A method quenches a steel pipe and an apparatus quenches a steel pipe by which a steel pipe having excellent and uniform quality can be acquired by applying uniform rapid cooling to the steel pipe in a longitudinal direction as well as in a circumferential direction of the steel pipe using a simple unit. Movements of a heated steel pipe in a direction parallel to and in a direction perpendicular to a pipe axis of the steel pipe are stopped, and cooling water is jetted onto an outer surface of the steel pipe from four or more spray nozzles arranged spirally outside the steel pipe while rotating the steel pipe about the pipe axis.

The present invention relates to a method for manufacturing a tubular product, characterized in that the tubular product is manufactured from steel comprising chromium in the range of 2.5 to 9.5 wt. % and silicon in an amount of more than 1.0 wt. %, and the method comprises the steps of austenitizing, quenching and tempering at a tempering temperature in the range of 300° C. to 550° C. Furthermore, the invention concerns a tubular product produced by this method.

A forming apparatus that forms a metal pipe material includes an electrode that holds the metal pipe material and supplies electric power to the metal pipe material to heat the metal pipe material, a forming die that quenches and forms the expanded metal pipe, and a member that suppresses quenching, in which a region where quenching is not performed in the metal pipe is adjusted by adjusting a length of the member.

The present invention provides a method for manufacturing a torsion beam, the method comprising: a planarization step, in which a protruding portion of an upper mold presses the opposite end portions in the width direction of the blank to be plastically deformed to be flat while the opposite end portions in the width direction of the blank are supported by a side cam to face each other; a welding and bonding step for bonding the planarized opposite end portions in the width direction of the blank via welding; and a quenching step for heating the welded and bonded blank within a range of 900 to 970° C. for a retaining time within a range of 1 to 20 minutes and for cooling down the blank in a treatment liquid including at least one of water and oil in a range of 20 to 90° C.

A method for producing thermomechanically produced hot strip products in which a steel alloy is melted; the steel alloy is adjusted so that a recrystallization during the hot rolling is suppressed; the final rolling temperature is greater than 800° C.; the melted steel alloy is cast into slab ingots and after being heated to a temperature above Ac.sub.3, the slab ingots are hot rolled until they reach a desired degree of deformation and a desired strip thickness; after the rolling, the strip is cooled to room temperature and for hardening purposes, is briefly heated to a temperature>Ac3 and cooled again, characterized in that the heating takes place with a temperature increase of more than 5 K/s, more than 10 K/s, with more than 50 K/s, or more than 100 K/s and is kept at a desired target temperature for a period of 0.5 to 60 s before cooling to yield improved mechanical properties. The hot strip products thus produced have a crystal structure that is up to 90% martensite, with the remainder being comprised of austenite and bainite.

A steel pipe or tube for pressure vessels having excellent quench crack resistance is provided. The steel pipe or tube for pressure vessels comprises: a specific chemical composition; and a metallic microstructure in which an average grain size of prior austenite grains is 500 μm or less, and an area fraction of microstructures other than ferrite is 50% or more.

The steel pipe according to the present disclosure contains a chemical composition consisting of, in mass %, C: 0.25 to 0.50%, Si: 0.05 to 0.50%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.25 to 3.00%, Ti: 0.002 to 0.050%, N: 0.0010 to 0.0100% and O: 0.0030% or less, with the balance being Fe and impurities. The steel pipe contains an amount of dissolved C within a range of 0.010 to 0.050 mass %. The tensile yield strength in the axial direction and the circumferential direction is 862 to 965 MPa, and the yield ratio in the axial direction is 90% or more. The tensile yield strength in the circumferential direction is 30 to 80 MPa higher than the compressive yield strength in the circumferential direction.

A martensitic stainless steel seamless pipe for oil country tubular goods having a yield stress of 758 MPa or more, and excellent sulfide stress corrosion cracking resistance, and a method for manufacturing the same. The martensitic stainless steel seamless pipe has a composition that contains, by mass %, C: 0.010% or more, Si: 0.5% or less, Mn: 0.05 to 0.50%, P: 0.030% or less, S: 0.005% or less, Ni: 4.6 to 8.0%, Cr: 10.0 to 14.0%, Mo: 1.0 to 2.7%, Al: 0.1% or less, V: 0.005 to 0.2%, N: 0.1% or less, Ti: 0.255 to 0.500%, Cu: 0.01 to 1.0%, Co: 0.01 to 1.0%, and the balance being Fe and incidental impurities. C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti satisfy a predetermined relationship.

A method of manufacturing tubing from a well-defined steel composition. in particular fat a suited gas inflator pressure vessel comprises the steps: a) producing a steel tubing from a steel composition including at least one hot rolling or hot forming pass: b) subjecting the steel tubing to a cold-drawing process to obtain desired dimensions. wherein the cold-drawing process comprises at least too pulls and before the first pull of the cold-drawn tug process an intermediate austenizing and quenching step: c) subsequently performing a final recovery heat treatment on the cold-drawn steel tubing at a temperature in the range of 200-600° C.

A martensitic stainless steel material contains, in mass %, C: 0.030% or less, Ni: 5.00 to 7.00%, Cr: 10.00 to 14.00%, and Cu: more than 1.00 to 3.50%. On two line segments LS of 1000 μm extending in a wall thickness direction with arbitrary two points as a center located at positions at a depth of 2 mm from the inner surface, respectively, a degree of Cr segregation ΔCr defined by Formula (1) described in the description, a degree of Mo segregation ΔMo defined by Formula (2) described in the description, and a degree of Cu segregation ΔCu defined by Formula (3) described in the description satisfy Formula (4):

ΔCr+ΔMo+ΔCu≤A  (4) where, when the yield strength is 758 to less than 862 MPa, A in Formula (4) is 0.70, and when the yield strength is 862 MPa or more, A in Formula (4) is 0.50.