Classifications

• • 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 by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
• • 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
• • 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
  • C22C38/18—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

Definitions

• Oil and natural gas transported by pipelines may contain hydrogen sulfide depending on their properties, and may be laid in an environment where hydrogen sulfide is contained in the seabed or soil.
• HIC hydrogen induced cracking
• SSC hydrogen sulfide stress corrosion cracking
• Fit for Purpose is to perform the HIC test and the SSC test under conditions that consider the severity of the real environment in order to obtain the requirements of the HIC resistance and SSC resistance for the line pipe.
• SSC resistance ISO 15156 classifies environmental severity by pH and H 2 S fraction. Therefore, compared to the conventional conditions where 100% H 2 S is blown into the solution A defined by NACE-TM0288 and NACE-TM0177, the target of HIC resistance and SSC resistance is easily satisfied. Can be set to manufacturing conditions compatible with the above.
• Non-Patent Document 1 evaluates the severity of the HIC test environment by pH and H 2 S fraction, and derives the limit length of MnS generated in the central segregation part.
• the severity of the HIC test environment is evaluated by the pH and H 2 S fraction, and the limit hardness at which HIC occurs is derived.
• the PHIC calculated by the expression (2) described later needs to satisfy the expression (3) described later.
• the P HIC is a parameter obtained by multiplying the thickening degree and carbon equivalent of the alloy elements in the center segregation area, it is possible to quantify the hardness of the center segregation area by P HIC.
• the cumulative rolling reduction is 50% or more, and a formula described later It performs rolling at a rolling start temperature consistent with T s as indicated by (5), it was found that it is necessary to integrate the (211) plane.
• T S ⁇ 174 log ([Nb] ([C] +12 [N] / 14)) + 1444-1.2t (5)
• T F ⁇ 910-310 [C] -80 [Mn] -20 [Cu] -55 [Ni] -15 [Cr] -80 [Mo] -0.6t (6)
• T ACS ⁇ 910-310 [C] -80 [Mn] -20 [Cu] -55 [Ni] -15 [Cr] -80 [Mo] -0.6 t (7)
• T Thickness at the end of rolling (mm)
• test environment for the HIC test in the present invention is 0.5 to 50% in terms of H 2 S fraction.
• N is preferably 0.0010 to 0.0060% and Ti / N (Ti content (mass%) / N content (mass%)) is preferably 1 to 5 from the viewpoint of improving toughness. More preferably, when it is 2 to 4, more excellent toughness is exhibited.
• ACRM 0 or more ACRM is an index for quantifying the morphology control of MnS by Ca.
• ACRM is 0 or more, the generation of MnS due to center segregation is suppressed, and the HIC resistance performance at the center of the plate thickness (tube thickness) is improved. Therefore, it is preferable to set the lower limit of ACRM to 0 and the lower limit to 0.2.
• the ACRM is defined by the following formula (1).
• ACRM ([Ca] ⁇ (1.23 [O] ⁇ 0.000365)) / (1.25 [S]) (1) However, in said formula (1), [Ca], [O], [S] represents content (mass%) of each element.
• V 0.060% or less
• V is an element that increases the strength, and in order to exhibit this effect, the V content is preferably 0.010% or more. However, if the V content exceeds 0.060%, the HAZ toughness and weldability are significantly impaired. Therefore, when adding V, it is preferable to make V amount into 0.060% or less, and it is more preferable that it is 0.050% or less.
• pH pH of the HIC test environment
• P H2S H 2 S fraction of HIC test environment (Vol%)
• the upper limit of the maximum value HV of the micro-Vickers hardness of the hard second phase contained in the center segregation portion and the microstructures of the surface layer and the back layer is set to 400 + 50 (pH-12) (1 + log (P H2S )) / 9.
• the temperature under the production conditions is the surface temperature of the steel material or steel plate.
• the surface temperature of a steel material or a steel plate can be measured by, for example, a radiation thermometer.
• the lower limit temperature of the slab heating temperature is set to 1000 ° C.
• the slab heating temperature is in the range of 1000 to 1200 ° C.
• a method having a two-stage process that is, a main welding process for performing the above-described process is preferable.
• pipe expansion is performed to remove residual welding stress and improve roundness of the steel pipe.
• the pipe expansion ratio ratio of the outer diameter change amount before and after the pipe expansion to the outer diameter of the pipe before the pipe expansion
• the tube expansion rate is preferably in the range of 0.5% to 1.2%.
• a coating treatment can be carried out for the purpose of preventing corrosion.
• the coating treatment for example, after heating to a temperature range of 200 to 300 ° C., a known resin may be applied to the outer surface.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Butt Welding And Welding Of Specific Article (AREA)

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Cited By (5)

Citations (7)

• 2015
  • 2015-09-18 WO PCT/JP2015/004813 patent/WO2016051727A1/ja active Application Filing
  • 2015-09-18 BR BR112017006565-7A patent/BR112017006565B1/pt active IP Right Grant
  • 2015-09-18 JP JP2016551522A patent/JP6237920B2/ja active Active

Patent Citations (7)

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