Abstract: A steel wire has tempered martensite, comprises, as essential components, by mass, C: 0.53 to 0.68%; Si: 1.2 to 2.5%; Mn: 0.2 to 1.5%; Cr: 1.4 to 2.5%; Al: 0.05% or less; further comprises, as a selective component, Ni: 0.4% or less; V: 0.4% or less; Mo: 0.05 to 0.5%; or Nb: 0.05 to 0.5%; and further comprises remainder essentially consisting of Fe and inevitable impurities, wherein the grain size number of prior austenite is 11.0 or larger, and the proof stress ratio (?0.2/?B), namely, a ratio of 0.2% proof stress (?0.2) to tensile strength (?B) is 0.85 or lower. Satisfying the above requirements makes it possible to produce a steel wire for high-strength spring excellent both in workability (cold workability), and in sag resistance and fatigue properties.

Abstract: Disclosed is a hard-drawn spring which exhibits fatigue strength and sag resistance equal or superior to springs produced using an oil-tempered wire. The hard-drawn spring is produced using a steel wire containing 0.5 to 0.7 mass % of C, 1.0 to 1.95 mass % of Si, 0.5 to 1.5 mass % of Mn and 0.5 to 1.5 mass % of Cr, with the balance being Fe and inevitable impurities. In the steel wire, the number of carbides having circle-equivalent diameters of 0.1 ?m or more is 5 particles/100 ?m2 or less.

Abstract: Disclosed is a hard-drawn spring which exhibits fatigue strength and sag resistance equal or superior to springs produced using an oil-tempered wire. The hard-drawn spring is produced using a steel wire containing 0.5 to 0.7 mass % of C, 1.0 to 1.95 mass % of Si, 0.5 to 1.5 mass % of Mn and 0.5 to 1.5 mass % of Cr, with the balance being Fe and inevitable impurities. In the steel wire, the number of carbides having circle-equivalent diameters of 0.1 ?m or more is 5 particles/100 ?m2 or less.

Abstract: The spring steel according to the present invention is a spring steel excellent in sag resistance and fatigue property containing: C: 0.5 to 0.8% by mass (hereinafter, referred to as %), Si: 1.2 to 2.5%, Mn: 0.2 to 1.5%, Cr: 1.0 to 4.0%, V: 0.5% or less (including 0%), P: 0.02% or less (excluding 0%), S: 0.02% or less (excluding 0%), Al: 0.05% or less (excluding 0%), and Fe and inevitable impurities as the balance, wherein the Si content and the Cr content satisfy the following formula (1): 0.8×[Si]+[Cr]?2.6??(1) (wherein, [Si] and [Cr] respectively represent the Si content (%) and the Cr content (%)). The spring steel is useful in improving both sag resistance and fatigue property.

Abstract: Disclosed is a hard-drawn spring which exhibits fatigue strength and sag resistance equal or superior to springs produced using an oil-tempered wire. The hard-drawn spring is produced using a steel wire containing 0.5 to 0.7 mass % of C, 1.0 to 1.95 mass % of Si, 0.5 to 1.5 mass % of Mn and 0.5 to 1.5 mass % of Cr, with the balance being Fe and inevitable impurities. In the steel wire, the number of carbides having circle-equivalent diameters of 0.1 ?m or more is 5 particles/100 ?m2 or less.

Abstract: Disclosed is a high-strength bolt having a tensile strength of 1,200 N/mm2 or more and superior in delayed fracture resistance and relaxation resistance, prepared by wire-drawing a bolt steel containing the following elements: C: 0.5 to 1.0% (mass %, the same shall apply hereinafter), Si: 0.55 to 3%, Mn: 0.2 to 2%, P: 0.03% or less (but not 0%), S: 0.03% or less (but not 0%), and Al: 0.3% or less (but not 0%), and containing proeutectoid ferrite, proeutectoid cementite, bainite and martensite at a total areal rate of less than 20% and pearlite in balance; cold-heading the wire into a bolt shape; and then bluing the bolt in a temperature range of 100 to 500° C.

