JPS6154103B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a piston ring material, and particularly to a pressure ring material suitable for application to a reciprocating internal combustion engine. In recent years, internal combustion engines have become more powerful and faster.
Increasingly, higher performance is required, and exhaust gas countermeasures must also be taken, and there is an increasing need for countermeasures to the problems of reduced horsepower and increased fuel consumption of internal combustion engines. Conventionally, cast iron pressure rings have been used as pressure rings for internal combustion engines, but it is difficult to manufacture pressure rings that are thin in the axial direction, resulting in relatively large cross-sectional areas and heavy weights, which result in large inertia. There is a problem in that it becomes easy to cause a fluttering phenomenon. In addition, cast iron pressure rings lack wear resistance and heat resistance, and cannot be installed close to the top of the piston, which is advantageous for exhaust gas countermeasures, and the spacing between pressure rings cannot be made small, which increases the weight of the piston. The problem was that it was heavy and could not be produced with high output or high speed. In an internal combustion engine, the pressure ring that maintains the airtightness of the combustion chamber has the greatest impact on its lifespan and performance, and the axial width of the pressure ring should be made as thin as possible while still ensuring sufficient airtightness. As a result, it has become a challenge to reduce the contact area with the cylinder wall to reduce friction loss, reduce the weight of the pressure ring itself, and further reduce the weight of the piston by reducing the distance between each pressure ring. Recently, in order to solve these problems, steel piston ring materials such as Si-Cr steel and 13Cr steel have begun to be used.Si-Cr steel is low-priced but has the heat resistance and fatigue resistance required for piston rings. ,
There is a problem with wear resistance, so the entire surface of the piston ring or the top and bottom three surfaces including the sliding surface are surface-treated before use. 13Cr steel has excellent heat resistance and wear resistance, is stronger than Si-Cr steel, and is used with surface treatment only on the sliding surface. The present invention solves the above-mentioned problems with cast iron pressure rings, and from the viewpoint of cost, we have created a pressure ring that is intermediate between Si-Cr steel and 13Cr steel.
In terms of properties, the material has performance similar to that of 13Cr steel, and provides a pressure ring material that can achieve high output and high speed for internal combustion engines while maintaining good airtightness, and is also easier to manufacture. It is. The pressure ring material according to the present invention will be described below. A partial sectional view of the internal combustion engine is shown in FIG. 1, a perspective view of the pressure ring is shown in FIG. 2, and a partial sectional view of the pressure ring is shown in FIG. 1 is a cylinder, 2 is a piston, 3 and 4 are pressure rings, 5 is an oil ring, 6 is an abutment gap, and 7 is a surface treatment layer. As a pressure ring, it has airtightness, wear resistance, seizure resistance,
Although it is necessary to have excellent breakage resistance, further improvements in these properties are required in order to increase the output and speed of internal combustion engines. In the present invention, in order to increase the rotational speed of the internal combustion engine without causing a fluttering phenomenon, and as a measure against exhaust gas and high output, the pressure ring is moved closer to the piston head and the weight of the piston is reduced. The material is stronger than the conventional steel ring material and the axial ring width is smaller than the conventional steel ring material.
It was developed keeping in mind that it is cheaper than 13Cr steel and has improved workability. That is, the present invention differs from conventional ordinary cast iron and special cast iron (ductile, malleable), as well as Si-Cr steel and 13Cr steel, as the material for the pressure ring, and the alloy composition is C0.4 to 0.7% by weight, Si0 .3~1.0
%, Mn0.5~1.0%, Cr2.0~9.0% martensitic stainless steel, heat treated to have a quenching and tempering hardness of H _R C40~50 to precipitate Cr carbides. It is. The pressure ring has a structure in which a surface hardening tank 7 is formed at least on the sliding surface that slides on the cylinder wall. Next, the reasons for limiting the composition of the pressure ring material of the present invention will be described. C is an important element that provides the necessary hardness and strength to the pressure ring material, and also contributes to improving wear resistance by forming fine hard Cr carbides. To obtain these effects, at least 0.4% or more is required. However, if it exceeds 0.7%, the toughness and processability when molded into a ring will be impaired, so this was set as the upper limit. Like Cr, which is added as a deoxidizing agent, Si is an element that imparts heat resistance at high temperatures. For this purpose, it is necessary to add 0.3% or more. However, if it exceeds 1.0%, workability will be impaired and toughness will also decrease, so the upper limit was set at 1.0%. Like Si, Mn is added as a deoxidizing agent and is an element that increases strength. As a deoxidizing agent, it is usually 0.3~
Although it is contained at about 0.45%, the lower limit was set at 0.5% to improve strength, and the upper limit was set at 1.0% because if it exceeded 1.0%, hot workability and cold workability during ring forming would be impaired. Cr forms a solid solution and imparts heat resistance and heat settling resistance, as well as improving corrosion resistance. In addition, some of them form carbides and are important elements that provide seizure resistance and wear resistance. In order to exhibit these effects, at least 2.0% or more is required from the balance with C. Moreover, if it exceeds 9.0%, the processability during ring molding will deteriorate, so this is the upper limit and the limited range is set to 2.0% to 9.0%. Table 1 shows the chemical compositions of the ring material of the present invention and the conventional ring material.

【table】

[Table] Table 2 shows the characteristics of the ring of the present invention and the conventional ring.

