Provided is a high-strength seamless steel pipe having the composition which contains, by mass %, 0.20 to 0.50% C, 0.05 to 0.40% Si, 0.3 to 0.9% Mn, 0.015% or less P, 0.005% or less S, 0.005 to 0.1% Al, 0.008% or less N, 0.6 to 1.7% Cr, 0.4 to 1.0% Mo, 0.01 to 0.30% V, 0.01 to 0.06% Nb, 0.0003 to 0.0030% B, and 0.0030% or less O (oxygen). The high-strength seamless steel pipe has the microstructure where a volume fraction of a tempered martensitic phase is 95% or more, and prior austenitic grains have a grain size number of 8.5 or more, and a segregation degree index Ps which is defined by a formula Ps=8.1 (X.sub.Si+X.sub.Mn+X.sub.Mo)+1.2X.sub.P relating to X.sub.M which is a ratio between a segregated portion content and an average content is set to less than 65.

Provided is a high-strength seamless steel pipe having the composition which contains, by mass %, 0.20 to 0.50% C, 0.05 to 0.40% Si, 0.3 to 0.9% Mn, 0.015% or less P, 0.005% or less S, 0.005 to 0.1% Al, 0.008% or less N, 0.6 to 1.7% Cr, 0.4 to 1.0% Mo, 0.01 to 0.30% V, 0.01 to 0.06% Nb, 0.0003 to 0.0030% B, and 0.0030% or less O (oxygen). The high-strength seamless steel pipe has the microstructure where a volume fraction of a tempered martensitic phase is 95% or more, and prior austenitic grains have a grain size number of 8.5 or more, and a segregation degree index Ps which is defined by a formula Ps=8.1 (X.sub.Si+X.sub.Mn+X.sub.Mo)+1.2X.sub.P relating to X.sub.M which is a ratio between a segregated portion content and an average content is set to less than 65.

A steel sheet includes, as a chemical composition, by mass %: C: 0.05-0.30%; Si: 0.2-2.0%; Mn: 2.0-4.0%; Al: 0.001-2.000%; P: 0.100% or less; S: 0.010% or less; N: 0.010% or less; Ti: 0-0.100%; Nb: 0-0.100%; V: 0-0.100%; Cu: 0-1.00%; Ni: 0-1.00%; Mo: 0-1.00%; Cr: 0-1.00%; W: 0-0.005%; Ca: 0-0.005%; Mg: 0-0.005%; a rare earth element (REM): 0-0.010%; B: 0-0.0030%; and a remainder of Fe and impurities, in which a metallographic structure contains, by area ratio, 95% or more of a hard structure and 0-5% of residual austenite, by mass % in a cross section in a thickness direction, C1/C2 which is a ratio of an upper limit C1 of a Mn content to a lower limit C2 of the Mn content is 1.5 or less, and a bake-hardening amount BH is 150 MPa or less.

A steel sheet includes, as a chemical composition, by mass %: C: 0.05-0.30%; Si: 0.2-2.0%; Mn: 2.0-4.0%; Al: 0.001-2.000%; P: 0.100% or less; S: 0.010% or less; N: 0.010% or less; Ti: 0-0.100%; Nb: 0-0.100%; V: 0-0.100%; Cu: 0-1.00%; Ni: 0-1.00%; Mo: 0-1.00%; Cr: 0-1.00%; W: 0-0.005%; Ca: 0-0.005%; Mg: 0-0.005%; a rare earth element (REM): 0-0.010%; B: 0-0.0030%; and a remainder of Fe and impurities, in which a metallographic structure contains, by area ratio, 95% or more of a hard structure and 0-5% of residual austenite, by mass % in a cross section in a thickness direction, C1/C2 which is a ratio of an upper limit C1 of a Mn content to a lower limit C2 of the Mn content is 1.5 or less, and a bake-hardening amount BH is 150 MPa or less.

A method of manufacturing a sliding camshaft for an internal combustion engine includes providing the sliding camshaft from a steel alloy having a carbon content between 0.25% and 0.60%. The sliding camshaft is then processed with a carbon infusing heat treatment process, such as carburization or carbonitriding. After the sliding camshaft has been processed with the carbon infusing heat treatment process, the sliding camshaft is then processed with a quenching heat treatment process, such as a mar-quenching heat treatment process.

A method of manufacturing a sliding camshaft for an internal combustion engine includes providing the sliding camshaft from a steel alloy having a carbon content between 0.25% and 0.60%. The sliding camshaft is then processed with a carbon infusing heat treatment process, such as carburization or carbonitriding. After the sliding camshaft has been processed with the carbon infusing heat treatment process, the sliding camshaft is then processed with a quenching heat treatment process, such as a mar-quenching heat treatment process.

Provided is a low alloy oil-well steel pipe having a yield strength of 827 MPa or more, and an excellent SSC resistance. The low alloy oil-well steel pipe according to the present invention consisting of: in mass %, C: more than 0.35 to 0.65%; Si: 0.05 to 0.50%; Mn: 0.10 to 1.00%; Cr: 0.40 to 1.50%; Mo: 0.50 to 2.00%; V: 0.05 to 0.25%; Nb: 0.01 to 0.040%; sol.Al: 0.005 to 0.10%; N: 0.007% or less; Ti: 0 to 0.012%; Ca: 0 to 0.005%; and a balance being Fe and impurities, the impurities including: P: 0.020% or less; S: 0.002% or less; O: 0.006% or less; Ni: 0.10% or less; Cu: 0.03% or less; and B: 0.0005% or less, wherein in a microstructure, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 200 particles/100 μm.sup.2 or more, and a yield strength is 827 MPa or more.

A method of joining a first work piece and a second workpiece. The first and second workpieces may be rotor wheels of a rotor for a turbomachine. At least one of the workpieces includes an oxide dispersion strengthened alloy material and the first and second work pieces may be joined by welding a cladding on at least one of the workpieces to the other of the workpieces, without welding a substrate of the at least one workpiece which includes an oxide dispersion strengthened alloy material.

A method and forming tool for hot forming and press hardening plate-shaped or preformed workpieces of sheet steel, wherein the workpiece is heated to a temperature above the austenitisation temperature and is then formed and quenched in a cooled forming tool having a punch and a female mold, wherein the female mold is coated in its drawing edge region with material in a material-uniting manner and/or is provided there with at least one insert part having a thermal conductivity at least 10 W/(m*K) lower than the thermal conductivity of the portion of the female mold adjacent to the drawing edge region and comes into contact with the workpiece when said workpiece is being hot formed and press hardened, the surface of the material having a transverse dimension within the range of 1.6 times to 10 times the positive radius of the female mold.

A method for producing a metallic component, The method includes the method steps of first machining (103) the component and thereafter cooling (105) the component from a first temperature down to a lower second temperature. The cooling (105) occurs after the machining (103) of the component.