WO2019069771A1 - Tôle d'acier, et procédé de fabrication de celle-ci - Google Patents

Tôle d'acier, et procédé de fabrication de celle-ci Download PDF

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Publication number
WO2019069771A1
WO2019069771A1 PCT/JP2018/035778 JP2018035778W WO2019069771A1 WO 2019069771 A1 WO2019069771 A1 WO 2019069771A1 JP 2018035778 W JP2018035778 W JP 2018035778W WO 2019069771 A1 WO2019069771 A1 WO 2019069771A1
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Prior art keywords
steel plate
steel
less
phase
amount
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Ceased
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PCT/JP2018/035778
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English (en)
Japanese (ja)
Inventor
和寿 柳田
中島　清孝
浩司 石田
大貴 今城
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Nippon Steel Corp
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Nippon Steel and Sumitomo Metal Corp
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Filing date
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Priority to JP2019500684A priority Critical patent/JP6536761B1/ja
Priority to KR1020197025144A priority patent/KR102027871B1/ko
Publication of WO2019069771A1 publication Critical patent/WO2019069771A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/108—Feeding additives, powders, or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • 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
    • C22C38/44—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
    • C22C38/50—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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present disclosure relates to a steel plate and a method of manufacturing a steel plate.
  • Examples of applications of the steel plate include ships, buildings, bridges, marine structures, LNG storage tanks, other large tanks, line pipes and the like (see, for example, Patent Documents 1 to 3).
  • the steel plate applied to these applications is a brittle crack propagation arresting property (BCA: stop a brittle crack at the base material even if a brittle crack occurs in a welded joint).
  • Brittle Crack Arrest hereinafter, may be referred to as "arrest”.
  • a steel plate applied to ships for example, it may be applied to an important member (for example, Hatch Side Coating, Upper Deck) of a container ship.
  • container ships have been increased in size for the purpose of reducing environmental load and increasing the efficiency of marine transportation.
  • thick steel plates are used as important members of container vessels. It has been found that when the plate thickness is increased, the crack may penetrate the hull if a brittle crack occurs in the welded joint.
  • CTOD Crack Tip Opening Displacement
  • Patent Document 1 discloses a high strength thick steel plate excellent in arrestability by controlling the composition of the high strength steel plate, microstructure, grain boundary density in the thickness direction, and texture in the thickness direction. ing.
  • the steel plate disclosed in Patent Document 1 has a specific chemical composition, and has a microstructure of 70% or less of ferrite and 30% or more of bainite in area ratio.
  • the grain boundary density at a quarter of the plate thickness is 400 mm / mm 2 to 1000 mm / mm 2
  • the area ratio of the ⁇ 100 ⁇ plane at a quarter of the plate thickness is 10% to 40%. .
  • the grain boundary density in half of the plate thickness is 300 mm / mm 2 to 900 mm / mm 2
  • the area ratio of ⁇ 110 ⁇ plane in half of the plate thickness is 40% to 70%.
  • the yield stress is 390 MPa to 690 MPa.
  • Patent Document 1 focuses on arrestability, it does not focus on joint CTOD characteristics in particular.
  • the melting method and the casting method have not been particularly studied.
  • the steel plate of the technology disclosed in Patent Document 1 satisfies both arrestability and joint CTOD characteristics at a high level. It was found that there is room for further improvement.
  • Patent Document 2 grain boundary ferrite and ferrite side plates formed along the ⁇ grain boundary of the weld heat affected zone near the melting line are refined, and intragranular transformation within the ⁇ grain of the weld heat affected zone near the melting line.
  • a steel plate having a yield strength of 460 MPa or more excellent in the CTOD characteristics of the weld heat affected zone is disclosed.
  • the steel plate disclosed in Patent Document 2 has a specific chemical composition, and further includes a specific TiN containing an Mg-Al oxide and a complex of sulfide and an oxide. There is a specific amount of specific particles contained.
  • Patent Document 2 focuses on the joint CTOD characteristics, it does not focus on the arrestability in particular. Further, the melting method and the casting method have not been particularly studied, and furthermore, the steel making method has not been specifically studied. Then, as a result of examining the technology disclosed in Patent Document 2 by the present inventors, the steel plate of the technology disclosed in Patent Document 2 also satisfies both the arrestability and joint CTOD characteristics at a high level. It was found that there is room for further improvement.
  • Patent Document 3 suppresses the hardening of the center segregated portion of the steel plate, uniformly disperses TiN in the steel uniformly, and crystallizes Ca sulfide, so that the yield stress is 420 MPa or more, and the multilayer welded portion
  • a steel plate which is excellent in the low temperature toughness of the weld heat affected zone.
  • the steel plate disclosed in Patent Document 3 has a specific chemical composition, and satisfies the relationship of H Vmax / H Vave ⁇ 1.35 + 0.006 / [C] ⁇ t / 500.
  • Patent Document 3 focuses on the joint CTOD characteristics, it does not focus on the arrestability in particular.
  • the melting method and the casting method have not been particularly studied.
  • the steel plate of the technology disclosed in Patent Document 3 also satisfies both the arrestability and the joint CTOD characteristics at a high level. It turned out that there is room for improvement.
  • the inventors of the present invention examined the steel plates disclosed in the above Patent Documents 1 to 3 and as a result, they have both high arrestability and joint CTOD characteristics at a high level that satisfy the more stringent standards than before, It was found that there is room for further improvement in order to obtain a steel plate with higher strength. Thus, a steel plate which is superior in both arrestability and joint CTOD characteristics and has higher strength than conventional steel plates which satisfy the more stringent standards has not been established yet. .
  • the present disclosure has been made in view of such circumstances, and has high strength and steel sheet that has both excellent arrestability and excellent joint CTOD characteristics that can satisfy even more stringent standards. It is provided.
  • the present disclosure includes the following aspects.
  • the surface temperature of the steel plate is Ar 3 point ⁇ 30 ° C. to recrystallization on the steel plate after rough rolling
  • finish rolling with a cumulative rolling reduction of 50% to 75% in a temperature range of a temperature T rex
  • the steel sheet after finish rolling has a cross section along the thickness direction of the steel sheet until the temperature at a quarter position from the surface of the steel sheet in the thickness direction reaches a temperature range of 0 ° C. to 600 ° C. Cooling at an average cooling rate of 1 ° C./s to 20 ° C./s at The manufacturing method of the steel plate which has.
  • a steel plate that is superior in both arrestability and joint CTOD characteristics and satisfies more stringent standards than conventional steel plates and that has high strength is required.
