Abstract: A steel material according to the present disclosure has a chemical composition consisting of, in mass %: C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.01 to 1.00%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr 0.55 to 1.10%, Mo: 0.70 to 1.00%, Ti: 0.002 to 0.020%, V: 0.05 to 0.30%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: less than 0.0020%, and the balance being Fe and impurities, and satisfying Formula (1) described in the specification. A grain diameter of a prior-austenite grain is 15.0 ?m or less, and an average area of precipitate which is precipitated in a prior-austenite grain boundary is 12.5×10?3 ?m2 or less. A yield strength is 758 to 862 MPa.

Abstract: The present invention relates to a high strength steel tube. In addition, the invention relates to a method of manufacturing a high strength steel tube. The method is characterized in that a hot rolled pre-tube is subjected to at least two hardening steps with a final tempering step, the pre-tube is heated to a quenching temperature of at least Ac3 temperature for hardening and is heated to a tempering temperature in the range of 400 to 600° C. for tempering.

Abstract: This disclosure relates to weldability of steel alloys that provide weld joints which retain hardness values in a heat affected zone adjacent to a fusion zone and which also have improved resistance to liquid metal embrittlement due to the presence of zinc coatings.

Abstract: The present invention relates to an air conditioner. In an air conditioner according to an embodiment, a scroll compressor having a refrigerating capacity of 23 kW to 58 kW and an amount of circulating refrigerant of 880 cc is used, a refrigerant mixture containing 50% or more of R32 is used as a refrigerant circulating the air conditioner, and a flexible stainless steel pipe having 1% or less of delta ferrite matrix structure on the basis of the grain size area is comprised in a refrigerant pipe. Therefore, the strength and hardness of the refrigerant pipe is maintained to be equal to or higher than those of a copper pipe, and the processability can be well maintained.

Abstract: The seamless steel pipe of the present embodiment consists of in mass %, C: 0.21 to 0.35%, Si: 0.10 to 0.50%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.010% or less, Al: 0.005 to 0.100%, N: 0.010% or less, Cr: 0.05 to 1.50%, Mo: 0.10 to 1.50%, Nb: 0.010 to 0.050%, B: 0.0003 to 0.0050%, and Ti: 0.002 to 0.050%, the balance being Fe and impurities. In a main body region of the seamless steel pipe, a grain size number of prior-austenite grain conforming to ASTM E112 is 7.0 or more, a difference between a maximum value and a minimum value of the grain size number is 1.0 or less, yield strength is 655 to less than 862 MPa, and a difference between a maximum value and a minimum value of tensile strength is 27.6 MPa or less.

Abstract: An process for the on-line quenching of seamless steel tube using residual heat, a method for manufacturing a seamless steel tube, and a seamless steel tube. The process for the on-line quenching of a seamless steel tube comprises the following steps: when the temperature of a tube is higher than Ar3, evenly spraying water along a circumferential direction of the tube so as to continuously cool the tube to be not higher than T° C., the cooling rate being controlled to be E1° C./s to E2° C./s to obtain a microstructure with martensite as the main composition, wherein T=Ms?95° C., Ms represents the martensitic phase transition temperature, E1=20×(0.5?C)+15×(3.2?Mn)?8×Cr?28×Mo?4×Ni?2800×B, and E2=96×(0.45?C)+12×(4.6?Mn), and the C, Mn, Cr, Ni, B and Mo in the equations each represents the mass percentages of corresponding elements in the seamless steel tube.

Abstract: The steel material according to the present invention 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: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.50%, Mo: 0.25 to 1.50%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.002 to 0.010% and O: 0.0100% or less, with the balance being Fe and impurities. The steel material also contains an amount of dissolved C within a range of 0.010 to 0.050 mass%. The steel material also contains an yield strength is in a range of 862 to less than 965 MPa, and an yield ratio is 90% or more.

