EP4092149B1 - Stahlplatte und stahlrohr - Google Patents

Stahlplatte und stahlrohr Download PDF

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Publication number
EP4092149B1
EP4092149B1 EP20914216.5A EP20914216A EP4092149B1 EP 4092149 B1 EP4092149 B1 EP 4092149B1 EP 20914216 A EP20914216 A EP 20914216A EP 4092149 B1 EP4092149 B1 EP 4092149B1
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steel plate
steel
surface layer
hardness
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English (en)
French (fr)
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EP4092149A4 (de
EP4092149A1 (de
Inventor
Taishi Fujishiro
Takuya Hara
Yasuhiro Shinohara
Naoki Doi
Izuru Minato
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/78—Combined heat-treatments not provided for above
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/10—Differential treatment of inner with respect to outer regions, e.g. core and periphery, respectively
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints

Definitions

  • the present invention relates to a steel plate and a steel pipe.
  • oil wells and gas wells of crude oil, natural gas, and the like
  • oil wells and gas wells will be collectively referred to as simply "oil wells”
  • oil wells and gas wells will be collectively referred to as simply "oil wells”
  • Patent Document 1 discloses a method for manufacturing high tensile strength steel having excellent SSC resistance and a 60 kgf/mm 2 -class tensile strength.
  • Patent Document 2 discloses a thick steel plate having a tensile strength of 570 to 720 N/mm 2 and having a small hardness difference between a welded heat-affected zone and a base material and a method for manufacturing the same.
  • Patent Document 3 describes a method for manufacturing a high-strength steel plate for a sour-gas-resistant line pipe having a X60-class or higher strength, the high-strength steel plate being capable of reducing surface hardness while preventing a decrease in the strength and the deterioration of DWTT characteristics.
  • the hardness of the surface of the steel plate can be reduced by performing tempering after quenching.
  • a Vickers hardness test is performed in the hardness evaluation with the test force set to 98 N (10 kgf). As the test force becomes higher, the measurement region becomes larger. That is, the average hardness of the metallographic structure that is included in a wide region is measured.
  • the test force is high, the size of an indentation itself also becomes several hundred micrometers. Therefore, it is not possible to measure the hardness of the outermost layer of the steel plate, for example, in a range of several hundred micrometers from the surface layer.
  • Patent Document 4 discloses a steel plate suitable for a line pipe for which the maximum hardness in the surface layer area is made to be 270 Hv or less to improve the SSC resistance and a steel pipe for which the steel plate is used as a base material.
  • Patent Document 5 discloses a steel plate suitable for a line pipe for which the maximum hardness in the surface layer area is made to be 250 Hv or less to improve the SSC resistance and a steel pipe for which the steel plate is used as a base material.
  • Patent Document 6 discloses an electric-resistance-welded steel pipe for a line pipe, in which the chemical composition of a matrix part contains, in % by mass, 0.04 to 0.12% of C, 0.01 to 0.50% of Si, 0.5 to 2.0% of Mn, 0.005 to 0.030% of Ti, 0.005 to 0.050% of Nb, 0.001 to 0.008% of N and a remainder made up by Fe and unavoidable impurities and, when the thickness of the matrix part is defined as t B and the thickness of an electric-resistance-welded part is defined as t S , the value determined by subtracting a value of the hardness of a 1/2t B part in the matrix part from a value of the hardness of an outer surface layer part B that is located at a depth of 1 mm from the outer surface of the matrix part is 30 HV10 or less, the value determined by subtracting a value of the hardness of a 1/2t S part in the electric-resistance-welded part from a value of the hardness
  • An object of the present invention is to solve the above-described problems and to provide a steel plate and a steel pipe having excellent SSC resistance and HIC resistance and excellent low temperature toughness.
  • HV0.1 means a "hardness symbol” in a case where a Vickers hardness test is performed with a test force set to 0.98 N (0.1 kgf) (refer to JIS Z 2244: 2009).
  • Such a steel pipe is suitable for a use in line pipes, and such a steel plate is suitable as a material for steel pipes for line pipes.
  • C is an element that improves the strength of steel.
  • the C content is set to 0.020% or more.
  • the C content is preferably 0.030% or more.
  • the C content is set to 0.080% or less.
  • the C content is preferably 0.060% or less and more preferably 0.055% or less.
  • Si is an element added for deoxidation.
  • the Si content is set to 0.01% or more.
  • the Si content is preferably 0.05% or more and more preferably 0.10% or more.
  • the Si content is set to 0.50% or less.
  • the Si content is preferably 0.40% or less and more preferably 0.30% or less.
  • Mn is an element that improves the strength and the toughness.
  • the Mn content is set to 0.50% or more.
  • the Mn content is preferably 1.00% or more and more preferably 1.20% or more.
  • the Mn content is set to 1.60% or less.
  • the Mn content is preferably 1.50% or less.
  • Nb is an element that forms a carbide or a nitride and contributes to improvement in the strength of steel.
  • Nb has an action of expanding the non-recrystallization temperature range toward the high temperature range and is thus an element that contributes to improvement in the toughness by grain refinement.
  • the Nb content is set to 0.001% or more.
  • the Nb content is preferably 0.005% or more and more preferably 0.010% or more.
  • the Nb content exceeds 0.100%, coarse carbide or nitride are formed, and the HIC resistance and the toughness deteriorate. Therefore, the Nb content is set to 0.100% or less.
  • the Nb content is preferably 0.080% or less and more preferably 0.060% or less.
  • N is an element that forms a nitride with Ti or Nb and contributes to the refinement of austenite grain sizes during heating.
  • the N content is set to 0.0010% or more.
  • the N content is preferably 0.0020% or more.
  • the N content exceeds 0.0100%, a coarse carbonitride is formed, and the HIC resistance and the toughness deteriorate. Therefore, the N content is set to 0.0100% or less.
  • the N content is preferably 0.0060% or less.
  • Ca is an element that forms CaS, suppresses the formation of MnS that extends in a rolling direction, and contributes to improvement in the HIC resistance.
  • the Ca content is set to 0.0001% or more.
  • the Ca content is preferably 0.0005% or more and more preferably 0.0010% or more.
  • the Ca content is set to 0.0050% or less.
  • the Ca content is preferably 0.0045% or less and more preferably 0.0040% or less.
  • the P is an element that is contained as an impurity.
  • the P content exceeds 0.030%, the SSC resistance and the HIC resistance deteriorate.
  • the toughness of the weld deteriorates. Therefore, the P content is set to 0.030% or less.
  • the P content is preferably 0.015% or less and more preferably 0.010% or less. An excess decrease in the P content leads to a significant increase in the manufacturing cost, and thus 0.001% is the substantial lower limit.
  • S is an element that is contained as an impurity and forms MnS that extends in the rolling direction during hot rolling to impair the HIC resistance.
  • the S content is set to 0.0025% or less.
  • the S content is preferably 0.0015% or less and more preferably 0.0010% or less. An excess decrease in the S content leads to a significant increase in the manufacturing cost, and thus 0.0001% is a substantial lower limit.
  • Ti is an element that forms a nitride and contributes to the refinement of grains.
  • the Ti content is set to 0.005% or more.
  • the Ti content is preferably 0.008% or more.
  • the Ti content exceeds 0.030%, not only does the toughness deteriorate, but a coarse nitride is also formed, and the HIC resistance deteriorates. Therefore, the Ti content is set to 0.030% or less.
