WO2014203347A1 - Matériau en acier, procédé pour sa production et citerne pour gnl - Google Patents

Matériau en acier, procédé pour sa production et citerne pour gnl Download PDF

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WO2014203347A1
WO2014203347A1 PCT/JP2013/066825 JP2013066825W WO2014203347A1 WO 2014203347 A1 WO2014203347 A1 WO 2014203347A1 JP 2013066825 W JP2013066825 W JP 2013066825W WO 2014203347 A1 WO2014203347 A1 WO 2014203347A1
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content
steel
residual
steel material
lower limit
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PCT/JP2013/066825
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Japanese (ja)
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川畑　友弥
崇之 加賀谷
孝浩 加茂
弘宜 若松
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新日鐵住金株式会社
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Priority to CN201380041820.9A priority Critical patent/CN104520461B/zh
Priority to PCT/JP2013/066825 priority patent/WO2014203347A1/fr
Priority to KR1020157003158A priority patent/KR101572786B1/ko
Priority to JP2013548641A priority patent/JP5561442B1/ja
Priority to EP13887092.8A priority patent/EP2871255B1/fr
Publication of WO2014203347A1 publication Critical patent/WO2014203347A1/fr

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    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous 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
    • C22C38/001—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
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • 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
    • C22C38/04—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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/40—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
    • 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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C1/00—Pressure vessels, e.g. gas cylinder, gas tank, replaceable cartridge
    • F17C1/12—Pressure vessels, e.g. gas cylinder, gas tank, replaceable cartridge with provision for thermal insulation

Definitions

  • the present invention relates to a cryogenic steel material excellent in toughness, a manufacturing method thereof, and an LNG tank to which the steel material is applied.
  • LPG Liquid Petroleum Gas: liquefied petroleum gas
  • LNG Liquid Natural Gas: liquefied natural gas
  • the present invention is mainly intended for use in the vicinity of ⁇ 165 ° C., which is a temperature environment for storing LNG in a liquid state.
  • Steel materials for producing cryogenic storage tanks for storing liquefied gas such as LPG or LNG are required to have excellent fracture toughness from the viewpoint of ensuring safety.
  • the LNG temperature environment is around ⁇ 165 ° C.
  • Brittle fracture propagation stop characteristics (hereinafter referred to as “arrest characteristics”) of the base metal and the welded joint are required.
  • the arrest characteristic is required as an important characteristic.
  • the base material characteristics reduction of impurities including P and S, reduction of C, three-stage heat treatment method (quenching (Q), two-phase region quenching (L), tempering (T)), etc. It has been controlled and improved in various ways.
  • Patent Document 1 discloses a steel material in which the Ni content is reduced to less than 8% for a low Ni type cryogenic steel.
  • Patent Document 1 discloses that increasing the amount of residual ⁇ improves the brittle crack propagation stopping characteristics of a steel sheet. Therefore, a steel sheet having a good V-notch Charpy absorbed energy v E -196 described in Patent Document 1 (in particular, Test Nos. 1-a to 1-h, 4 to 12, and 22 to described in Patent Document 1). 35), various fracture toughness tests were carried out. As a result, each sample had a DT (Dynamic Tear) energy at -196 ° C.
  • DT Dynamic Tear
  • Patent Document 2 discloses that a large amount of highly stable residual ⁇ (residual austenite) is obtained by rolling at a specified cumulative reduction ratio and then performing offline QT (Quenching and Tempering) or DQT (Direct-Quenching and Tempering) treatment. The technology to be secured is described. However, in order to stabilize the residual ⁇ , Ni or Mn in the residual ⁇ needs to be concentrated as compared with the structure around the residual ⁇ . Also, if the cooling after tempering is slow, the fracture resistance properties of the steel are impaired. Patent Document 2 does not describe any of these findings. Moreover, although the Example shown by patent document 2 contains 9% or more of Ni by mass%, the amount of residual (gamma) prescribed
  • Patent Document 3 discloses a so-called CR-DQT (Controlled Rolling, Direct-Quenching, and Tempering) or CR-DQLT (Controlled) which is subjected to low-temperature heating after low-temperature heating, water cooling to a temperature of 200 ° C. or less, and heat treatment. Rolling, Direct-Quenching, Lamellarizing, and Tempering processes are described. Although these processes are the same as those of the present invention, the invention described in Patent Document 3 has a small cumulative rolling amount, and does not include an embodiment having a cumulative rolling ratio of 50% or more defined in the present invention example. When the cumulative rolling reduction is low, the above-described concentration of Ni or Mn is not sufficiently performed, so that it is considered that the residual ⁇ is not stable.
  • Patent Document 3 does not include a description relating to the cooling rate after tempering and the concentration of Ni or Mn in the residual ⁇ , which is greatly related to the characteristics of the steel material. These facts suggest that the invention described in Patent Document 3 does not have high fracture resistance.
  • Patent Document 4 focuses on the segregation ratio of Ni, but it is essential in Patent Document 4 to perform soaking diffusion treatment in order to reduce this segregation ratio. This is not preferable from the viewpoint of economy or lead time.
  • Patent Document 4 relates to a so-called CR-DQT or CR-DQLT process as in Patent Document 3. Although this process itself is the same as that of the present invention, in Patent Document 4, there is no description about the cooling rate after tempering, and there is no provision regarding the concentration of Ni and Mn in the residual ⁇ .
  • the technique described in 4 cannot be said to be a technique that can stably satisfy extremely high fracture resistance.
  • the present invention has been made in view of such a situation, and its purpose is to achieve both economic efficiency and fracture resistance characteristics by achieving both the provision of extremely high fracture resistance characteristics and the suppression of the price of steel materials.