Abstract: Disclosed is, as a high-strength steel plate of API X80 grade or higher with a thickness of 38 mm or more, a steel plate for structural pipes or tubes that exhibits excellent resistance to PWHT and excellent toughness at the heat-affected zone, particularly at the butting faces joined by welding, without addition of large amounts of alloying elements. The steel plate for structural pipes or tubes disclosed herein has a specific chemical composition, in which the steel plate has mechanical properties including: (a) a 0.5% yield strength of 555 MPa or more; (b) a tensile strength of 625 MPa or more; and (c) a Charpy absorption energy vE?10° C. at ?10° C. at its mid-thickness part of 250 J or more, and maintains the mechanical properties (a) to (c) even after subjection to heat treatment at 650° C. for 2 hours.

Abstract: The invention provides a production method for stabilizers which produces with high productivity in a compact production line, without tempering. The production method for stabilizers of the invention includes: forming a steel bar material containing at least C: 0.15 wt % to 0.39 wt %, Mn, B and Fe into a product shape by bending; and quenching the bent steel bar material in a medium having a heat transfer coefficient higher than or close to that of water.

Abstract: A forming method for a vehicle body member may include a tube making process of forming a steel pipe by welding a steel plate coil; a non-circular tube making process of primary preforming the steel pipe formed in the tube making process so as to have a cross section of a predetermined shape; a bending process of bending and secondarily preforming the steel pipe preformed firstly in the non-circular tube making process; and a hot stamping process of heating the secondarily preformed steel pipe, inserting the heated steel pipe into a mold to form a desired shape, and then, quenching the heated steel pipe to form a vehicle body member, thereby easily forming a vehicle body member having high rigidity.

Abstract: A seamless steel pipe having a specific chemical composition. A ratio of Ti to N is in a range of 2.0 to 5.0. The steel pipe has a microstructure including tempered martensite having a volume ratio of 95% or more, and prior austenite grains having a grain size number of 8.5 or more. In a cross-section perpendicular to a rolling direction of the steel pipe a number of nitride-based inclusions having a particle size of 4 ?m or more is 100 or less per 100 mm2, a number of nitride-based inclusions having a particle size of less than 4 ?m is 1000 or less per 100 mm2, a number of oxide-based inclusions having a particle size of 4 ?m or more is 40 or less per 100 mm2, and a number of oxide-based inclusions having a particle size of less than 4 ?m is 400 or less per 100 mm2.

Abstract: Provided is a low alloy oil-well steel pipe having a yield strength of 793 MPa or more, and an excellent SSC resistance. A low alloy oil-well steel pipe according to the present invention includes a chemical composition consisting of: in mass %, C: 0.25 to 0.35%; Si: 0.05 to 0.50%; Mn: 0.10 to 1.50%; Cr: 0.40 to 1.50%; Mo: 0.40 to 2.00%; V: 0.05 to 0.25%; Nb: 0.010 to 0.040%; Ti: 0.002 to 0.050%; sol. Al: 0.005 to 0.10%; N: 0.007% or less; B: 0.0001 to 0.0035%; and Ca: 0 to 0.005%; and a balance being Fe and impurities. In a microstructure of the low alloy oil-well steel pipe, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 100 particles/100 ?m2 or more. The above low alloy oil-well steel pipe has a yield strength of 793 MPa or more.

Abstract: The steel material according to the present invention contains, in mass %, C: 0.15 to 0.45%, Si: 0.10 to 1.0%, Mn: 0.10 to 0.8%, P: 0.050% or less, S: 0.010% or less, Al: 0.01 to 0.1%, N: 0.010% or less, Cr: 0.1 to 2.5%, Mo: 0.35 to 3.0%, Co: 0.05 to 2.0%, Ti: 0.003 to 0.040%, Nb: 0.003 to 0.050%, Cu: 0.01 to 0.50%, and Ni: 0.01 to 0.50%, and satisfies the following Formulae. A prior-austenite grain diameter of its microstructure is less than 5 ?m, and a block diameter of its microstructure is less than 2 ?m. The microstructure contains a total of 90% by volume or more of tempered martensite and tempered bainite. C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15?Co/6+??0.70??(1) (3C+Mo+3Co)/(3Mn+Cr)?1.0??(2).