Abstract: The spring steel according to the present invention is a spring steel excellent in sag resistance and fatigue property containing: C: 0.5 to 0.8% by mass (hereinafter, referred to as %), Si: 1.2 to 2.5%, Mn: 0.2 to 1.5%, Cr: 1.0 to 4.0%, V: 0.5% or less (including 0%), P: 0.02% or less (excluding 0%), S: 0.02% or less (excluding 0%), Al: 0.05% or less (excluding 0%), and Fe and inevitable impurities as the balance, wherein the Si content and the Cr content satisfy the following formula (1): 0.8×[Si]+[Cr]?2.6??(1) (wherein, [Si] and [Cr] respectively represent the Si content (%) and the Cr content (%)). The spring steel is useful in improving both sag resistance and fatigue property.

Abstract: A steel wire has tempered martensite, comprises, as essential components, by mass, C: 0.53 to 0.68%; Si: 1.2 to 2.5%; Mn: 0.2 to 1.5%; Cr: 1.4 to 2.5%; Al: 0.05% or less; further comprises, as a selective component, Ni: 0.4% or less; V: 0.4% or less; Mo: 0.05 to 0.5%; or Nb: 0.05 to 0.5%; and further comprises remainder essentially consisting of Fe and inevitable impurities, wherein the grain size number of prior austenite is 11.0 or larger, and the proof stress ratio (?0.2/?B), namely, a ratio of 0.2% proof stress (?0.2) to tensile strength (?B) is 0.85 or lower. Satisfying the above requirements makes it possible to produce a steel wire for high-strength spring excellent both in workability (cold workability), and in sag resistance and fatigue properties.

Abstract: Disclosed is a steel wire rod for hard-drawn springs capable of exhibiting fatigue strength and sag resistance equivalent to or higher than springs made of an oil-tempered wire. The steel wire rod contains carbon in a range from 0.5 to less than 0.7 mass %, silicon in a range from 1.4 to 2.5 mass %, manganese in a range from 0.5 to 1.5 mass %, chromium in a range from 0.05 to 2.0 mass %, and vanadium in a range from 0.05 to 0.40 mass %, and has an area ratio Rp with respect to pearlite which satisfies the mathematical expression (1): Rp(area %)?55×[C]+61??(1) where [C] denotes the content (mass %) of carbon.

Abstract: Disclosed is a hard-drawn spring which exhibits fatigue strength and sag resistance equal or superior to springs produced using an oil-tempered wire. The hard-drawn spring is produced using a steel wire containing 0.5 to 0.7 mass % of C, 1.0 to 1.95 mass % of Si, 0.5 to 1.5 mass % of Mn and 0.5 to 1.5 mass % of Cr, with the balance being Fe and inevitable impurities. In the steel wire, the number of carbides having circle-equivalent diameters of 0.1 ?m or more is 5 particles/100 ?m2 or less.

Abstract: Disclosed herein is a high-strength high-carbon steel wire which, owing to its high strength as well as good ductility, is excellent in resistance to strain aging embrittlement and longitudinal cracking. The steel wire is characterized by having a chemical composition (in mass %) including C: 0.75-1.20%, Si: 0.1-1.5%, Mn: 0.3-1.2%, P: no more than 0.02%, S: no more than 0.02%, Al: no more than 0.005%, and N: no more than 0.008%, with the remainder being Fe and inevitable impurities. The steel wire is further characterized by having worked pearlite structure containing lamellar cementite in amorphous form, a diameter (D) ranging from 0.15 to 0.4 mm, a metal lubricating film as the surface layer whose main phase is composed of at least one of Cu, Ni, and Zn or an alloy thereof, and tensile strength no lower than (3500×D−0.145) MPa and no higher than (3500×D−0.145+87×[C]−5) MPa, where [C] denotes C content in %.

Abstract: A wire rod for drawing which is superior in drawability as well as twisting characteristics, and a method for producing the wire rod. The wire rod is characterized in that the raw material thereof is a eutectoid steel or hypereutectoid steel containing 0.1-2.0 mass % Si and 0.2-2.0 mass % Mn and the pearlite structure therein accounts for no less than 80 area % of microstructure and the maximum length of ferrite as the second phase therein is no larger than 10 &mgr;m. The wire rod is produced by drawing with a true strain of 1.5 or above and subjecting the wire rod to patenting at a heating temperature defined by a specific equation.