  • An object of the present invention is to provide an excellent steel material, a manufacturing method thereof, and an LNG tank.
  • the present inventors have adopted a steel having a Ni content effective in securing low temperature toughness in a range of 6.6% to 8.0% by mass, A wide range of prototype tests were conducted, and the correspondence with the characteristics was examined. As a result, the following findings (a) to (h) were obtained.
  • A Fracture resistance required to maintain liquid and air tightness when the cryogenic storage tank material is subjected to an earthquake force is brittle fracture occurrence characteristics and brittleness in the unlikely event that fracture occurs. It is a brittle crack propagation stop characteristic (arrest characteristic) that can stop the propagation of cracks due to fracture.
  • Residual ⁇ is a structure having an extremely high brittle crack propagation stopping function. When this structure is finely dispersed, the arrest properties of the material are remarkably improved.
  • the amount of residual ⁇ can be evaluated by an X-ray diffraction method.
  • the particle size of residual ⁇ is an average major axis of 0.85 ⁇ m or less, the steel material exhibits good arrest characteristics.
  • the major axis of the residual ⁇ indicates the length of the residual ⁇ along the longest direction of the residual ⁇ when the cross section is observed.
  • the residual ⁇ is preferably measured by collecting a sample at a position (1/4) of the thickness t of the steel material.
  • the residual ⁇ is in a metastable state, and the steel material easily undergoes martensitic transformation due to plastic deformation.
  • the geometric shape of the residual ⁇ is close to a sphere, and when the quantity is specifically defined, the upper limit of the average aspect ratio of the residual ⁇ is 2 .5 is desirable.
  • the aspect ratio of the residual ⁇ is the ratio of the longest diameter (L) of the residual ⁇ , that is, the longest diameter of the residual ⁇ to the shortest diameter (W), that is, the shortest diameter of the residual ⁇ , that is, L / W. .
  • the lower limit of the aspect ratio is 1.
  • the steel material is heated to a temperature range of 620 ° C. to 720 ° C. and then water-cooled, if necessary. Processing may be performed.
  • the lower limit of the cooling rate until the steel surface temperature is reduced to 300 ° C. or less after the tempering treatment is set to 0.5 ° C./s in order to obtain good characteristics. Is necessary.
  • annular plate is a part of the above ground LNG tank that is subjected to a large plastic strain during a severe earthquake.
  • Such a steel material excellent in low-temperature toughness has high fracture safety and can be applied to the annular plate in the LNG tank.
  • the present invention has been completed on the basis of the above-mentioned knowledge.
  • the gist of the LNG tank is steel.
  • the chemical components are mass%, C: 0.01 to 0.12%, Si: 0.01 to 0.30%, Mn: 0.4 to 2 0.0%, Ni: 6.6 to 8.0%, Al: 0.002 to 0.08%, N: 0.0050% or less, P: 0.05% or less, S: 0.008% or less, Cu : 0-1.0%, Cr: 0-1.0%, Mo: 0-0.5%, V: 0-0.10%, B: 0-0.0050%, Nb: 0-0.
  • the lower limit of the amount of residual ⁇ at the (1/4) t position of the steel sheet thickness t is 4.0% by volume
  • the upper limit of the average value is 2.5
  • the upper limit of the average value of the major axis is 0.85 ⁇ m
  • the average Mn concentration and the average Ni concentration in the residual ⁇ satisfy the following formulas (A) and (B), respectively.
  • [Mn] retained ⁇ is an average Mn concentration in the residual ⁇
  • [Mn] ⁇ is an average Mn concentration in the ferrite phase
  • [Ni] retained ⁇ is an average Ni concentration in the residual ⁇
  • Ni] ⁇ represents the average Ni concentration in the ferrite phase.
  • the chemical component is C: 0.02% to 0.07% Si: 0.01% to 0.10%, Mn: 0.6% to 1.0% Ni: 7.0 to 7.8% Cu: 0 to 0.30%, Cr: 0 to 0.80%, Mo: 0 to 0.20%, V: 0 to 0.05%, B may be 0 to 0.0005%, Nb may be 0 to 0.02%, Ti may be 0 to 0.02%, and Sn may be 0 to 0.01%.
  • the chemical component may be Cr: 0.30 to 0.60% and Mo: 0.05 to 0.15% by mass%. .
  • the steel material according to any one of the above (1) to (3) is a steel plate having a thickness of 3 mm to 100 mm, a yield stress of 585 MPa or more, and a tensile strength of 690 MPa to 885 MPa. Good.
  • C 0.01 to 0.12% C is an element necessary for ensuring the strength of the base material.
  • the C content is less than 0.01%, the required strength cannot be secured, and the formation of lath martensite in FL (Fusion Line) becomes insufficient during welding, and the HAZ near the FL Since the toughness of (Heat Affected Zone) also decreases, the lower limit of the C content needs to be 0.01%.
  • the content of C exceeds 0.12%, the toughness of HAZ, particularly HAZ near FL, is significantly deteriorated. Therefore, the C content is 0.01% to 0.12%.
  • the lower limit of the C content may be 0.02%, 0.03%, or 0.04%.
  • the upper limit of the C content may be 0.10%, 0.08%, 0.07%, or 0.06%.
  • Si 0.01 to 0.30%
  • Si is an element necessary as a deoxidizer.
  • the lower limit of the Si content needs to be 0.01%.
  • Si and the tempering process of martensite as quenched are greatly related.
  • Si content exceeds 0.30%, Si is supersaturated in the welding cooling process. This suppresses the decomposition and precipitation reaction of C from the martensite in the form of solid solution to cementite. By suppressing the decomposition and precipitation reaction of C, self-tempering is delayed and the toughness of the weld is lowered.