Abstract: Electric resistance welded steel pipe securing the high strength and high toughness demanded from oil well pipe in recent years. The metal structure in a region having a width of 0.5 mm in both the thickness directions from a reference point, when using a point defined as a point ¼ of the thickness in the thickness direction from the surface in the base material part of the steel as the reference point, consists of polygonal ferrite: 10 area % or less and a balance: bainitic ferrite. The thickness is 15 mm or more.

Abstract: A steel contains, by weight: C: 0.2% to 0.5%, Si: 0.1% to 0.5%, Mn: 0.1% to 1%, P: 0.03% or less, S: 0.005% or less, Cr: 0.3% to 1.5%, Mo: 0.3% to 1%, Al: 0.01% to 0.1%, V: 0.1% to 0.5%, Nb: 0.01% to 0.05%, Ti: 0 to 0.01%, W: 0.3% to 1%, N: 0.01% or less, the remainder of the chemical composition of the steel being constituted by Fe and impurities or residuals resulting from or necessary to steel production and casting processes. The steel can be used to produce seamless tubes with a yield strength after heat treatment of 861 MPa or more.

Abstract: A rolled steel material for fracture splitting connecting rods consists of, C: 0.30 to 0.40%, Si: 0.60 to 1.00%, Mn: 0.50 to 1.00%, P: 0.04 to 0.07%, S: 0.04 to 0.13%, Cr: 0.10 to 0.30%, V: 0.05 to 0.14%, Ti: more than 0.15% to 0.20% or less, N: 0.002 to 0.020%, and optionally may contain Cu, Ni, Mo, Pb, Te, Ca, and Bi, with the balance being Fe and impurities. fn1, defined by Formula (1), ranges from 0.65 to 0.80. Relative to the V content in the steel material, a V content in coarse precipitates having a particle size of 200 nm or more is 70% or less, and relative to the Ti content in the steel material, a Ti content in the coarse precipitates is 50% or more.

Abstract: 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 ?m2 or more, and a yield strength is 827 MPa or more.

Abstract: 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.

Abstract: 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 (XSi+XMn+XMo)+1.2XP relating to XM which is a ratio between a segregated portion content and an average content is set to less than 65.

Abstract: A steel for oil country tubular goods includes, as a chemical composition, by mass %, C, Si, Mn, Al, Mo, P, S, O, N, and a balance containing Fe and impurities, wherein a full width at half maximum HW of a crystal plane corresponding to a (211) crystal plane of an ? phase and a carbon content expressed in mass % in the chemical composition satisfy HW×C1/2?0.38, the carbon content and a molybdenum content expressed in mass % in the chemical composition satisfy C×Mo?0.6, a number of M2C carbides having a hexagonal crystal structure and having an equivalent circle diameter of 1 nm or more is 5 pieces or more per one square micron, and an yield strength is 758 MPa or more.

Abstract: A high-carbon steel sheet has a chemical composition represented by, in mass %, C: 0.60% to 0.90%, Mn: 0.30% to 1.50%, and Cr: 0.20% to 1.00%, and others, and has a structure represented by a concentration of Mn contained in cementite: 2% or more and 8% or less, a concentration of Cr contained in cementite: 2% or more and 8% or less, an average grain diameter of ferrite: 10 ?m or more and 50 ?m or less, an average particle diameter of cementite: 0.3 ?m or more and 1.5 ?m or less, and a spheroidized ratio of cementite: 85% or more.

Abstract: A heating step, in which a stainless member is heated to a temperature within or above a heating phase-transformation temperature range (Ar) in which the stainless member is phase-transformed, is executed. A cooling step in which the stainless member heated in the heating step is cooled to a temperature below a cooling phase-transformation temperature range (Mr) in which the stainless member is phase-transformed, is executed. In the cooling step, cooling of the stainless member is suppressed in a control temperature range including the cooling phase-transformation temperature range (Mr).

