Abstract: A modified cross-section wire material is formed into piston rings such as oil-control rings for use in an engine. An apparatus of the present invention for forming the modified cross-section wire material has a forming unit (15) comprising in combination a non-powered pre-stage four-roll turks-head (16) and a powered post-staged four-roll turks-head (17). Disposed in tandem and downstream of the forming unit (15) is a non-powered finishing four-roll turks-head (21). A forming roll of the powered turks-head (17) has a diameter equal to or larger than 70 times as much as a height-of a flange of the material. In forming, the material is kept at a tension equal to or less than 300 N between the non-powered turks-head stand (16) and the powered turks-head (17), and at a tension of from 50 to 200 N between the forming unit (15) and the finishing turks-head (21).

Abstract: A modified cross-section wire material is formed into piston rings such as oil-control rings for use in an engine. An apparatus of the present invention for forming the modified cross-section wire material has a forming unit (15) comprising in combination a non-powered pre-stage four-roll turks-head (16) and a powered post-staged four-roll turks-head (17). Disposed in tandem and downstream of the forming unit (15) is a non-powered finishing four-roll turks-head (21). A forming roll of the powered turks-head (17) has a diameter equal to or larger than 70 times as much as a height-of a flange of the material. In forming, the material is kept at a tension equal to or less than 300 N between the non-powered turks-head stand (16) and the powered turks-head (17), and at a tension of from 50 to 200 N between the forming unit (15) and the finishing turks-head (21).

Abstract: A two-piece oil ring, for use in an internal combustion engine, with the oil ring being made from a martensitic stainless steel material having high consisting essentially of more than 0.8 wt % but less than 0.95 wt % of C, not more than 1.0 wt % of Si, not more than 1.0 wt % of Mn, from 15.0 wt % to 20.0 wt % of Cr and a balance substantially Fe and incidental impurities. The oil ring has a hardness ranging from HV300 to HV450 and a substantially H- or X-shaped cross-section. A web portion interconnecting left and right halves of the H- or X-shaped cross-section has a thickness not greater than 0.3 in terms of the ratio of the total thickness of the ring. Oil passage holes are formed in the web portion. A nitrided layer is formed on the sliding surface thereof which makes a sliding contact with the inner surface of a cylinder of the engine. The material may further contain suitable amounts of at least one of Mo, W, V, Nb, Ni and Co.