JPS6121302B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to piston ring materials, and particularly to piston ring materials for automobile engines. In recent years, internal combustion engines, especially automobile engines, have been required to have increasingly higher performance, with a strong trend toward higher output and higher speeds.In addition to low fuel consumption, they must also have measures against exhaust gases, and in the case of automobiles, these problems must be solved. Various studies have been made to achieve this goal. In this regard, weight reduction and miniaturization are inevitably important conditions,
High output and low fuel consumption have become the mainstream of automobile engines after solving the pollution problem. Among these, the performance of the piston ring installed between the piston and the cylinder is also required to be wear resistant and to have excellent resistance to heat damage, and one of the requirements for diesel engines is to have particularly excellent corrosion resistance. It's becoming more and more. Conventionally, carbon steel casting rings or silicone chrome steel oil-tempered wires have been used for piston rings for automobile engines, but casting rings cannot be made thin in the axial direction, and it is also difficult to manufacture rings that are thin in the axial direction. Since the chrome steel ring has low high-temperature strength, it has a relatively large cross-sectional area and is heavy, and has a problem in that it has a large inertia and is prone to fluttering. Therefore, the ring cannot be installed close to the top of the piston, which is advantageous for exhaust gas countermeasures, and the spacing between the rings cannot be made small, which increases the weight of the piston, making it impossible to achieve high output and high speed. was also added. Furthermore, it lacks abrasion resistance, corrosion resistance, and resistance to heat set, and to compensate for these properties, surface coating treatments such as full surface plating have become common practice. In order to solve these problems, the present invention has higher strength, wear resistance, corrosion resistance, and heat settability resistance than conventional piston ring materials, and maintains good airtightness without causing the flutter ring phenomenon. However, the purpose is to provide a lightweight piston ring that can achieve high output and high speed in automobile engines. The material of the present invention has an alloy composition of C0.6 to 1.0 by weight.
%, Si1.5% or less, Mn1.0% or less, Ni2.0% or less,
It is a martensitic stainless steel containing 11.0 to 13.0% Cr, 0.4 to 1.5% Mo, and 1.5% or less of V, and is used in a quenched and tempered state. The material of the present invention contains undissolved carbides in a heat-treated state, has high resistance to tempering softening, has high strength under high temperatures such as in a pressure ring, and has excellent airtightness with the cylinder wall. In addition, it has particularly excellent wear resistance and heat settability resistance, and while conventional steel piston rings were treated with a coating on the entire surface, this was simplified and the inventive material has a coating treatment on all surfaces other than the sliding surface with the cylinder. That is not needed. As mentioned above, the material of the present invention further enhances wear resistance and heat settling resistance by adding Mo and V to conventional martensitic stainless steel, and simplifies processes such as plating. In addition, piston rings need to have excellent cold and warm bending properties for ring processing after heat treatment, and this piston is also characterized by the addition of Ni to improve its processability. It is a ring material. The reason for limiting the composition of the material of the present invention will be described below. C combines with Cr, Mo, and V to increase the base hardness of steel materials, forming carbides and imparting wear resistance.For this purpose, at least 0.6% is required, and more than 1.0%. Since the processability of the ring becomes extremely poor, the range was limited to 0.6 to 1.0%. Ni is useful for improving toughness and oxidation resistance when used as piston rings, and improves cold and warm bending workability even when the amount of C is high.
If it exceeds 2%, it will have a negative effect on wear resistance and heat resistance, so the upper limit was set at 2%. Cr combines with C to form a hard carbide, which improves wear resistance and seizure resistance, as well as heat set resistance. However, if it exceeds 13%, heat treatment hardness decreases and toughness deteriorates, so the range is 11.0~
It was limited to 13.0%. Like Cr, Mo combines with C to form carbide,
To improve heat resistance and wear resistance at high temperatures.
Furthermore, by increasing the corrosion resistance, it is effective as a piston ring for diesel engines where corrosion resistance is a problem. In order for Mo to exert this effect, at least 0.4% is required,
Moreover, since no increase in the effect was observed even if the content exceeded 1.5%, it was limited to 0.4 to 1.5%. V combines with C to form carbide, which improves wear resistance and heat set resistance, and also works to refine grains, improving ring processability, but 1.5%
Since there is no need for more than that, the upper limit was set at 1.5%. Si is usually added as a deoxidizing agent, but it also has the effect of improving heat resistance. However, if it exceeds 1.5%, the bending workability deteriorates, so the upper limit is set at 1.5%.
limited to. Mn is also normally used as a deoxidizing agent, but it also has the effect of improving bending workability. However, it is not necessary for the content to exceed 1.0%, and the upper limit of the content is limited to 1.0%. Next, the effects of the material of the present invention will be explained using examples. Table 1 shows the chemical compositions of the inventive material and the conventional material.