Abstract: A steel has a chemical composition consisting of, by mass percent, C: 0.15-0.65%, Si: 0.05-0.5%, Mn: 0.1-1.5%, Cr: 0.2-1.5%, Mo: 0.1-2.5%, Ti: 0.005-0.50%, Al: 0.001-0.50%, and optionally at least one element selected from Nb: ?0.4%, V: ?0.5%, and B: ?0.01%, Ca: ?0.005%, Mg: ?0.005%, and REM: ?0.005%, and the balance of Fe and impurities, wherein Ni, P, S, N and O as impurities are Ni: ?0.1%, P: ?0.04%, S: ?0.01%, N: ?0.01%, and O: ?0.01%. The steel is hot-worked into a shape and then sequentially subjected to heating the steel to a temperature exceeding the Ac1 transformation point and lower than the Ac3 transformation point and cooling. Then, a step of reheating the steel to a temperature not lower than the Ac3 transformation point and quenching the steel by rapid cooling, and a step of tempering the steel at a temperature not higher than the Ac1 transformation point are performed.

Abstract: A seamless steel pipe has a yield strength of 400 MPa or less and excellent HIC resistance. The seamless steel pipe includes: a chemical composition consisting, in mass %, of, C: 0.01 to 0.20%, Si: 0.05 to 0.50%, Mn: 0.3 to 2.0%, P: 0.02% or less, S: 0.01% or less, Cr: 0.02 to 0.2%, sol.Al: 0.001 to 0.100%, O: 0.0050% or less, N: 0.0100% or less, Ca: 0 to 0.0050%, Ti: 0 to 0.012%, and Nb: 0 to 0.012%, the balance being Fe and impurities; and a structure consisting, in area ratio, of 10 to 50% of ferrite and 0 to less than 5% of pearlite, the balance being tempered bainite and/or tempered martensite, and the number of inclusions each having a grain diameter of 50 mm or more is not more than 15 per 100 mm2, and the seamless steel pipe has a yield strength of 400 MPa or less.

Abstract: A non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss at not only a commercial frequency but also a high frequency zone, which has a chemical composition including C: not more than 0.0050 mass %, Si: more than 1.5 mass % but not more than 5.0 mass %, Mn: not more than 0.10 mass %, sol. Al: not more than 0.0050 mass, P: more than 0.040 mass % but not more than 0.2 mass %, S: not more than 0.0050 mass %, N: not more than 0.0040 mass % and Ca: 0.001-0.01 mass % and the remainder being Fe and inevitable impurities and a compositional ratio of CaO in oxide-based inclusions existing in a steel sheet of not less than 0.4 and/or a compositional ratio of Al2O3 of not less than 0.3, and a hot rolled steel sheet used as a raw steel material thereof.

Abstract: There is provided a seamless steel pipe for line pipe, wherein a chemical composition consists, by mass percent, of C: 0.03-0.10%, Si: ?0.50%, Mn: 1.0-2.0%, P: ?0.050%, S: ?0.005%, Cr: 0.05-1.0%, Mo: 0.01-0.30%, Al: 0.001-0.10%, N: ?0.01%, Ni: 0.04-2.0%, Ca: 0.0005-0.0050%, Cu: 0-2.0%, Ti: 0-0.05%, Nb: 0-0.05%, V: 0-0.10%, the balance: Fe and impurities, and satisfies the conditions of Cu+Ni: ?0.10%, and Mo+V: ?0.30%, wherein in a scale formed on the surface of the steel pipe, metal particles consisting mainly of Ni or Cu having an average circle-equivalent diameter of 0.1-5 ?m exist, and a distance from a boundary between the base metal of the steel pipe and the scale to a region in which the metal particles do not exist is 20 ?m or longer.

Abstract: A steel contains, by weight: C: 0.3% to 0.5%, Si: 0.1% to 0.5%, Mn: 1% or less, P: 0.03% or less, S: 0.005% or less, Cr: 0.3% to 1%, Mo: 1% to 2%, W: 0.3% to 1%, V: 0.03% to 0.25%, Nb: 0.01% to 0.15%, Al: 0.01% to 0.1%, the remainder of the chemical composition of the steel being constituted by Fe and impurities or residuals resulting from or necessary to steel production and casting processes. The steel can be used to produce seamless tubes for hydrocarbon wells with a yield strength after heat treatment of 862 MPa or more or even 965 MPa or more.

