A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: more than 0.6% to 1.5% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.05% to 0.3%, Nb: 0.001% to 0.020%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 m or more is 100 or less per 100 mm.sup.2, the number of nitride-based inclusions having a grain size of less than 4 μm is 1000 or less per 100 mm.sup.2, the number of oxide-based inclusions having a grain size of 4 μm or more is 40 or less per 100 mm.sup.2, and the number of oxide-based inclusions having a grain size of less than 4 μm is 400 or less per 100 mm.sup.2, and methods of producing the same.

A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: more than 0.6% to 1.5% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.05% to 0.3%, Nb: 0.001% to 0.020%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 m or more is 100 or less per 100 mm.sup.2, the number of nitride-based inclusions having a grain size of less than 4 μm is 1000 or less per 100 mm.sup.2, the number of oxide-based inclusions having a grain size of 4 μm or more is 40 or less per 100 mm.sup.2, and the number of oxide-based inclusions having a grain size of less than 4 μm is 400 or less per 100 mm.sup.2, and methods of producing the same.

A high temperature iron-chromium-aluminium (FeCrAl) alloy tube extending along a longitudinal axis, wherein the tube is formed from a continuous strip of a high temperature FeCrAl alloy and comprises a helical welded seam. The high temperature FeCrAl alloy tube is manufactured by feeding a continuous strip of the high temperature FeCrAl alloy toward a tube shaping station, helically winding the strip such that long edges of the strip abut each other and a rotating tube moving forward in a direction parallel to its longitudinal axis is formed, and continuously joining said abutting long edges together in a welding process directly when the tube is formed, whereby a welded tube comprising a helical welded seam is obtained.

A process for preparing a multi-thickness welded steel vehicle rail, the process comprises the steps of: (a) forming a first tube having a first outer diameter, an inner diameter and a first wall thickness; (b) forming a second tube having the first outer diameter, a second inner diameter and a second wall thickness different than the first wall thickness; (c) swaging a first end of the first tube to a second outer diameter less than the second inner diameter of the second tube; (d) inserting the swaged first end of the first tube into an end of the second tube to form a joint; (e) welding the first tube and the second tube together to form a weld at the joint to form a tube blank with a heat affected zone of lower metal strength in the area of the weld; (f) preheating the tube blank to create a common crystalline microstructure along a length of the tube blank; (g) introducing the tube blank into a blow molding tool having inner molding walls; (h) molding the tube blank at an elevated temperature by expanding the tube blank against the inner molding walls of the molding tool by injecting a pressurized medium into an interior cavity of the tube blank; and (i) quenching the tube blank by replacing the pressurized medium with a cooling medium through the molding tool and the tube blank to achieve a rapid cooling effect on the tube blank and to create a completed vehicle rail with essentially uniform material strength across the weld. A completed vehicle rail has an overlapped welded structure and uniform microcrystalline structure along the length of the rail.

An alloy pipe and a method for producing the same are disclosed. The alloy pipe of the present invention contains, as a component composition, in terms of % by mass, Cr: 11.5-35.0%, Ni: 23.0-60.0%, and Mo: 0.5-17.0%, has an austenitic phase as a microstructure, has a Mo concentration (% by mass) in a grain boundary of the austenitic phase that is 4.0 times or less than a Mo concentration (% by mass) within grains of the austenitic phase, and has a tensile yield strength in a pipe axial direction of 689 MPa or more and a ratio (compressive yield strength in a pipe axial direction)/(tensile yield strength in a pipe axial direction) of 0.85 to 1.15.

The present disclosure is directed and formulations and methods to provide alloys having relative high strength and ductility. The alloys may be provided in seamless tubular form and characterized by their particular alloy chemistries and identifiable crystalline grain size morphology. The alloys are such that they include boride pinning phases. In what is termed a Class 1 Steel the alloys indicate tensile strengths of 700 MPa to 1400 MPa and elongations of 10-70%. Class 2 Steel indicates tensile strengths of 800 MPa to 1800 MPa and elongations of 5-65%. Class 3 Steel indicates tensile strengths of 1000 MPa to 2000 MPa and elongations of 0.5-15%.

An apparatus line for manufacturing seamless steel pipes and tubes includes: a heating apparatus for heating a steel raw material; a piercing apparatus for piercing the heated steel raw material thus forming a hollow material; and a rolling apparatus for applying working to the hollow material to form a seamless steel pipe having a predetermined shape. A cooling apparatus is arranged on an exit side of the rolling apparatus. A heated steel raw material is worked by the rolling apparatus after being pierced by the piercing apparatus, and thereafter, using a surface temperature of a hollow piece before being cooled by the cooling apparatus as a cooling start temperature, the hollow piece is cooled to a cooling stop temperature differing by 50° C. or more from the cooling start temperature and being equal to or above 600° C. at an average cooling speed of 1.0° C./s or more in terms of an outer surface temperature.

An apparatus line for manufacturing seamless steel pipes and tubes includes: a heating apparatus for heating a steel raw material; a piercing apparatus for piercing the heated steel raw material thus forming a hollow material; and a rolling apparatus for applying working to the hollow material to form a seamless steel pipe having a predetermined shape. A cooling apparatus is arranged on an exit side of the rolling apparatus. A heated steel raw material is worked by the rolling apparatus after being pierced by the piercing apparatus, and thereafter, using a surface temperature of a hollow piece before being cooled by the cooling apparatus as a cooling start temperature, the hollow piece is cooled to a cooling stop temperature differing by 50° C. or more from the cooling start temperature and being equal to or above 600° C. at an average cooling speed of 1.0° C./s or more in terms of an outer surface temperature.

Disclosed is a high strength, high-temperature corrosion resistant martensitic stainless steel characterized by comprising the following chemical elements in percentages by mass: 0<C≤0.05%, 0.1-0.2% of Si, 0.20-1.0% of Mn, 11.0-14.0% of Cr, 4.0-6.0% of Ni, 1.5-2.5% of Mo, 0.001%-0.10% of N, 0.03-0.2% of V, 0.01-0.1% of Nb, 0.01-0.04% of Al, and the balance being Fe and inevitable impurities. In addition, also disclosed are tubing and casing manufactured from the above-mentioned high strength, high-temperature corrosion resistant martensitic stainless steel, and a method for manufacturing the tubing and the casing. The high strength, high-temperature corrosion resistant martensitic stainless steel of the present disclosure has an excellent high temperature corrosion resistance to carbon dioxide and chloride ions, as well as excellent low-temperature impact toughness and a high-temperature strength degradation resistance.

A high-nitrogen nickel-free austenitic stainless steel seamless thin-walled tube, a high-safety nickel-free metal-based drug-eluting vascular stent manufactured therefrom, and manufacturing methods therefor. In the process of manufacturing a stent tube, the nitrogen content of a material is further increased by means of stage-by-stage nitriding, so as to obtain a high-nitrogen nickel-free austenitic stainless steel seamless thin-walled tube having the nitrogen content of 0.8-1.2% as a metal stent platform material. By using rolling line contact type electrochemical polishing, the surface of the stent forms a micron-scale protrusion-recess structure by means of crystal grains having different orientations, thus improving a binding force between a metal stent material and a drug coating. The vascular stent has the characteristics of high fatigue life, high biological safety, and a high binding force between the drug coating and a substrate.