[Table] The degree of strength loss is the load required to bend a 5φ x 150 round bar to a radius of curvature of 25R at room temperature, and the load required to bend a 5φ x 150 round bar to a radius of curvature of 25R at room temperature, and the load required to bend a 5φ x 150 round bar to a radius of curvature of 25R after heating it at 300℃ for 1 hour in a state bent to 25R, returning it to its natural state and bending it again to the same radius of curvature. It shows the rate of decrease in the required load, and the lower the rate of decrease, the less the decrease in tension. In Table 2, the reduction rate of the cast iron ring is assumed to be 1, and the ratio of the reduction rate of each steel type to that is shown. As can be seen from the table, the pressure ring material of the present invention has a high modulus of elasticity and high tensile strength, and the degree of tension loss is approximately 40% lower than that of a cast iron ring. From the perspective of the structure and operation of an internal combustion engine, a pressure ring is attached to a piston, has a defined abutment when inserted into a cylinder, has self-tension,
It is in contact with the cylinder wall. In the combustion chamber during operation of an internal combustion engine, a tension drop occurs due to the temperature increase resulting from the combustion of fuel. If the degree of tension reduction is large, gas leakage occurs during the compression process, a predetermined compression pressure cannot be obtained, the pressure decreases, and the thermal efficiency also decreases. Furthermore, the blow-through of combustion gas destroys the oil film on the cylinder wall, causing seizure and galling. Therefore, by reducing the degree of tension reduction in the pressure ring material as in the present invention, the high performance of the internal combustion engine can be maintained. In other words, various materials can be considered as the material for the pressure ring, but we decided to use a structure with a martensitic structure in which Cr carbide is precipitated so that the alloy composition has the above composition and the hardness is H _R C40 to 50. Therefore, the axial width of the pressure ring is approximately
It can be reduced to 1/2 the size of conventional cast iron rings, and has properties similar to those of 13Cr steel, making it possible to increase the output and speed of internal combustion engines. Table 3 shows the relative evaluation of the required characteristics of pressure ring materials.

[Table] Advantage ◎＞○＞△
In a steel pressure ring, a wire is wound into a ring shape and cut into the shape shown in FIG. 2, so the workability of the material is important. Particularly during winding, sufficient elongation and uniform elongation are required to prevent breakage and uneven winding. As can be seen from Tables 2 and 3, the steel of the present invention has better workability than 13Cr steel, and is particularly superior in uniform elongation. Furthermore, since the degree of wear on the outer periphery of the pressure ring affects its airtightness, it is necessary to reduce the wear as much as possible in order to achieve high output and high speed internal combustion engines. Therefore, in the present invention, the pressure ring is not made of only one material, but is made of abrasion-resistant and seizure-resistant material so that the pressure ring maintains good airtightness due to self-tension on the cylinder wall during operation of the internal combustion engine. This is characterized in that at least the sliding surface of the pressure ring that slides on the cylinder wall is provided with a surface heat-treated layer that is hard and has good seizure resistance. As for surface treatment,
Hard Cr plating, porous Cr plating, composite plating, Cr thermal spraying, Mo thermal spraying, and various other surface treatments can be applied as appropriate. In particular, make the surface treatment layer hard.
When the Cr plating layer is used, the sliding surface of the pressure ring that slides on the cylinder wall has a high hardness of H _V 850 or higher, a small coefficient of friction, and excellent wear resistance, seizure resistance, and corrosion resistance. The sliding surface of the pressure ring exhibits good airtightness, and as mentioned above, the pressure ring material itself has a high elastic modulus, high strength, and low tension reduction, resulting in good airtightness due to the self-tension of the pressure ring itself. Because these properties work together, the pressure ring material of the present invention exhibits excellent functionality. In the present invention, the pressure ring material is made of martensitic stainless steel having the above-mentioned composition, so that the pressure ring material itself has sufficient corrosion resistance for use in internal combustion engines. The pressure ring material of the present invention is composed of the above-mentioned components, but from the viewpoint of improving corrosion resistance and increasing strength, Mo, Ni,
V and other elements may be contained as appropriate. Also, among the outer circumferential surfaces of the pressure ring, at least the sliding surface of the pressure ring that slides on the cylinder wall must have a surface treatment layer. It goes without saying that a surface treatment layer may be provided. As described above, the pressure ring material of the present invention has excellent airtightness, seizure resistance, breakage resistance, etc., and can reduce the pressure ring weight and piston weight, reduce energy loss due to inertia, and reduce the resistance to the cylinder wall. The contact area can be reduced, friction loss can be reduced, and it is possible to achieve high output of the internal combustion engine and at the same time achieve exhaust gas control effects.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of the internal combustion engine, FIG. 2 is a perspective view of the pressure ring, and FIG. 3 is a partial sectional view of the pressure ring. 1: cylinder, 2: piston, 3, 4: pressure ring, 5: oil ring, 6: gap,
7: Surface treatment layer.

Claims (1)

[Claims] 1. C0.4-0.7%, Si0.3-1.0%, Mn0.5 in weight%
Consists of martensitic stainless steel consisting of ~1.0%, Cr2.0~9.0%, balance impurities and iron,
A pressure ring material characterized in that a surface treatment layer is formed on at least the sliding surface of a ring with a quenched and tempered hardness of H _R C 40 to 50 and that slides against a cylinder wall, thereby exhibiting excellent wear resistance and seizure resistance. 2. The pressure ring material according to claim 1, wherein the surface treatment layer is a hard Cr plating layer.