  • the present inventors further tightened by controlling the microstructure (tissue morphology, tissue particle size, amount of inclusions, and center segregation). It was found that a steel plate having both excellent arrestability and excellent joint CTOD characteristics that can satisfy even the above standards and having high strength can be obtained, and the steel plate according to the present disclosure is completed.
  • the present inventors also examined in detail the method of manufacturing a steel plate in order to control the microstructure (the structure morphology, the particle size of the structure, the amount of inclusions, and the center segregation).
  • a numerical range represented using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value.
  • “%” indicating the content of a component (element) means “mass%”.
  • the content of C (carbon) may be denoted as “C amount”.
  • the term “step” is not limited to an independent step, and if the intended purpose of the step is achieved even if it can not be clearly distinguished from other steps, this term included.
  • the steel plate according to the present disclosure is in mass%, C: 0.03% to 0.14%, Si: 0.01% to 0.50%, Mn: 1.20% to 2.50%, P: 0.030% or less, S: 0.020% Nb: 0.003% to 0.050%, Ti: 0.003% to 0.050%, Al: 0.001% to 0.100%, N: 0.0010% to 0.0080%, O (oxygen): 0.0050% or less, Ca: 0% to 0.0100%, Mg: 0% to 0.0100%, REM: 0% to 0.0100%, Zr: 0% to 0.0100% , Te: 0% to 0.0100%, V: 0% to 0.150%, Cu: 0% to 1.00%, Ni: 0% to 2.00%, Cr: 0% to 1.00% Mo: 0% to 0.50%, B: 0% to 0.0050%, and the balance: Fe and impurities have a chemical composition
  • the steel plate according to the present disclosure may or may not include at least one selected from the group consisting of Ca, Mg, REM, Zr, Te, V, Cu, Ni, Cr, Mo, and B. May be Therefore, the lower limit value of these elements is 0%. When these elements are contained, the lower limit may be more than 0%.
  • C 0.03% to 0.14%
  • base material the required strength of the steel plate
  • the amount of C is set to 0.03% to 0.14%.
  • the preferable lower limit of the amount of C is 0.04% or more, more preferably 0.05% or more.
  • the preferable upper limit of the amount of C is 0.12% or less, more preferably 0.10% or less.
  • Si 0.01% to 0.50%
  • Si is a deoxidizing element and is an element effective for solid solution strengthening. If the amount of Si is less than 0.01%, the effect of containing Si can not be obtained, so the lower limit of the amount of Si is made 0.01% or more. On the other hand, if the Si content exceeds 0.50%, the weldability and the required joint CTOD characteristics become inferior. Therefore, the amount of Si is set to 0.01% to 0.50%.
  • the preferable lower limit of the amount of Si is 0.05% or more, more preferably 0.10% or more.
  • the upper limit of the amount of Si is preferably 0.40% or less, more preferably 0.30% or less.
  • Mn is an effective element for improving the strength and toughness of the base material, and the content of Mn is 1.20% or more.
  • the content of Mn is 1.20% or more.
  • the upper limit is 2.50%. Therefore, the amount of Mn is set to 1.20% to 2.50%.
  • the preferable lower limit of the amount of Mn is 1.40% or more, more preferably 1.60% or more.
  • the preferable upper limit of the amount of Mn is 2.20% or less, more preferably 2.00% or less.
  • (P: 0.030% or less) P is present in the steel sheet as an impurity.
  • the upper limit of the amount of P is set to 0.030% or less.
  • the upper limit of the amount of P is preferably 0.020% or less, more preferably 0.010% or less.
  • the lower the amount of P the lower the amount. However, from the viewpoint of the manufacturing cost, it may be 0.001% or more.
  • (S: 0.020% or less) S is present in the steel sheet as an impurity.
  • the upper limit of the amount of S is made 0.020% or less.
  • the upper limit of the amount of S is preferably 0.015% or less, more preferably 0.010% or less, still more preferably 0.005% or less, and still more preferably 0.002% or less.
  • the lower the amount of S the lower the amount. However, from the viewpoint of the manufacturing cost, it may be 0.001% or more.
  • Nb suppresses the recrystallization temperature, contributes to the refinement of the structure by the addition of a small amount, and is an element effective for securing the strength of the base material.
  • the Nb content is set to 0.003% to 0.050%.
  • the preferable lower limit of the amount of Nb is 0.006% or more, more preferably 0.010% or more.
  • the upper limit of the Nb content is preferably 0.040% or less, more preferably 0.030% or less.
  • Ti is an element that contributes to the improvement of toughness through the refinement of the structure of the base material and the weld by the addition of a small amount. In addition, Ti also functions as a deoxidizing element. On the other hand, excessive addition of Ti hardens the weld and significantly deteriorates toughness, resulting in inferior joint CTOD characteristics. Therefore, the amount of Ti is set to 0.003% to 0.050%.
  • the preferable lower limit of the amount of Ti is 0.006% or more, more preferably 0.010% or more.
  • the preferable upper limit of the amount of Ti is 0.035% or less, more preferably 0.020% or less.
  • Al 0.001% to 0.100% Since Al is a deoxidizing element, the amount of Al is made 0.001% or more. On the other hand, the excessive addition of Al impairs the surface quality of the steel slab and forms an inclusion harmful to toughness, so the upper limit of the amount of Al is 0.100%. Therefore, the Al content is set to 0.001% to 0.100%.
  • the preferable lower limit of the amount of Al is 0.010% or more, more preferably 0.020% or more.
  • the upper limit of the amount of Al is preferably 0.060% or less, more preferably 0.040% or less.
  • N (N: 0.0010% to 0.0080%) N forms a nitride together with Al to improve the joint toughness, so the lower limit of the N amount is made 0.0010% or more. However, if the content of N is excessive, embrittlement and elongation decrease due to solid solution N occur, so the upper limit of the amount of N is made 0.0080% or less. Therefore, the N content is set to 0.0010% to 0.0080%.
  • the preferable lower limit of the N amount is 0.0015% or more, more preferably 0.0020% or more.
  • the preferable upper limit of the amount of N is 0.0060% or less, more preferably 0.0040% or less.
  • O oxygen
  • the upper limit of the amount of O is made 0.0050% or less.
  • the lower limit of O is not particularly defined because the amount of O is preferably as small as possible.
  • the lower limit of the amount of O may be 0.0005% or more.
  • the preferable lower limit of the amount of O may be 0.0007% or more, and may be 0.0010% or more.
