Abstract: A material for use as self-lubricating sliding parts, which consists of a steel containing, by mass, from not less than 0.4% to less than 1.5% of C (carbon), 0.1 to 3.0% of Si, 0.1 to 3.0% of Mn, from inclusive zero to 0.5% of Cr, 0.05 to 3.0% of Ni, 0.3 to 2.0% of Al, 0.3 to 20% in total (Mo+W+V) of at least one element selected from the group consisting of Mo, W (tungsten) and V (vanadium), and 0.05 to 3.0% of Cu, wherein there can be observed graphite particles having an average particle size of not more than 3 ?m in a section of the metal structure of the steel. The steel is also used as piston rings. In the steel, the graphite particles observed in the structural section occupy an area rate of not less than 1% in the overall area of the structural section, and have an average particle size of not more than 3 ?m. The steel may further contain not more than 0.3% of S and/or not more than 0.01% of Ca. The steel is subjected to nitriding treatment for use.

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: There are disclosed a piston ring material and a piston ring both having such superior properties contradictory each other as the sliding property required in a piston ring and the mechanical properties of a steel wire material subjected to a manufacture process. The piston ring material or the piston ring consists essentially, by mass, of not less than 0.3% but less than 0.8% C, 0.1 to 3.0% Si, 0.1 to 3.0% Mn, 0.03 to 0.3% S, 0.3 to 6.0% Cr, preferably 3.0 to 6.0% or 0.3 to 1.0% Cr, 0 to 3.0% Cu, and the balance Fe, and the distribution state of sulfide inclusions with a maximum diameter/minimum size≧3 observed on structure parallel to the outer peripheral surface of the formed piston ring is such that an intersecting angle made between straight lines passing the maximum size of two of the sulfide inclusions is not more than 30 degrees. Further, the area ratio of nonmetallic inclusions occupying the structure is 2.

Abstract: There are disclosed a piston ring material and a piston ring both having such superior properties contradictory each other as the sliding property required in a piston ring and the mechanical properties of a steel wire material subjected to a manufacture process. The piston ring material or the piston ring consists essentially, by mass, of not less than 0.3% but less than 0.8% C, 0.1 to 3.0% Si, 0.1 to 3.0% Mn, 0.03 to 0.3% S, 0.3 to 6.0% Cr, preferably 3.0 to 6.0% or 0.3 to 1.0% Cr, 0 to 3.0% Cu, and the balance Fe, and the distribution state of sulfide inclusions with a maximum diameter/minimum size≧3 observed on structure parallel to the outer peripheral surface of the formed piston ring is such that an intersecting angle made between straight lines passing the maximum size of two of the sulfide inclusions is not more than 30 degrees. Further, the area ratio of nonmetallic inclusions occupying the structure is 2.

Abstract: A high-strength low-thermal-expansion alloy consisting of, by weight, 0.06 to 0.50% C, 25 to 65% in total of one or both of 65% or less Co and less than 30% Ni, and balance of Fe as a main component, other optional elements and unavoidable impurities, and having a primary phase of austenite phase and martensite phase induced by working. A wire is made from the alloy.