  • the Si content is set to 0.01% to 0.30%. From the viewpoint of improving the toughness of the welded portion, the Si content should be as low as possible.
  • the upper limit of the Si content is 0.20%, 0.15%, or 0.10. % May be used.
  • the lower limit of the Si content may be 0.02%, 0.03%, or 0.04%.
  • Mn 0.4 to 2.0%
  • Mn is an element necessary as a deoxidizer, for ensuring the strength and toughness of the base material, and for ensuring the hardenability of the HAZ. If the Mn content is less than 0.4%, these effects cannot be obtained, and furthermore, ferrite side plates are generated in the HAZ, so that the formation of lath martensite becomes insufficient and the toughness of the welded portion is reduced. The lower limit of the content of is 0.4%. On the other hand, if the Mn content exceeds 2.0%, the base material characteristics may be uneven in the thickness direction due to the central segregation of Mn. Therefore, the Mn content is set to 0.4% to 2.0%.
  • the lower limit of the Mn content may be 0.50%, 0.60%, or 0.70%.
  • the upper limit of the Mn content may be 1.5%, 1.2%, 1.0%, or 0.9%.
  • P 0.05% or less P is present in the steel as an impurity, segregates at the grain boundary, and causes toughness to decrease. If the P content exceeds 0.05%, hot cracking may occur during welding, so the P content is limited to 0.05% or less. In order to improve toughness, the P content should be as small as possible.
  • the upper limit of the P content is 0.03%, 0.02%, 0.01%, 0.008%, or 0. It may be 0.006%. There is no need to specifically define the lower limit of the P content, and the lower limit is 0%. However, reducing P more than necessary leads to a cost increase during refining, so the lower limit of the P content may be 0.0001% or 0.0005%.
  • S 0.008% or less S is present in the steel as an impurity, and if it is too much, it promotes center segregation or causes a large amount of stretched MnS that causes brittle fracture. If the S content exceeds 0.008%, the mechanical properties of the base material and the HAZ deteriorate. For this reason, content of S shall be 0.008% or less.
  • the upper limit of the S content may be 0.006%, 0.004%, 0.003%, or 0.002%. Since the S content should be as small as possible, it is not necessary to define the lower limit of the S content, and the lower limit is 0%. From the problem of refining costs, the lower limit of the S content may be 0.0001% or 0.0003%.
  • Ni 6.6 to 8.0%
  • Ni is the most basic element necessary for securing toughness as a low-temperature steel material.
  • a Ni content of 6.6% or more is required.
  • the higher the Ni content the higher the low-temperature toughness.
  • the cost increases accordingly, so the upper limit of the Ni content is 8.0%. Therefore, the target of Ni content is 6.6% to 8.0%.
  • the Ni content is preferably 6.7% or more, and the lower limit of the Ni content may be 6.8%, 6.9%, or 7.0% as necessary.
  • the upper limit of Ni content may be 7.8%, 7.6%, or 7.4%. However, even if the Ni content is more than 8.0%, the characteristics required as a low-temperature steel material can be obtained.
  • Al 0.002 to 0.080%
  • Al is an element generally contained as a deoxidizer, but in the case of the steel material according to the present embodiment, it has a function of delaying self-tempering of martensite, similar to Si. . Therefore, it is desirable that the Al content be as small as possible.
  • the Al content exceeds 0.080% and becomes excessive, the decomposition precipitation reaction of C into cementite from martensite, which is supersaturated with C in the welding cooling process, is suppressed as in the case of Si described above. In some cases, the toughness of the welded portion may be reduced.
  • the Al content is less than 0.002%, a sufficient deoxidizing effect cannot be obtained. Therefore, the Al content is set to 0.002% to 0.080%.
  • the lower limit of the Al content may be 0.005%, 0.010%, 0.015%, or 0.020%.
  • the upper limit of the Al content may be 0.060%, 0.050%, or 0.040%.
  • N 0.0050% or less N is present in steel as an impurity and causes deterioration of HAZ toughness through an increase in solid solution N or formation of precipitates. Therefore, N content is required to ensure HAZ toughness. The amount should be low. If the N content exceeds 0.0050%, the HAZ toughness may deteriorate significantly, so the N content is set to 0.0050% or less. In order to improve the HAZ toughness, the upper limit of the N content may be 0.0045% or 0.0040%. There is no need to define the lower limit of the N content, and the lower limit is 0%. However, the lower limit of the N content may be set to 0.0001% or 0.0010% from the problem of cost during refining.
  • the steel material according to the present embodiment is composed of Fe and impurities in addition to the above components.
  • the impurities are components mixed in due to various factors of the raw material, such as ore or scrap, or the manufacturing process when the steel material is industrially manufactured, and in a range that does not adversely affect the present invention. It means what is allowed.
  • the steel material according to the present embodiment further includes one or more of Cu, Cr, Mo, V, B, Nb, Ti, Sn, Ca, Mg, and REM in addition to the above components. Also good. There is no particular need to define the lower limit of the content of these components, and the lower limit is 0%. Further, even if these alloy elements are intentionally added to the steel material according to the present embodiment or mixed as impurities, if the content is within the specified range, the steel material is claimed in the scope of the present invention. Interpreted as in.
  • Cu 0 to 1.00% Cu can be contained as needed.
  • the strength of the base material can be improved.
  • the upper limit of the Cu content is 1.00%.
  • the upper limit of the preferable Cu content is 0.80% or 0.60%, and the upper limit of the more preferable Cu content is 0.30%.
  • the lower limit of the Cu content may be 0.10%.
  • Cr 0 to 1.00% Cr can be contained as needed.
  • the carbon dioxide gas corrosion resistance is improved, and the strength can be improved as a result of the improvement of the hardenability.