  • the upper limit of the amount of O is preferably 0.0040% or less, more preferably 0.0030% or less.
  • Ca 0% to 0.0100%
  • Ca is a deoxidizing element, and is an element that suppresses the formation of coarse inclusions by forming sulfides, forms a fine oxide, and suppresses the formation of harmful inclusions. Therefore, Ca may be contained.
  • the amount of Ca exceeds 0.0100%, coarse oxides, sulfides and acid sulfides are formed, and the joint CTOD characteristics become inferior. Therefore, the amount of Ca is set to 0% to 0.0100%.
  • the upper limit of the amount of Ca is preferably 0.0070% or less, more preferably 0.0040% or less.
  • the lower limit of the amount of Ca is preferably made 0.0001% or more. More preferably, it is 0.0010% or more, particularly preferably 0.0020% or more.
  • Mg is a deoxidizing element, and is an element that suppresses the formation of coarse inclusions by forming sulfides, forms a fine oxide, and suppresses the formation of harmful inclusions. Therefore, Mg may be contained. However, when the Mg content exceeds 0.0100%, coarse oxides, sulfides and acid sulfides are formed, and the joint CTOD characteristics become inferior. Therefore, the amount of Mg is set to 0% to 0.0100%.
  • the preferable upper limit of the amount of Mg is 0.0070% or less, more preferably 0.0040% or less. In order to obtain the effect by the above-mentioned effect more certainly, it is preferable to make the lower limit of the amount of Mg into 0.0001% or more. More preferably, it is 0.0010% or more, particularly preferably 0.0020% or more.
  • REM 0% to 0.0100%
  • REM is a deoxidizing element, is an element that suppresses the formation of coarse inclusions by forming sulfides, forms a fine oxide, and suppresses the formation of harmful inclusions. Therefore, REM may be contained.
  • the REM amount is 0% to 0.0100%.
  • the upper limit of the REM amount is preferably 0.0070% or less, more preferably 0.0040% or less.
  • the lower limit of the amount of REM is preferably made 0.0001% or more.
  • REM is a general term for Sc, Y, and a total of 17 elements of lanthanoids. As REM, one or more elements out of 17 elements in total may be included. The content of REM refers to the total content of these elements.
  • Zr 0% to 0.0100%
  • Zr is an element that contributes to the improvement of toughness through the refinement of the structure of the base material and the weld by the addition of a small amount.
  • Zr also functions as a deoxidizing element. Therefore, Zr may be contained.
  • the amount of Zr is set to 0% to 0.0100%.
  • the preferable upper limit of the amount of Zr is 0.0070% or less, more preferably 0.0040% or less.
  • the lower limit of the amount of Zr is preferably made 0.0001% or more. More preferably, it is 0.0010% or more, particularly preferably 0.0020% or more.
  • Te 0% to 0.0100%
  • Te is an element that contributes to the improvement of toughness by grain refinement. Therefore, Te may be contained. However, the effect is saturated even if the amount of Te exceeds 0.0100%. Therefore, the Te content is set to 0% to 0.0100%.
  • the upper limit of the amount of Te is preferably 0.0070% or less, more preferably 0.0040% or less.
  • the lower limit of the amount of Te is preferably set to 0.0001% or more in order to obtain the effect by the above action more reliably. More preferably, it is 0.0010% or more, particularly preferably 0.0020% or more.
  • V is an element that contributes to the increase in strength of the base material by precipitation strengthening. Therefore, V may be contained. However, if the V content exceeds 0.150%, the joint toughness is impaired. Therefore, the V amount is set to 0% to 0.150%.
  • the preferable upper limit of the amount of V is 0.080% or less, more preferably 0.060% or less.
  • the lower limit of the amount of V is preferably set to 0.001% or more in order to obtain the effect by the above action more reliably. More preferably, it is 0.010% or more, and particularly preferably 0.020% or more.
  • Cu 0% to 1.00%
  • Cu is an element which improves the hardenability and is effective for strengthening the base material. Therefore, Cu may be contained. However, if the amount of Cu exceeds 1.00%, the decrease in toughness accompanying the increase in hardness of the joint becomes remarkable. Therefore, the amount of Cu is set to 0% to 1.00%.
  • the upper limit of the amount of Cu is preferably 0.80% or less, more preferably 0.60% or less.
  • the lower limit of the amount of Cu is preferably 0.01% or more in order to obtain the effect by the above action more reliably. More preferably, it is 0.05% or more, particularly preferably 0.10% or more.
  • Ni is an element effective for securing the strength and improving the toughness of the base material. Therefore, Ni may be contained. However, even if the amount of Ni exceeds 2.00%, the effect of containing Ni saturates and the cost increases. Therefore, the amount of Ni is set to 0% to 2.00%.
  • the upper limit of the amount of Ni is preferably 1.50% or less, more preferably 1.00% or less.
  • the lower limit of the amount of Ni is preferably 0.01% or more. More preferably, it is 0.10% or more, particularly preferably 0.20% or more.
  • Cr 0% to 1.00% Cr is an element which improves the hardenability and is effective in increasing the strength of the base material. Therefore, Cr may be contained. However, if the amount of Cr exceeds 1.00%, the toughness decreases with the increase in the hardness of the joint. Therefore, the amount of Cr is set to 0% to 1.00%.
  • the upper limit of the amount of Cr is preferably 0.80% or less, more preferably 0.60% or less.
  • the lower limit of the amount of Cr is preferably 0.01% or more. More preferably, it is 0.05% or more, particularly preferably 0.10% or more.
  • Mo 0% to 0.50%
  • Mo is an element that improves the hardenability and is effective in increasing the strength of the base material. Therefore, Mo may be contained. However, when the Mo content exceeds 0.50%, the toughness decreases with the increase in hardness of the joint. Therefore, the Mo content is 0% to 0.50%.
  • the preferable upper limit of the Mo amount is 0.40% or less, more preferably 0.30% or less. In order to obtain the effect by the above-mentioned effect more certainly, it is preferable to make the lower limit of Mo amount into 0.01% or more. More preferably, it is 0.05% or more, particularly preferably 0.10% or more.
  • B is an element contributing to the improvement of the base material strength by enhancing the hardenability by the addition of a small amount. Therefore, B may be contained. However, when the B content exceeds 0.0050%, the joint CTOD characteristics become inferior. Therefore, the B content is 0% to 0.0050%.
