JPH0647685B2 - Aluminum powder metallurgy sliding member and manufacturing method thereof - Google Patents

Description

The present invention relates to an aluminum powder metallurgy sliding member and a method for manufacturing the same, and in particular, aluminum powder metallurgy suitable for automobile pistons, valve lifters, cylinder liners, shift forks and the like. The present invention relates to a sliding member and a manufacturing method thereof.

[Conventional technology]

As a material for sliding members such as automobile valve lifters and pistons, aluminum alloys which are lightweight and have relatively high strength are generally used. In order to improve the wear resistance of this sliding member, it has been proposed to use a hypereutectic Si-Al alloy, which is particularly excellent in wear resistance, among aluminum alloys. Crystal Si-A
Cast with l alloy and ECM treatment only on the sliding surface (electro chemi
A method has been proposed in which the aluminum base material is removed by cal machining) to cause the primary crystal silicon to protrude, and then polishing is performed to further improve wear resistance (US Pat. No. 3,333,579).

By the way, the sliding member such as the cylinder liner according to the above-mentioned U.S. Pat. No. 3,333,579 is cast using a hypereutectic Si-Al alloy as a whole, so that it cannot be said to be sufficient in terms of strength and toughness. However, there is a problem that its application to parts that require high strength and high toughness is limited.

In addition, the aluminum base material wears out due to long-term use,
The primary crystal silicon may fall off and cause abnormal wear.

Therefore, it is conceivable to use a powder metallurgy aluminum alloy having advantages such as high strength, high toughness, and high heat resistance as compared with the cast aluminum alloy.

[Problems to be solved by the invention]

However, the sliding member made of a hypereutectic Si-Al alloy formed by hot working (a type of powder processing) such as hot extrusion has a dense structure and is superior in strength, toughness, and heat resistance to cast materials. , Grain size of primary silicon is several tens of μ in case of cast material
Since it is generally as small as 10 μm or less as compared with about m, there is a problem of poor wear resistance.

Further, since the hypereutectic Si-Al alloy sliding member formed by powder metallurgy has no oil pool, seizure does not occur when used in combination with similar materials or under severe operating conditions such as high surface pressure. There is a problem that it easily occurs.

Therefore, while taking advantage of the strength, toughness, and heat resistance of the hyper-eutectic Si-Al alloy powder metallurgy sliding member, wear resistance,
A device for improving the seizure resistance has been required.

[Means for solving problems]

The above problems are solved by the aluminum powder metallurgical sliding member and the manufacturing method thereof according to the present invention described below.

That is, the sliding member made of aluminum powder metallurgy according to the present invention is a hypereutectic Si-Al formed by powder metallurgy into a predetermined shape and having a base material layer having a primary crystal grain size of 1 μm to 8 μm.
A sliding member made of alloy powder metallurgy, wherein at least the sliding surface of this sliding member is 0.1 mm from the surface.
The grain size of primary silicon is 25 μm over the above depth.
It is characterized in that a sliding layer having a porosity of 2% to 30% is formed with a thickness of up to 100 μm. ...... First invention Further, the method for manufacturing an aluminum powder metallurgical sliding member of the present invention comprises forming a rough shaped material from a hypereutectic Si-Al alloy powder and partially degassing the rough shaped material. Performing or without degassing at all, after forming a sliding member of a predetermined shape in which the primary crystal grain size of the base material layer is 1 μm to 8 μm by hot working, at least on the sliding surface Irradiate with high density energy to re-melt, 0.1 ℃ / sec ～ 7.0 ℃ /
It is characterized by cooling at a rate of temperature decrease of 2 seconds. ......
Second Invention Hereinafter, the present invention will be described in more detail.

In the present invention, as a method for forming the hypereutectic Si-Al alloy powder using powder metallurgy, hot forming such as hot extrusion, hot drawing, and sintering forging can be used. By these methods, the hypereutectic Si-Al alloy powder is formed into a predetermined shape such as a cylinder liner, a valve lifter, and a piston.

