| 摘要 |
According to an aspect of the present invention, a piston ring for use in internal combustion engines is provided that is made of matensite-based stainless steel material containing C of not less than 0.4 and not more than 0.8 weight percent, Si of not less than 0.16 and not more than 0.4 weight percent, Mn of not less than 0.1 and not more than 0.4 weight percent, and Cr of not less than 2.0 and not more than 11.0 weight percent, where the steel material of the piston ring has mainly chromium carbide precipitated in the base texture thereof. The steel material of the first compression ring then has a nitriding layer formed thereon. According to another aspect of the present invention, a combination of compression rings, including a first compression ring 1 and a second compression ring 2, for use in internal combustion engines, is provided. The first compression ring 1 is made of martensite-based stainless steel material containing C of not less than 0.16 and not more than 1.4 weight percent, and Cr of not less than 12 and not more than 23.0 weight percent, where the steel material of the first compression ring 1 has mainly chromium carbide precipitated in the base texture thereof. The steel material of the first compression ring 1 then has a nitriding layer 11 of hardness of not less than Hv1050 formed thereon. The second compression ring 2 is made of the same steel material as the piston ring first described above, with mainly chromium carbide likewise precipitated in the base texture thereof The steel material of the second compression ring 2 then has a nitriding layer 22 of hardness of less than Hv1050 formed thereon. With the arrangement above, according to the present invention, piston rings have an advantage of excellent bending workability during the ring forming process. Likewise, a combination of first and second compression rings 1 and 2, has an advantage of reducing the total manufacturing cost of the combination of the compression rings, and an excellent abrasion resistance, with a second compression ring exhibiting excellent cold workability during the ring forming process.
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