  • the Ti content is preferably 0.020% or less.
  • Al is an element added for deoxidation.
  • the Al content is set to 0.010% or more.
  • the Al content is preferably 0.015% or more.
  • the Al content is set to 0.040% or less.
  • the Al content is preferably 0.035% or less.
  • O is an impurity element that remains inevitably after deoxidation.
  • an O content exceeds 0.0040%, an oxide is formed to degrade the toughness and the HIC resistance. Therefore, the O content is set to 0.0040% or less.
  • the O content is preferably 0.0030% or less.
  • the O content is preferably as small as possible, but an excess decrease in the O content leads to a significant increase in the manufacturing cost. Therefore, 0.0010% is a substantial lower limit.
  • each element symbol in the formulae represents the amount (mass%) of each element contained in steel and is regarded as 0 (zero) in a case where the corresponding element is not contained.
  • Mo, Cr, Cu, and Ni are elements that contribute to improvement in hardenability.
  • Ceq which is an index of hardenability to be described below
  • the total amount of these elements is set to 0.05% or more.
  • the total amount of these elements is preferably 0.07% or more and more preferably 0.10% or more.
  • the total amount of Mo, Cr, Cu, and Ni exceeds 2.00%, the hardness of steel increases to degrade the SSC resistance. Therefore, the total amount of Mo, Cr, Cu, and Ni is set to 2.00% or less.
  • the total amount is preferably 1.00% or less and more preferably 0.90% or less.
  • the amount of each of Mo, Cr, Cu, and Ni is preferably 1.00% or less and more preferably 0.50% or less.
  • W is an effective element for improvement in the strength of steel. Therefore, W may be contained as necessary. In order to obtain the above-described effect, the W content is preferably 0.01% or more and more preferably 0.05% or more.
  • the W content exceeds 1.00%, there is a case where the hardness increases to degrade the SSC resistance and degrade the toughness. Therefore, even in a case where W is contained, the W content is set to 1.00% or less.
  • the W content is preferably 0.50% or less and more preferably 0.30% or less.
  • V 0% to 0.200%
  • V is an element that forms a carbide or a nitride and contributes to improvement in the strength of steel. Therefore, V may be contained as necessary. In order to obtain the above-described effect, the V content is preferably 0.010% or more and more preferably 0.030% or more.
  • the V content exceeds 0.200%, the toughness of steel deteriorates. Therefore, even in a case where V is contained, the V content is set to 0.200% or less.
  • the V content is preferably 0.100% or less and more preferably 0.080% or less.
  • Zr is an element that forms a carbide or a nitride and contributes to improvement in the strength of steel. Therefore, Zr may be contained as necessary. In order to obtain the above-described effect, the Zr content is preferably 0.0001% or more and more preferably 0.0005% or more.
  • the Zr content exceeds 0.0500%, there is a case where the toughness of steel deteriorates. Therefore, even in a case where Zr is contained, the Zr content is set to 0.0500% or less.
  • the Zr content is preferably 0.0200% or less and more preferably 0.0100% or less.
  • Ta is an element that forms a carbide or a nitride and contributes to improvement in the strength. Therefore, Ta may be contained as necessary. In order to obtain the above-described effect, the Ta content is preferably 0.0001 % or more and more preferably 0.0005% or more.
  • the Ta content exceeds 0.0500%, there is a case where the toughness of steel deteriorates. Therefore, even in a case where Ta is contained, the Ta content is set to 0.0500% or less.
  • the Ta content is preferably 0.0200% or less and more preferably 0.0100% or less.
  • B is an element that is segregated at grain boundaries in steel to significantly contribute to improvement in the hardenability. Therefore, B may be contained as necessary. In order to obtain the above-described effect, the B content is preferably 0.0001% or more and more preferably 0.0005% or more.
  • the B content exceeds 0.0020%, there is a case where the toughness of steel deteriorates. Therefore, even in a case where B is contained, the B content is set to 0.0020% or less.
  • the B content is preferably 0.0015% or less and more preferably 0.0012% or less.
  • REM is an element that controls the form of a sulfide-based inclusion and contributes to improvement in the SSC resistance, the HIC resistance and the toughness. Therefore, REM may be contained as necessary. In order to obtain the above-described effect, the REM content is preferably 0.0001% or more and more preferably 0.0010% or more.
  • the REM content exceeds 0.0100%, a coarse oxide is formed, which causes not only a decrease in the cleanliness of steel, but also the deterioration of the HIC resistance and the toughness. Therefore, even in a case where REM is contained, the REM content is set to 0.0100% or less.
  • the REM content is preferably 0.0060% or less.
  • REM refers to a total of 17 elements of Sc, Y, and lanthanoids, and the REM content means the total amount of these elements.
  • Mg is an element that forms a fine oxide to suppress the coarsening of grains and contribute to improvement in the toughness. Therefore, Mg may be contained as necessary. In order to obtain the above-described effect, the Mg content is preferably 0.0001% or more and more preferably 0.0010% or more.
  • the Mg content exceeds 0.0100%, an oxide agglomerates and coarsens, the HIC resistance deteriorates, and the toughness deteriorates. Therefore, even in a case where Mg is contained, the Mg content is set to 0.0100% or less.
  • the Mg content is preferably 0.0050% or less.
  • Hf is an element that forms a sulfide, suppresses the formation of MnS extended in the rolling direction, and contributes to improvement in the HIC resistance. Therefore, Hf may be contained as necessary.
  • the Hf content is preferably 0.0001% or more and more preferably 0.0005% or more.
  • the Hf content is set to 0.0050% or less.
  • the Hf content is preferably 0.0040% or less and more preferably 0.0030% or less.
  • Re is an element that forms a sulfide, suppresses the formation of MnS extended in the rolling direction, and contributes to improvement in the HIC resistance. Therefore, Re may be contained as necessary.
  • the Re content is preferably 0.0001% or more and more preferably 0.0005% or more.
  • the Re content is set to 0.0050% or less.
  • the Re content is preferably 0.0040% or less and more preferably 0.0030% or less.
  • the remainder is Fe and impurities.
  • impurities mean components that are mixed in from a raw material such as ore or a scrap or due to a variety of factors in manufacturing steps at the time of industrially manufacturing steel and are allowed to an extent that the steel plate according to the present embodiment is not adversely affected.
  • Ceq is a value that serves as an index of hardenability and is represented by the following formula (ii).
  • Ceq is set to 0.30 to 0.50.
  • Ceq is preferably 0.33 or more and preferably 0.45 or less.
  • each element symbol in the formulae represents the amount (mass%) of each element contained in steel and is regarded as zero in a case where the corresponding element is not contained.
  • ⁇ Metallographic structure in thickness middle portion including, by area%, 0% to 80% of polygonal ferrite and one or two selected from acicular ferrite and bainite and remainder being M-A phase>
  • the metallographic structure in a thickness middle portion includes, by area%, 0% to 80% of polygonal ferrite and one or two selected from acicular ferrite and bainite, and the remainder is an M-A phase.
  • a structure including polygonal ferrite, acicular ferrite and/or bainite is formed.
  • the area ratio of the polygonal ferrite exceeds 80%, it becomes difficult to obtain a required strength, and the HIC resistance also deteriorates. Therefore, the area ratio of the polygonal ferrite is set to 80% or less.
