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 (Ae.sub.1 point+25 C.) to (Ae.sub.1 point+105 C.), cooling a forged article to a temperature of Ae.sub.1 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 (Ae.sub.1 point+25 C.) to (Ae.sub.1 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.

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 (Ae.sub.1 point+25 C.) to (Ae.sub.1 point+105 C.), cooling a forged article to a temperature of Ae.sub.1 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 (Ae.sub.1 point+25 C.) to (Ae.sub.1 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.

The present invention provides an annealed steel material having a composition containing, in mass %, 0.28C0.42, 0.01Si1.50, 0.20Mn1.20, 4.80Cr6.00, 0.80Mo3.20, 0.40V1.20, and 0.002N0.080, with the balance being Fe and unavoidable impurities; in which the annealed steel material has a cross-sectional size of a thickness of 200 mm or more and a width of 250 mm or more, and a hardness of 100 HRB or less; and in which a diameter of a largest ferritic grain observed in a microstructure is 120 m or less in terms of a perfect circle equivalent, an area ratio of carbides is 3.0% or more and less than 10.5%, and an average particle diameter of the carbides is 0.18 m or more and 0.29 m or less.

Disclosed is a cold forged gear steel. In addition to Fe and inevitable impurities, the cold forged gear steel further comprises the following chemical elements in mass percentage: 0.15-0.17% of C, 0.10-0.20% of Si, 1.0-1.10% of Mn, 0.80-0.90% of Cr and 0.02-0.04% of Al. Correspondingly, further disclosed is a manufacturing method for the cold forged gear steel, comprising the steps of: (1) smelting and casting; (2) heating; (3) forging or rolling; and (4) spheroidizing annealing: heating to and keeping at 750-770? C., then cooling with a cooling rate of 5-15? C./h to and keeping at 700-720? C., cooling with a cooling rate of 3-12? C./h to and keeping at 660-680? C., and cooling with a cooling rate of 5-20? C./h to 500? C. or below, and then tapping and cooling.

Disclosed is a cold forged gear steel. In addition to Fe and inevitable impurities, the cold forged gear steel further comprises the following chemical elements in mass percentage: 0.15-0.17% of C, 0.10-0.20% of Si, 1.0-1.10% of Mn, 0.80-0.90% of Cr and 0.02-0.04% of Al. Correspondingly, further disclosed is a manufacturing method for the cold forged gear steel, comprising the steps of: (1) smelting and casting; (2) heating; (3) forging or rolling; and (4) spheroidizing annealing: heating to and keeping at 750-770? C., then cooling with a cooling rate of 5-15? C./h to and keeping at 700-720? C., cooling with a cooling rate of 3-12? C./h to and keeping at 660-680? C., and cooling with a cooling rate of 5-20? C./h to 500? C. or below, and then tapping and cooling.

A high carbon hot rolled steel sheet and a method for manufacturing the same are provided, wherein excellent cold workability and excellent hardenability are obtained stably. The high carbon hot rolled steel sheet has a composition containing C: 0.20% to 0.48%, Si: 0.1% or less, Mn: 0.5% or less, P: 0.03% or less, S: 0.01% or less, sol. Al: more than 0.10% and 1.0% or less, N: 0.005% or less, B: 0.0005% to 0.0050%, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, and a microstructure composed of ferrite and cementite, wherein the average grain size of the above-described ferrite is 10 to 20 m and the spheroidization ratio of the above-described cementite is 90% or more.

Disclosed herein is a mechanical structure steel for cold-working that includes C, Si, Mn, P, S, Al, and N and has a metal microstructure including proeutectoid ferrite and pearlite, in which a total area ratio of the proeutectoid ferrite and the pearlite with respect to the entire microstructure is 90% or more, while an area ratio Af of the proeutectoid ferrite with respect to the entire microstructure satisfies a relationship of AfA where an A value is represented by formula (1) below, an average circle equivalent diameter of a bcc-Fe crystal grain is in a range of 15 to 30 m, and a pearlite lamellar spacing is 0.20 m or less on average:

A=(103128[C(%)])0.80(%)(1)

where [C (%)] in the formula (1) indicates the C content in percent by mass.

A bearing steel includes 1.0 to 1.3 wt % carbon; 0.9 to 1.6 wt % silicon; 0.5 to 1.0 wt % manganese; 1.5 to 2.5 wt % nickel; 1.5 to 2.5 wt % chromium; 0.2 to 0.5 wt % molybdenum; 0.01 to 0.06 wt % aluminum; 0.01 to 0.1 wt % copper; at least one selected from the group consisting of more than 0 wt % and less than 0.38 wt % vanadium and more than 0 wt % and less than 0.02 wt % niobium; and a balance of iron.

A bearing steel includes 1.0 to 1.3 wt % carbon; 0.9 to 1.6 wt % silicon; 0.5 to 1.0 wt % manganese; 1.5 to 2.5 wt % nickel; 1.5 to 2.5 wt % chromium; 0.2 to 0.5 wt % molybdenum; 0.01 to 0.06 wt % aluminum; 0.01 to 0.1 wt % copper; at least one selected from the group consisting of more than 0 wt % and less than 0.38 wt % vanadium and more than 0 wt % and less than 0.02 wt % niobium; and a balance of iron.

A steel alloy for bearings contains: 0.6 to 0.9 wt. % carbon, 0.1 to 0.5 wt. % silicon, 0.1 to 1.5 wt. % manganese, 1.5 to 2.0 wt. % chromium, 0.2 to 0.6 wt. % molybdenum, 0 to 0.25 wt. % nickel, 0 to 0.3 wt. % copper, 0 to 0.2 wt. % vanadium, 0 to 0.2 wt. % cobalt, 0 to 0.2 wt. % aluminium, 0 to 0.1 wt. % niobium, 0 to 0.2 wt. % tantalum, 0 to 0.05 wt. % phosphorous, 0 to 0.03 wt. % sulphur, 0 to 0.075 wt. % tin, 0 to 0.075 wt. % antimony, 0 to 0.075 wt. % arsenic, 0 to 0.01 wt. % lead, up to 350 ppm nitrogen, up to 100 ppm oxygen, up to 50 ppm calcium, up to 50 ppm boron, up to 50 ppm titanium, the balance being iron, together with any other unavoidable impurities. Furthermore, the steel alloy contains (i) molybdenum and silicon in a weight ratio of 0.4<Mo/Si<6.0 and (ii) molybdenum and chromium in a weight ratio of 0.1<Mo/Cr<0.4.