Abstract: Provided is a steel for carbonitrided bearing which excels in hardenability and also excels in toughness, wear resistance, and surface-originated flaking life after quenching and tempering. A steel for carbonitrided bearing of the present embodiment has a chemical composition containing, in mass %, C: 0.22 to 0.45%, Si: not more than 0.50%, Mn: 0.40 to 1.50%, P: not more than 0.015%, S: not more than 0.005%, Cr: 0.30 to 2.0%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.10%, N: not more than 0.030%, and O: not more than 0.0015%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2). 1.20<0.4Cr+0.4Mo+4.5V<2.60??(1) 2.7C+0.4Si+Mn+0.8Cr+Mo+V>2.

Abstract: A high-strength bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to this invention has a chemical composition consisting of, in mass %, C: 0.22 to 0.40%, Si: 0.10 to 1.50%, Mn: 0.20 to less than 0.40%, P: 0.020% or less, S: 0.020% or less, Cr: 0.70 to 1.45%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.045%, B: 0.0003 to 0.0040%, N: 0.0015 to 0.0080% and O: 0.0020% or less, with a balance being Fe and impurities, and satisfying Formula (1) and Formula (2), and with the high-strength bolt having a tensile strength of 1000 to 1300 MPa. 0.50?C+Si/10+Mn/5+5Cr/22?0.85??(1) Si/Mn>1.0??(2) Where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1) and Formula (2).

Abstract: A steel for induction hardening according to the present invention includes a chemical composition consisting of, in mass percent: C: 0.58 to 0.68%, Si: 0.70 to 1.40%, Mn: 0.20 to 1.40%, P: less than 0.020%, S: 0.025% or less, Al: more than 0.06% to 0.15%, N: 0.0020 to 0.0080%, O: 0.0015% or less, and Ca: 0.0005 to 0.005%, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). The steel microstructure is made up of ferrite and pearlite. In the steel, a ratio of a number of composite inclusions to a total number of Al2O3 inclusions and the composite inclusions is 20% or more. C+Si/7+Mn/5+Cr/9+Mo/2.5?1.05??(1) C+Si/10+Mn/20+Cr/25?0.70??(2) Cr/Si?0.

Abstract: A steel for induction hardening according to the present invention includes a chemical composition consisting of, in mass percent: C: 0.53 to less than 0.58%, Si: 0.70 to 1.40%, Mn: 0.20 to 1.40%, P: less than 0.020%, S: 0.025% or less, Al: more than 0.06% to 0.15%, N: 0.0020 to 0.0080%, O: 0.0015% or less, B: 0.0003 to 0.0040%, Ti: 0.010 to 0.050%, and Ca: 0.0005 to 0.005%, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). The steel microstructure is made up of ferrite and pearlite. A ratio of a number of composite inclusions is 20% or more. C+Si/7+Mn/5+Cr/9+Mo/2.5?0.98??(1) C+Si/10+Mn/20+Cr/25?0.70??(2) Cr/Si?0.

Abstract: A steel for induction hardening according to the present invention includes a chemical composition consisting of, in mass percent: C: 0.58 to 0.68%, Si: 0.70 to 1.40%, Mn: 0.20 to 1.40%, Al: 0.005 to 0.060%, N: 0.0020 to 0.0080%, and Ca: 0.0005 to 0.005%, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). The steel microstructure is made up of ferrite and by area fraction, 85% or more of pearlite. In the steel, a ratio of a number of composite inclusions to a total number of Al2O3 inclusions and the composite inclusions that contain 2.0% or more of SiO2 and 2.0% or more of CaO is 20% or more. C+Si/7+Mn/5+Cr/9+Mo/2.5?1.05??(1) C+Si/10+Mn/20+Cr/25?0.70??(2) Cr/Si?0.

Abstract: A steel for induction hardening according to the present invention includes a chemical composition consisting of, in mass percent: C: 0.53 to less than 0.58%, Si: 0.70 to 1.40%, Mn: 0.20 to 1.40%, P: less than 0.020%, S: less than 0.020%, Al: 0.005 to 0.060%, N: 0.0020 to 0.0080%, O: 0.0015% or less, B: 0.0003 to 0.0040%, Ti: 0.010 to 0.050%, and Ca: 0.0005 to 0.005%, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). The steel microstructure is made up of ferrite and pearlite. A ratio of a number of composite inclusions is 20% or more. C+Si/7+Mn/5+Cr/9+Mo/2.5?0.98??(1) C+Si/10+Mn/20+Cr/25?0.70??(2) Cr/Si?0.

Abstract: Rolled wire rod effectively suppressing fracturing at the time of cold forging and excellent in hydrogen embrittlement resistance after quenching and tempering following spheroidization annealing even without spheroidization annealing before cold forging or even if shortening the time period of spheroidization annealing is provided wherein it has a predetermined composition and wherein if the contents of Ti, N, and S (mass %) are respectively [Ti], [N], and [S], if [S]?0.0010, [Ti] is (4.5×[S]+3.4×[N]) or more and (0.008+3.4×[N]) or less, while if [S]?0.0010, [Ti] is (4.5×[S]+3.4×[N]) or more and (8.0×[S]+3.4×[N]) or less, the internal structure is a mixed structure of ferrite and pearlite with an area rate of a ferrite fraction of 40% or more, and a mean area of sulfides present in a range from a surface to a D/8 position is 6 ?m2 or less in the case of a diameter of D (mm) in a cross-section at a plane including the axial direction, and a mean aspect ratio of the sulfides is 5 or less.