  • the upper limit of the Cr content is 1.00%.
  • the upper limit of the Cr content may be 0.80%, 0.60%, or 0.50%. There is no need to define the lower limit of the Cr content, and the lower limit is 0%.
  • the lower limit of the Cr content may be 0.05%.
  • the lower limit of the Cr content may be 0.10%.
  • a more preferable lower limit of the Cr content is 0.20%. If necessary, the lower limit of the Cr content may be 0.30% or 0.40%.
  • Mo 0 to 0.50% Mo can be contained as required.
  • Mo When Mo is contained, there is an effect of improving the strength and toughness of the base material.
  • the Mo content exceeds 0.50%, the hardness of the HAZ increases and the toughness and SSC resistance may be impaired, so the upper limit of the Mo content is 0.50%.
  • the upper limit of the preferable Mo content is 0.30%.
  • the upper limit of the Mo content may be 0.20%, 0.15%, or 0.12%.
  • the lower limit is 0%.
  • V 0 to 0.10%
  • V can be contained as required. Inclusion of V has an effect of improving the strength of the base material mainly due to carbonitride precipitation during tempering. However, if the V content exceeds 0.10%, the effect of improving the strength of the base metal is saturated and the toughness may be deteriorated. Therefore, the upper limit of the V content is 0.10%. There is no need to define the lower limit of the V content, and the lower limit is 0%. In order to improve toughness, the upper limit of the V content may be 0.08%, 0.06%, or 0.04%. In addition, when obtaining the effect of improving the strength of the base material due to V, the lower limit of the V content may be 0.015% or 0.02%.
  • B 0 to 0.0050% B can be contained as required. Inclusion of B has an effect of improving the strength of the base material. However, if the B content exceeds 0.0050%, precipitation of coarse boron compounds may be caused to deteriorate toughness, so the upper limit of the B content is set to 0.0050%. In order to prevent toughness deterioration, the upper limit of the B content may be 0.0040%, 0.0030%, or 0.0020%. There is no need to define the lower limit of the B content, and the lower limit is 0%. In addition, when obtaining the effect of improving the strength of the base material by B, it is preferable that the lower limit of the B content is 0.0003%. A more preferable lower limit of the B content is 0.0005% or 0.0010%. When the effect of improving the base material strength by B is not required, the upper limit of the B content may be 0.0010%, 0.0005%, 0.0003%, or 0.0002%.
  • Nb 0 to 0.10% Nb can be contained as necessary.
  • Nb When Nb is contained, there is an effect of refining the structure and improving the low temperature toughness. However, if the Nb content exceeds 0.10%, coarse carbides or nitrides may be formed and the toughness may be lowered, so the upper limit of the Nb content is 0.10%. There is no need to define the lower limit of the Nb content, and the lower limit is 0%. In order to prevent a decrease in toughness, the upper limit of the Nb content may be 0.08%, 0.06%, or 0.04%. In addition, when acquiring the effect of improving the low temperature toughness by Nb, it is good also considering the minimum of content of Nb as 0.01% or 0.02%.
  • Ti 0 to 0.10% Ti can be contained as required. Ti is mainly used as a deoxidizing element, but has the effect of further miniaturizing the structure by forming an oxide phase containing Al, Ti, and Mn. However, if the Ti content exceeds 0.10%, the oxide formed will be Ti oxide or Ti-Al oxide, and the dispersion density will decrease, especially in the heat-affected zone of the small heat input weld zone. Since the ability to refine the structure may be lost, the upper limit of the Ti content is set to 0.10%. The upper limit of the preferable Ti content is 0.07% or 0.05%. There is no need to define the lower limit of the Ti content, and the lower limit is 0%. In addition, when obtaining the effect of refining the structure by Ti, the lower limit of the Ti content may be 0.02% or 0.03%.
  • Sn 0 to 0.50% Sn can be contained as necessary.
  • Sn When Sn is contained, it becomes Sn 2+ and dissolves in the steel material surface deposit, and has an action of inhibiting corrosion by an inhibitor action in an acidic chloride solution. Further, rapidly reducing the Fe 3+, by having an effect of reducing the Fe 3+ concentration of the oxidizing agent, since inhibit corrosion promoting effect of Fe 3+, thereby improving the weather resistance in high airborne salt environments.
  • the upper limit of the Sn content is 0.50%.
  • the upper limit of preferable Sn content is 0.20%.
  • the upper limit of the Sn content may be limited to 0.10%, 0.05%, or 0.01%. There is no need to define the lower limit of the Sn content, and the lower limit is 0%.
  • the lower limit of Sn when obtaining the corrosion resistance and weather resistance effect by Sn, the lower limit of Sn may be set to 0.03% or 0.05%.
  • Ca 0 to 0.004% Ca can be contained as needed.
  • Ca When Ca is contained, it reacts with S in the steel to form oxysulfide (oxysulfide) in the molten steel. Since this oxysulfide does not extend in the rolling direction by rolling unlike MnS and the like, it is spherical after rolling. This spherical oxysulfide has an effect of suppressing weld cracking or hydrogen-induced cracking starting from the tip of an elongated inclusion.
  • the upper limit of the Ca content is set to 0.004%. In order to surely avoid a decrease in toughness, the upper limit of the Ca content may be 0.003%.
  • the lower limit of the Ca content there is no need to define the lower limit of the Ca content, and the lower limit is 0%.
  • the lower limit of the Ca content may be 0.0003% or 0.0005%.
  • Mg 0 to 0.0020% Mg can be contained as needed.
  • Mg a fine Mg-containing oxide is generated, which is effective in reducing the ⁇ particle size.
  • the upper limit of the Mg content is set to 0.0020%.