Abstract: A high-strength bolt having excellent delayed fracture resistance and stress relaxation resistance in addition to a tensile strength of 1200 N/mm2 or higher is disclosed. A steel material for the high-strength bolt includes C: 0.50 to 1.0% by mass (hereinafter, referred to simply as “%”), Si: 0.5% or less (not including 0%), Mn: 0.2 to 1%, P: 0.03% or less (including 0%) and S: 0.03% or less (including 0%). The steel material has pro-eutectoid ferrite, pro-eutectoid cementite, bainite and martensite structures at less than 20% in total and a pearlite structure as the remainder. The high-strength bolt is produced by drawing the steel material severely to obtain a steel wire, forming the steel wire into a bolt shape through a cold heading, and subjecting the shaped steel wire to a blueing treatment at a temperature within a range of 100 to 400° C.

Abstract: Disclosed herein is a high-strength high-carbon steel wire which, owing to its high strength as well as good ductility, is excellent in resistance to strain aging embrittlement and longitudinal cracking.

Abstract: A high-strength bolt having excellent delayed fracture resistance and stress relaxation resistance in addition to a tensile strength of 1200 N/mm2 or higher is disclosed. A steel material for the high-strength bolt includes C: 0.50 to 1.0% by mass (hereinafter, referred to simply as “%”), Si: 0.5% or less (not including 0%), Mn: 0.2 to 1%, P: 0.03% or less (including 0%) and S: 0.03% or less (including 0%). The steel material has pro-eutectoid ferrite, pro-eutectoid cementite, bainite and martensite structures at less than 20% in total and a pearlite structure as the remainder. The high-strength bolt is produced by drawing the steel material severely to obtain a steel wire, forming the steel wire into a bolt shape through a cold heading, and subjecting the shaped steel wire to a blueing treatment at a temperature within a range of 100 to 400 ° C.

Abstract: A wire rod for drawing which is superior in drawability as well as twisting characteristics, and a method for producing the wire rod.

Abstract: A spring steel which is superior in both shaving properties and green drawing properties, which are important in spring production. A process for making the spring steel into wire rods for good springs. A rolled spring steel superior in workability characterized in that it has the following mechanical properties. Tensile strength≦1200 MPa 30%≦reduction of area≦70% A process for producing a steel wire rod for springs from said spring steel, said process comprising drawing, shaving, and oil tempering, which are carried out sequentially, said drawing being optionally followed by prescribed treatment.

Abstract: Disclosed herein are a high-carbon steel wire having high strength and superior in resistance to longitudinal cracking, a steel for said high-carbons steel wire, and a process for producing said steel. The high-carbon steel wire is characterized in that the essential components are C (0.65-1.2 wt %), Si (0.1-2.0 wt %), Mn (0.2-2.0 wt %), and Fe, the main phase is pearlite, and the ferrite area ratio is less than 0.40 % in the surface layer up to a depth of 50 &mgr;m from the surface. The high-carbon steel may further contain B (0.0003-0.0050 wt %), Ti (less than 0.030 wt %), and N (less than 0.0050 wt %), with the amount of B, Ti, and N satisfying the following equation 0.03≦B/(Ti/3.43−N)≦5.0 The resulting steel wire produced in the usual way contains ferrite in an amount less than 0.40 wt % in its surface layer. This low ferrite content is responsible for good resistance to longitudinal cracking because ferrite causes longitudinal cracking to start from it.

Abstract: A non-heat treated wire or bar steel for springs which is characterized by having in its as-rolled state a tensile strength of 120-150 kgf/mm2 and a bending breakage rate no higher than 15% when tested according to JIS Z-2248 under the condition of r/d=2.8 where r (mm) denotes the inside radius of the bending curvature and d (mm) denotes the diameter of the as-rolled stock.

Abstract: A steel wire is composed mainly of fine pearlite and/or coarse pearlite, where the lamellar cementite in the pearlite is amorphous or amorphous-like. Alternatively, the wire may be composed mainly of bainite, where the cementite in the bainite is amorphous or amorphous-like. To manufacture the steel wire, a starting steel product is subjected repeatedly to patenting and cold drawing, and then subjected to final drawing at a true strain of 2.0 or above while cooling. The steel wire is higher in strength and toughness than wire whose lamellar cementite consists of nano crystals. The steel wire does not suffer any delamination when subjected to torsion.