Abstract: There is provided a method for manufacturing a seamless steel pipe for line pipe, capable of improving the toughness of the seamless steel pipe for line pipe. A round billet having a chemical composition, by mass percent, of C: 0.02 to 0.15%, Si: at most 0.5%, and Mn: 0.5 to 2.5%, the balance being Fe and impurities, is heated. The heated round billet is piercing-rolled to produce a hollow shell. The hollow shell is elongated and rolled and sized to produce a seamless steel pipe. The seamless steel pipe is water cooled, and the water cooling is stopped when the temperature of the seamless steel pipe reaches at most 450° C. The water-cooled seamless steel pipe is quenched, and the quenched seamless steel pipe is tempered.

Abstract: The present invention provides a steel which simultaneously satisfies a plurality of characteristics, specifically, a steel for tubes with excellent sulfide stress cracking resistance, including, C: 0.2 to 0.7%; Si: 0.01 to 0.8%; Mn: 0.1 to 1.5%; S: not more than 0.005%; P: not more than 0.03%; Al: 0.0005 to 0.1%; Ti: 0.005 to 0.05%; Ca: 0.0004 to 0.005%; N: not more than 0.007%; Cr: 0.1 to 1.5%; and Mo: 0.2 to 1.0%; the balance being Fe, Mg and impurities, being characterized in that: the content of Mg is not less than 1.0 ppm and not more than 5.0 ppm; and inclusions of not less than 50% of the total number of those in steel have such a morphology that Mg—Al—O-based oxides exist at the central part of the inclusion, Ca—Al-based oxides enclose the Mg—Al—O-based oxides, and Ti-containing-carbonitrides further exist on a periphery of the Ca—Al-based oxides.

Abstract: A high-strength seamless steel pipe for oil wells excellent in sulfide stress cracking resistance which comprises, on the percent by mass basis, C: 0.1 to 0.20%, Si: 0.05 to 1.0%, Mn: 0.05 to 1.0%, Cr: 0.05 to 1.5%, Mo: 0.05 to 1.0%, Al: 0.10% or less, Ti: 0.002 to 0.05% and B: 0.0003 to 0.005%, with a value of equation “C+(Mn/6)+(Cr/5)+(Mo/3)” of 0.43 or more, with the balance being Fe and impurities, and in the impurities P: 0.025% or less, S: 0.010% or less and N: 0.007% or less. The seamless steel pipe may contain a specified amount of one or more element(s) of V and Nb, and/or a specified amount of one or more element(s) of Ca, Mg and REM. The seamless steel pipe can be produced at a low cost by adapting an in-line tube making and heat treatment process having a high production efficiency since a reheating treatment for refinement of grains is not required.

Abstract: The present invention relates to a process for producing a pipe, particularly for supplying fuel to an engine, comprising the steps of: prearranging a pipe made of stainless steel (1), executing a hot-pressing operation at at least one end (3) of the pipe (1); and subjecting the at least one end (3) of the pipe (1) to heat treatment, followed by cooling.

Abstract: There is provided a seamless steel pipe having high strength and high toughness even if having a thick wall. A seamless steel pipe according to the present embodiment consists of: in mass %, C: 0.03 to 0.08%, Si: not more than 0.25%, Mn: 0.3 to 2.0%, P: not more than 0.05%, S: not more than 0.005%, Al: 0.001 to 0.10%, Cr: 0.02 to 1.0%, Ni: 0.02 to 1.0%, Mo: 0.02 to 0.8%, N: 0.002 to 0.008%, Ca: 0.0005 to 0.005%, and Nb: 0.01 to 0.1%, the balance being Fe and impurities, and has a wall thickness of not less than 50 mm.

Abstract: A high-strength welded steel pipe is obtained by welding a seam weld portion of a steel plate that are formed in a pipe shape. In the high-strength welded steel pipe, a base metal of the steel plate includes, by mass %, C: 0.010% to 0.080%, Si: 0.01% to 0.50%, Mn: 0.50% to 2.00%, S: 0.0001% to 0.0050%, Ti: 0.003% to 0.030%, Mo: 0.05% to 1.00%, B: 0.0003% to 0.0100%, O: 0.0001% to 0.0080%, N: 0.006% to 0.0118%, P: limited to 0.050% or less, Al: limited to 0.008% or less, and the balance of Fe and inevitable impurities, Ceq is 0.30 to 0.53, Pcm is 0.10 to 0.20, [N]?[Ti]/3.4 is less than 0.003, the average grain size of the prior ? grains in heat affected zones in the steel plate is 250 ?m or less, and the prior ? grains include bainite and intragranular bainite.