  • the area ratio of the polygonal ferrite is preferably 60% or less.
  • the area ratio of the polygonal ferrite is preferably set to 20% or more.
  • a structure mainly including acicular ferrite and bainite is preferably formed as the metallographic structure in the thickness middle portion.
  • the total area ratio of the acicular ferrite and the bainite is more preferably 90% or more.
  • the remainder other than the polygonal ferrite, the acicular ferrite, and the bainite is an M-A phase.
  • the M-A phase is preferably 5.0% or less.
  • the M-A phase may not be included.
  • the effective grain size in the thickness middle portion is 15.0 ⁇ m or less.
  • the effective grain size is preferably 10.0 ⁇ m or less.
  • ⁇ Metallographic structure in surface layer including, by area%, total of 95% or more of one or two selected from acicular ferrite and bainite and remainder being M-A phase>
  • the metallographic structure in the surface layer that is a range of 1.0 mm in the thickness direction from the surface, a structure including one or two selected from acicular ferrite and bainite with the remainder of an M-A phase is formed.
  • the cooling rate of the surface layer is relatively fast compared to that in steel, and martensite is likely to be formed in a cooling process after hot rolling. When this martensite remains in the final structure without being sufficiently affected by a tempering effect, the SSC resistance deteriorates. Therefore, as the metallographic structure in the surface layer, a structure mainly including acicular ferrite and/or bainite is formed. In addition, in order to set the maximum hardness of the surface layer within a range to be described below, it is desirable to set the hardness of the surface layer to be extremely uniform. When acicular ferrite or bainite is included in the surface layer, an effect on setting the hardness uniform can be obtained, which is preferable.
  • the total area ratio of the acicular ferrite and the bainite is preferably 97% or more, more preferably 98% or more, and still more preferably 99% or more and may be 100%.
  • the remainder is an M-A phase.
  • the M-A phase may not be included.
  • acicular ferrite refers to a structure formed of one or more selected from quasi-polygonal ferrite ( ⁇ q), Widmanstetten ferrite ( ⁇ w), and granular bainite ( ⁇ B ) as defined in Non-Patent Document 1.
  • Bainite means a structure including bainitic ferrite ( ⁇ ° B ) having a substructure in grains.
  • M-A phase martensite-austenite constituent
  • ⁇ austenite
  • the area ratio of each phase in the metallographic structure and the effective grain size in the thickness middle portion are obtained as described below.
  • test pieces having an overall thickness are cut out from a position of a 1/4 position (1/4 width) of the plate width from one end portion in the width direction of the steel plate such that a cross section in the L (longitudinal) direction from a steel sample becomes an observed section and are each used for structure observation and for grain size measurement.
  • the test piece for structure observation is polished in a wet manner to finish the test piece into a mirror surface, and then a metallographic structure is revealed using an etching solution.
  • an etching solution Nital is used.
  • the structures of the surface layer and the thickness middle portion are observed at a magnification of 100 times to 1000 times using an optical microscope or SEM on the L-direction cross section, and each structure is confirmed. After that, the kind of each structure is confirmed at a magnification of 200 times or 500 times.
  • the polygonal ferrite ⁇ p has a rounded polygonal shape and is a recovered structure in which a substructure such as a lath or block that looks like cementite, residual austenite, an M-A phase, bainite, and martensite is not present in grains.
  • the quasi-polygonal ferrite shows a complicated shape and is similar particularly to granular bainite in some cases, but, similar to the polygonal ferrite, does not include any substructure due to diffusion transformation, and is a structure that straddles prior austenite grain boundaries.
  • the Widmanstetten ferrite is ferrite having a needle-like shape.
  • the granular bainite shows a complicated shape and has no clear substructure recognized compared with bainite and is thus similar to the quasi-polygonal ferrite, but is different from the quasi-polygonal ferrite in that the granular bainite is a structure that includes cementite, residual austenite, and an M-A phase in grains or does not straddle prior austenite grain boundaries.
  • the granular bainite is a structure that includes cementite, residual austenite, and an M-A phase in grains or does not straddle prior austenite grain boundaries.
  • a structure formed of one or more of quasi-polygonal ferrite, Widmanstetten ferrite, and granular bainite is defined as acicular ferrite, there is no need to distinguish quasi-polygonal ferrite and granular bainite.
  • the bainite is a structure including bainitic ferrite having a substructure in grains.
  • Bainite can be distinguished into upper bainite including residual austenite or an M-A phase between lath-shaped bainitic ferrite (BI type), upper bainite including cementite between lath-shaped bainitic ferrite (BII type), lath-shaped lower bainite including cementite in lath-shaped bainitic ferrite (BIII type), and lower bainite including cementite in plate-shaped bainitic ferrite; however, in the present embodiment, all of them are included in bainite.
  • each structure is determined based on the above-described characteristics at the time of determination.
  • the test piece for structure observation is polished in a wet manner to finish the test piece into a mirror surface, and then a metallographic structure is revealed using an etching solution.
  • an etching solution LePera is used.
  • the structure is observed at a magnification of 500 times using an optical microscope, and the area ratio is measured.
  • the thickness middle portion is observed using a SEM-EBSD device, a region surrounded by high-angle grain boundaries with an inclination angle of 15° or more is defined as a grain, and the grain size of the grain is obtained, thereby obtaining the effective grain size.
  • a region surrounded by grain boundaries with an angle difference of 15° or more measured with OIM Analysis of TSL Solutions, which is EBSD analysis software is defined as a grain, and the average diameter of a circle having the same area as the grain (equivalent circle diameter) is regarded as the grain size.
  • a region having an equivalent circle diameter of 0.5 ⁇ m or less is ignored.
  • the average value by the Area Fraction method is used as the effective grain size.
  • the area ratio of the polygonal ferrite may be measured based on the difference in shape in the observation using an optical microscope or SEM as described above; however, since there is no substructure such as a lath or block that looks like bainite or martensite in polygonal ferrite grains, the same polygonal ferrite fraction can be obtained by measuring the area ratio of a structure having no intragranular angle difference, which is attributed to the lath or block.
  • the step interval at the time of EBSD measurement is set to 0.5 ⁇ m so that the angle difference between substructures such as a lath or a block in the bainite structure is measured.
  • the hardness in the surface layer is evaluated by a Vickers hardness test in which the test force is set to 0.98 N (0.1 kgf).
  • the maximum hardness of the surface layer is 250 HV0.1 or less, the SSC resistance improves. Therefore, the maximum hardness of the surface layer is set to 250 HV0.1 or less.
  • the maximum hardness of the surface layer which is a range from the surface to a depth of 1.0 mm, is measured as described below.
  • 300 mm x 300 mm steel plates are cut out by gas cutting from 1/4, 1/2, and 3/4 positions of the plate width in the width direction of the steel plate from an end portion of the steel plate in the width direction, and block test pieces having a length of 20 mm and a width of 20 mm are collected by mechanical cutting from the center of the cut-out steel plates and polished by mechanical polishing.
  • the hardness is measured with a Vickers hardness meter (load: 0.1 kgf) at a total of 100 points (10 points at 1.0 mm intervals in the width direction at each of 10 depth points at 0.1 mm intervals in the plate thickness direction from a position 0.1 mm deep from the surface in the plate thickness direction as a starting point). That is, the hardness is measured at a total of 300 points in three block test pieces.
