Micro alloyed steels with a yield strength of at least 485 MPa (70 ksi) with outstanding toughness behavior, good weldability and improved sulphide stress cracking resistance for line pipes, for applications as process pipes, flowlines or risers in the oil and gas industry. Tubular products, such as seamless pipes, can be made from this steel. A process for manufacturing tubular products can be performed with this steel. The seamless pipes can be used for line pipes, flowlines and risers in the oil and gas industry.

The present invention relates to a steel material having excellent corrosion resistance for use in an oil tanker, a crude oil tank, and the like and, particularly to a steel material having excellent corrosion resistance in a dew condensation environment containing a sulfide gas and a method for producing the same.

An electric resistance welded steel pipe and a method for manufacturing the same are provided. The present invention relates to an electric resistance welded steel pipe including a base metal zone and a weld. In the electric resistance welded steel pipe, steel microstructures at a wall-thickness-wise middle of the base metal zone are steel microstructures in which a bcc phase is present in a volume fraction greater than or equal to 80%, an average grain size is less than or equal to 15.0 m, and an A value, defined by a predetermined equation, is 0.55 or greater and 0.85 or less; a yield ratio in a pipe axis direction is less than or equal to 90%; and a Charpy absorbed energy at 40 C. of the base metal zone is greater than or equal to 100 J.

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 m.sup.2 or more, and a yield strength is 827 MPa or more.

The present invention includes: a conveying mechanism (110) that conveys a workpiece (200) in the longitudinal direction; a supporting mechanism (120) that is arranged on the downstream side in the conveyance direction of the workpiece (200) from the conveying mechanism (110); and a heating mechanism (130) that is arranged on the downstream side in the conveyance direction of the workpiece (200) from the supporting mechanism (120) and heats the workpiece (200), in which the supporting mechanism (120) is formed to include support rolls (121) that abut on an outer surface of the workpiece (200) and each include a hollow structure (122) allowing a cooling medium to pass therethrough therein.

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.

The steel material according to this invention contains, in mass %, C: 0.15 to 0.45%, Si: 0.10 to 1.0%, Mn: 0.10 to less than 0.90%, P: 0.05% or less, S: 0.01% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Cr: 0.1 to 2.5%, Mo: 0.35 to 3.0%, and Co: 0.50 to 3.0%, and satisfies expressions (1) and (2), and contains 90% or more of tempered martensite by volume ratio:
C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15Co/6+0.50(1 )
(3C+Mo+3Co)/(3Mn+Cr)1.0(2 )
Effective B=B11(NTi/3.4)/14(3 ) where, in expression (1) is 0.250 when effective B (mass %) defined by expression (3) is 0.0003% or more, and is 0 when the effective B is less than 0.0003.

Provided is a coolant spray module system for a heat treatment metal product, comprising: a first coolant spray module (1), wherein the first coolant spray module (1) comprises a first module housing (10), a first module cover (20), and a first nozzle (30), wherein the first nozzle (30) is fixed between the first module housing (10) and the first module cover (20) by first nozzle fixing blocks (13) and second nozzle fixing blocks (23), wherein the coolant spray module system sprays the coolant onto the heat treatment metal product to quench and clean the heat treatment metal product.

A preferable aspect of the present invention provides: an ultra-high-strength hot-rolled steel sheet containing, by weight, one or two of 0.40-0.60% of C, 0.7-1.5% of Mn, 0.3% or less (excluding 0%) of Si, 0.03% or less (including 0%) of P, 0.004% or less (including 0%) of S, 0.04% or less (excluding 0%) of Al, 0.3% or less (excluding 0%) of Cr, 0.3% or less (excluding 0%) of Mo, 0.9-1.5% of Ni, and 0.9-1.5% of Cu, 1.1% or more of Cu+Ni, 0.04% or less (excluding 0%) of Ti, 0.005% or less (excluding 0%) of B, 0.006% or less (excluding 0%) of N, and the balance Fe and other impurities, the alloy elements satisfying relational formulas 1 and 2 below, wherein a microstructure of the hot-rolled steel sheet comprises, by volume, 7% or more of ferrite and 93% or less of perlite; a steel pipe and a member each using the same; and manufacturing methods therefor. [Relational formula 1] (Mn/Si) #3 (weight ratio) [Relational formula 2] (Ni/Si) #1 (weight ratio)

The seamless steel pipe 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 0.070%, Cr: 0.30 to 1.50%, Mo: 0.25 to 2.00%, Ti: 0.002 to 0.020%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, rare earth metal: 0.0001 to 0.0015%, Ca: 0.0001 to 0.0100%, N: 0.0100% or less and O: 0.0020% or less, with the balance being Fe and impurities, and satisfying Formula (1) described in the description. A predicted maximum major axis of inclusions is 150 m or less, the predicted maximum major axis being predicted by means of extreme value statistical processing. The yield strength is within a range of 758 to 862 MPa.