Abstract: The present invention describes a method of manufacturing a near-net shaped hollow shaft useful for high power applications such as gearboxes for wind energy industry. The method involves providing a concast bloom (of a round or rectangular or of any polygonal cross section) or an as-cast round ingot from which a hollow perform is prepared using hollow die punching, followed by process of heat treatment, proof-machining and stress relieving.

Abstract: A steel has a chemical composition consisting of, by mass percent, C: 0.15-0.65%, Si: 0.05-0.5%, Mn: 0.1-1.5%, Cr: 0.2-1.5%, Mo: 0.1-2.5%, Ti: 0.005-0.50%, Al: 0.001-0.50%, and optionally at least one element selected from Nb: ?0.4%, V: ?0.5%, and B: ?0.01%, Ca: ?0.005° A, Mg: ?0.005%, and REM: ?0.005%, and the balance of Fe and impurities, wherein Ni, P, S, N and O as impurities are Ni: ?0.1%, P: ?0.04%, S: ?0.01%, N: ?0.01%, and O: ?0.01%. The steel is hot-worked into a shape and then sequentially subjected to heating the steel to a temperature exceeding the Ac1 transformation point and lower than the Ac3 transformation point and cooling. Then, a step of reheating the steel to a temperature not lower than the Ac3 transformation point and quenching the steel by rapid cooling, and a step of tempering the steel at a temperature not higher than the Ac1 transformation point are performed.

Abstract: Process for manufacturing seamless precision steel tubes with improved isotropic toughness at low temperature for hydraulic cylinders comprising the following steps; —(i) providing a steel having a composition comprising 0.06-0.15% by weight of carbon, 0.30-2.5% by weight of Mn, and 0.10-0.

Abstract: A seamless steel pipe has a composition containing, by mass %, C: 0.15 to 0.50%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.0%, P: 0.015% or less, S: 0.005% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Cr: 0.1 to 1.7%, Mo: 0.40 to 1.1%, V: 0.01 to 0.12%, Nb: 0.01 to 0.08%, Ti: 0.03% or less, and B: 0.0005 to 0.003%, a structure composed of a tempered martensite phase as a main phase with a prior austenite grain size of 8.5 or more, and a hardness distribution in which in four portions 90° apart from each other in the circumferential direction, hardness is 295 HV10 or less in any one of an inner surface-side region at 2.54 to 3.81 mm from the inner surface of the pipe, an outer surface side-region at the same distance from the outer surface of the pipe, and a center of the thickness.

Abstract: The present invention provides a thick welded steel pipe excellent in low temperature toughness in which contents of Mn and Mo satisfy (Expression 1) below, Pcm obtained by (Expression 2) below is 0.16 to 0.19, and a metal structure of a base material steel plate consists of ferrite being 30 to 95% in an area ratio and a low temperature transformation structure, and in a metal structure of a coarse-grained HAZ, an area ratio of grain boundary ferrite is 1.5% or more, the total area ratio of the grain boundary ferrite and intragranular ferrite is not less than 11% nor more than 90%, an area ratio of MA is 10% or less, and its balance is composed of bainite. 1.2325?(0.85×[Mn]?[Mo])?1.5215??(Expression 1) and Pcm=[C]+[Si]/30+([Mn]+[Cu]+[Cr])/20+[Ni]/60+[Mo]/15+[V]/10??(Expression 2).

