Abstract: A component comprising a core part and a surface layer is provided. The core part contains C: 0.01%? and <0.20%, Si: ?1.0%, Mn: 1.5%? and ?3.0%, P: 0.02% or less, S: ?0.06%, Cr: 0.30%? and ?3.0%, Mo: 0.005%? and ?0.40%, V: 0.02%? and ?0.5%, Nb: 0.003%? and ?0.20%, Al: 0.010%? and ?2.0%, Ti: 0.005%< and <0.025%, N: ?0.0200%, Sb: 0.0005%? and ?0.02%, and the balance consisting of Fe and incidental impurities; and a steel microstructure that contains bainite phase in an area ratio of more than 50%. The surface layer has high nitrogen and carbon contents relative to the chemical composition of the core part.

Abstract: A case hardening steel having excellent fatigue resistance is provided at relatively low production cost. A case hardening steel has a chemical composition containing C: 0.10% to 0.30%, Si: 0.10% to 1.20%, Mn: 0.30% to 1.50%, S: 0.010% to 0.030%, Cr: 0.10% to 1.00%, B: 0.0005% to 0.0050%, Sb: 0.005% to 0.020%, and N: 0.0150% or less in a predetermined range, and further containing Al: 0.010%?Al?0.120% in the case where B?(10.8/14)N?0.0003%, and 27/14[N?(14/10.8)B+0.030]?Al?0.120% in the case where B?(10.8/14)N<0.0003%.

Abstract: A case hardening steel suitable as raw material for producing a mechanical structural part having high rotating bending fatigue strength and pitting fatigue strength at relatively low cost and a method of producing the case hardening steel are provided. A case hardening steel comprises a chemical composition containing, in mass %, C, Si, Mn, P, S, Cr, Mo, Al, N, and O in a predetermined relationship, with a balance being Fe and inevitable impurities, wherein ?I?80 (where I denotes an area (?m2) of an oxide-based inclusion located in a fish eye central portion at a fracture surface after subjecting the case hardening steel to carburizing-quenching and tempering and then performing a rotating bending fatigue test).

Abstract: A component comprising a core part and a surface layer is provided. The core part contains C: 0.01%? and <0.20%, Si: ?1.0%, Mn: 1.5%? and ?3.0%, P: 0.02% or less, S: ?0.06%, Cr: 0.30%? and ?3.0%, Mo: 0.005% ? and ?0.40%, V: 0.02% ? and ?0.5%, Nb: 0.003% ? and ?0.20%, Al: 0.010%? and ?2.0%, Ti: 0.005%< and <0.025%, N: <0.0200%, Sb: 0.0005% ? and ?0.02%, and the balance consisting of Fe and incidental impurities; and a steel microstructure that contains bainite phase in an area ratio of more than 50%. The surface layer has high nitrogen and carbon contents relative to the chemical composition of the core part.

Abstract: A case hardening steel suitable as raw material for producing a mechanical structural part having high rotating bending fatigue strength and pitting fatigue strength at relatively low cost and a method of producing the case hardening steel are provided. A case hardening steel comprises a chemical composition containing, in mass %, C, Si, Mn, P, S, Cr, Mo, Al, N, and O in a predetermined relationship, with a balance being Fe and inevitable impurities, wherein ?I?80 (where I denotes an area (?m2) of an oxide-based inclusion located in a fish eye central portion at a fracture surface after subjecting the case hardening steel to carburizing-quenching and tempering and then performing a rotating bending fatigue test).

Abstract: The present invention provides a steel for nitrocarburizing having excellent mechanical workability before nitrocarburizing, and showing excellent fatigue properties after nitrocarburizing, which is suitable for applying in mechanical structural components for automobiles etc. prepared by adjusting the composition so that it contains in mass %, C: 0.01% or more and less than 0.10%, Si: 1.0% or less, Mn: 0.5% to 3.0%, P: 0.02% or less, S: 0.06% or less, Cr: 0.3% to 3.0%, Mo: 0.005% to 0.4%, V: 0.02% to 0.5%, Nb: 0.003% to 0.15%, Al: 0.005% to 0.2%, and Sb: 0.0005% to 0.02%, and the balance including Fe and incidental impurities, and setting the area ratio of bainite phase to the whole microstructure to more than 50%.