  • the upper limit of the amount of B is preferably 0.0040% or less, more preferably 0.0030% or less. In order to obtain the effect by the above action more reliably, the lower limit of the amount of B is preferably made 0.0001% or more. More preferably, it is 0.0005% or more, particularly preferably 0.0010% or more.
  • the balance is Fe and impurities.
  • the impurity refers to a component contained in the raw material or a component mixed in the process of production, which is not intentionally contained in the steel sheet.
  • the steel plate according to the present disclosure has a carbon equivalent Ceq of 0.30% to 0.55% determined by the following equation (1).
  • C, Mn, Cr, Mo, V, Cu, and Ni in Formula (1) represent the content (mass%) of each element contained in a steel plate.
  • 0 mass% is substituted and calculated as content of the applicable element in Formula (1).
  • the carbon equivalent When the carbon equivalent is less than 0.30%, it becomes difficult to satisfy the strength characteristics (tensile strength, yield stress) required for the steel plate as the base material. When the carbon equivalent exceeds 0.55%, it becomes difficult to satisfy the required arrestability and joint CTOD characteristics.
  • the lower limit value of the carbon equivalent is preferably 0.35% or more, more preferably 0.40% or more.
  • the upper limit of the carbon equivalent is preferably 0.52% or less, more preferably 0.49% or less.
  • the steel plate according to the present disclosure has a metallographic structure (micro-structure at a quarter position in the plate thickness direction from the steel plate surface of the cross section along the plate thickness direction (hereinafter may be referred to as "quarter plate thickness”). Structure, area fraction, 10.0% to 75.0% of ferrite phase, 10.0% to 90.0% of bainite phase, 0% to 15.0% of pearlite phase, and martensite / austenite mixed phase (Hereinafter, it may be referred to as "MA phase”.) It is composed of 0% to 1.0% tissue morphology.
  • the average particle diameter (diameter) measured by the electron beam backscattering diffraction method of all the phases (ferrite phase, bainite phase, pearlite phase, and MA phase) is 20 micrometers or less.
  • the sum of the area fractions of the ferrite phase, the bainite phase, the pearlite phase, and the MA phase is 100%.
  • the reasons for limitation of the microstructure (the morphology of the steel sheet, the average particle size of the structure, the amount of inclusions, and the center segregation) of the steel plate according to the present disclosure will be described.
  • the 1 ⁇ 4 position in the thickness direction from the surface of the steel plate of the cross section along the thickness direction represents a 2 mm square range around the 1 ⁇ 4 position.
  • the ferrite phase contributes to the strength and arrestability of the base material.
  • the area fraction exceeds 75.0%, the strength of the base material becomes inferior.
  • the area fraction of the ferrite phase is set to 10.0% to 75.0%.
  • the preferred range of the area fraction of the ferrite phase is 20.0% to 50.0%.
  • the bainite phase mainly contributes to the strength of the base material. If the area fraction of the bainite phase is less than 10.0%, the strength of the base material becomes inferior. On the other hand, when the area fraction of the bainite phase exceeds 90.0%, arrestability becomes inferior. Therefore, the area fraction of the bainite phase is 10.0% to 90.0%.
  • the preferred range of the area fraction of the bainite phase is 50.0% to 80.0%.
  • the perlite phase may be contained in the microstructure.
  • the area fraction of the pearlite phase becomes excessive, the strength of the base material becomes inferior. Therefore, when the pearlite phase is included, the area fraction of the pearlite phase is 15.0% or less.
  • the preferable upper limit of the area fraction of the pearlite phase is 10.0% or less.
  • the pearlite phase may not be contained. That is, the lower limit value of the pearlite phase is 0%.
  • MA phase 0% to 1.0% Since the MA phase lowers the joint CTOD characteristics, when the area fraction of the MA phase becomes excessive, the joint CTOD characteristics become inferior. Therefore, when the MA phase is included, the area fraction of the MA phase is 1.0% or less.
  • the lower limit is not particularly defined as the amount of MA phase is as small as possible. The MA phase may not be included.
  • the area fractions of the ferrite phase, the bainite phase, the pearlite phase, and the MA phase are measured as follows.
  • the metallographic structure of a cross section in the direction perpendicular to the rolling direction of the steel plate (so-called C direction cross section) and a cross section perpendicular to the width direction of the steel plate (so-called L direction cross section) It is determined by taking a picture and analyzing the image.
  • a cross section in the direction perpendicular to the rolling direction of the steel plate C direction cross section
  • a cross section in the direction perpendicular to the width direction of the steel plate L direction cross section
  • the L-direction cross-section observation sample and the C-direction cross-section observation sample are collected from the 1 ⁇ 4 position from the width direction end face of the steel plate at four positions.
  • the collected sample is subjected to nital etching, and after etching, eight fields of view are taken at a magnification of 500 with a total of L direction cross section (four fields of view) and C direction cross section (four fields of view) using an optical microscope.
  • binarization processing is performed on the obtained tissue photograph using image analysis software, and image analysis is performed.
  • the area ratio is determined using the phase that appears white as a ferrite phase, the phase that appears black as a pearlite phase, and the phase that appears gray as a bainite phase or an MA phase (martensitic / austenitic mixed phase).
  • the nital-etched portion is repeller-etched, and image analysis is performed on a portion that appears gray by nital etching to determine what is white as the MA phase (martensitic-austenitic mixed phase) and the area ratio.
  • the area ratio of the above-mentioned MA phase (the martensite / austenite mixed phase) is subtracted from the area ratio which appeared gray by nital etching, and this is defined as the area ratio of the bainite phase.
  • the average particle diameter of all the phases is set to 20 ⁇ m or less (preferably 15 ⁇ m or less, more preferably 10 ⁇ m or less). The smaller the average particle size of all the phases, the better the improvement in arrestability.
  • the lower limit of the average particle diameter of all phases is not particularly limited, and, for example, 1 ⁇ m or more can be mentioned, and 5 ⁇ m or more can be mentioned.
  • the average grain size of all phases is measured by the electron back scattering pattern (EBSP) which can measure the crystal orientation information with a wide field of view with high accuracy.
  • the EBSP method can also measure the grain size of complex structures such as bainite. Specifically, it is measured by the following method. The EBSP method is repeated while moving the measurement position by 1 ⁇ m for a 500 ⁇ m ⁇ 500 ⁇ m area of 1/4 part of plate thickness.
  • a boundary where the crystal orientation difference between adjacent grains is 15 ° or more is defined as a grain boundary, and the area fraction weighted average value of the equivalent circle diameter (diameter) surrounded by the grain boundaries is determined, Average particle size.