  • the upper limit of the preferable Mg content is 0.0010%.
  • the lower limit of Mg is preferably set to 0.0002%.
  • a more preferable lower limit of the Mg content is 0.0004%.
  • REM 0 to 0.0020% REM (rare earth element) can be contained as required.
  • REM When REM is contained in steel, it has the effect of refining the structure of the weld heat affected zone and further binding S to fix S. If REM is excessively contained, inclusions may be formed and the cleanliness of the weld may be lowered. However, inclusions formed by the inclusion of REM have a relatively small influence on toughness degradation. If the content is 0.0020% or less, a reduction in the toughness of the base material due to the inclusion of REM is acceptable. Therefore, the upper limit of the content of REM is set to 0.0020%. The upper limit of the preferable REM content is 0.0010%.
  • the lower limit of the REM content is preferably set to 0.0002%.
  • a more preferable lower limit of the REM content is 0.0003%.
  • REM is a general term for 17 elements in which Y and Sc are combined with 15 elements of lanthanoid, and one or more of these elements can be contained.
  • the term “REM content” means the total content of these elements.
  • the steel material according to the present embodiment contains the above components, and the balance contains iron and impurities.
  • the welded steel material according to the present embodiment contains the following alloy elements in addition to the above components for the purpose of further improving the strength, toughness, etc. of the steel material itself, or as impurities from secondary materials such as scrap. May be. Since Sb impairs the toughness of HAZ, the upper limit of the Sb content may be 0.03%.
  • the upper limit of the Sb content may be 0.01%, 0.005%, 0.003%, or 0.001%. Since As impairs the toughness of HAZ, the upper limit of the As content may be 0.02%. If necessary, the upper limit of the As content may be 0.005%, 0.003%, or 0.001%. Moreover, in order to improve strength and toughness, the upper limits of the Pb, Zr, Zn and W contents may be set to 0.1%, 0.01% or 0.005%. There is no particular need to determine the lower limit of the content of these elements, and it is 0%. Co may be contained as an impurity in Ni. Since Co impairs HAZ toughness, the upper limit of the Co content may be 0.5%, 0.3%, 0.1%, or 0.05%. There is no particular need to determine the lower limit of the Co content, and the lower limit is 0%.
  • the lower limit of the residual ⁇ amount at the (1/4) t position of the sheet thickness t is 4.0% by volume.
  • the residual ⁇ in the steel material is a brittle crack in the steel material. Contributes to improved propagation stop characteristics. As a result, an effect of improving toughness in a low temperature environment can be expected. In order to obtain this effect, it is necessary that the lower limit of the residual ⁇ amount at the (1/4) t position of the steel sheet thickness t is 4.0% by volume. In order to improve toughness, the lower limit of the residual ⁇ amount may be 4.5% by volume, 5.0% by volume, 5.5% by volume, 6.0% by volume, or 6.5% by volume.
  • the upper limit of the residual ⁇ amount is not particularly specified, but if there is too much residual ⁇ , the yield strength may decrease, so the upper limit of the residual ⁇ amount is 20.0% by volume or 15.0% by volume. It is good.
  • the reason why the residual ⁇ amount is evaluated at the (1/4) t position of the sheet thickness t is to perform evaluation at an average position in the entire sheet thickness.
  • the tempering temperature T (° C.) satisfies the following formula (3)
  • the lower limit of the residual ⁇ amount at the (1/4) t position of the plate thickness t can be set to 4.0 vol%.
  • Ac 1 is defined by the following equation (4).
  • FIG. 1 shows the steel No. described in Table 1.
  • a slab having one chemical component is heated to 950 ° C., then rolled to achieve a cumulative reduction of 70% at 850 ° C. or lower, immediately cooled to room temperature immediately after rolling, and subsequently tempered at various tempering temperatures. It is a graph which shows the relationship between tempering temperature and residual (gamma) amount in the various steel materials manufactured by water-cooling after that.
  • the cumulative rolling reduction is a percentage ((t1 ⁇ t2) / t1 ⁇ a value obtained by dividing the difference between the plate thickness t1 at the start of rolling and the plate thickness t2 at the end of rolling by the plate thickness t1 at the start of rolling. 100).
  • the tempering temperature is too low, there are too few regions to reversely transform to ⁇ , so the amount of residual ⁇ is small.
  • the tempering temperature is too high, the generated ⁇ becomes unstable and during cooling. Since it undergoes martensitic transformation, the amount of residual ⁇ decreases. Therefore, it can be understood that a large amount of residual ⁇ can be secured by satisfying the expression (3).
  • the upper limit of the average value of the aspect ratio of residual ⁇ is 2.5 and the upper limit of the average value of the major axis is 0.85 ⁇ m.
  • the residual ⁇ in the ⁇ structure (ferrite structure) is a metastable state. And easily undergoes martensitic transformation by undergoing plastic deformation. Residual ⁇ needs to be dispersed in order to improve the brittle fracture occurrence characteristics or propagation stop characteristics, and when it disappears after an earthquake, the desired fracture resistance characteristics are not exhibited.
  • the strain applied to the residual ⁇ particles varies greatly depending on the distribution pattern of the residual ⁇ particles, and the more fine the residual ⁇ particles are in a spherical shape, the more the strain is distributed. The rate drops. Therefore, it is necessary to set the upper limit of the average value of the aspect ratio of the residual ⁇ particles obtained by cross-sectional observation to 2.5 and the upper limit of the average value of the major axis of the residual ⁇ particles obtained by cross-sectional observation to 0.85 ⁇ m. . Since the toughness is improved as the average aspect ratio of the residual ⁇ particles is smaller, the upper limit of the average aspect ratio may be 2.3 or 2.0.