Abstract: The steel for nitrocarburizing has a chemical composition that contains C: 0.01% or more and less than 0.20%, Si: 1.0% or less, Mn: 1.5% or more and 3.0% or less, P: 0.02% or less, S: 0.06% or less, Cr: 0.30% or more and 3.0% or less, Mo: 0.005% or more and 0.40% or less, V: 0.02% or more and 0.5% or less, Nb: 0.003% or more and 0.20% or less, Al: 0.010% or more and 2.0% or less, Ti: more than 0.005% and less than 0.025%, N: 0.0200% or less, Sb: 0.0005% or more and 0.02% or less, and the balance consisting of Fe and incidental impurities; and a steel microstructure that contains bainite phase in an area ratio of more than 50%.

Abstract: A case hardening steel having excellent fatigue resistance is provided at relatively low production cost. A case hardening steel has a chemical composition containing C: 0.10% to 0.30%, Si: 0.10% to 1.20%, Mn: 0.30% to 1.50%, S: 0.010% to 0.030%, Cr: 0.10% to 1.00%, B: 0.0005% to 0.0050%, Sb: 0.005% to 0.020%, and N: 0.0150% or less in a predetermined range, and further containing Al: 0.010%?Al?0.120% in the case where B?(10.8/14)N ?0.0003%, and 27/14[(N?(14/10.8)B+0.030]?Al?0.120% in the case where B?(10.8/14)N<0.0003%.

Abstract: A steel has a predetermined chemical composition with a balance being Fe and incidental impurities, wherein a sum of Cu content and Ni content is 0.15 mass % or more, and a crystal grain size after forming into a stabilizer shape and quenching is in a range of 7.5 to 10.5 in prior austenite crystal grain size number. Thus, a highly durable stabilizer steel that has a tensile strength of 1200 MPa or more and excellent normal-temperature and low-temperature toughness and is used in an environmentally friendly manufacturing process at lower cost can be realized.

Abstract: A steel, having a high corrosion resistance and low-temperature toughness, for a vehicle suspension spring part, the steel includes 0.21 to 0.35% by mass of C, more than 0.6% by mass but 1.5% by mass or less of Si, 1 to 3% by mass of Mn, 0.3 to 0.8% by mass of Cr, 0.005 to 0.080% by mass of sol. Al, 0.005 to 0.060% by mass of Ti, 0.005 to 0.060% by mass of Nb, not more than 150 ppm of N, not more than 0.035% by mass of P, not more than 0.035% by mass of S, 0.01 to 1.00% by mass of Cu, and 0.01 to 1.00% by mass of Ni, the balance being Fe and unavoidable impurities, with Ti+Nb?0.07% by mass, wherein crystal grains of the steel after hardening have a prior austenite grain size number of 7.5 to 10.5, and the steel having a tensile strength of not less than 1,300 MPa.

Abstract: The present invention provides a steel for nitrocarburizing having excellent mechanical workability before nitrocarburizing, and showing excellent fatigue properties after nitrocarburizing, which is suitable for applying in mechanical structural components for automobiles etc. prepared by adjusting the composition so that it contains in mass %, C: 0.01% or more and less than 0.10%, Si: 1.0% or less, Mn: 0.5% to 3.0%, P: 0.02% or less, S: 0.06% or less, Cr: 0.3% to 3.0%, Mo: 0.005% to 0.4%, V: 0.02% to 0.5%, Nb: 0.003% to 0.15%, Al: 0.005% to 0.2%, and Sb: 0.0005% to 0.02%, and the balance including Fe and incidental impurities, and setting the area ratio of bainite phase to the whole microstructure to more than 50%.

Abstract: According to the present invention, it is possible to obtain steel for nitrocarburizing having a predetermined chemical composition, a bainite area ratio exceeding 50% and excellent machinability by cutting before nitrocarburizing, and having strength and toughness equivalent to conventional steel, such as SCr420 carburized steel material, and excellent fatigue properties after nitrocarburizing.

Abstract: A low carbon resulfurized free cutting steel consisting of 0.04 to 0.15% of C, more than 0.10% and 0.70% or less of Si, 0.85 to 1.50% of Mn, 0.040 to 0.120% of P, 0.250% or more and less than 0.400% of S, less than 0.005% of Al, more than 0.0020% and 0.0120% or less of O, and more than 0.0070% and 0.0150% or less of N, all by mass percentage, and the balance of Fe and inevitable impurities, and satisfying a formula (1) and a formula (2), as follows: 0.15%?Si %+2×P %?(5×Al %+10×O %+3×N %)?0.75%??(1), and ([Mn %]5)/15<S %<([Mn %]5)/2??(2).

