A case hardening steel material having a chemical composition consists of, by mass percent, C: 0.15 to 0.23%, Si: 0.01 to 0.15%, Mn: 0.65 to 0.90%, S: 0.010 to 0.030%, Cr: 1.65 to 1.80%, Al: 0.015 to 0.060%, and N: 0.0100 to 0.0250%, further containing, as necessary, one or more kinds selected from Cu and Ni of predetermined amounts, the balance being Fe and impurities; 25≦Mn/S≦85, 0.90≦Cr/(Si+2Mn)≦1.20, and 1.16Si+0.70Mn+Cr≧2.20; P, Ti and O in the impurities being P≦0.020%, Ti≦0.005%, and O≦0.0015%; and having a structure consisting of 20 to 70% in an area ratio being ferrite; and the portion other than the ferrite being one or more kinds of pearlite and bainite. The steel material is used suitably as a raw material of the carburized part such as a CVT pulley shaft.

A case hardening steel material having a chemical composition consists of, by mass percent, C: 0.15 to 0.23%, Si: 0.01 to 0.15%, Mn: 0.65 to 0.90%, S: 0.010 to 0.030%, Cr: 1.65 to 1.80%, Al: 0.015 to 0.060%, and N: 0.0100 to 0.0250%, further containing, as necessary, one or more kinds selected from Cu and Ni of predetermined amounts, the balance being Fe and impurities; 25≦Mn/S≦85, 0.90≦Cr/(Si+2Mn)≦1.20, and 1.16Si+0.70Mn+Cr≧2.20; P, Ti and O in the impurities being P≦0.020%, Ti≦0.005%, and O≦0.0015%; and having a structure consisting of 20 to 70% in an area ratio being ferrite; and the portion other than the ferrite being one or more kinds of pearlite and bainite. The steel material is used suitably as a raw material of the carburized part such as a CVT pulley shaft.

A process for producing a spring or torsion bar from a steel wire by hot forming may involve providing a steel wire; thermomechanically forming the steel wire; cooling the steel wire thermomechanically; cutting the steel wire to length to give rods; heating the rods; hot forming the rods; and tempering the rods to give a spring or torsion bar, comprising quenching the rods to give a spring or torsion bar to a first cooling temperature, reheating the spring or torsion bar to a first annealing temperature, and cooling the spring or rod to a second cooling temperature. Further, in some examples, the cooling of the steel wire may be cooled to a temperature below a minimum recrystallization temperature such that at least a partly ferritic-pearlitic structure is established in the steel wire.”

A process for producing a spring or torsion bar from a steel wire by hot forming may involve providing a steel wire; thermomechanically forming the steel wire; cooling the steel wire thermomechanically; cutting the steel wire to length to give rods; heating the rods; hot forming the rods; and tempering the rods to give a spring or torsion bar, comprising quenching the rods to give a spring or torsion bar to a first cooling temperature, reheating the spring or torsion bar to a first annealing temperature, and cooling the spring or rod to a second cooling temperature. Further, in some examples, the cooling of the steel wire may be cooled to a temperature below a minimum recrystallization temperature such that at least a partly ferritic-pearlitic structure is established in the steel wire.”

Provided is a steel for nitrocarburizing that can ensure hardened case depth by suppressing precipitation of Cr, V, and Nb in a part of the surface layer very close to the surface. The provided steel comprises: a specific chemical composition satisfying 9.5≤([Cr]/52+[V]/50.9+[Nb]/92.9+M)×10.sup.3≤18.5, with the balance being Fe and inevitable impurities; and a steel microstructure in which an area ratio of bainite phase with respect to the entire microstructure is more than 50%.

A steel wire for drawing includes, as a chemical composition, by mass %: C: 0.9% to 1.2%, Si: 0.1% to 1.0%, Mn: 0.2% to 1.0%, and Cr: 0.2% to 0.6%, limits Al, N, P, and S to be predetermined ranges, and includes one or more selected from the group consisting of Mo: 0% to 0.20%, and B: 0% to 0.0030%, a remainder of Fe and impurities; in which a metallographic structure includes pearlite, a volume fraction of the pearlite is 95% or higher, an average lamellar spacing of the pearlite is 50 nm to 75 nm, an average length of cementite in the pearlite is 2.0 μm to 5.0 μm, and a ratio of the number of grains of cementite with a length of 0.5 μm or smaller to the cementite in the pearlite is 20% or lower.

A steel wire rod includes, in terms of mass %, 0.95-1.10% C, 0.10-0.70% Si, 0.20-1.20% Mn, 0.90-1.60% Cr, 0-0.25% Mo, 0-25 ppm B, 0-0.020% P, 0-0.020% S, 0-0.0010% O, 0-0.030% N, and 0.010-0.100% Al. In a surface area of the steel wire rod, the Vickers hardness is HV 300 to HV 420, the area ratio of pearlite is 80% or more, and the area ratio of pro-eutectoid cementite is 2.0% or less. In an inner area of the steel wire rod, the area ratio of pearlite is 90% or more, and the area ratio of pro-eutectoid cementite is 5.0% or less. In the steel wire rod, the area ratio of pearlite blocks having an equivalent circle diameter of more than 40 μm is 0.62% or less, and the difference in Vickers hardness between the surface area and a center portion is HV 20.0 or less.

A nickel-titanium alloy is made to be wholly or substantially free of titanium-rich oxide inclusions by including yttrium in an amount up to 0.15 wt. %, with the balance of the alloy being nickel and titanium in approximately equal proportion. For example, a NiTiY alloy may have a composition including, in weight percent based on total alloy weight: between 50 and 60 wt. % nickel; between 40 and 50 wt. % titanium; and between 0.01 and 0.15 wt. % yttrium. The resulting alloy is capable of being drawn into various forms, e.g., fine medical-grade wire, without exhibiting an unacceptable tendency to develop surface defects or to fracture or crack during cold drawing or forging. The resulting final forms exhibit favorable fatigue strength and fatigue-resistant characteristics.

A stainless steel spring with excellent corrosion resistance and fatigue strength is provided by performing: a process of drawing a steel wire at a specific degree of drawing ε, the steel wire containing, in percentage by mass, C in an amount of 0.08% or lower, Si in an amount of 0.3% to 2.0%, Mn in an amount of 3.0% or lower, Ni in an amount of 8.0% to 10.5%, Cr in an amount of 16.0% to 22.0%, Mo in an amount of 0.5% to 3.0%, and N in an amount of 0.15% to 0.23%, with a remainder being made up of Fe and impurities; a process of obtaining a coiled steel wire; a process of heat treatment at from 500° C. to 600° C., and from 20 minutes to 40 minutes; a process of nitriding to form a nitride layer having a thickness of from 40 μm to 60 μm on a surface of the steel wire; a process of shot peening; and a process of heat treatment.

Provided is a wire rod that has superior machinability by cutting regardless of the type of tool material and the type of lubricant and even in the case where no lubricant is used. A wire rod for cutting work comprises: a specific chemical composition; and Vickers hardness that satisfies the following expressions (1) and (2) in the case where an average aspect ratio of ferrite grains at a position of ¼ of a diameter from a surface of the wire rod for cutting work is more than 2.8, and satisfies the following expressions (3) and (4) in the case where the average aspect ratio is 2.8 or less,
H.sub.ave≤350  (1)
H.sub.σ≤30  (2)
H.sub.ave≤250  (3)
H.sub.σ≤20  (4).