  • the steel plate according to the present disclosure is an oxide, a sulfide, and an oxysulfide having a circle equivalent diameter of 2 ⁇ m or more at a quarter position in the plate thickness direction from the surface of the steel plate in a cross section along the plate thickness direction.
  • the sum total of content of an oxide, a sulfide, and an acid sulfide whose circle equivalent diameter is 2 micrometers or more is 50 pieces / mm ⁇ 2 > or less as a number density.
  • an acid sulfide represents the complex of an oxide and a sulfide.
  • oxides, sulfides and acid sulfides contained in 1 ⁇ 4 part of plate thickness mean inclusions (hereinafter, oxides, sulfides and acid sulfides are collectively referred to simply as “inclusions”. There is a case. Hereinafter, the reasons for limitation of inclusions will be described.
  • the lower limit value of the content of the above-mentioned inclusions contained in 1/4 part of board thickness is not particularly limited, and, for example, 10 / mm 2 or more can be mentioned.
  • the equivalent circle diameter and the content (number density) of oxides, sulfides and oxysulfides contained in 1/4 part of plate thickness of steel sheet are measured using a scanning electron microscope (SEM: Scanning Electron Microscope) It is preferable to measure with a wide visual field. Specifically, it is measured by the following method. Specifically, from the surface of the steel plate to the thickness direction 1 ⁇ 4 of the cross section in the direction perpendicular to the rolling direction of the steel plate (C direction cross section) and the cross section in the direction perpendicular to the width direction of the steel plate (L direction cross section) Take a sample. Then, a cross section perpendicular to the rolling direction of the steel plate (so-called C direction cross section) is polished and observed.
  • SEM Scanning Electron Microscope
  • a cross section perpendicular to the width direction of the steel plate is polished and observed.
  • the acceleration voltage is 15 kV
  • the current is 89 ⁇ A to 91 ⁇ A
  • the L-direction cross section and the C direction cross-section make the observation field area 180 mm 2 to 200 mm 2 .
  • Each observation visual field area of the cross section in the C direction is 90 mm 2 to 100 mm 2 .
  • the SEM / WDX analysis first identifies particles having a circle equivalent diameter (diameter) of 2 ⁇ m or more which is observed in the observation field of view.
  • the composition of each particle is then analyzed by WDX to identify oxides, sulfides and acid sulfides according to the following definition.
  • the particle density of the inclusions is determined by taking a SEM particle image of the particles and counting the number of each particle by image analysis.
  • the analysis of inclusions may be automatically and continuously measured using software attached to the SEM.
  • inclusions corresponding to the following conditions are determined as an oxide, a sulfide, and an acid sulfide. That is, as inclusions, all elements other than Fe contained in the steel plate according to the present disclosure are elements to be analyzed, and the mass% for each object to be analyzed is calculated. The total of all elements to be analyzed is 100% by mass.
  • inclusions with an O (oxygen) content of 10% by mass or more as oxides, inclusions with an S content of 3% by mass or more as sulfides, and O (oxygen) content as 10% Inclusions having a% or more content and a S content of 3% by mass or more are referred to as an acid sulfide.
  • the steel plate according to the present disclosure it is important that central segregation be controlled to a suitable range.
  • the steel plate according to the present disclosure adopts the following index as an index representing central segregation.
  • the steel plate according to the present disclosure has a cross section along the thickness direction, with respect to a Mn concentration (Mn (1/4) ) at a 1/4 position from the surface of the steel plate to the thickness direction,
  • the ratio (Mn (1/2) / (Mn (1/2) ) ratio of Mn concentration (Mn (1/2) ) at half position in the plate thickness direction from the surface of the steel sheet (hereinafter sometimes referred to as "plate thickness 1/2 part" ) Mn (1/4) is 0.90 to 1.80.
  • the 1 ⁇ 2 position in the thickness direction from the surface of the steel plate of the cross section along the thickness direction represents a 2 mm square range around the 1 ⁇ 2 position.
  • the 1 ⁇ 4 position in the thickness direction from the surface of the steel plate of the cross section along the thickness direction represents a 2 mm square range around the 1 ⁇ 4 position.
  • Mn is centrally segregated during continuous casting to form an embrittled zone at the center of the plate thickness, which affects the joint CTOD characteristics. Therefore, the ratio (Mn (1/2) / Mn) of the concentration (Mn (1/2) ) of Mn in the plate thickness 1/2 part to the concentration (Mn (1/4) ) of Mn in the plate thickness 1/4 part Let (1/4) ) be 0.90 to 1.80. If (Mn (1/2) / Mn (1/4) ) exceeds 1.80, the Mn concentration at the center of the plate thickness becomes too high, so the joint CTOD characteristics deteriorate.
  • Mn (1/2) / Mn (1/4) it is practically difficult to stably obtain a steel sheet with Mn (1/2) / Mn (1/4) less than 0.90.
  • the preferred range of Mn (1/2) / Mn (1/4) is 0.95 to 1.70, and the more preferred range is 1.00 to 1.60.
  • Mn (1/2) / Mn (1/4) is determined as follows. First, a sample for measurement of Mn concentration collected from 1/4 part of plate thickness and a sample for measurement of Mn concentration collected from 1/2 part of plate thickness are prepared. Next, for each sample, an electron probe microanalyzer (EPMA: Electron Probe MicroAnalyzer, measurement conditions; acceleration voltage: 15 kV, beam diameter: 20 ⁇ m, irradiation time: 20 ms, taking a 2 mm square range of the sample as a measurement range) The maximum value of the concentration of Mn when the measurement range of 2 mm square is measured is measured by the measurement pitch: 20 ⁇ m.
  • EPMA Electron Probe MicroAnalyzer
  • Mn (1/2) / Mn (1/4) is calculated with the maximum concentrations obtained from the respective samples as Mn (1/2) and Mn (1/4) , respectively.
  • Each sample is taken from the C direction cross section and the L direction cross section, and the measurement is performed on the C direction cross section and the L direction cross section.
  • the thickness of the steel plate according to the present disclosure is not particularly limited, and may be, for example, 50 mm or more, and may further be 50 mm to 100 mm.
  • the tensile strength (TS) of the steel plate according to the present disclosure is not particularly limited, and is preferably 510 MPa or more (preferably 510 MPa to 720 MPa, more preferably 570 MPa to 720 MPa) from the viewpoint of achieving high strength.