  • the upper limit of the average value of the major axis may be 0.80 ⁇ m or 0.75 ⁇ m.
  • the lower limit of the average value of the major axis need not be specified, but is usually 0.05 ⁇ m.
  • the lower limit of Mn concentration and the lower limit of Ni concentration in each residual ⁇ are set to 1. It is extremely important to make it 4 times.
  • the lower limit of the cumulative reduction rate of 850 ° C. or less in the hot rolling process is set to 50%, and the cooling rate after tempering is 0.5 ° C./s. It is necessary to make it larger. 2 shows the steel No. described in Table 1. A slab having one chemical component is heated to 960 ° C., then rolled at various cumulative reduction rates, immediately cooled to room temperature immediately after rolling, and subsequently tempered at 570 ° C. (with water cooling after tempering).
  • FIG. 5 is a graph showing the relationship between the cumulative reduction ratio of 850 ° C. or less and the concentration ratios of Ni and Mn ([M] ⁇ / [M] ⁇ ) in various steel materials manufactured by the above.
  • the concentration ratios of Ni and Mn are values obtained by dividing [Mn] retained ⁇ and [Ni] retained ⁇ by [Mn] ⁇ and [Ni] ⁇ , respectively. From FIG. 2, it can be seen that a concentration ratio of 1.4 or more can be obtained by satisfying the expressions (1) and (2) by setting the lower limit of the cumulative rolling reduction to 50%.
  • FIG. 3 shows the relationship between the concentration ratios of Ni and Mn and DT (Dynamic Tear) energy, which is a typical fracture characteristic evaluation parameter.
  • the DT energy exceeds 1500 J.
  • FIG. 3 shows that the DT energy exceeds 1500 J by setting the lower limit of the concentration ratios of Ni and Mn to 1.4.
  • the lower limit of the concentration ratio is 1.5 or 1.6, a higher DT energy can be obtained, which is preferable.
  • the steel material according to the present embodiment can be produced through the following steps. However, it is not limited to the following manufacturing method.
  • the casting conditions are not stipulated.
  • An ingot-splitting slab may be used, or a continuous cast slab may be used. From the viewpoint of production efficiency, yield, and energy saving, it is preferable to use a continuously cast slab.
  • the thickness of the steel material to be manufactured is 3 mm to 100 mm, mainly 6 mm to 50 mm.
  • the manufactured steel material may be a steel plate.
  • the slab heating temperature is controlled to 920 ° C. to 980 ° C.
  • the lower limit of the slab heating temperature is preferably 920 ° C.
  • the upper limit of the heating temperature of the slab is set to 970 ° C. so that the ⁇ grains are not excessively coarsened and the fracture resistance is not impaired.
  • (C-2) Rolling process In the hot rolling process, the heated slab is rolled. Specifically, the rolling may be divided into rough rolling and finish rolling.
  • the slab thickness at the end of the rough rolling it is preferable to reduce the slab thickness at the end of the rough rolling until it becomes 3 to 8 times the product thickness (steel material thickness). If the slab thickness after rough rolling is reduced to 3 times or more of the product sheet thickness, it can be sufficiently reduced by subsequent finish rolling, and the toughness of the product steel can be improved. On the other hand, if the slab thickness after the rough rolling is reduced to 8 times or less of the product thickness, the finish rolling temperature in the subsequent finish rolling (temperature at which the finish rolling is finished) can be easily controlled to 700 ° C. or more. .
  • finish rolling the slab subjected to rough rolling in this way is continuously reduced without cooling to a product with a predetermined thickness.
  • the lower limit of the cumulative rolling reduction at 850 ° C. or lower is set to 50%. Increasing the amount of reduction at a relatively low temperature is effective in actively introducing a deformation zone, leaving a large amount of residual ⁇ finally produced, and further reducing the average aspect ratio of the residual ⁇ . . This is because the stretched residual ⁇ is divided when the amount of reduction is large. Further, in order to positively introduce deformation bands, it is desirable to lower the finish rolling start temperature as much as possible so that the final rolling temperature (finish rolling temperature) during finish rolling is 700 ° C. to 730 ° C.
  • (C-3) Cooling step In the cooling step, it is desirable to accelerate cooling the steel material after finish rolling. In particular, as the plate thickness increases, it becomes more difficult to ensure the toughness of the steel material. Therefore, in a steel material with a thick plate thickness, it is better that the cooling rate of the accelerated cooling after the rolling process is faster. Specifically, when the plate thickness is 15 mm or less, the lower limit of the cooling rate at the central portion of the steel plate thickness t, that is, at the (1/2) t position of the plate thickness t is 3 ° C./s. When the plate thickness exceeds 15 mm, the lower limit of the cooling rate is 10 ° C./s.
  • the upper limit of the cooling rate at the (1/2) t position of the plate thickness t is not particularly defined, but may be 50 ° C./s in consideration of the facility capacity.
  • the lower limit of the cooling start temperature is set to 660 ° C. in order to make the steel metal structure sufficiently quenched and to obtain a fine residual ⁇ and a concentration ratio of 1.4 or more by subsequent tempering treatment or the like.
  • Accelerated cooling is preferably performed until the surface temperature of the steel material is 250 ° C. or lower.
  • this cooling stop temperature exceeds 250 ° C., a phenomenon occurs in which the transformation to the martensite structure becomes incomplete or the dislocation in the martensite structure is recovered by the autotemper effect, and as a result, Fine residual ⁇ is not effectively generated by the heat treatment, and the possibility that the strength is insufficient increases.
  • the upper limit of the cooling stop temperature is preferably 200 ° C or 150 ° C.
  • the lower limit of the cooling stop temperature is not particularly defined, but may be 50 ° C. or room temperature in consideration of the facility capacity.
