| 摘要 |
PURPOSE:To improve the yield of products by working a striplike annealed steel blank material into a ring shape, heating the same to a hardening temp., and plastically screwing down the shape while quickly cooling the same by means of dies at the time of producing a hardened piston ring made of steel. CONSTITUTION:A striplike steel material made by rolling or drawing is annealed to soften, and is hot- or cold-worked to a piston ring shape. Next, the work 1 is heated to a hardening temp., after which it is placed on a female die 4, and a male die 3 is put thereon. While it is quickly cooled by a middle die 2 at above the temp. at which martensite transformation initiates, it is screwed down in an arrow direction, whereby it is plastically screwed down and straightened to have the roundness and flatness of a ring; at the same time, it is hardened, whereby the piston ring of high hardness, high strength and a correct shape is produced at a high yield. |