  • the yield stress (YP) is preferably 390 MPa or more (preferably 390 MPa to 650 MPa, more preferably 460 MPa to 650 MPa).
  • the tensile strength (TS) of the steel plate according to the present disclosure is measured using a No. 1B tensile test piece of JIS Z 2241 (2011).
  • the yield stress (YP) means the proof stress of the permanent elongation method at the time of permanent elongation 0.2% of JIS Z2241 (2011).
  • brittle crack propagation stopping toughness value at test temperature minus 10 ° C. in a temperature gradient type ESSO test K ca (hereinafter also referred to as "arrest toughness value K ca-10 ° C.”.)
  • Arrest toughness value K ca-10 ° C There 6000 N / mm 1.5 or more (preferably, 8000 N / mm 1.5 or more) may be a.
  • Arrest toughness value K ca -10 ° C is defined by the NK Classification Society Steel Ship Regulations Inspection Guideline K, Appendix K3.12.2-1. Measure according to (2016) “Testing Procedure for Thermal Gradient ESSO Test and Thermal Gradient Double Tensile Test”.
  • the steel plate according to the present disclosure has an opening displacement ⁇ c (hereinafter referred to as “opening” at a test temperature minus 10 ° C. in a crack tip opening displacement test of the welded part (hereinafter may be referred to as “CTOD test of welded part”).
  • the displacement ⁇ c ⁇ 10 ° C. may be referred to as“ 0.10 mm or more (preferably 0.20 mm or more) ”.
  • the opening displacement ⁇ c ⁇ 10 ° C. is measured in accordance with BS 7448 standard (British Standard) Part 1 (1991) and BS 7448 standard (British Standard) Part 2 (1997).
  • submerged arc welding SAW welding
  • SAW welding submerged arc welding
  • the form of the metal structure, the average particle diameter of each phase of the metal structure, the amount of inclusions, and the center segregation are controlled to satisfy the above-mentioned conditions.
  • Tensile strength (TS), yield stress (YP), arrest toughness value K ca -10 ° C , and opening displacement ⁇ c -10 ° C even when the plate thickness is 50 mm or more (for example, 50 mm to 100 mm)
  • the value of the above range can be satisfied.
  • the steel plate according to the present disclosure can be obtained, for example, by a manufacturing method having the following steps.
  • a step of performing deoxidation treatment by adding a deoxidizing element so that the final dissolved oxygen amount becomes 20 ppm or less in a molten steel whose dissolved oxygen amount has been adjusted to 50 ppm or less (deoxidation treatment step); Continuous casting of the deoxidized molten steel at a throughput of 0.80 to 5.00 tons (0.80 ton / 5.00 to 5.00 ton / min) per minute, and center solidification of the slab during continuous casting
  • the phase ratio is in the range of 0.5 to 1.0
  • the amount of reduction is 1 to 1.5 mm (1 mm / m to 1.5 mm / m) with a reduction gradient of 1 mm to 1 mm in the casting advancing direction with respect to the slab.
  • a step of obtaining a billet by applying a light pressure of 1 mm to 15 mm (casting step), The billet is heated in a temperature range of 950 ° C. to 1150 ° C. and rough rolling is performed on the heated billet, and then the surface temperature of the steel plate is Ar 3 point ⁇ 30 ° C. to recrystallization temperature on the steel plate after rough rolling
  • a step (finishing step) of performing finish rolling with a cumulative rolling reduction of 50% to 75% in a temperature range of T rex The steel sheet after finish rolling has a cross section along the thickness direction of the steel sheet until the temperature at a quarter position from the surface of the steel sheet in the thickness direction reaches a temperature range of 0 ° C. to 600 ° C. Cooling at an average cooling rate of 1 ° C./s to 20 ° C./s (cooling step). Each step will be described below.
  • adjustment of the amount of dissolved oxygen in molten steel before adding deoxidizing element is performed.
  • the amount of dissolved oxygen in the molten steel exceeds 50 ppm, it is difficult to adjust the final amount of dissolved oxygen in the molten steel to 20 ppm or less by adding a deoxidizing element described later. Therefore, adjustment of the amount of dissolved oxygen in molten steel before adding a deoxidizing element is 50 ppm or less (preferably 40 ppm or less, more preferably 30 ppm or less).
  • the lower limit of the amount of dissolved oxygen in the molten steel before adding the deoxidizing element is not particularly limited, and may be adjusted to, for example, more than 20 ppm. Note that ppm is on a mass basis.
  • the method for adjusting the dissolved oxygen content of the molten steel to 50 ppm or less is not particularly limited, and examples thereof include performing using a RH (Ruhrstahl-Heraeus) vacuum degassing apparatus.
  • RH Rasterstahl-Heraeus
  • a deoxidizing element is added to the molten steel after the dissolved oxygen content of the molten steel becomes 50 ppm or less, and the final dissolved oxygen content in the molten steel after addition of the deoxidizing element is adjusted to 20 ppm or less.
  • the final amount of dissolved oxygen in the molten steel after addition of the deoxidizing element exceeds 20 ppm, it becomes difficult to control the number density of inclusions of oxides, sulfides and acid sulfides to a predetermined amount or less.
  • the final amount of dissolved oxygen in the molten steel after addition of the deoxidizing element should be as low as possible.
  • the amount of final dissolved oxygen in the molten steel after deoxidation element addition 15 ppm or less is preferable, for example, and 10 ppm or less is more preferable.
  • the lower limit of the final amount of dissolved oxygen in the molten steel after addition of the deoxidizing element is not particularly limited, and may be, for example, 5 ppm or more.
  • the deoxidizing element at least one selected from the group consisting of Al, Ca, Si, Ti, Mg, Zr, and REM is used.
  • the addition order of the deoxidizing elements is not particularly limited.
  • Al and a deoxidizing element other than Al may be simultaneously added, or after adding Al, a deoxidizing element other than Al may be added.
  • RH vacuum degassing apparatus For adjustment of the final dissolved oxygen content of the molten steel after adding the deoxidizing element by the RH vacuum degassing apparatus, for example, it is preferable to reflux the molten steel for 10 to 60 minutes at a degree of vacuum of 1 to 5 torr ( ⁇ 133 Pa to 667 Pa). .
  • a chemical composition is adjusted in consideration of a yield so that each element may become desired content.
  • the method of adding each element is not particularly limited as long as it can be contained in the steel sheet so that the chemical composition satisfies the above conditions.