[Table] Namely, No. 1 to No. 7 are materials of the present invention, No. 8 is a cast material, and No. 9 is a silicrome steel material. Next, Table 2 shows the hardness, abrasion resistance, tensile strength at operating temperature (300℃), and heat settling resistance when the steel materials with the compositions shown in Table 1 are processed into piston rings and made into ring products. Measured and summarized. However, the heat settling resistance was measured at a thickness of 5 mm after a prescribed treatment. The detailed measurement method will be described later.

[Table] Inventive materials No. 1 to No. 7 in Table 2 are melted in an electric furnace and then subjected to hot plastic working to form a 5.5 mm coil. A ring material of 1.54 mm x 3.35 mm was processed by appropriately combining strain relief annealing, and then quenching and tempering was performed to restrain the shape and produce a piston ring product. Also, the conventional material No.
No. 8 was made into a cast ring, and No. 9 was oil tempered in a coiled state, heat treated, bent and straightened, and finished into a ring product. As for the measurement method, as mentioned above, for heat resistance, the length is 5 mm.
After heat treating each 150mm piece to the hardness shown in Table 2, the load required to bend it to a radius of curvature of 25mmR at room temperature and 300℃ x 1 ^hour in the bent state.
After heating, return to the straight-stretched state and return to room temperature again as before.
This shows the degree of reduction in load when bent to a radius of curvature of 25 mmR. In addition, wear resistance is the specific wear amount determined by Okoshi type rapid wear tester, and the mating material is JIS.SCM21 annealed material, friction distance is 400m, final load is 6.8Kg, and wear rate is 1.34m/sec.
It is. As is clear from Table 2, the invention materials No. 1~
It can be seen that No. 7 is superior to conventional steel materials in terms of wear resistance, high temperature strength, and resistance to heat set. Next, Table 3 shows a comparison of the corrosion resistance of the conventional material and the material of the present invention. The exhaust gas in the engine room is at a high temperature, and piston rings in particular are required to have corrosion resistance because they are affected by the high temperature oxidizing gas in the engine combustion chamber. Therefore, conventional piston ring materials have typically been coated with Cr plating to provide corrosion and wear resistance. The material of the present invention has excellent corrosion resistance against sulfate ions contained in exhaust gas as shown in Table 3, indicating that plating on surfaces other than the sliding surfaces is not necessary.

[Table] As explained above, by using the material of the present invention, the performance of automobile piston rings is improved, the piston rings can be made smaller, and the number of manufacturing steps for the piston rings can be reduced. This has the effect of increasing the engine output and speed.

Claims (1)

[Claims] 1 Weight% C0.6-1.0%, Si1.5% or less, Mn1.0
% or less, Ni2% or less, Cr11.0~13.0%, Mo0.5~
A piston ring material that contains less than 1.5% and V1.5%, with the remainder being Fe and impurities, and has excellent wear resistance, corrosion resistance, and heat set resistance at the operating temperature of piston rings.