  • the point is regarded as an abnormal point and is not adopted unless two or more abnormal points continuously appear in the plate thickness direction, and the next highest value is regarded as the maximum hardness.
  • the highest value thereof is adopted as the maximum hardness.
  • the tensile strength is not particularly limited; however, for line pipes that are used in H 2 S environments where the steel plate according to the present embodiment is assumed to be used, it is ordinary to use X52, X60, or X65-grade materials in many cases.
  • the tensile strength is preferably 480 MPa or more and more preferably 500 MPa or more.
  • the tensile strength exceeds 700 MPa, there is a case where the SSC resistance or the HIC resistance deteriorates. Therefore, the tensile strength is preferably 700 MPa or less.
  • the tensile strength is obtained by working a round bar-like tensile test piece such that the longitudinal direction of the test piece becomes parallel to the width direction of the steel plate and performing a tensile test according to API 5L.
  • the plate thickness of the steel plate according to the present embodiment is not particularly limited. However, from the viewpoint of improving the transport efficiency of a fluid flowing through a line pipe that has been produced using the steel plate according to the present embodiment, the plate thickness is preferably 16.0 mm or more and more preferably 19.0 mm or more.
  • the hardness of the surface layer is increased by work hardening during the forming of a steel pipe, and, normally, as the wall thickness increases, the hardness of the surface layer increases.
  • the plate thickness is preferably 35.0 mm or less, more preferably 30.0 mm or less, and still more preferably 25.0 mm or less.
  • the steel pipe according to the present embodiment has a base material portion made of a tubular steel plate and a weld that is provided at an abutment portion of the steel plate and extends in the longitudinal direction of the steel plate.
  • a steel pipe can be obtained by working the steel plate according to the present embodiment into a tubular shape and welding the abutment portion.
  • the reasons for limiting the chemical composition, metallographic structure, and the maximum hardness of the surface layer of the base material portion (steel plate) of the steel pipe according to the present embodiment are the same as those for the steel plate according to the present embodiment.
  • test pieces having an overall thickness are cut out from a position at 90° from a seam weld in the steel pipe such that a cross section in the L (longitudinal) direction becomes the observed section and are each used for structure observation and for grain size measurement.
  • the 90° position corresponds to the 114 or 3/4 position of the plate width of the steel plate.
  • the maximum hardness of the surface layer is measured by the following method.
  • 300 mm x 300 mm steel plates are each cut out by gas cutting from a three o'clock, six o'clock, or nine o'clock position in a case where the weld of the steel pipe is defined at zero o'clock (position at 90°, 180°, or 270° from the seam weld), and block test pieces having a length of 20 mm and a width of 20 mm are collected by mechanical cutting from the center of the cut-out steel plates and polished by mechanical polishing.
  • the hardness is measured with a Vickers hardness meter (load: 0.1 kgf) at a total of 100 points (10 points at 1.0 mm intervals in the width direction at each of 10 depth points at 0.1 mm intervals in the plate thickness direction from 0.1 mm deep from the surface as a starting point). That is, the hardness is measured at a total of 300 points in three block test pieces.
  • the maximum hardness of the surface layer is determined to be 250 HV0.1 or less.
  • the tensile strength is not particularly limited; however, for line pipes that are used in H 2 S environments, it is ordinary to use X52, X60, or X65-grade materials in many cases. In order to satisfy such a requirement, the tensile strength is preferably 480 MPa or more and more preferably 500 MPa or more.
  • the tensile strength exceeds 700 MPa, there is a case where the SSC resistance or the HIC resistance deteriorates. Therefore, the tensile strength is preferably 700 MPa or less.
  • the tensile strength is obtained by collecting a round bar-like test piece from a position at 180° from the seam portion of the steel pipe such that the longitudinal direction becomes parallel to the width direction of the steel plate and performing a tensile test according to API 5L.
  • the wall thickness of the steel pipe according to the present embodiment is not particularly limited. However, from the viewpoint of improving the transport efficiency of a fluid flowing through a line pipe, the wall thickness is preferably 16.0 mm or more and more preferably 19.0 mm or more.
  • the hardness of the surface layer is increased by work hardening during the forming of a steel pipe, and, normally, as the wall thickness increases, the hardness of the surface layer increases.
  • the wall thickness is preferably 35.0 mm or less, more preferably 30.0 mm or less, and still more preferably 25.0 mm or less.
  • the weld of the steel pipe according to the embodiment is not particularly limited when obtained by SAW welding or the like under normal conditions.
  • the steel plate according to the present embodiment is used as a material
  • the steel plate is welded by SAW welding or the like using 3 electrodes or 4 electrodes with a heat input within a condition range of 2.0 kJ/mm to 10 kJ/mm depending on the plate thickness, whereby the maximum hardness becomes 250 Hv or less, which is preferable.
  • a tempering treatment suam heat treatment
  • the weld is heated
  • the hardness of the weld may be measured with a load of 0.1 kgf in the same manner as for the hardness of the base material portion, but may be measured with a load of 10 kgf or a load of 5 kgf as described in NACE MR0175/ISO15156-2.
  • the steel plate according to the present embodiment and the steel pipe according to the present embodiment have the above-described configuration, the effects can be obtained; however, for example, a manufacturing method as described below makes it possible to stably obtain the steel plate and the steel pipe, which is preferable. That is, the steel plate and the steel pipe can be manufactured by the following method, but the manufacturing method thereof is not limited to this method.
  • the steel plate according to the present embodiment can be obtained by a manufacturing method including the following steps.
  • the heating temperature before hot rolling is set to 1000°C to 1300°C
  • the finish rolling start temperature of the hot rolling is set to Ar3 to 900°C
  • the finish rolling finishing temperature is set to Ar3°C or higher.
  • the heating temperature exceeds 1300°C, grains become coarse, and there is a concern that it may become impossible to obtain a predetermined effective grain size.
  • the heating temperature is lower than 1000°C, there is a possibility that it may not be possible to secure a predetermined finish rolling temperature.
  • the rolling start temperature exceeds 900°C, the grains become coarse, and there is a concern that it may become impossible to obtain a predetermined effective grain size.
  • the rolling start temperature is lower than Ar3°C, there is a possibility that it may not be possible to secure a predetermined finish rolling temperature.
  • the finish rolling finishing temperature is set to Ar3°C or higher.
  • Ar3 varies with the chemical composition, the heating temperature, the hot rolling conditions, and the plate thickness (cooling rate during air cooling), but is approximately 760°C to 790°C as long as the chemical composition, the plate thickness, and the strength are within the range of the steel plate according to the present embodiment.
  • the cooling rate is desirably increased after the end of the hot rolling.
  • the cooling rate is fast, there is a concern that the hardness of the surface layer may increase. Therefore, in order to satisfy both, controlled cooling after the end of the hot rolling is important.
  • a steel plate having the above-described metallographic structure by performing a first cooling step, a holding step, a second cooling step, a third cooling step, and a fourth cooling step, which will be described below, in order on the steel plate (hot rolled steel plate) after the hot rolling step.
  • the second cooling step is optional and may not be performed.
  • accelerated cooling is performed at an average cooling rate of 30 °C/s or faster from a temperature of Ar3°C or higher, for example, 790°C to 830°C, to a bainitic transformation region of a Bs point to an Ms point in terms of the surface temperature of the steel plate.
