JPH01182667A - Manufacture of piston ring - Google Patents

Abstract

PURPOSE:To improve abrasion resistance and fatigue strength by forming starting material into such one that compactifies medium-high carbon content metal powder made up of a powder metallurgy process, in the manufacture of a piston ring, which forms a billet into a wire rod by plastic working and, after being refined, performs its bending. CONSTITUTION:Medium-high carbon content metal powder is, in general, manufactured by a water atomizing process, and it is compactified by a hot hydrostatic press and, after obtaining a billet, it is applied to hot working and cold working and finished into a wire rod. If this medium-high carbon metal powder is used for a starting material, an eutectiv carbide is very small and dispersed uniformly so that hot workability is remarkably improved and simultaneously any flaw due to the cold working is conspicuously restrained from occurring, and thus it largely conduces to the shortening of work routing and improvement in ring bending workability. If a piston ring is manufactured from this medium- high carbon content metal powder, a uniform, fine hard carbide can be formed, so that abrasion resistance and fatigue strength both are sharply improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of manufacturing piston rings used in internal combustion engines such as automobile engines, with the main purpose of maintaining airtightness of the combustion chamber. be.

[Conventional technology]

In the development process of piston rings for automobile engines, etc., for the purpose of weight reduction, there was a shift from cast iron rings to steel rings made by a melting process that allowed for thinner walls.
1-22131, Special Publication No. 57-8302, Special Publication No. 58-
46542. Many materials have been proposed, such as Japanese Patent Publication No. 61-21302.

Recently, the requirements for piston rings have become even more strict due to the increased power output associated with the spread of diesel engines and turbochargers.As a countermeasure to this problem, a ring that slides on the cylinder is used as a way to improve wear resistance and seizure resistance. Attempts have been made to spray metal or ceramic on the outer periphery, or to use composite plating in which hard particles are dispersed.

[Problem that the invention seeks to solve]

Piston rings are important parts of internal combustion engines, and improvements in their seizure resistance, wear resistance, mechanical properties, etc. directly lead to higher engine performance, so compared to conventional steel piston rings, Materials with higher properties are desired. For this purpose, it is effective to strengthen the base and generate hard carbides, and high carbon and high alloying is effective for such materials. However, in the conventional melting method, the eutectic carbides that crystallize during the solidification process of ingots cannot be sufficiently refined during the subsequent plastic working, resulting in large carbides or stringer-like carbides in the base material of the product. This results in the formation of micro-segregation, which not only makes it difficult to exhibit the required characteristics as a piston ring, but also makes it impossible to perform cold working or even hot working, especially in the case of high carbon content.

In addition, the wire rod produced by plastic working has a final HRC of approximately HRC38~
After quenching and tempering to a hardness of 45, it is cold bent into a ring shape, but there are no giant carbides or stringers in the base material.
If a large amount of carbides are present, there is a problem of breakage during bending, and as a special example, there is a case where warm bending is performed as previously proposed by the applicant of the present application (Japanese Patent Application No. 175,670/1982). However, even if attempts are made to strengthen the matrix and increase the amount of hard carbides for the purpose of further improving the performance of piston rings, there is a limit to how high carbon high alloy steel manufactured by ingot manufacturing can avoid the above problems.

On the other hand, if a surface treatment such as ceramic spraying or composite plating that disperses hard particles is applied to the outer periphery of the ring that slides on the cylinder as described above, not only will the inner surface of the cylinder become more abrasive, but the surface treatment It has the disadvantage that layer separation and cracks occur, causing fatigue failure of the ring material.

In order to solve these problems, the present invention has developed a method for manufacturing piston rings that has excellent wear resistance and fatigue strength by uniformly and finely dispersing hard carbides in a strong base, and is also effective in plastic working and bending workability. The goal is to provide the following.

[Means for solving problems]

The present invention has been made in order to solve such problems, and is a piston ring manufacturing method in which a wire rod is made by plastic working, tempered, and then bent. This is a method of manufacturing a piston ring characterized in that it is made of compacted carbon-containing metal powder.

In the present invention, the medium-high carbon-containing metal powder may be general-purpose die steel or high-speed tool steel, but it can also be applied to high-carbon, high-alloy systems that cannot be plastically worked using conventional melting methods. Can be done.

These medium-high carbon-containing metal powders are generally manufactured by water atomization or gas atomization, and after being consolidated by hot isostatic pressing (hereinafter referred to as HIP) to obtain a billet, hot working and cold working are performed. It is finished into a wire rod by applying

One of the objects of the present invention is to improve the plastic workability of such medium-high carbon content metals. According to the conventional melting method, the huge eutectic carbides present in the ingot significantly impair hot workability, and also become a source of flaws during cold working, reducing the area reduction rate per pass. Due to the necessity and low throughput limits, annealing treatments often had to be carried out. On the other hand, when the medium-high carbon content metal powder of the present invention is used as a starting material, the eutectic carbides are extremely small and uniformly dispersed, so hot workability is significantly improved and the occurrence of flaws due to cold working is significantly reduced. It was found that this greatly contributed to shortening the work process and improving the bending workability of the ring. Furthermore, the powder method of the present invention has made it possible to manufacture wire rods from high carbon-containing metals that could not be processed using conventional melting methods.