In the first invention, the sliding layer is formed on at least the sliding surface of the sliding member over a depth of 0.1 mm or more.
Here, if the sliding layer is not less than 0.1 mm, sufficient wear resistance and seizure resistance cannot be obtained.

This sliding layer is provided with primary crystal silicon having a particle size of 25 μm to 100 μm and pores of 2% to 30%. Here, the grain size range of the primary crystal silicon is 25 μm to 100 μm.
The reason is that if it is less than 25 μm, sufficient abrasion resistance cannot be obtained, and if it exceeds 100 μm, the mating member may be damaged. The reason why the porosity is set to 2% to 30% is that if it is less than 2%, the oil storage effect is small and sufficient seizure resistance cannot be obtained.
This is because if it exceeds 30%, the strength becomes insufficient and damage may occur.

Further, the base material layer of this sliding member has a grain size of primary silicon of 1
It is formed with a thickness of 8 μm. Here, the particle size is 1 μm to 8 μ
The primary crystal silicon of m is fine silicon formed by the hot working described above, and obtains strength, toughness, and heat resistance.

In the second invention, the hypereutectic Si-Al alloy powder is molded into a rod-shaped or rectangular shape to obtain a rough-shaped material. Conventionally, degassing treatment is performed from this rough shape material, but in the case of the present invention, degassing treatment is not performed at all or partial degassing treatment is performed and then hot working is performed. A sliding member is obtained in which the primary crystal grain size of the base material layer is 1 μm to 8 μm. Next, at least the sliding surface of the sliding member formed into a predetermined shape is irradiated with high-density energy to form a remelted sliding layer. At this time, TIG arc as a high-density energy source,
A laser, a plasma arc, etc. can be used. In addition, the cooling rate of the sliding member after remelting was set to 0 in order to control the grain size of primary crystal silicon to 25 μm to 100 μm.
It is necessary to set the temperature to about 1 ° C / sec to 7 ° C / sec. Therefore, for example, when manufacturing a valve lifter as a sliding member, the remelting treatment is performed after heating the valve lifter to about 200 ° C.

[Action]

The aluminum powder metallurgical sliding member of the present invention has a grain size of primary crystal silicon of the sliding layer of 25 μm to 100 μm, which is about 3 to 100 times that of the conventional powder metallurgical sliding member. Wear resistance is greatly improved.

Further, since pores are formed in the sliding layer, these pores serve as oil reservoirs. Therefore, the seizure resistance is significantly improved. When the cast aluminum alloy of US Pat. No. 3,333,579 is used, oil pools are formed and seizure resistance is improved, but in the case of US Pat. No. 3,333,579, if the primary crystal silicon on the surface is worn On the other hand, in the case of the present invention, even if the surface is abraded and the pores as the oil pool disappear, new pores appear on the surface of the sliding layer, so that the oil pool can be kept good for a long period of time. Seizure resistance can be maintained.

Further, the primary crystal silicon and the pores having the above grain size are formed only in the sliding layer, and the other portion (base material layer) is hypereutectic Si-
Since the Al alloy powder is hot-worked as it is, the advantages of excellent strength, toughness, and heat resistance can be directly utilized as compared with the case of using cast aluminum.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

(First Example) Here, FIG. 1 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the first example of the present invention.

25% by weight% Si-3% Cu-0.5% Mg-balance Al
A gas atomized powder of a hypereutectic Si—Al alloy made of is preformed to form a rough shape material. Next, this crude material was formed into a rod-shaped member having a diameter of 40 mm by hot extrusion without degassing. The density ratio of this rod-shaped member was 99.8%, the grain size of primary crystal silicon was 1 μm to 8 μm, and the tensile strength was 35 kgf / mm ² .

This rod-shaped member was sliced into 10 mm thick pieces to prepare a plurality of sample pieces, and one end surface of each sample piece had a circular reference of φ23 mm, and an annular portion with a width of 10 mm was used as a high-density energy source.
Remelting treatment was performed using IG arc. At this time, T
In the IG remelting treatment, after heating the sample piece to 200 ° C.,
Average current: 150 using φ3.2mm tungsten electrode
A, feed rate: 1.5 mm / sec.