Abstract: A method of production of high-strength hollow bodies from multiphase martensitic steels includes a heating process, a forming process and a cooling process. A heating device heats hollow steel stock to the austenitic temperature of the material from which the stock is made. The stock is then converted by deformation in a forming device into a hollow body having the final shape. A cooling device thereafter cools the hollow body such that the material with the original austenite microstructure refined by deformation during the forming process cools to a temperature at which incomplete transformation of austenite to martensite occurs. The retained austenite stabilization is performed in an annealing device by diffusion-based carbon partitioning within the material from which the hollow body is made. The hollow body is cooled in a cooling device to ambient temperature after stabilization.

Abstract: A steel pipe with a wall thickness over 30 mm is subjected to heat treatment of quenching and tempering using a temperature range of at least not less than 750° C. during the heating stage, makes it possible to obtain a heavy-wall seamless steel pipe having excellent toughness by resulting grain refinement. Quenching is by performing water cooling after heating the steel pipe to a temperature in the range of not less than 900° C. to not more than 1000° C. by using, as a heating means, induction heating at a frequency of not more than 200 Hz. Tempering is performed at a temperature in the range of not less than 500° C. to not more than 750° C. Preferably, after the heating by induction heating, a soaking treatment is performed in the temperature range of not less than 900° C. to not more than 1000° C. for 10 minutes or less followed by water cooling.

Abstract: Embodiments of the present disclosure comprise carbon steels and methods of manufacturing thick walled pipes (wall thickness greater than or equal to about 35 mm) there from. In one embodiment, a steel composition is processed that yields an average prior austenite grain size greater than about 15 or 20 ?m and smaller than about 100 ?m. Using this composition, a quenching sequence is provided that yields a microstructure of greater than or equal to about 50% by volume, and less than or equal to about 50% by volume, lower bainite, without substantial ferrite, upper bainite, or granular bainite. After quenching, pipes may be tempered. The quenched and tempered pipes may exhibit yield strengths greater than about 450 MPa (65 ksi) or 485 (70 ksi). Mechanical property measurements find the quenched and tempered pipes suitable for 450 MPa grade and 485 MPa grade, and resistance to sulfide stress corrosion cracking.

Abstract: The present invention provides a high-strength steel plate having excellent resistance to cutting crack, excellent Charpy absorbed energy, excellent DWTT properties, a low yield ratio, and a tensile strength of 900 MPa or more, a method of producing the steel plate, and a high-strength steel pipe using the steel plate. As solving means, a steel plate contains, by % by mass, 0.03 to 0.12% of C, 0.01 to 0.5% of Si, 1.5 to 3% of Mn, 0.01 to 0.08% of Al, 0.01 to 0.08% of Nb, 0.005 to 0.025% of Ti, 0.001 to 0.01% of N, and at least one component of 0.01 to 2% of Cu, 0.01 to 3% of Ni, 0.01 to 1% of Cr, 0.01 to 1% of Mo, and 0.01 to 0.1% of V; wherein the contents of Ca, O, and S satisfy the equation below; the microstructure includes ferrite and a second hard phase, the area fraction of ferrite being 10 to 50%; cementite in the second phase has an average grin size of 0.5 ?m or less; and the total amount of Nb and the like contained in carbides thereof present in steel is 10% or less of the total content in steel.

Abstract: A seamless steel pipe for line pipe having high strength and high toughness contains, by mass percent, C: 0.02 to 0.10%, Si: at most 0.5%, Mn: 0.5 to 2.0%, Al: 0.01 to 0.1%, P: at most 0.03%, S: at most 0.005%, Ca: at most 0.005%, and N: at most 0.007%, and further contains at least one selected from a group consisting of Ti: at most 0.008%, V: less than 0.06%, and Nb: at most 0.05%, the balance being Fe and impurities. A carbon equivalent Ceq defined by Formula (1) is at least 0.38, a content of Ti, V and Nb satisfies Formula (2), and the size of carbo-nitride containing at least one of Ti, V, Nb and Al is at most 200 nm, Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15??(1) Ti+V+Nb<0.06??(2).