  • the accelerated cooling up to the above-described bainitic transformation region makes it possible to suppress the formation of polygonal ferrite and martensite in the metallographic structure of the surface layer of the steel plate.
  • the cooling stop temperature in the first cooling step becomes higher than the Bs point, there is a concern that polygonal ferrite may be formed in the metallographic structure of the surface layer in the following holding step.
  • the cooling stop temperature in the first cooling step is lower than the Ms point, there is a concern that martensite may be formed in the metallographic structure of the surface layer.
  • the average cooling rate is slower than 30 °C/s, there is a concern that polygonal ferrite may be formed in the middle of cooling.
  • the upper limit of the average cooling rate is not particularly limited.
  • the average cooling rate in the first cooling step is a cooling rate calculated by dividing a change in the surface temperature by the difference between the cooling start time and the cooling end time.
  • the Bs point (°C) is represented by the following formula (iii) and means the formation start temperature of acicular ferrite and bainite.
  • Bs 830 ⁇ 270 ⁇ C ⁇ 90 ⁇ Mn ⁇ 37 ⁇ Ni ⁇ 70 ⁇ Cr ⁇ 83 ⁇ Mo
  • each element symbol in the formulae represents the amount (mass%) of each element contained in steel and is regarded as zero in a case where the corresponding element is not contained.
  • Ms 545 - 330 ⁇ C + 2 ⁇ Al - 14 ⁇ Cr - 13 ⁇ Cu - 23 ⁇ Mn - 5 ⁇ Mo - 4 ⁇ Nb- 13 ⁇ Ni - 7 ⁇ Si + 3 ⁇ Ti + 4 ⁇ V
  • each element symbol in the formulae represents the amount (mass%) of each element contained in steel and is regarded as zero in a case where the corresponding element is not contained.
  • the temperature of the surface layer is retained within a temperature range of the Ms point to the Bs point (bainitic transformation region) by performing slow cooling.
  • the temperature is retained within the above-described bainitic transformation region for 3.0 seconds or longer, thereby controlling the metallographic structure in the surface layer to be a metallographic structure mainly including acicular ferrite and bainite.
  • the holding temperature is lower than the Ms point, martensite is formed, and it is not possible to set the maximum hardness of the surface layer to 250 HV0.1 or less.
  • the holding time is not sufficient, untransformed austenite transforms into martensite in the subsequent step, and it is not possible to set the maximum hardness of the surface layer to 250 HV0.1 or less. Therefore, in order to control the metallographic structure to a metallographic structure mainly including acicular ferrite and bainite, in the holding step, the temperature of the surface layer is retained in the bainitic transformation region for 3.0 seconds or longer.
  • the present step in order to retain the temperature of the surface layer in the bainitic transformation region for 3.0 seconds or longer while performing slow cooling, it is extremely important to perform accelerated cooling at an average cooling rate of 30 °C/s or faster to the bainitic transformation region of the Bs point to the Ms point in the first cooling step.
  • the temperature of the thickness middle at the start of the holding step is maintained at a temperature higher than the temperature of the surface layer for a certain period of time. Therefore, the surface layer after the first cooling step tends to be reheated (the temperature is increased) by heat conduction with the thickness middle.
  • slow cooling is performed with an amount of water small enough to suppress the heat recuperation by heat conduction, which makes it possible to retain the temperature of the surface layer in the bainitic transformation region for 3.0 seconds or longer.
  • the surface layer is cooled and retained as described above, but the thickness middle portion is slowly cooled.
  • the temperature of the thickness middle portion at the completion of the holding step is preferably 700°C or higher, and the average cooling rate of the thickness middle portion during the first cooling step and the holding step is preferably 15 °C/s or slower.
  • the cooling of the surface and heat recuperation by which the surface temperature after the heat recuperation becomes 550°C or higher are repeated two or more times in the second cooling step, whereby it is possible to control the cooling rate of the center and to increase the polygonal ferrite fraction.
  • the fraction of fine polygonal ferrite grains, which are formed in this second cooling step is increased, it is possible to refine the average grain size in the entire metallographic structure of a complex structure that is obtained in the end.
  • the second cooling step is preferably performed.
  • the surface temperature is cooled to a low temperature compared with the internal temperature.
  • the surface temperature is reheated such that the difference between the internal temperature and the surface temperature becomes small due to heat conduction from the inside when the accelerated cooling is temporarily stopped. Since the center temperature is cooled by heat conduction attributed to the temperature difference from the surface layer, when the temperature of the surface layer is reheated, the cooling rate of the center decreases. Therefore, when the heat recuperation and cooling of the surface layer are repeated, it is possible to control the cooling rate of the center and to increase the polygonal ferrite fraction.
  • the surface temperature is decreased to 500°C or lower by the accelerated cooling after the holding step, and the cooling and heat recuperation of the surface layer, which reheats the surface layer to 550°C or higher, is repeated two or more times, it is possible to retain the center temperature in the ferritic transformation region and to efficiently increase the polygonal ferrite fraction.
  • the cooling and heat recuperation is performed less than twice in the second cooling step, there is a concern that it may not be possible to secure a sufficient transformation time to increase the polygonal ferrite fraction in the thickness middle portion.
  • the heat recuperation of the surface of the steel plate is caused by heat conduction with the internal temperature, in a case where the heat recuperation temperature is less than 550°C, the thickness middle portion is also retained in the bainitic transformation region, and there is a concern that the polygonal ferrite fraction may not be increased.
  • accelerated cooling is performed at an average cooling rate of 10 °C/s or faster.
  • the surface temperature is cooled in an accelerated manner to the Ms point or lower, and the final heat recuperation temperature after the stop of the cooling is set to the Bs point or lower.
  • the surface temperature of the steel plate is cooled in an accelerated manner to the Ms point or lower for the purpose of increasing the average cooling rate.
  • the surface temperature of the steel plate is cooled to the Ms point or lower, it is possible to increase the cooling rate of the thickness middle portion by heat conduction.
  • the average cooling rate is an average cooling rate of the wall thickness middle portion that is obtained by dividing a change in the temperature of the thickness middle portion by the cooling time (the difference between the cooling start time and the cooling end time).
  • the change in the temperature of the thickness middle portion can be obtained from the surface temperature by heat conduction calculation.
  • the thickness middle portion is cooled in an accelerated manner by heat conduction with the surface; however, when the cooling is stopped, the surface is reheated by heat conduction with the thickness middle portion. Since the heat recuperation proceeds until the temperature of the surface coincides with the thickness middle portion, the final heat recuperation temperature after the cooling corresponds to the cooling stop temperature in the thickness middle portion.
  • the final heat recuperation temperature is set to the Bs point or lower, it is possible to form a structure including fine acicular ferrite and/or bainite in the thickness middle portion.
  • the final heat recuperation temperature becomes higher than the Bs point, the generated polygonal ferrite grows, and the structure becomes coarse.
  • the cooling may be temporarily stopped and the surface temperature of the steel plate may be set to the Ms point or higher once or more by heat recuperation.
  • the surface temperature is cooled to a low temperature compared with the internal temperature.
  • the surface temperature can be reheated by heat conduction with the internal temperature when the accelerated cooling is temporarily stopped. For example, even when the surface temperature decreases to 400°C or lower by the accelerated cooling, if the internal temperature at the time of stopping the cooling is 700°C or higher, the steel plate can be reheated to a temperature of 550°C or higher by imparting an appropriate heat recuperation time.