As a result, a sample piece A having an annular sliding layer (treatment layer) with a width of 10 mm and a depth of 3.8 mm centering on φ23 mm was obtained. In FIG. 1 showing the cross section of this sample piece A, 1 is primary crystal silicon, 2 is pores, 3 is a base material, a region is a remelted portion at a temperature above the liquidus, b is The region is the part where the temperature is between the eutectic and liquidus, and the region c is hypereutectic Si
-Al alloy powder metallurgical base material. The grain size of primary crystal silicon in the sliding layer of this sample piece A was 25 μm to 70 μm, and the porosity was 27%.

Second Example Here, FIG. 2 is a micrograph (× 100) showing the metallographic structure of the surface of the sliding layer of the sample obtained in the second example of the present invention.

The second embodiment is different from the first embodiment in that degassing is performed on the rough-shaped material by about 1/2 of complete degassing, and otherwise the same as in the first embodiment. To prepare a sample piece B which was remelted.

The particle size of the primary crystal silicon in the sliding layer of the sample piece B obtained as a result was the same as that in the first example, and the porosity was 7%.
In FIG. 2, black circles are pores.

(Third Embodiment) The third embodiment is different from the first embodiment in that degassing is performed on the rough material for about 3/4 of complete degassing, and the other is substantially the same. A sample C subjected to the remelting treatment was manufactured in the same manner as in Example 1.

The grain size of the primary crystal silicon in the sliding layer of the sample piece C obtained as a result was the same as that in the first example, and the porosity was 3%.

(First Comparative Example) Here, FIG. 3 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the first comparative example, and FIG. 4 is a schematic diagram of the sample obtained in the first comparative example. It is a micrograph (x100) which shows the metal structure of the sliding layer surface.

The difference between the first comparative example and the first example is that the rough profile is completely degassed and that the sliding surface is not remelted. A sample piece D was manufactured in the same manner as in the example.

The particle size of the primary crystal silicon of the sample piece D obtained as a result was 10 μm or less in all, as shown in FIGS. 3 and 4, and the porosity was about 0%.

Second Comparative Example Here, FIG. 5 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the second comparative example.

The second comparative example is different from the first embodiment in that the rod-shaped member is manufactured by casting instead of hot extrusion which is powder metallurgy, and the fifth embodiment is substantially the same as the first embodiment. A sample piece E shown in the figure was manufactured.

The particle size of the primary crystal silicon of the sample piece E obtained as a result is 1st
The porosity was almost 0% as in the example.

Third Comparative Example Here, FIG. 6 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the third comparative example.

The third comparative example is different from the second comparative example in that the cast rod-shaped member is sliced into a predetermined thickness and then the portion corresponding to the re-melted annular portion in the first embodiment is subjected to ECM treatment. The sample piece F shown in FIG. 6 was manufactured in substantially the same manner as in the second comparative example.

The particle size of the primary crystal silicon of the sample piece F obtained as a result is the second
It was the same as the comparative example, and the porosity was about 0%.

(Fourth Comparative Example) Here, FIG. 7 is a schematic configuration diagram schematically showing in the vicinity of a sliding layer of the sample obtained in the fourth comparative example, and FIG. 8 is a diagram of the sample obtained in the fourth comparative example. It is a micrograph (x100) which shows the metal structure of the sliding layer surface.

In the fourth comparative example, the point different from the first example is that the rough shape material was completely degassed, and the sample piece G was manufactured in substantially the same manner as in the first example.

The grain size of the primary crystal silicon of the sample piece G obtained as a result was substantially the same as that in the first example, as shown in FIGS. 7 and 8, and the porosity was approximately 0%.