Abstract: A method for suppressing shock and storage cracking when manufacturing seamless steel pipes comprises hot piercing and hot rolling a billet consisting of, by mass percent controlled amounts of C, Si, Mn, Cr, Mo, Ti, and Al, with the balance being Fe and impurities of Ni, P, S, N, and O also in controlled amounts. Further heat treatment is performed, wherein a hot rolled steel pipe is direct quenched from a temperature of not lower than the Ar3 transformation point and the pipe is then subjected to heat treatment at a temperature of not lower than 450° C. and not higher than the Ac1 transformation point in heat treatment equipment for performing direct quenching. The steel pipe subjected to the heat treatment is reheated, quenched from a temperature of not lower than the Ac3 transformation point, and tempered at a temperature of not higher than the Ac1 transformation point.

Abstract: This high-strength steel pipe includes, by mass %, C: 0.02% to 0.09%, Mn: 0.4% to 2.5%, Cr: 0.1% to 1.0%, Ti: 0.005% to 0.03%, Nb: 0.005% to 0.3%, and a balance consisting of Fe and inevitable impurities, in which Si, Al, P, S, and N are limited to 0.6% or less, 0.1% or less, 0.02% or less, 0.005% or less, 0.008% or less, respectively, the bainite transformation index BT is 650° C. or less, and the microstructure thereof is a single bainite microstructure including first bainite and second bainite, the first bainite being a gathered microstructure of bainitic ferrite including no carbide, and the second bainite being a mixed microstructure of bainitic ferrite including no carbide and cementite between the bainitic ferrites.

Abstract: Embodiments of the present disclosure comprise carbon steels and methods of manufacture. In one embodiment, quenching and tempering procedure is performed in which a selected steel composition is formed and heat treated to yield a slightly tempered microstructure having a fine carbide distribution. In another embodiment, a double austenizing procedure is disclosed in which a selected steel composition is formed and subjected to heat treatment to refine the steel microstructure. In one embodiment, the heat treatment may comprise austenizing and quenching the formed steel composition a selected number of times (e.g., 2) prior to tempering. In another embodiment, the heat treatment may comprise subjecting the formed steel composition to austenizing, quenching, and tempering a selected number of times (e.g., 2). Steel products formed from embodiments of the steel composition in this manner (e.g., seamless tubular bars and pipes) will possess high yield strength, e.g.

Abstract: The present invention is to provide a method for producing duplex stainless steel seamless pipe in which a duplex stainless steel billet can be inhibited from generating an oxide scale on the surface thereof during heating and the generation of outer surface flaw can also be prevented. The billet is heated in the a heating furnace for 1.5 hours or more and 4.0 hours or less at a heating temperature of 1250° C. or more and 1320° C. or less while regulating the average concentration of sulfur dioxide (SO2) gas in the atmosphere within the furnace to 0.01 volume % or less.

Abstract: There is provided a high-strength steel tube having excellent chemical conversion treatability and excellent formability and a method for manufacturing the high-strength steel tube. More specifically, in processing a mother steel sheet containing, on the basis of mass percent, 0.05% or more C, more than 0.7% Si, and 0.8% or more Mn into a pipe shape, the sum total of absolute circumferential surface strains each applied in individual process steps of the processing is 5% or more as nominal strain. A welded steel tube thus manufactured using a steel sheet even containing more than 0.7% Si can have excellent chemical conversion treatability without mechanical grinding or chemical pickling treatment.

Abstract: A high-strength steel machined product giving excellent hardenability has a metal microstructure with excellent balance of strength and toughness and high stability of retained austenite. The product is composed of an ultra-high low-alloy TRIP steel having a metal microstructure which contains an appropriate quantity of two or more of Cr, Mo, and Ni, and an appropriate quantity of one or more of Nb, Ti, and V, and having an appropriate value of carbon equivalent; the metal microstructure has a mother-phase structure composed mainly of lathy bainitic ferrite with a small amount of granular bainitic ferrite and polygonal ferrite, and has a secondary-phase structure composed of fine retained austenite and martensite.

Abstract: A seamless expandable oil country tubular article, which has a superior pipe expansion property in a expanding process at an expand ratio of more than about 30% although having a high strength such as a tensile strength (TS) of about 600 MPa or more, and a manufacturing method thereof, the seamless expandable oil country tubular goods being in an as-rolled state or being processed, optionally necessary, by inexpensive nonthermal-refining type heat treatment.