The second purpose of the present invention is to improve the characteristics of piston rings, and when piston rings are manufactured from metal powder containing medium to high carbon, they produce more uniform, fine, hard, Since carbides can be formed, wear resistance and fatigue strength can be significantly improved.

〔Example〕

The following description will be given based on examples of the present invention.

Ingots were obtained from die steel, high speed tool steel, and high Cr Ill having the chemical compositions shown in Table 1 by a powder method or an ingot method.

For sample work to sample 3, powdered steel was obtained by gas atomization and then consolidated by HIP to create an ingot.

HIP treatment is performed at a heating temperature of 1160°C and 1000 atm.
The test was carried out under the condition of holding for a certain period of time. In order to obtain sufficient compaction, the heating temperature must be 1000° C. or higher, lower than the melting temperature of the material, and 500 atmospheres or higher.

Samples 4 to 6 were melted in the atmosphere in an electric furnace and cast to obtain ingots.

These ingots are hot-forged and then hot-rolled to
．． It was made into a 5nnφ coil. This coil was drawn and then cold rolled into a flat wire with cross-sectional dimensions of 3 mm (w) x 2 mm (1).

Table 2 shows the evaluation of the plastic working conditions in each manufacturing process for each sample.

In addition, a part of each sample finished into a flat wire was tempered to 11RC4.
2, the average elongation was measured and the results are also listed in Table 2.

Samples 1 to 3 shown in Table 1 are produced by the method of manufacturing from powder according to the present invention, and Samples 1 and 2 are high-speed tool steel and die steel containing high carbon that cannot be plastically worked. is a high Cr stainless steel that can be manufactured from melting.
US440B, and Samples 4 to 6 are general-purpose high-speed steel 5KH55 and die steel 5 made by ingots using conventional melting methods.
KDII and the comparative steel are high Cr stainless steel EUS440B corresponding to sample 3 of the powder method.

As shown in Table 2, sample 1 and sample 2 cannot be slugged using the normal melting method due to the huge eutectic carbide in the ingot, whereas in the case of the powder method, Because the eutectic carbide becomes ultra-fine, hot working is not only easy, but also exhibits the same or larger limit in cross-sectional area reduction in cold working compared to sample 4 and sample 5, which are ingots. I understand that.

In addition, when comparing 5US440B between the powder method and the melting method, sample 6 made by the melting method has a limit of area reduction in continuous wire drawing of about 40%, while sample 3 made by the powder method has a limit of about 60%. , indicating that it is highly effective in shortening the wire drawing work.

As mentioned above, when these flat wires are used as piston ring materials, they are generally tempered to a hardness of HRCa 8 to 45 and then subjected to bending, although this depends on the material selected. In order to further improve abrasion resistance, even higher hardness is required, but in terms of bending, higher hardness will cause problems such as breakage.
Currently, materials are used after being tempered to a much lower hardness than the original hardness of the material.

As shown in Table 2, the uniform elongation of the samples manufactured using the powder method of the present application and tempered is greater than that of the samples obtained from the melting method, so they are tempered to a higher hardness and then bent. This also makes it possible to contribute to improving the wear resistance of the piston ring.

A piston ring manufactured by the manufacturing method of the present invention is as follows.

In addition to being able to perform surface treatments such as plating and nitriding on sliding parts, which have traditionally been done, wear resistance and fatigue strength are further improved compared to piston rings manufactured from steel using conventional melting methods. This also allows for thinner walls.

〔Effect of the invention〕

When medium-high carbon content metal powder produced by the powder metallurgy method of the present invention is used as a starting material, it not only has excellent hot workability and cold workability that cannot be obtained with conventional melted steel piston rings, but also has excellent toughness. is significantly improved, so
The higher hardness makes bending easier, contributing to improvements in wear resistance and fatigue strength, and the high carbon and high alloy properties improve the required characteristics of piston rings, making it extremely useful industrially. It is something.

Claims (1)

[Scope of Claims] 1. A piston ring manufacturing method in which a wire rod is formed by plastic working, and the wire rod is heat-refined and then bent, in which the starting material is a compacted medium-high carbon-containing metal powder made by powder metallurgy. A method for manufacturing a piston ring, characterized by the following. 2. Medium-high carbon content metal powder is die steel, high speed tool steel,
The method for manufacturing a piston ring according to claim 1, wherein the piston ring is made of one or more types of high Cr steel.