  • the measurement of the amount of dissolved oxygen before adding the deoxidizing element and the final amount of dissolved oxygen after adding the deoxidizing element are free from existing oxygen as a simple substance which is not oxidized as a compound with other compounds. Measure the state oxygen. Specifically, the amount of dissolved oxygen before adding the deoxidizing element and the final amount of dissolved oxygen after adding the deoxidizing element are determined by a known method of electromotive force measurement (for example, “in converter furnace by electromotive force measurement "Rapid analysis of molten steel oxygen” (see Ikuta et al., Iron and Steel, Japan Iron and Steel Institute, 1972, No. 10, pp. 125-132).
  • molten steel having a predetermined chemical composition which has undergone deoxidation treatment, is continuously cast at a throughput of 0.80 ton / min to 5.00 ton / min.
  • the throughput of the molten steel is preferably 3.00 ton / min to 4.50 ton / min in that the number density of inclusions is further controlled.
  • throughput refers to the production rate (ton / min) of slabs produced per minute.
  • the throughput can be obtained by the following equation.
  • Throughput (ton / min) casting width (mm) ⁇ casting thickness (mm) ⁇ casting speed (mm / min) ⁇ molten steel density (ton / mm 3 )
  • the molten steel density is determined by the metal type of the molten steel, but in the present disclosure, the molten steel density is 7.85 ⁇ 10 ⁇ 9 (ton / mm 3 ).
  • the light reduction is 1.0 mm / m to 1.5 mm / m (preferably) to the slab when the central solid phase ratio of the slab at the end of solidification of the slab is in the range of 0.5 to 1.0.
  • the reduction is always 1 mm to 15 mm with a reduction gradient of 1.0 mm / m to 1.5 mm / m. There is no need to carry out a light reduction.
  • the light reduction is 1 mm to 15 mm at a reduction gradient of 1.0 mm / m to 1.5 mm / m at any timing during which the central solid phase ratio is in the range of 0.5 to 1.0.
  • the light reduction to be For example, while the central solid phase ratio is in the range of 0.5 to 0.8, or in the range of 0.6 to 0.8, or in the range of 0.6 to 0.7, At the timing, the pressure reduction gradient may be in the range of 1.0 mm / m to 1.5 mm / m, and the light reduction may be performed so that the amount of pressure reduction is 1 mm to 15 mm.
  • the central solid phase ratio can be defined as the solid phase ratio of the molten portion in the central portion of the cast slab thickness direction and in the cast slab width direction.
  • the central solid phase rate can be determined by heat transfer and solidification calculation. As heat transfer and solidification calculation, enthalpy method, equivalent specific heat method, etc. are widely known, and any method may be used.
  • Rolling process Next, the steel slab obtained through the casting process is heated at a predetermined temperature, and rough rolling is performed on the heated steel slab. Then, finish rolling is performed on the steel plate after rough rolling so that the surface temperature of the steel plate becomes a predetermined cumulative rolling reduction at a predetermined temperature.
  • This process is a process of refining austenite grains by heating a steel piece, efficiently accumulating strain in austenite by predetermined finish rolling, and contributing to the grain refinement of a microstructure. And, this process affects the arrestability.
  • the billet is heated in a temperature range of 950 ° C. to 1150 ° C. (preferably 1000 ° C. to 1100 ° C.).
  • a temperature range of 950 ° C. to 1150 ° C. (preferably 1000 ° C. to 1100 ° C.).
  • austenitization becomes sufficient and austenite grains are refined.
  • the heating temperature of the steel piece is set to 1150 ° C. or less, coarsening of austenite is suppressed and austenite grains are refined. And, by setting this temperature range, excellent arrestability can be obtained.
  • heating temperature represents the average temperature of the total thickness of a billet.
  • the steel slab after heating is roughly rolled, and the steel plate after rough rolling is subjected to finish rolling.
  • the finish rolling is performed such that the cumulative rolling reduction is 50% to 75% in the temperature range where the surface temperature of the steel sheet is Ar 3 point ⁇ 30 ° C. to the recrystallization temperature T rex .
  • the temperature range of the finish rolling represents the surface temperature of the steel plate, and the rolling is started after the surface temperature of the steel plate reaches Ar 3 point ⁇ 30 ° C. to the recrystallization temperature T rex .
  • the surface temperature of the steel sheet is in a temperature range of Ar 3 point ⁇ 30 ° C. to the recrystallization temperature T rex , the coarsening of each phase of the microstructure is suppressed.
  • ferrite is finely divided to obtain good arrestability. If the start temperature of finish rolling is Ar 3 -30 ° C. or higher, two-phase zone rolling (rolling in a temperature range where ferrite + austenite two phase exists) will not be performed, so coarse worked ferrite (ferrite formed during rolling) Generation is suppressed. On the other hand, if the recrystallization temperature is equal to or lower than the Rex temperature, rolling in the non-recrystallization region is performed, and coarsening of ferrite is suppressed.
  • the cumulative rolling reduction is set to 50% to 75% (preferably 55% to 65%).
  • Ar 3 is represented by the following formula (2)
  • the recrystallization temperature T rex is represented by the following formula (3).
  • T rex -91900 [Nb *] 2 + 9400 [Nb *] + 770 (However, in Formula (3), [Nb *] is represented by following formula (4).
  • T represents the heating temperature of a billet, and a unit represents celsius temperature (degreeC).
  • Formula (4) Sol 910-310 [ C] +65 [Si] -80 [Mn] -20 [Cu] -55 [Ni] -15 [Cr] -80 [Mo]
  • T rex -91900 [Nb *] 2 + 9400 [Nb *] + 770
  • Nb (10 ( -6770 / (T + 273) +2.26 )) / (C + 12/14 ⁇ N)
  • [Nb] ⁇ [Sol. In the case of Nb], the relationship of [Nb *] [Nb] is satisfied.
  • [Nb] represents the Nb content (% by mass), and [Sol. Nb] is Sol. Nb (solid solution Nb) (mass%) is represented. )
  • the plate thickness after rough rolling is the same as the plate thickness at the time of starting finish rolling.
  • the steel plate after finish rolling has a cooling rate of 1 ° C / s to 20 ° C / s at a plate thickness of 1/4 of the steel plate, and a temperature of 0 ° C to 600 ° C at a plate thickness of 1/4 of a steel plate Cool down to area. That is, the cooling stop temperature is a temperature range of 0 ° C. to 600 ° C. as a temperature at a thickness of 1/4 of the steel plate.
  • the cooling method is not particularly limited, and examples thereof include methods such as water cooling.
