A high-strength cold-rolled steel sheet comprises: a chemical composition that contains C, Si, Mn, P, S, N, Al, Ti, Nb, and B with a balance consisting of Fe and inevitable impurities, and satisfies [mol % N]/[mol % Ti]<1; and a steel microstructure in which: an area fraction of ferrite is 30% or more and 60% or less; a total area fraction of tempered martensite and bainite is 35% or more and 65% or less; an area fraction of quenched martensite is 15% or less; an area fraction of retained austenite is 1% or more and 10% or less; an area fraction of low-Mn ferrite having a Mn concentration of 0.8×[% Mn] or less is 5% or more and 40% or less; a result of subtracting the area fraction of the low-Mn ferrite from the area fraction of the ferrite is 10% or more; an area fraction of a residual microstructure is less than 3%; and an average grain size of the low-Mn ferrite is 10 μm or less.

A wear-resistant copper-zinc alloy includes in mass %, 28 to 55% Zn, 0.5 to 2% P, and a balance of Cu and unavoidable impurities, and the wear-resistant copper-zinc alloy has an electrical conductivity of 10 to 33% IACS and a hardness of 3.6[Zn]-55 HBW or more, where [Zn] denotes the Zn content in mass %. Alternatively, a wear-resistant copper-zinc alloy includes in mass %, 40 to 55% Zn, 1 to 6% Mn, and a balance of Cu and unavoidable impurities, and the wear-resistant copper-zinc alloy has an electrical conductivity of 10 to 33% IACS and a hardness of 3.6[Zn]-55 HBW or more, where [Zn] denotes the Zn content in mass %.

An object of the present invention is to improve machining speed by realizing both conductive properties and discharge performance with regard to an electrode wire for wire electric discharge machining, the electrode wire being obtained by plating a steel wire with a copper-zinc alloy. Another object is to suppress the occurrence of separation, cracking, and the like of plating in a wire-drawing step of an electrode wire. An electrode wire for wire electric discharge machining of the present invention includes a steel wire (11) serving as a core wire, and a plating layer (12) that covers the steel wire and that is composed of a copper-zinc alloy, in which an average zinc concentration of the plating layer is 60% to 75% by mass, a conductivity of the plating layer is 10% to 20% IACS, and a wire diameter is 30 to 200 μm.

An object of the present invention is to improve machining speed by realizing both conductive properties and discharge performance with regard to an electrode wire for wire electric discharge machining, the electrode wire being obtained by plating a steel wire with a copper-zinc alloy. Another object is to suppress the occurrence of separation, cracking, and the like of plating in a wire-drawing step of an electrode wire. An electrode wire for wire electric discharge machining of the present invention includes a steel wire (11) serving as a core wire, and a plating layer (12) that covers the steel wire and that is composed of a copper-zinc alloy, in which an average zinc concentration of the plating layer is 60% to 75% by mass, a conductivity of the plating layer is 10% to 20% IACS, and a wire diameter is 30 to 200 μm.

There are provided a copper alloy for a bearing and a bearing in which a Mn—Si compound is prevented from being broken and becoming a foreign matter. The copper alloy for a bearing and the bearing according to the present invention contain 25 wt % or more and 48 wt % or less of Zn, 1 wt % or more and 7 wt % or less of Mn, 0.5 wt % or more and 3 wt % or less of Si and 1 wt % or more and 10 wt % or less of Bi, the balance consisting of inevitable impurities and Cu, and are characterized in that the average width value among Mn—Si primary crystal particles dispersed in a sliding surface on which a counter shaft slides is 3 μm or more.

The present invention relates to a high-plasticity free-cutting zinc alloy, which includes the following components in percentage of weight: 1-10% Cu, 0.1-3.0% Bi, 0.01-1.5% Mn, 0.001-1% Ti and/or 0.01-0.3% Zr, optional component X, optional component Y, and a remainder component being Zn having less than or equal to 0.01% unavoidable impurities, wherein component X amounts to 0-1.0% and includes at least one element selected from Cr, V, Nb, Ni and Co; and component Y amounts to 0-1.0% and includes at least one element selected from B, As, P and rare earth metal. Compared with existing zinc alloys, the present invention has good machinability, higher plasticity and improved processability, which can be widely used in F connectors, pen manufacturing, socket connectors, locks and etc.

The present invention relates to a high-plasticity free-cutting zinc alloy, which includes the following components in percentage of weight: 1-10% Cu, 0.1-3.0% Bi, 0.01-1.5% Mn, 0.001-1% Ti and/or 0.01-0.3% Zr, optional component X, optional component Y, and a remainder component being Zn having less than or equal to 0.01% unavoidable impurities, wherein component X amounts to 0-1.0% and includes at least one element selected from Cr, V, Nb, Ni and Co; and component Y amounts to 0-1.0% and includes at least one element selected from B, As, P and rare earth metal. Compared with existing zinc alloys, the present invention has good machinability, higher plasticity and improved processability, which can be widely used in F connectors, pen manufacturing, socket connectors, locks and etc.

The present invention relates to the preparation methods and applications of biodegradable zinc-copper alloys, which can be applied to medical implant materials. The alloy of present invention is mainly composed of copper (1-10 wt. %), the balance of zinc and trace impurity elements. As-cast alloy ingot is homogenized and then hot processed to refine microstructure. The mechanical properties of the alloys are improved due to the refined microstructure. The alloys are capable of being further fabricated into micro-tubes, wires and plates. There are many advantages of these Zn alloys such as excellent mechanical properties, easy to process, appropriate corrosion resistance, good biocompatibility and so on, which correspondingly can be applied to many kinds of biodegradable medical implant devices. With excellent mechanical properties, good biocompatibility and degrading completely in 6-18 months, the Zn alloys meet the requirements of implant materials for mechanical properties and biosafety.

The present invention relates to the preparation methods and applications of biodegradable zinc-copper alloys, which can be applied to medical implant materials. The alloy of present invention is mainly composed of copper (1-10 wt. %), the balance of zinc and trace impurity elements. As-cast alloy ingot is homogenized and then hot processed to refine microstructure. The mechanical properties of the alloys are improved due to the refined microstructure. The alloys are capable of being further fabricated into micro-tubes, wires and plates. There are many advantages of these Zn alloys such as excellent mechanical properties, easy to process, appropriate corrosion resistance, good biocompatibility and so on, which correspondingly can be applied to many kinds of biodegradable medical implant devices. With excellent mechanical properties, good biocompatibility and degrading completely in 6-18 months, the Zn alloys meet the requirements of implant materials for mechanical properties and biosafety.

There are provided a copper alloy for a bearing and a bearing, which can prevent seizure in Mn-Si primary crystals. The copper alloy for a bearing and the bearing according to the present invention contain 25 wt % or more and 48 wt % or less of Zn, 1 wt % or more and 7 wt % or less of Mn, 0.5 wt % or more and 3 wt % or less of Si, and 1 wt % or more and 10 wt % or less of Bi, the balance consisting of inevitable impurities and Cu, and are characterized in that, in a sliding surface on which a counter material slides, the proportion of triangles having an area of 5000 μm.sup.2 or more and including no Bi particle with a circle equivalent diameter of 10 μm or more, among triangles having the closest three Mn-Si primary crystals as apices, is 20 % or less.