Abstract: Provided is a carbonitrided bearing part which has high hardenability and toughness, and is excellent in wear resistance and surface-originated flaking life. A carbonitrided bearing part of the present embodiment has a chemical composition containing, in mass %, C: 0.15 to 0.45%, Si: not more than 0.50%, Mn: 0.40 to 1.50%, P: not more than 0.015%, S: not more than 0.005%, Cr: 0.30 to 2.0%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.10%, N: not more than 0.030%, and O: not more than 0.0015%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2). At surface, C concentration is 0.7 to 1.2%, N concentration is 0.15 to 0.6%, and Rockwell hardness HRC is 58 to 65. 1.20<0.4Cr+0.4Mo+4.5V<2.60??(1) 2.7C+0.4Si+Mn+0.8Cr+Mo+V>2.

Abstract: A ball bearing not allowing locations where the surface pressure becomes locally higher at a race at the time of a high load and thereby keeping cracking from occurring and in turn realizing a longer lifespan is provided. A pair of races (12, 14) and at least one rolling element (16) movably clamped between the pair of races move are provided. A cross-sectional profile line (14a) of a part of each of the pair of races contacting the rolling element has the smallest radius of curvature at a position (P) sticking out the most in the first direction (D1) over which the pair of races face. The cross-sectional profile line becomes larger in radius of curvature the further from the position (P) in a second direction (D2) vertical to the first direction (D1) in the cross-section. The cross-sectional profile line is comprised of a single function.

Abstract: A steel for induction hardening according to the present invention includes a chemical composition consisting of, in mass percent: C: 0.58 to 0.68%, Si: 0.70 to 1.40%, Mn: 0.20 to 1.40%, P: less than 0.020%, S: less than 0.020%, Al: 0.005 to 0.060%, N: 0.0020 to 0.0080%, 0: 0.0015% or less, V: 0.01 to 0.25%, B: 0.0003 to 0.0040%, Ti: 0.010 to 0.050%, and Ca: 0.0005 to 0.005%, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). The steel microstructure is made up of ferrite and pearlite. A ratio of a number of composite inclusions is 20% or more. C+Si/7+Mn/5+Cr/9+Mo/2.5?1.05 ??(1) C+Si/10+Mn/20+Cr/25?0.70 ??(2) Cr/Si?0.

Abstract: A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 ?m or less; and a number density of a void having a circle equivalent diameter of 0.02 ?m to 3.0 ?m is 2000 mm?2 or less in the metallographic structure.

Abstract: A rolling sliding member includes a base part and a surface layer. The base part has a composition that includes 0.30 mass % to 0.45 mass % of carbon, 0.15 mass % to 0.45 mass % of silicon, 0.40 to 1.50 mass % of manganese, 0.60 mass % to 2.00 mass % of chromium, 0.10 mass % to 0.35 mass % of molybdenum, 0.20 mass % to 0.40 mass % of vanadium, and 0.005 mass % to 0.100 mass % of aluminum, and a remainder of iron and inevitable impurities. The surface layer is positioned around the base part. The surface layer has a Vickers hardness of 700 to 800 and a retained austenite content of 25 volume % to 50 volume %. The thickness of a grain boundary oxide layer satisfies Formula: thickness of grain boundary oxide layer?equivalent diameter of rolling sliding member×1.4×10?3.

Abstract: There is provided a spring steel including predetermined chemical composition, in which ([Ti mass %]?3.43×[N mass %])/[S mass %]>4.0, and [Ni mass %]+[Cu mass %]<0.75 are satisfied, and an appearance frequency of MnS is less than 20% among inclusions having an equivalent circle diameter of 1 ?m or more which are observed at a 1/4 position of a diameter from a surface.

Abstract: A case hardening steel includes, as a chemical composition, by mass %, C: 0.10% to 0.30%, Si: 0.02% to 1.50%, Mn: 0.30% to 1.80%, S: 0.003% to 0.020%, Cr: 0.40% to 2.00%, Al: 0.005% to 0.050%, Ti: 0.06% to 0.20%, Bi: 0.0001% to 0.0050%, Mo: 0% to 1.50%, Ni: 0% to 3.50%, V: 0% to 0.50%, B: 0% to 0.0050%, Nb: 0% or more and less than 0.040%, P: limited to 0.050% or less, N: limited to 0.0060% or less, O: limited to 0.0025% or less, and a remainder including an iron and impurities, and satisfies Ti/S?6.0, in which, in a longitudinal section, a maximum diameter of Ti-based precipitates predicted by extreme value statistics under a condition that an inspection standard area is 100 mm2, a number of inspections is 16 visual fields, and an area where prediction is performed is 30,000 mm2, is 40 ?m or less.