  • the steel plate When the steel plate is reheated, a high self-tempering effect can be obtained compared with a case where normal accelerated cooling is performed, and thus it is possible to decrease the hardness of the surface layer. Even after that, the accelerated cooling is intermittently performed, which makes it possible to repeat cooling and heat recuperation.
  • the heat recuperation is more preferably performed, for example, twice or more.
  • cooling is performed to 300°C or lower such that the average cooling rate until 300°C becomes 200 °C/hr or faster.
  • the average cooling rate until 300°C is slower than 200 °C/hr, it is not possible to obtain a predetermined strength.
  • the steel plate according to the present embodiment is formed into a tubular shape, both end portions of the steel plate formed in a tubular shape are abutted and welded (seam-welded), thereby forming the steel pipe according to the present embodiment.
  • the forming of the steel plate according to the present embodiment into the steel pipe is not limited to specific forming method.
  • the steel pipe can be manufactured by performing UO pipe making.
  • UO pipe making method for example, a rolled steel plate (material) having an edge portion grooved by cutting is C-pressed to form the rolled steel plate into a C shape, then, U-pressed to form the steel plate into a U shape, and furthermore, O-pressed to form the steel plate into an O shape, thereby forming the steel plate into a cylindrical shape.
  • seams which are end portions, are abutted and temporarily welded, the inner surfaces are welded, the outer surfaces are welded, and furthermore, pipe expansion is performed as necessary.
  • the welding is also not limited to specific welding, but is preferably submerged arc welding (SAW). As long as the maximum hardness of the weld of the steel pipe according to the present embodiment is within the above-described range, welding conditions and the like are not limited.
  • the steel plate according to the present embodiment is used as a material
  • the steel plate is welded by SAW welding or the like using 3 electrodes or 4 electrodes with a heat input within a condition range of 2.0 kJ/mm to 10 kJ/mm depending on the plate thickness, whereby the maximum hardness of the surface layer becomes 250 HV0.1 or less, which is preferable.
  • a seam heat treatment in which the weld is heated to the Ac1 point (°C) or lower and tempered may be performed.
  • a first cooling step, a holding step, a third cooling step, and a fourth cooling step were performed in order under conditions shown in Table 2-1 to Table 2-4, and then the steel pieces were cooled to room temperature while cooling and heat recuperation were repeated, thereby manufacturing steel plates (a second cooling step was not performed).
  • the first cooling step, the holding step, the second cooling step, the third cooling step, and the fourth cooling step were performed in order under conditions shown in Table 2-1 to Table 2-4, and the steel pieces were cooled to room temperature, thereby manufacturing steel plates.
  • the surface temperatures of all of the steel plates were once decreased to 500°C or lower in cooling before heat recuperation.
  • Second cooling conditions Heating temperature (°C) Finish rolling start temperature (°C) Finish rolling finishing temperature (°C) Surface layer average cooling rate (°C/s) Surface layer cooling stop temperature (°C) Average holding temperature (°C) Holding time (s) Number of times of heat recuperation (times) First heat recuperation highest temperature (°C) 1 A 1200 855 812 98 660 630 4.5 2 610 2 A 1250 855 816 70 630 600 9.0 0 - 3 A 1180 855 818 60 700 680 5.0 0 - 4 A 1180 860 818 110 320 580 3.5 1 550 5 A 1200 860 820 90 660 640 2.0 0 6 A 1150 850 806 98 660 580 4.0 2 560 7 B 1200 855 815 78 660 635 4.0 2 590 8 B 1180 860 820 100 650 620 5.5 1 600 9 B 1130 850 805 98 650 620 5.5 0 -
  • Second cooling conditions Heating temperature (°C) Finish rolling start temperature (°C) Finish rolling finishing temperature (°C) Surface layer average cooling rate (°C/s) Surface layer cooling stop temperature (°C) Average holding temperature (°C) Holding time (s) Number of times of heat recuperation (times) First heat recuperation highest temperature (°C) 101 A 1150 845 802 98 660 630 4.5 3 610 102 A 1150 850 806 70 630 600 9.0 2 610 103 A 1150 835 790 10 630 630 3.0 2 570 104 A 1130 850 808 60 700 680 5.0 2 610 105 A 1130 850 808 110 320 580 3.0 2 610 106 A 1150 850 810 90 660 640 2.0 2 610 107 A 1200 855 816 98 660 580 4.0 3 650 108 B 1150 845 805 78 660 635 4.0 2 590 109 B 1130 850 810 100 650
  • test pieces for structure observation test pieces for grain size measurement, tensile test pieces, test pieces for hardness measurement, DWTT test pieces, impact test pieces, SSC test pieces, and an HIC test pieces were collected and used for corresponding tests.
  • test piece for structure observation a test piece was collected from a position of a W/4 position in the plate width direction such that an L-direction cross section became an observed section, polished in a wet manner to finish the test piece into a mirror surface, and then Nital-etched to reveal the metallographic structure.
  • the structure was observed at 4 visual fields using an optical microscope at a magnification of 500 times, and the area ratios of each structure in the surface layer (a position 0.1 mm from the surface) and in the thickness middle portion were measured.
  • test piece for grain size measurement a test piece was collected from the same position as for the test piece for structure observation such that an L-direction cross section became an observed section, the thickness middle portion was observed using a SEM-EBSD device, and the grain sizes of grains surrounded by high-angle grain boundaries with an inclination angle of 15° or more were obtained, thereby obtaining an average effective grain size.
  • a round bar-like tensile test piece was worked such that the longitudinal direction of the test piece became parallel to the width direction of the steel plate, and a tensile test was performed. From the result, the tensile strength (MPa) was obtained.
  • the steel plate was determined to have a preferable strength as a steel plate for a line pipe.
  • the maximum hardness of the surface layer was measured using the test piece for hardness measurement. Specifically, 300 mm x 300 mm steel plates were cut out by gas cutting from 1/4, 1/2, and 3/4 positions in the width direction of the steel plate from an end portion of the steel plate in the width direction, and block test pieces having a length of 20 mm and a width of 20 mm were collected by mechanical cutting from the center of the cut-out steel plates and polished by mechanical polishing. In one block test piece, the hardness was measured with a Vickers hardness meter (load: 0.1 kgf) at a total of 100 points (10 points at 1.0 mm intervals in the width direction at each of 10 depth points at 0.1 mm intervals in the plate thickness direction from 0.1 mm deep from the surface as a starting point).
  • load 0.1 kgf
  • the hardness was measured at a total of 300 points in three block test pieces. Even when there was one measurement point where the hardness exceeded 250 HV as a result of the measurement, the point was regarded as an abnormal point and was not adopted unless two or more abnormal points continuously appeared in the plate thickness direction, and the next highest value was regarded as the maximum hardness. On the other hand, in a case where there were two or more measurement points with hardness of more than 250 HV continuously present in the plate thickness direction, the highest value thereof was adopted as the maximum hardness.
  • the DWTT test piece was collected from a 1/4 position in the width direction of the steel plate such that the longitudinal direction of the test piece became parallel to the width direction of the steel plate.
  • a DWTT test was performed using this DWTT test piece at test temperatures of -20°C and -30°C, and the DWTT shear fracture area was measured.
  • the DWTT test was performed according to API standard 5L3.
