A shaft part excellent in static torsional strength and torsional fatigue strength containing, by mass %, essential elements of C: 0.35 to 0.70%, Si: 0.01 to 0.40%, Mn: 0.5 to 2.6%, P: 0.050% or less, S: 0.005 to 0.020%, Al: 0.010 to 0.050%, N: 0.005 to 0.025%, and O: 0.003% or less, further containing optional elements, having a balance of Fe and impurities, having a chemical composition satisfying formula (1), having at least one hole at an outer circumferential surface, having a volume ratio (R1) of 4 to 20% of retained austenite at a position of a 2 mm depth from the outer circumferential surface, having a volume ratio of retained austenite at a position of a 2 mm depth from the outer circumferential surface in an axial direction of the hole and at a position of a 20 μm depth from the surface of the hole as R2, and having a reduction rate Δγ of 40% or more of retained austenite found by the formula (A): Δγ=[(R1−R2)/R1]×100: Formula (1): 15.0≤25.9C+6.35Mn+2.88Cr+3.09Mo+2.73Ni≤27.2 (Notations of elements in formula are contents of the elements).

A fastening device for connecting a first housing part of a steam or gas turbine to a second housing part of the turbine. The screw is made of a parent metal with a high degree of stress relaxation.

A fastening device for connecting a first housing part of a steam or gas turbine to a second housing part of the turbine. The screw is made of a parent metal with a high degree of stress relaxation.

In this cast austenitic stainless steel, in a cross section when heated at 1000° C., an average number Nc per unit area of carbides having an equivalent circle diameter of 500 nm or larger in a center portion of an austenite crystal grain is 6.0×10.sup.−2 particles/μm.sup.2 or more, and, when an average number per unit area of the carbides having an equivalent circle diameter of 500 nm or larger in a vicinity of a grain boundary in an austenite crystal grain is represented as Ngb, Ngb/Nc is 1.3 or less.

The invention relates to a steel alloy comprising, in percent by mass:—0.17 to 0.23 carbon;—1.40 to 1.60 silicon;—0.50 to 0.60 manganese;—up to 0.020 phosphor;—up to 0.020 sulfur;—up to 0.30 chrome;—up to 0.12 molybdenum;—up to 0.80 nickel;—up to 0.30 copper;—up to 0.03 vanadium; the remainder being iron and incidental impurities.

The invention relates to a steel alloy comprising, in percent by mass:—0.17 to 0.23 carbon;—1.40 to 1.60 silicon;—0.50 to 0.60 manganese;—up to 0.020 phosphor;—up to 0.020 sulfur;—up to 0.30 chrome;—up to 0.12 molybdenum;—up to 0.80 nickel;—up to 0.30 copper;—up to 0.03 vanadium; the remainder being iron and incidental impurities.

A bar-shaped steel product extends unidirectionally and has a chemical composition including, by mass %, 0.001 to 0.20% of C, 0.01 to 3.0% of Si, 0.01 to 2.0% of Mn, 0.01 to 5.0% of Ni, 7.0 to 35.0% of Cr, 0.01 to 5.0% of Mo, 0.01 to 3.0% of Cu, 0.001 to 0.10% of N, 0.2 to 2.0% of Nb, optional element(s), and a balance consisting of Fe and inevitable impurities, and has 0.5 or less of a rolling-direction-crystal-orientation RD//<100> fraction (an area ratio of crystal having 20 degrees or less of an orientation difference between a <100> orientation and a rolling direction).

A seamless steel pipe has a t/D.sub.out of 0.05 to 0.40, where t is a wall thickness (mm) of the seamless steel pipe, and D.sub.out is an outside diameter (mm) of the seamless steel pipe. The seamless steel pipe has a maximum depth d.sub.max (mm)≤0.350 mm for defects in an inner surface of the steel pipe on a cross section perpendicular to a pipe axis. The seamless steel pipe has an average defect depth d.sub.ave (mm)≤0.200 mm for defects having a depth of 0.050 mm or more in the inner surface of the steel pipe. The seamless steel pipe, per millimeter of an inner circumferential length of the pipe, has at most 30 defects having a depth of 0.050 mm or more in the inner surface of the steel pipe.

A method for producing a machine component excellent in pitting resistance characteristics and toughness includes a carburizing step, performed on a steel material containing 0.13-0.30% C and 0.90-2.00% Cr in mass % and at least one of Si, Mn, Ni, Mo, Nb, V, Ti, B, Al, and N, balance Fe and unavoidable impurities; heating the material to 850-1030° C. to attain carbon concentration in a surface of 0.8-1.5%; cooling the material at an average rate of 5° C./sec or lower from a temperature higher than the A.sub.cm point of a surface layer to a cooling end temperature that is at least 50° C. lower than the A.sub.1 point to cause the surface layer to have a pearlite or bainite structure with dispersion; spheroidizing annealing at a temperature not higher than the A.sub.cm point at the surface layer; heating the material to not higher than the A.sub.cm point at the surface layer; and performing tempering.

The invention relates to a turnout rail production technology, in particular to a deeply-hardened-surface turnout rail with high degree of undercooling and the preparation method thereof. The invention aims to solve the technical problem by providing a deeply-hardened-surface turnout rail with high degree of undercooling featured in even hardness distribution and a deeply hardened surface layer and the preparation method thereof. The method is described as follows: feeding molten iron for converter smelting.fwdarw.furnace rear argon blowing station.fwdarw.LF refining.fwdarw.RH vacuumization.fwdarw.casting steel blanks.fwdarw.slow cooling in the slow cooling pit.fwdarw.austenitic homogenization.fwdarw.rail rolling.fwdarw.heat treatment; in the converter smelting process, adding 0.2-0.3% Cr, 0.04-0.06 V and 0.75-0.80% C; the heat treatment process is divided into two cooling stages. The turnout rail prepared with the method described in the invention has a deeper deeply-hardened surface layer; the hardness is distributed more evenly, the anti-contact fatigue performance is higher and the resistance to wearing is ideal.