  • DQT Direct-Quenching and Tempering
  • DQLT Direct-Quenching, Lamellarizing, and Tempering
  • (C-4) L treatment process When a sufficiently hardened structure is obtained, the L treatment (steel material was heated to a temperature range of two phases of ferrite and austenite, which has been conventionally used in 9% Ni steel) It is not always necessary to perform the water-cooling process later in this embodiment, and a steel material exhibiting sufficient characteristics can be obtained by performing only the tempering process. However, if the steel material is heated to a two-phase temperature range of ferrite and austenite, the toughness can be improved by refining the metal structure and generating a stable austenite phase, so that the temperature ranges from 620 ° C to 720 ° C as necessary. You may implement the L process process which performs a water cooling process after heating.
  • the temperature range of heating in the L treatment step is preferably 640 ° C to 700 ° C.
  • tempering step is extremely important for realizing the present invention, and is an essential process that requires detailed control. If the tempering temperature is too low, the amount of ⁇ produced is insufficient, and the amount of residual ⁇ itself decreases. In addition, if the tempering temperature is too low, temper embrittlement may occur, resulting in a deterioration of the fracture resistance. Conversely, when the tempering temperature is too high, the amount of ⁇ during heating increases, but the concentration of Ni and Mn in the residual ⁇ decreases. In this case, a large amount of residual ⁇ is transformed during subsequent cooling, or even if transformation does not occur during cooling, it is transformed and disappears only by being exposed to a very low temperature.
  • the range of the tempering temperature is governed by the thermodynamic equilibrium behavior, and has a property that varies depending on the chemical composition of the steel material. Specifically, it is necessary that the lower limit of the tempering temperature T is 3.8 ⁇ Ni ⁇ 33 + Ac 1 and the upper limit is 6.3 ⁇ Ni ⁇ 0.4 + Ac 1 . That is, it is necessary to satisfy the following expression (3).
  • the coefficient described in Formula (3) was calculated
  • the tempering temperature is preferably more than Ac 1 .
  • the cooling rate after heating in the tempering process is low, the fracture resistance is impaired due to the reason that a partial bainite transformation proceeds due to the diffusion movement of carbon.
  • the lower limit of the cooling rate in the central portion of the plate thickness until the surface temperature becomes 300 ° C. or lower needs to be 0.5 ° C./s.
  • the upper limit of the cooling rate after heating in the tempering step is not particularly defined, it may be 50 ° C./s in consideration of the upper limit of the equipment capacity.
  • the lower limit of the cooling stop temperature is not particularly defined, but may be 50 ° C. or room temperature in consideration of the facility capacity.
  • V notch test piece full size test piece
  • a V-notch test piece with a plate thickness and width of 10 mm could not be collected, so a sub-size test piece was collected.
  • the criteria for determining the quality are YS: 585 MPa or more, TS: 690 MPa or more, V-notch Charpy absorbed energy value per unit area v E -196 : 150 J / cm 2 or more, absorbed energy DT -196 (J ): Accepting 1500J or more.
  • a test piece having a plate thickness of less than 15 mm was subjected to a precrack Charpy test.
  • the test piece for the pre-crack Charpy test has a crack depth of 2 mm with respect to a test piece width of 10 mm as in the case of a normal V-notch Charpy.
  • the evaluation method of the residual ⁇ amount is as follows. A test piece for residual ⁇ measurement was taken from a (1/4) t position of the thickness t of the steel material, and the residual ⁇ amount (% by volume) was measured by X-ray diffraction. The measured cross section was an L cross section (a plane parallel to the rolling direction and perpendicular to the steel sheet surface). Furthermore, the shape of residual ⁇ was evaluated by thin film observation with a transmission electron microscope. 20 or more residual ⁇ particles were observed, the average aspect ratio of these particle samples and the average size of the major axis were measured, and the average value in the sample was calculated. Further, the concentration of Mn and Ni in the residual ⁇ was evaluated by the following method.
  • the average Mn concentration and the average Ni concentration in the residual ⁇ were measured by EDX (Energy Dispersive X-ray spectroscopy) quantitative analysis, and compared with the average Mn concentration and the average Ni concentration in the ferrite phase, respectively. ) And Formula (2) are evaluated.
  • the average Mn concentration and the average Ni concentration in the ferrite phase were the bulk values (chemical analysis results) of the steel material.
  • [Mn] retained ⁇ average Mn concentration in residual ⁇
  • [Mn] ⁇ average Mn concentration in ferrite phase
  • [Ni] retained ⁇ average Ni concentration in residual ⁇
  • [Ni] ⁇ ferrite
  • the average Ni concentration in the phase is represented respectively.
  • Test No. 1-c steel the water cooling stop temperature after rolling exceeds the specified range.
  • Test No. 1-d steel the cooling rate after tempering falls below the specified range.
  • Steel No. 1-e Test No. with heating temperature below specified range.
  • Test No. 1 in which the finish rolling temperature was lowered due to the slab thickness after completion of the rough rolling with respect to the steel thickness of 1-j and the product thickness product exceeding the specified range.
  • the 1-l steel material lacked strength (yield strength YS, tensile strength TS).
  • Test No. 1-c steel, Test No. 1-d steel, Test No. Steel No. 1-e Test No. with tempering temperature below specified range.
  • 1-f steel Test No.
  • L processing temperature exceeds specified range.
  • the 1-p steel material lacked arrest properties (DT absorbed energy: DT- 196 or absorbed energy at -196 ° C. obtained by a precrack Charpy test).
  • Steel No. 34 has a C content of steel No. 34.
  • Test No. 35 made of 35 steel.
