JPS6119703B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to piston ring materials, and particularly to a combination piston ring material for internal combustion engines. In recent years, internal combustion engines have been required to have increasingly higher performance, higher output, and higher speeds.In addition, they must also have measures against exhaust gases, and there is a need for countermeasures to the problems of reduced horsepower and increased fuel consumption of internal combustion engines. is increasing. Regarding these problems, piston rings that maintain the airtightness of the combustion chamber of an internal combustion engine have a great influence on the performance of the internal combustion engine, and countermeasures have especially become necessary. Conventionally, cast carbon steel rings or silicone chrome steel oil-tempered wire have been used for oil rings in internal combustion engines, but cast rings are difficult to manufacture because they are thin in the axial direction, and silicone rings are difficult to manufacture. Because of its low high-temperature strength, it has a relatively large cross-sectional area and is heavy, resulting in large inertia and a problem in that it is prone to fluttering. Cast metal rings and silicone chrome rings also lack abrasion resistance and heat settability, and the rings cannot be installed close to the top of the piston, which is advantageous in reducing exhaust gas, and the spacing between the rings cannot be made small. As a result, the weight of the piston became heavy, making it impossible to achieve high output and high speed. The present invention was made in view of these problems, and has higher strength and wear resistance than conventional ring materials.
The present invention relates to an oil ring material that has excellent heat resistance and is capable of achieving high output and high speed of an internal combustion engine while maintaining good airtightness without causing a flutter phenomenon. That is, the present invention has an alloy composition of C0.5 to 0.8%,
Cr10.0~15.5%, Si2.0%, Mn2.0%, and in some cases W0.3~3.0%, V0.1~1.0%,
It is a martensitic stainless steel containing 0.01 to 0.3% Nb, used in a heat-treated state, and contains about 5 to 15% undissolved carbides. It also has high resistance to tempering softening and extremely high strength at high temperatures. , has excellent airtightness with the cylinder. It also has good wear resistance and heat resistance. Furthermore, as a feature of the present invention, in conventional materials, a surface treatment layer such as Cr plating is formed on the sliding surface in order to lower the coefficient of friction with the cylinder wall, but with the present invention material, there is no need for a surface treatment layer, and the temperature is sufficiently high. By adding W, V and Nb to conventional martensitic stainless steel, it is possible to improve performance and simplify the process at the same time. The reasons for limiting the composition of the present invention will be described below. C imparts high strength and wear resistance, and for that purpose it is necessary to contain at least 0.5%. However, if the C content is high, bending workability deteriorates and ring straightening becomes difficult, so the upper limit was set at 0.8%. Cr combines with C to form carbide, which improves wear resistance and seizure resistance, as well as heat set resistance. However, if too much Cr is present, heat treatment hardness decreases and formability deteriorates. The claim range was 15.5%. Si is usually contained as a deoxidizing agent, but it also has the effect of improving heat resistance. However, if it is contained in a large amount, processability deteriorates, so the claimed range is up to 2%. Mn is also normally contained as a deoxidizing agent, but it has the effect of improving bending workability. However, if the content is too large, the hardness decreases, so the claimed range is 2% or less. W has the effect of increasing wear resistance and heat set resistance, and for this purpose, it is necessary to contain it in an amount of 0.3% or more, but even if it is contained in more than 3%, there is no effect commensurate with the content, so the claimed range is set at 3% as the upper limit. And so. Like W, V also increases wear resistance and heat set resistance. For the above effect, V needs to be 0.1% or more,
If it exceeds 1%, the effect will not increase much and workability will deteriorate, so the claimed range is 0.1 to 1.0%. Nb has the effect of increasing wear resistance and heat settling resistance, and at the same time making crystal grains finer and improving bending workability. For this purpose, 0.01% is effective, but if it exceeds 0.3%, workability is significantly deteriorated, so the claimed range is 0.01 to 0.3%. Next, the effects of the present invention will be explained using examples.
Table 1 shows the chemical compositions of the steel materials of the present invention, conventional steel materials, and comparative steel materials.

【table】

【table】

[Table] The inventive steels and the comparative N steels in Table 2 A to C are cast by the conventional electric steel manufacturing method, hot plastic worked to form a coil, and then cold-formed. Plastic working and annealing were repeated to obtain the desired dimensions, the ring was formed at high temperature, and the shape was then restrained during quenching heat treatment to produce a piston ring product. Conventional materials L are cast, M are coiled, cold worked, oil tempered, heat treated, and straightened. However, Table 2 shows a comparison of the properties of the ring products after heat treatment. However, the heat resistance is φ5
When m/m, each heat treatment is applied to make the hardness of each symbol, and a length of 150 round bar is made at room temperature with a curvature diameter of 25mmR.
The load required to bend the
It shows the reduction rate of the load required to return to the natural state after heating at 300°C for 1 hour and bend it again to the same radius of curvature, and the smaller the number, the better the heat settability resistance. In addition, wear resistance indicates the specific wear amount measured by an Okoshi type rapid wear tester. The test conditions were: mating material JISSCM21 annealed material, friction distance 400m, final load 6.8Kg, wear rate: 1.34m/sec. According to Table 2, the steel materials A to C of the present invention are superior to conventional materials in terms of wear resistance, high temperature strength, and resistance to heat set. The oil ring according to the present invention can reduce ring weight and piston weight, and can reduce energy loss due to inertia. In addition, it has excellent airtightness and durability, and when used in a pressure ring, there is no need for surface coating such as plating, making it possible to increase the output and speed of an internal combustion engine.
Although martensitic stainless steel without W, V, and Nb was used as a comparative material, Table 2 also shows that the effects of wear resistance and thermal settability are enhanced by the inclusion of W, V, and Nb. it is obvious.

Claims (1)

[Claims] 1 C0.5-0.8%, Si2.0%, Mn2.0% by weight
and Cr10.0~15.5%, W0.3~3.0%, V0.1~
A steel piston ring material containing at least one of Nb 1.0% and 0.01 to 0.3% Nb, with the balance consisting of Fe and impurities, and has excellent wear resistance and heat settability resistance at the operating temperature of piston rings.