  • the impact test piece was made into a 10 mm-wide test piece having a 2 mm V notch. Three test pieces described above were cut out from a 1/4 position in the width direction of the steel plate such that the longitudinal direction of the test piece became parallel to the width direction of the steel plate, a Charpy impact test was performed at -100°C, and three average absorbed energies were obtained.
  • NACE TM 0316 As an SSC test, a 4-point bending test in which the inner surface of the steel pipe was used as a test surface to evaluate the SSC sensitivity of the outermost layer was performed according to NACE TM 0316. The test pieces were collected from a center in the width direction and from a 1/4 position in the width direction of the steel plate such that the longitudinal direction of the test piece became parallel to the width direction of the steel plate. At that time, the load stress was set to correspond to 90% of the actual YS (yield strength) of the test piece, and, as a testing solution, NACE Solution A regulated in NACE TM 0177 was used.
  • test piece was immersed for 720 hours under a condition in which 0.1 MPa of hydrogen sulfide was saturated in a solution containing 5% salt and 0.5% acetic acid, and then the presence or absence of the occurrence of SSC was observed. The other conditions followed NACE TM 0177. In addition, test pieces in which SSC did not occur were determined as pass (OK), and test pieces in which SSC occurred were determined as fail (NG).
  • the HIC test piece was made into an overall thickness test piece having a length of 100 mm and a width of 20 mm.
  • an HIC test was performed according to NACE TM 0284. Specifically, the test piece was immersed for 96 hours under a condition in which 0.1 MPa of hydrogen sulfide was saturated in a solution containing 5% salt and 0.5% acetic acid, and then the crack area ratio was obtained. Test pieces for which the crack area ratio was 6% or less were determined as pass (OK), and test pieces for which the crack area ratio was more than 6% were determined as fail (NG). In addition, test pieces for which the crack area ratio was 3% or less were determined as particularly excellent (Ex).
  • the polygonal ferrite area ratios were 20% or more, and the effective grain sizes were 10.0 ⁇ m or less, the DWTT shear fracture areas obtained after the DWTT test at -30°C were also 85% or more, the absorbed energies of the Charpy impact test at -100°C were 150 J or more, and the low temperature toughness was particularly excellent.
  • Test Nos. 3 to 5, 10 to 12, 27 to 29, 103 to 107, 110, 124, and 125 did not satisfy any of the regulations of the present invention.
  • Example 1 the steel plates that had obtained favorable characteristics were formed into a tubular shape by the UO pipe making method, welded from the inner and outer surfaces of steel pipes by submerged arc welding, and expanded to produce UOE steel pipes.
  • the welding conditions 3 electrodes were used on the inner surface side, 4 electrodes were used on the outer surface side, and the heat input was set within a range of 2.0 kJ/mm to 10 kJ/mm depending on the plate thickness.
  • 300 mm x 300 mm steel plates were each cut out by gas cutting from a three o'clock, six o'clock, or nine o'clock position in a case where the weld of the steel pipe was defined at zero o'clock (position at 90°, 180°, or 270° from the seam weld), and block test pieces having a length of 20 mm and a width of 20 mm were collected by mechanical cutting from the center of the cut-out steel plates and polished by mechanical polishing.
  • the hardness is measured with a Vickers hardness meter (load: 0.1 kgf) at a total of 100 points (10 points at 1.0 mm intervals in the width direction at each of 10 depth points at 0.1 mm intervals in the plate thickness direction from 0.1 mm deep from the surface as a starting point). That is, the hardness was measured at a total of 300 points in three block test pieces.
  • a round bar-like test piece was collected from a position at 180° from the seam portion of the steel pipe such that the longitudinal direction became parallel to the width direction of the steel plate, and a tensile test was performed according to API 5L.
  • the steel plate and the steel pipe according to the present invention can be suitably used as line pipes for transporting crude oil and natural gas containing a large amount of H 2 S.

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Claims (8)

  1. Stahlplatte umfassend, als eine chemische Zusammensetzung, in Masse-%:
    C: 0,020% bis 0,080%;
    Si: 0,01% bis 0,50%;
    Mn: 0,50% bis 1,60%;
    Nb: 0,001% bis 0,100%;
    N: 0,0010% bis 0,0100%;
    Ca: 0,0001% bis 0,0050%;
    P: 0,030% oder weniger;
    S: 0,0025% oder weniger;
    Ti: 0,005% bis 0,030%;
    Al: 0,010% bis 0,040%;
    O: 0,0040% oder weniger;
    Mo: 0% bis 2,00%;
    Cr: 0% bis 2,00%;
    Cu: 0% bis 2,00%;
    Ni: 0% bis 2,00%;
    W: 0% bis 1,00%;
    V: 0% bis 0,200%;
    Zr: 0% bis 0,0500%;
    Ta: 0% bis 0,0500%;
    B: 0% bis 0,0020%;
    REM: 0% bis 0,0100%;
    Mg: 0% bis 0,0100%;
    Hf: 0% bis 0,0050%;
    Re: 0% bis 0,0050%; und
    einen Rest: Fe und Verunreinigungen,
    wobei die folgende Formel (i) erfüllt ist,
    Ceq, dargestellt durch die folgende Formel (ii), 0,30 bis 0,50 beträgt,
    eine metallographische Struktur in einem mittleren Dickenabschnitt umfasst, in Flächenprozent, 0% bis 80% von polygonalem Ferrit und ein oder zwei, ausgewählt aus nadelförmigem Ferrit und Bainit, ein Rest eine M-A-Phase ist, und eine effektive Korngröße 15,0 µm oder weniger beträgt,
    eine metallographische Struktur in einer Oberflächenschicht, die in einer Dickenrichtung ein Bereich von 1,0 mm von einer Oberfläche ausgehend ist, umfasst, in Flächenprozent, insgesamt 95% oder mehr von einem oder zwei, die ausgewählt sind aus nadelförmigem Ferrit und Bainit, und ein Rest eine M-A-Phase ist, und
    eine maximale Härte in der Oberflächenschicht 250 HV0,1 oder weniger beträgt,
    wobei das Flächenprozent von polygonalem Ferrit, das Flächenprozent von nadelförmigem Ferrit und Bainit und die effektive Korngröße gemäß den in der Beschreibung beschriebenen Verfahren bestimmt werden, und die maximale Härte in der Oberflächenschicht durch einen Vickers-Härtetest gemäß JIS Z 224:2009 ermittelt wird, bei dem die Prüfkraft auf 0,98 N (0,1 kgf) eingestellt wird, 0,05 ≤ Mo + Cr + Cu + Ni ≤ 2,00
    Figure imgb0016
     Ceq = C + Mn / 6 + Ni + Cu / 15 + Cr + Mo + V / 5
    Figure imgb0017
    hierbei steht jedes Elementsymbol in den Formeln für eine Menge (Masse-%) jedes im Stahl enthaltenen Elements und wird als Null betrachtet, wo ein entsprechendes Element nicht enthalten ist.
  2. Stahlplatte nach Anspruch 1,
    wobei ein Flächenprozent des polygonalen Ferrits in der metallografischen Struktur des mittleren Dickenabschnitts 0% bis weniger als 20% beträgt.
  3. Stahlplatte nach Anspruch 1,
    wobei ein Flächenprozent des polygonalen Ferrits in der metallografischen Struktur des mittleren Dickenabschnitts 20% bis 80% beträgt, und die effektive Korngröße 10,0 µm oder weniger beträgt.