Abstract: A bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to an embodiment of the present invention consists of, in mass %, C: 0.32 to 0.39%, Si: 0.15% or less, Mn: 0.40 to 0.65%, P: 0.020% or less, S: 0.020% or less, Cr: 0.85 to 1.25%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.050%, B: 0.0010 to 0.0030%, N: 0.0015 to 0.0080%, 0: 0.0015% or less, Mo: 0 to 0.05%, V: 0 to 0.05%, Cu: 0 to 0.50%, Ni: 0 to 0.30%, and Nb: 0 to 0.05%, with the balance being Fe and impurities. The bolt satisfies Formula (1) and Formula (2), and has a tensile strength of 1000 to 1300 MPa and satisfies Formula (3). 4.9?10C+Si+2Mn+Cr+4Mo+5V?6.1 ??(1) Mn/Cr?0.55 ??(2) [dissolved Cr]/Cr?0.

Abstract: A high-strength bolt is provided that has high strength and excellent hydrogen embrittlement resistance characteristics. A bolt according to this invention has a chemical composition consisting of, in mass %, C: 0.22 to 0.40%, Si: 0.10 to 1.50%, Mn: 0.20 to less than 0.40%, P: 0.020% or less, S: 0.020% or less, Cr: 0.70 to 1.45%, Al: 0.005 to 0.060%, Ti: 0.010 to 0.045%, B: 0.0003 to 0.0040%, N: 0.0015 to 0.0080% and O: 0.0020% or less, with a balance being Fe and impurities, and satisfying Formula (1) and Formula (2), and with the high-strength bolt having a tensile strength of 1000 to 1300 MPa. 0.50?C+Si/10+Mn/5+5Cr/22?0.85??(1) Si/Mn>1.0??(2) Where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1) and Formula (2).

Abstract: The rolled rod for cold-forged thermally refined articles according to the present invention has a chemical composition consisting, in mass %: C: 0.22 to 0.40%, Si: 0.35 to 1.5%, Mn: 0.20 to 0.40%, P: less than 0.020%, S: less than 0.015%, Cr: 0.70 to 1.45%, Al: 0.005 to 0.060%, Ti: 0.01 to 0.05%, B: 0.0003 to 0.0040%, N: 0.0020 to 0.0080%, and O: 0.0020% or less, with the balance being Fe and impurities, and that satisfies Formula (1) and Formula (2), wherein a total area fraction of pro-eutectoid ferrite and pearlite is 90% or more, an area fraction of the pro-eutectoid ferrite is 30% or more, and the rolled rod has a tensile strength of 700 MPa or less. 0.50?C+Si/10+Mn/5+5Cr/22?0.85??(1) Si/Mn>1.

Abstract: A roughly shaped material for a rolling bearing of the present invention is produced by forging a steel composed of a high-carbon chrome bearing steel containing 0.7 mass % to 1.2 mass % of a carbon, and 0.8 mass % to 1.8 mass % of a chromium to a predetermined shape while heating the steel to a forging temperature in a range of (Ae1 point+25° C.) to (Ae1 point+105° C.), cooling a forged article to a temperature of Ae1 point or lower, and performing an annealing in which the forged article that is obtained is heated to a soaking temperature in a range of (Ae1 point+25° C.) to (Ae1 point+85° C.), the forged article is retained for 0.5 hours or longer, and the forged article is cooled down to 700° C. or lower at a cooling rate of 0.30° C./s or slower.

Abstract: An age-hardenable steel having a composition consisting of: C: 0.05 to 0.20%, Si: 0.01 to 0.50%, Mn: 1.5 to 2.5%, S: 0.005 to 0.08%, Cr: more than 0.50% and not more than 1.6%, Al: 0.005 to 0.05%, V: 0.25 to 0.50%, Mo: 0 to 1.0%, Cu: 0 to 0.3%, Ni: 0 to 0.3%, Ca: 0 to 0.005%, and Bi: 0 to 0.4%, the balance being Fe and impurities. Within the impurities, P?0.03%, Ti<0.005%, and N<0.0080%, and [C+0.3Mn+0.25Cr+0.6Mo?0.68], [C+0.1Si+0.2Mn+0.15Cr+0.35V+0.2Mo?1.05], and [?4.5C+Mn+Cr?3.5V?0.8Mo?0.12]. The steel has hardness before aging of not more than 310 HV. After aging, the fatigue strength is not less than 480 MPa and absorbed energy at 20° C. is not less than 12 J.

Abstract: A bearing constituent member includes a base material including steel and a carbonitrided layer that is a surface layer on the steel, the steel including 0.3 to 0.45 mass % of carbon, 0.5 mass % or lower of silicon, 0.4 to 1.5 mass % of manganese, 0.3 to 2 mass % of chromium, 0.1 to 0.35 mass % of molybdenum, 0.2 to 0.4 mass % of vanadium, and a remainder of iron and unavoidable impurities. Surface Vickers hardness at a position at a depth of 50 ?m from a surface of a rolling sliding surface is 700 to 800, internal hardness is 550 to 690 in terms of Vickers hardness, and an amount of residual austenite in a range from the surface to a depth of 10 ?m is at least 30 vol %.