Abstract: Steel, excellent in corrosion resistance and low-temperature toughness, for a vehicle suspension spring part, includes 0.15 to 0.35% by mass of C, more than 0.6% by mass but 1.5% by mass or less of Si, 1 to 3% by mass of Mn, 0.3 to 0.8% by mass of Cr, 0.005 to 0.080% by mass of sol. Al, 0.005 to 0.060% by mass of Ti, 0.005 to 0.060% by mass of Nb, not more than 150 ppm of N, not more than 0.035% by mass of P, not more than 0.035% by mass of S, 0.01 to 1.00% by mass of Cu, and 0.01 to 1.00% by mass of Ni, the balance consisting of Fe and unavoidable impurities, with Ti+Nb?0.07% by mass. The steel has a tensile strength of not less than 1,300 MPa.

Abstract: According to one embodiment, a high-strength stabilizer steel for vehicles having excellent corrosion resistance and low-temperature toughness, containing 0.07 to 0.20% C, more than 0.6% and 1.5% or less Si, 1 to 3% Mn, 0.1 to 1.0% Cr, 0.005 to 0.080% sAl, 0.005 to 0.060% Ti, 0.005 to 0.060% Nb, 0.070% or less Ti+Nb, 150 ppm or less N, 0.035% or less P, 0.035% or less S, 0.01 to 1.00% Cu, 0.01 to 1.00% Ni, the remainder being Fe, and unavoidable impurities, wherein a structure before molding a stabilizer is any one of a bainite, a martensite, and a mixed structure of bainite/martensite and an original austenitic crystal grain size number after a heat treatment of the stabilizer is Gh 9 or more.

Abstract: A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 ?m, prior austenite has a grain diameter of 30 ?m or less, and the ratio by volume of the residual austenite is less than 25%.

Abstract: According to one embodiment, a high-strength stabilizer steel for vehicles having excellent corrosion resistance and low-temperature toughness, containing 0.07 to 0.20% C, more than 0.6% and 1.5% or less Si, 1 to 3% Mn, 0.1 to 1.0% Cr, 0.005 to 0.080% sAl, 0.005 to 0.060% Ti, 0.005 to 0.060% Nb, 0.070% or less Ti+Nb, 150 ppm or less N, 0.035% or less P, 0.035% or less S, 0.01 to 1.00% Cu, 0.01 to 1.00% Ni, the remainder being Fe, and unavoidable impurities, wherein a structure before molding a stabilizer is any one of a bainite, a martensite, and a mixed structure of bainite/martensite and an original austenitic crystal grain size number after a heat treatment of the stabilizer is Gh 9 or more.

Abstract: A low carbon resulfurized free cutting steel consisting of 0.04 to 0.15% of C, more than 0.10% and 0.70% or less of Si, 0.85 to 1.50% of Mn, 0.040 to 0.120% of P, 0.250% or more and less than 0.400% of S, less than 0.005% of Al, more than 0.0020% and 0.0120% or less of O, and more than 0.0070% and 0.0150% or less of N, all by mass percentage, and the balance of Fe and inevitable impurities, and satisfying a formula (1) and a formula (2), as follows: 0.15%?Si %+2×P %?(5×Al %+10×O %+3×N %)?0.75%??(1), and ([Mn %]5)/15<S %<([Mn %]5)/2??(2).

Abstract: A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 ?m, prior austenite has a grain diameter of 30 ?m or less, and the ratio by volume of the residual austenite is less than 25%.

Abstract: A steel part having a long rolling contact fatigue life and capable of further increasing the life of a bearing under severer using condition than usual conditions. The steel part includes steel having a composition containing 0.7% by mass to 1.1% by mass of C, 0.5% by mass to 2.0% by mass of Si, 0.4% by mass to 2.5% by mass of Mn, 1.6% by mass to 5.0% by mass of Cr, 0.1% by mass to less than 0.5% by mass of Mo, 0.010% by mass to 0.050% by mass of Al, less than 0.0015% by mass of Sb as an impurity, and the balance composed of Fe and inevitable impurities, the steel being hardened and tempered. In the steel structure of a portion from the surface to a depth of 5 mm, residual cementite has a grain diameter of 0.05 to 1.5 ?m, prior austenite has a grain diameter of 30 ?m or less, and the ratio by volume of the residual austenite is less than 25%.