(Evaluation Test) Each of the sample pieces A to G obtained in the above Examples and Comparative Examples was cut into a size of 30 mm × 30 mm × 5 mm to produce a wear test piece. Then, a seizure limit test was performed using these wear test pieces. At this time, SCr420 (JIS G4104) was carburized and quenched as a counterpart test piece and an aluminum alloy (JIS A
C2 B) cylindrical test pieces (both sizes are 20 mm in inner diameter, 25.6 mm in outer diameter, and 16 mm in length) were used, and the test conditions were set as follows by a mechanical testing laboratory type friction wear tester. .

Sliding speed: 2.4 m / sec Lubricating oil: Low viscosity oil Oil temperature: 60 ° C This seizure limit test increases the surface pressure by 12.5 kg / cm ² every 2 minutes up to 250 kg / cm ² It was carried out by measuring the surface pressure when attached.

The results of this seizure limit test are shown in Table 1.

However, the unit of seizure surface pressure is kg / cm ² .

From Table 1, in the test piece of this example, the base material remains a fine silicon structure which is advantageous in terms of strength and toughness, and only the surface layer has a silicon particle diameter excellent in wear resistance. ,
It can be seen that the seizure resistance is significantly improved as compared with the second comparative example and the fourth comparative example. It can be said that the improvement in seizure resistance also improves the wear resistance. Also,
It can be seen that with respect to the third comparative example, seizure resistance equal to or higher than that of the third comparative example is obtained in a state in which there is no risk of the silicon particles falling off. Furthermore, the effect of oil accumulation due to pores is
It can be seen that when the mating member is the same type of aluminum alloy, it appears remarkably.

Although the specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and includes various embodiments within the scope of the claims.

〔The invention's effect〕

As described above, the aluminum powder metallurgical sliding member and the manufacturing method thereof according to the present invention have the following effects.

(A) Since the primary crystal grain size of the sliding layer is large, the wear resistance is improved.

(B) Since the pores of the sliding layer function as oil reservoirs, seizure resistance is improved.

(C) Since the portion other than the sliding layer (base material layer) has a fine silicon structure, it has excellent strength, toughness, and heat resistance.

(D) An aluminum powder metallurgical sliding member can be manufactured without significantly changing the conventional method of manufacturing a powder metallurgical sliding member. Therefore, manufacturing can be performed relatively easily.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram schematically showing the vicinity of a sliding layer of the sample obtained in the first embodiment of the present invention, and FIG. 2 is a sliding layer of the sample obtained in the second embodiment of the present invention. A micrograph (× 100) showing the metal structure of the surface, FIG. 3 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the first comparative example, and FIG. 4 is obtained in the first comparative example. A micrograph (× 100) showing the metallographic structure of the sliding layer surface of the obtained sample, FIG. 5 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the second comparative example, FIG. Is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the third comparative example, and FIG. 7 is a schematic configuration diagram schematically showing the vicinity of the sliding layer of the sample obtained in the fourth comparative example. FIG. 8 is a micrograph (× 100) showing the metal structure of the surface of the sliding layer of the sample obtained in the fourth comparative example. 1 …… Primary crystal 2 …… Porosity 3 …… Base material

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-57-198237 (JP, A) JP-A-52-109415 (JP, A)

Claims (2)

[Claims] 1. A sliding member made of a hypereutectic Si-A alloy powder metallurgy formed into a predetermined shape by powder metallurgy and having a base material layer having a primary crystal grain size of 1 μm to 8 μm. At least the sliding surface of the moving member, 0.1mm from the surface
The grain size of primary silicon is 25 μm over the above depth.
A sliding member made of aluminum powder metallurgy, characterized in that a sliding layer having a porosity of 2% to 30% is formed with a thickness of -100 μm. 2. A raw material is formed from a hypereutectic Si-A alloy powder, and the raw material is partially degassed or is not degassed at all, and is subjected to hot working. After forming a sliding member having a predetermined shape in which the primary crystal grain size of the material layer is 1 μm to 8 μm, at least the sliding surface is irradiated with high-density energy to be remelted, and 0.1 ° C./sec. 7.0 ° C
A method for manufacturing a sliding member made of aluminum powder metallurgy, characterized in that the sliding member is cooled at a cooling rate of / sec.