  • Steel No. 35 has a Si content and Test No. 36 made of 36 steel. Since the steel material No. 36 has an excessively high Mn content, the strength characteristics (yield strength and tensile strength) are not a problem, but the fracture characteristics (brittle crack initiation characteristics and arrest characteristics) are insufficient.
  • steel no. Test No. 38 made of 38 steel. Steel No. 38 has an Al content of Steel No.
  • Test No. 39 made of 39 steel. Since the steel No. 39 had an excessively high N content, the tensile strength was insufficient, and the residual ⁇ was not sufficient and the fracture characteristics were insufficient. Steel No. whose C content is lower than the specified value.
  • Test No. 40 made of 40 steel. No. 40 steel, and No. whose Mn content is lower than the specified value.
  • Test No. 42 made of 42 steel. Forty-two steel materials lacked both strength and fracture properties. Steel No. whose Si content is below the specified value.
  • Test No. 41 made of 41 steel. Steel No. 41 and steel No. 1 with an Al content below the specified value.
  • Steel No. 44-No. 56 is one of P, S, Cu, Cr, Mo, V, Nb, Ti, B, Sn, Al, Mg, and REM. 44-No. The steel material No. 56 has deteriorated fracture characteristics.
  • the steel material having a Ni content of 6.6% to 8.0% by mass according to the present invention is excellent in economic efficiency and fracture resistance.
  • This steel material is suitable for use as an inner tank member or an annular plate of an LNG tank.

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Abstract

L'invention concerne un matériau en acier présentant une teneur en γ retenu, mesurée en une position correspondant à un 1/4 de l'épaisseur t de la plaque du matériau en acier, d'au moins 4,0 % en volume. Le γ retenu présente une forme telle que le rapport d'aspect moyen est d'au plus 2,5 et la longueur moyenne du grand axe est d'au plus 0,85 µm et la concentration moyenne en Mn et la concentration moyenne en Ni dans le γ retenu satisfont respectivement à [Mn]retenu γ>[Mn]α×1,4 et [Ni]retenu γ>[Ni]α×1,4.
PCT/JP2013/066825 2013-06-19 2013-06-19 Matériau en acier, procédé pour sa production et citerne pour gnl WO2014203347A1 (fr)

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CN201380041820.9A CN104520461B (zh) 2013-06-19 2013-06-19 钢材及其制造方法以及lng罐
PCT/JP2013/066825 WO2014203347A1 (fr) 2013-06-19 2013-06-19 Matériau en acier, procédé pour sa production et citerne pour gnl
KR1020157003158A KR101572786B1 (ko) 2013-06-19 2013-06-19 강판 및 그 제조 방법 및 lng 탱크
JP2013548641A JP5561442B1 (ja) 2013-06-19 2013-06-19 鋼板およびｌｎｇタンク
EP13887092.8A EP2871255B1 (fr) 2013-06-19 2013-06-19 Acier, procédé pour sa production et cuve pour gnl

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WO2023276429A1 (fr) * 2021-06-28 2023-01-05 Ｊｆｅスチール株式会社 Tôle d'acier et son procédé de production
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CN105567924A (zh) * 2016-03-07 2016-05-11 江苏大学 提高Cr-Ni-Mo-V系高淬透性高强钢抗拉强度的方法
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KR102043523B1 (ko) * 2017-12-24 2019-11-12 주식회사 포스코 용접부 인성이 우수한 저온용 강재 및 그 제조방법
CN111270169A (zh) * 2018-12-05 2020-06-12 河南城建学院 一种具有优异低温韧性的含Ni合金钢板及其生产方法
JP6813132B2 (ja) 2018-12-20 2021-01-13 Ｊｆｅスチール株式会社 缶用鋼板およびその製造方法
KR102195678B1 (ko) * 2018-12-27 2020-12-29 닛폰세이테츠 가부시키가이샤 니켈 함유 강판
CN110129676A (zh) * 2019-05-27 2019-08-16 南京钢铁股份有限公司 一种LNG储罐用7Ni钢板及生产工艺
CN112375981A (zh) * 2020-11-02 2021-02-19 舞阳钢铁有限责任公司 一种大厚度天然气用钢板及其生产方法
CN112779472B (zh) * 2020-12-28 2022-01-07 东北大学 一种低温韧性优异的1GPa级海洋工程用钢板及其制备方法

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WO2021117382A1 (fr) * 2019-12-12 2021-06-17 Ｊｆｅスチール株式会社 Tôle d'acier et procédé de fabrication d'une telle tôle d'acier
JPWO2021117382A1 (ja) * 2019-12-12 2021-12-09 Ｊｆｅスチール株式会社 鋼板およびその製造方法
JP7156500B2 (ja) 2019-12-12 2022-10-19 Ｊｆｅスチール株式会社 鋼板およびその製造方法
CN114829646B (zh) * 2019-12-12 2024-09-13 杰富意钢铁株式会社 钢板及其制造方法
JP2021165431A (ja) * 2020-04-08 2021-10-14 Ｊｆｅスチール株式会社 鋼板およびその製造方法
JP7251512B2 (ja) 2020-04-08 2023-04-04 Ｊｆｅスチール株式会社 鋼板およびその製造方法
WO2023276429A1 (fr) * 2021-06-28 2023-01-05 Ｊｆｅスチール株式会社 Tôle d'acier et son procédé de production
JPWO2023276429A1 (fr) * 2021-06-28 2023-01-05
JP7396507B2 (ja) 2021-06-28 2023-12-12 Ｊｆｅスチール株式会社 鋼板およびその製造方法
WO2024203651A1 (fr) * 2023-03-31 2024-10-03 Ｊｆｅスチール株式会社 Feuille d'acier et son procédé de production

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