS. 1A and 1B are metallurgical micrographs of the sintered alloy according to the present invention magnified 100 times and 400 times, respectively. FIG. 2 is a graph showing the results of the wear resistance test.

Claims (1)

[Claims] 1. Mixing Fe-based alloy powder containing Cr and powder containing one or more of P, Si, and B,
0.1 to 4% by weight of one or more of P, Si, and B
A mixed powder containing 1 to 20% by weight of Cr and 1 to 3% by weight of C is prepared, this mixed powder is molded into a predetermined shape, and a copper infiltration material is placed on the surface of the obtained molded body. and a method for producing a high-density, wear-resistant sintered alloy, which comprises heating the molded body to a temperature higher than the liquid phase generation temperature and higher than the melting temperature of the copper infiltrant.