A method for producing an alloy steel composition includes the following steps: performing a first heat treatment on an alloy steel composition and maintaining for a first time period to soften the alloy steel composition; performing a first cooling treatment on the softened alloy steel composition; performing a treatment on the softened the alloy steel composition to form a workpiece; performing a second heat treatment on the workpiece and maintaining for a second time period; and performing a second cooling treatment on the workpiece to make the workpiece become to be a Bainite structure, and a cooling rate of the second cooling treatment is high than the cooling rate of the first cooling treatment.

A piston ring and a method of forming a piston ring. A masking agent is applied to a selective area on an exterior surface of a piston ring. The masking agent inhibits the subsequent application of additional coatings to the selective area on the exterior surface of the piston ring. In one form, the masking agent may inhibit the subsequent application of a nitride layer to the selective area on the exterior surface of the piston ring. A recess may be formed in an outer peripheral side of the piston ring, and a thermal spray coating may be formed within the recess in the outer peripheral side of the piston ring.

A piston ring and a method of forming a piston ring. A masking agent is applied to a selective area on an exterior surface of a piston ring. The masking agent inhibits the subsequent application of additional coatings to the selective area on the exterior surface of the piston ring. In one form, the masking agent may inhibit the subsequent application of a nitride layer to the selective area on the exterior surface of the piston ring. A recess may be formed in an outer peripheral side of the piston ring, and a thermal spray coating may be formed within the recess in the outer peripheral side of the piston ring.

A method for producing a steel sheet for packaging includes: cold-rolling a hot-rolled steel sheet made from a steel having a carbon content of 10 to 1000 ppm by weight, the steel of the hot-rolled steel sheet having a predetermined recrystallization temperature (T.sub.R); heating the cold-rolled steel sheet to a predetermined heating temperature (T.sub.E), where T.sub.R≤T.sub.E, the heating performed at least partially in the presence of a nitrogen donor at least until T.sub.R is reached such that when the cold-rolled steel sheet is heated, nitrogen from the nitrogen donor is diffused at least into a near-surface region of the cold-rolled sheet steel and incorporated in the near-surface region, as a result of which the T.sub.R in the near-surface region is increased by a value ΔT, where T.sub.E<T.sub.R+ΔT. Using this method, high-strength steel sheets having a multilayer microstructure can be produced.

A method for producing a steel sheet for packaging includes: cold-rolling a hot-rolled steel sheet made from a steel having a carbon content of 10 to 1000 ppm by weight, the steel of the hot-rolled steel sheet having a predetermined recrystallization temperature (T.sub.R); heating the cold-rolled steel sheet to a predetermined heating temperature (T.sub.E), where T.sub.R≤T.sub.E, the heating performed at least partially in the presence of a nitrogen donor at least until T.sub.R is reached such that when the cold-rolled steel sheet is heated, nitrogen from the nitrogen donor is diffused at least into a near-surface region of the cold-rolled sheet steel and incorporated in the near-surface region, as a result of which the T.sub.R in the near-surface region is increased by a value ΔT, where T.sub.E<T.sub.R+ΔT. Using this method, high-strength steel sheets having a multilayer microstructure can be produced.

A piston ring may include a stainless steel base having between 8% and 15% by weight of chromium, together with other elements and impurities, and having a hardness between 350 HV and 420 HV. The piston ring may also include a superficial nitrided layer having a depth of no more than 60 μm and an average hardness measured upon the surface exceeding 800 HV. The nitrided layer may include a plurality of nitride particles, which may have a maximum size of 5 μm and may be distributed over between 4% and 8% of an area of the nitrided layer.

A piston ring may include a stainless steel base having between 8% and 15% by weight of chromium, together with other elements and impurities, and having a hardness between 350 HV and 420 HV. The piston ring may also include a superficial nitrided layer having a depth of no more than 60 μm and an average hardness measured upon the surface exceeding 800 HV. The nitrided layer may include a plurality of nitride particles, which may have a maximum size of 5 μm and may be distributed over between 4% and 8% of an area of the nitrided layer.

An embodiment of the invention describes a method of treating an article to improve its corrosion resistance. The method includes the step of nitriding the article in a cyanide-free nitriding bath to obtain a nitrided article, heating the nitrided article in an atmosphere having nitrogen and carbon-carburizing to obtain a nitrided oxidised article. Further, in certain embodiments, the oxidised nitrided article may be coated with a metallic layer. The oxidised nitrided article with the metallic coating has improved corrosion resistance.

There is provided a compact for a magnet which can produce a magnetic member having high coercive force. The compact for a magnet is produced by compression-molding a rare earth-iron-based alloy powder containing a plurality of particles of a rare earth-iron-based alloy containing a rare earth element and iron, wherein the rare earth-iron-based alloy satisfies configurations (a) to (c) below and has 5% by volume or more and 20% by volume or less of voids formed therein. (a) Having a structure containing 10% by mass or more and 30% by mass or less of Sm, 10% by mass or less of Mn, and the balance consisting of Fe and inevitable impurities. (b) A composition, Sm.sub.2MN.sub.xFe.sub.17-x (x=0.1 or more and 2.5 or less). (c) An average crystal grain diameter of 700 nm or less.

There is provided a compact for a magnet which can produce a magnetic member having high coercive force. The compact for a magnet is produced by compression-molding a rare earth-iron-based alloy powder containing a plurality of particles of a rare earth-iron-based alloy containing a rare earth element and iron, wherein the rare earth-iron-based alloy satisfies configurations (a) to (c) below and has 5% by volume or more and 20% by volume or less of voids formed therein. (a) Having a structure containing 10% by mass or more and 30% by mass or less of Sm, 10% by mass or less of Mn, and the balance consisting of Fe and inevitable impurities. (b) A composition, Sm.sub.2MN.sub.xFe.sub.17-x (x=0.1 or more and 2.5 or less). (c) An average crystal grain diameter of 700 nm or less.