  4. Stahlplatte gemäß einem der Ansprüche 1 bis 3, ferner umfassend, als chemische Zusammensetzung, in Masse-%, eines oder mehrere, ausgewählt aus:
    W: 0,01 % bis 1,00%;
    V: 0,010% bis 0,200%;
    Zr: 0,0001% bis 0,050%;
    Ta: 0,0001% bis 0,0500%; und
    B: 0,0001% bis 0,0020%.
  5. Stahlplatte gemäß einem der Ansprüche 1 bis 4, ferner umfassend, als chemische Zusammensetzung, in Masse-%, eines oder mehrere, ausgewählt aus:
    REM: 0,0001% bis 0,0100%;
    Mg: 0,0001% bis 0,0100%;
    Hf: 0,0001% bis 0,0050% und
    Re: 0,0001% bis 0,0050%.
  6. Stahlrohr, umfassend:
    einen Grundmaterialabschnitt, der aus einer Stahlrohrplatte hergestellt ist; und
    eine Schweißnaht, die an einem Anschlagabschnitt der Stahlplatte vorgesehen ist und sich in einer Längsrichtung der Stahlplatte erstreckt,
    wobei die Stahlplatte enthält, als eine chemische Zusammensetzung, in Masse-%:
    C: 0,020% bis 0,080%;
    Si: 0,01% bis 0,50%;
    Mn: 0,50% bis 1,60%;
    Nb: 0,001% bis 0,100%;
    N: 0,0010% bis 0,0100%;
    Ca: 0,0001% bis 0,0050%;
    P: 0,030% oder weniger;
    S: 0,0025% oder weniger;
    Ti: 0,005% bis 0,030%;
    Al: 0,010% bis 0,040%;
    O: 0,0040% oder weniger;
    Mo: 0% bis 2,00%;
    Cr: 0% bis 2,00%;
    Cu: 0% bis 2,00%;
    Ni: 0% bis 2,00%;
    W: 0% bis 1,00%;
    V: 0% bis 0,200%;
    Zr: 0% bis 0,0500%;
    Ta: 0% bis 0,0500%;
    B: 0% bis 0,0020%;
    REM: 0% bis 0,0100%;
    Mg: 0% bis 0,0100%;
    Hf: 0% bis 0,0050%;
    Re: 0% bis 0,0050%; und
    einen Rest: Fe und Verunreinigungen,
    wobei die folgende Formel (i) erfüllt ist,
    Ceq, dargestellt durch die folgende Formel (ii), 0,30 bis 0,50 beträgt,
    eine metallographische Struktur in einem mittleren Dickenabschnitt umfasst, in Flächenprozent, 0% bis 80% von polygonalem Ferrit und ein oder zwei, ausgewählt aus nadelförmigem Ferrit und Bainit, ein Rest eine M-A-Phase ist, und eine effektive Korngröße 15,0 µm oder weniger beträgt,
    eine metallographische Struktur in einer Oberflächenschicht, die in einer Dickenrichtung ein Bereich von 1,0 mm von einer Oberfläche ausgehend ist, umfasst, in Flächenprozent, insgesamt 95% oder mehr von einem oder zwei, die ausgewählt sind aus nadelförmigem Ferrit und Bainit, und ein Rest eine M-A-Phase ist, und
    eine maximale Härte in der Oberflächenschicht 250 HV0,1 oder weniger beträgt,
    wobei das Flächenprozent von polygonalem Ferrit, das Flächenprozent von nadelförmigem Ferrit und Bainit und die effektive Korngröße gemäß den in der Beschreibung beschriebenen Verfahren bestimmt werden, und die maximale Härte in der Oberflächenschicht durch einen Vickers-Härtetest gemäß JIS Z 224:2009 ermittelt wird, bei dem die Prüfkraft auf 0,98 N (0,1 kgf) eingestellt wird, 0,05 ≤ Mo + Cr + Cu + Ni ≤ 2,00
    Figure imgb0018
     Ceq = C + Mn / 6 + Ni + Cu / 15 + Cr + Mo + V / 5
    Figure imgb0019
    hierbei steht jedes Elementsymbol in den Formeln für eine Menge (Masse-%) jedes im Stahl enthaltenen Elements und wird als Null betrachtet, wo ein entsprechendes Element nicht enthalten ist.
  7. Stahlrohr nach Anspruch 6,
    wobei das Flächenprozent des polygonalen Ferrits in der metallografischen Struktur des mittleren Wanddickenabschnitts 0% bis weniger als 20% beträgt.
  8. Stahlrohr nach Anspruch 6,
    wobei ein Flächenprozent des polygonalen Ferrits in der metallografischen Struktur des mittleren Wanddickenabschnitts 20% bis 80% beträgt, und die effektive Korngröße 10,0 µm oder weniger beträgt.
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Family Cites Families (15)

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JPS55146711A (en) * 1979-05-02 1980-11-15 Shimano & Co Ltd Production of tubular body
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JP4276341B2 (ja) 1999-09-02 2009-06-10 新日本製鐵株式会社 引張強さ５７０〜７２０Ｎ／ｍｍ２の溶接熱影響部と母材の硬さ差が小さい厚鋼板およびその製造方法
JP2002327212A (ja) 2001-02-28 2002-11-15 Nkk Corp 耐サワーラインパイプ用鋼板の製造方法
JP5292784B2 (ja) * 2006-11-30 2013-09-18 新日鐵住金株式会社 低温靱性に優れた高強度ラインパイプ用溶接鋼管及びその製造方法
JP5803270B2 (ja) 2011-05-24 2015-11-04 Ｊｆｅスチール株式会社 耐圧潰性に優れた高強度耐サワーラインパイプ及びその製造方法
JP5751012B2 (ja) 2011-05-24 2015-07-22 Ｊｆｅスチール株式会社 耐圧潰性および耐サワー性に優れた高強度ラインパイプの製造方法
JP5751013B2 (ja) * 2011-05-24 2015-07-22 Ｊｆｅスチール株式会社 耐圧潰性および耐サワー性に優れた高強度ラインパイプの製造方法
EP3042976B1 (de) 2013-08-30 2020-05-13 Nippon Steel Corporation Stahlblech für dickwandiges hochfestes leitungsrohr mit aussergewöhnlicher korrosionsbeständigkeit, quetschfestigkeitseigenschaften und duktilität bei niedrigen temperaturen sowie leitungsrohr
BR112018000633A2 (pt) * 2015-07-31 2018-09-18 Nippon Steel & Sumitomo Metal Corporation chapa de aço laminada a quente de alta resistência
JP6319539B1 (ja) 2017-09-19 2018-05-09 新日鐵住金株式会社 鋼管及び鋼板
EP3686303B1 (de) * 2017-09-19 2021-12-29 Nippon Steel Corporation Stahlrohr und stahlplatte
WO2019058422A1 (ja) 2017-09-19 2019-03-28 新日鐵住金株式会社 鋼管及び鋼板
KR102457409B1 (ko) * 2018-06-29 2022-10-24 닛폰세이테츠 가부시키가이샤 강관 및 강판
EP3872205A4 (de) * 2019-02-19 2021-09-01 Nippon Steel Corporation Elektrisches widerstandsgeschweisstes stahlrohr für ein leitungsrohr

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