  • a cooling rate By cooling at a cooling rate of 1 ° C / sec to 20 ° C / sec at a plate thickness of 1 ⁇ 4 part and cooling to a temperature range of 0 ° C to 600 ° C at a plate thickness of 1 ⁇ 4 part A predetermined amount of ferrite phase and a predetermined amount of bainite phase are obtained.
  • the cooling rate and the cooling stop temperature are the calculated cooling rate and the calculated cooling stop temperature at a quarter of the plate thickness.
  • a cooling rate is an average cooling rate from a cooling start to a cooling stop.
  • the preferable manufacturing method for obtaining the steel plate according to the present disclosure further includes a step (tempering step) of tempering the steel plate after the cooling step in a temperature range of 350 ° C. to 650 ° C., if necessary. It is also good.
  • tempering process After cooling the steel plate, if necessary, it may be tempered by heat treatment in a temperature range of 350 ° C. to 650 ° C. (preferably 450 ° C. to 550 ° C.) to adjust the strength and toughness of the steel plate.
  • the tempering temperature is 350 ° C. or more, the effect of improving the toughness by strain removal is enhanced.
  • the tempering temperature is set to 650 ° C. or less, strength reduction can be suppressed.
  • the manufacturing method of the steel plate which concerns on this indication is not limited to the above-mentioned manufacturing method. Even if the manufacturing method of a steel plate is a manufacturing method other than the above-mentioned, if the steel plate is within the specified range, the steel plate is considered to be included in the range of the steel plate according to the present disclosure.
  • an example demonstrates in more detail an example of a desirable embodiment in a manufacturing method of a steel plate concerning this indication, and a steel plate.
  • the following example is not a thing of the property which limits the manufacturing method of the steel plate which concerns on this indication, and a steel plate.
  • the steel sheet and the method for producing the steel sheet according to the present disclosure can be modified and implemented as long as they can be applied to the purpose described above or later, and all of them are included in the technical scope of the present disclosure. .
  • Example 1 shows the chemical composition of the steel plate.
  • the dissolved oxygen amount before the addition of the deoxidizing element and the final dissolved oxygen amount of the molten steel after the addition of the deoxidizing element are adjusted so as to obtain the values shown in Table 2;
  • the chemical composition of the molten steel was adjusted so that Next, the prepared molten steel was continuously cast to obtain a billet so as to have the throughput, the reduction gradient, and the reduction amount shown in Table 2.
  • the steel slab was heated under the heating conditions shown in Table 2, and subjected to finish rolling and cooling under the finish rolling conditions and cooling conditions shown in Table 2 to obtain steel plates. And about the temperature shown in Table 2, it tempered about a part of obtained steel plate.
  • the plate thicknesses of the obtained steel plates are shown in Table 3.
  • the number density of the above inclusions (oxide, sulfide, and acid sulfide) was measured according to the method described above.
  • the Mn concentration (Mn (1/4) ) at a 1/4 position from the surface of the steel plate to the cross section along the thickness direction The ratio (Mn (1/2) / Mn (1/4) 2) of the Mn concentration (Mn (1/2) ) at the 1/2 position in the thickness direction was measured according to the method described above.
  • the opening displacement ⁇ c (opening displacement ⁇ c ⁇ 10 ° C. ) at a test temperature of ⁇ 10 ° C. in the crack tip opening displacement test of the weld was measured according to the method described above. The results of measurement of these characteristics are shown in Table 3.
  • ⁇ fraction indicates the area fraction of ferrite phase
  • B fraction indicates the area fraction of bainite phase
  • P fraction indicates the area fraction of pearlite phase
  • MA fraction Represents the area fraction of the martensite / austenite mixed phase, respectively.
  • Average particle size represents the average particle size (diameter) of all phases of the ferrite phase, the bainite phase, the pearlite phase, and the martensite-austenite mixed phase.
  • Numberer of inclusions of 2 ⁇ m or more represents the total number density of oxides, sulfides, and oxysulfides having a circle equivalent diameter (diameter) of 2 ⁇ m or more.
  • T / 2 Mn ⁇ t / 4 Mn is the Mn concentration (Mn (1/2) ) at the plate thickness 1/2 part to the Mn concentration (Mn ( 1/4) ) at the plate thickness 1/4 . It represents the ratio (Mn (1/2) / Mn (1/4) ).
  • the plate thickness is 50 mm-100 mm
  • arresting toughness value K ca-10 ° C. is, it is 6000 N / mm 1.5 or more
  • the opening displacement .delta.c - It is understood that 10 ° C. is 0.10 mm or more.
  • Nos. 1 to 21 have a tensile strength of 510 MPa to 720 MPa and a yield stress of 390 MPa to 650 MPa. That is, Nos. 1 to 21 within the range defined by the steel plate according to the present disclosure have both excellent arrestability and excellent joint CTOD characteristics even with a plate thickness of 50 mm to 100 mm, and have high strength. It turns out that it is a certain steel plate.
  • the joint CTOD characteristics were particularly inferior in all steel plates.
  • No. 22, No. 24 to No. 27, and No. 29 to No. 32 were within the component range defined by the steel plate according to the present disclosure, the microstructure was a structure outside the defined range, and therefore arrested And at least one of the joint CTOD characteristics was inferior.
  • No. 23 and No. 28 were within the component range defined in the steel plate according to the present disclosure, No. 28 is outside the prescribed range of the ferrite phase, and No. 23 is 0% of the area ratio of the bainite phase It is. Therefore, the steel sheet has inferior strength (at least one of tensile strength and yield stress) although it has excellent arrestability and excellent joint CTOD characteristics.
  • the steel plate according to the present disclosure is a steel plate having high strength that has both excellent arrestability and excellent joint CTOD characteristics that can satisfy even more stringent standards. Therefore, according to the steel plate according to the present disclosure, in particular, it can be suitably applied to important members of a container ship (for example, Hatch Side Coating, Upper Deck).

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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Continuous Casting (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

L'invention concerne une tôle d'acier qui présente une composition chimique prédéfinie, qui présente un équivalent en carbone représenté par une formule spécifique compris dans une plage de valeurs prédéfinie, qui présente une structure métallique en une position au 1/4 dans la direction de son épaisseur depuis sa surface (partie 1/4 de l'épaisseur), configurée en proportion surfacique, par １０％ à ７５％ d'une phase de ferrite, １０％ à ９０％ d'une phase de bainite, ０％ à １５％ d'une phase de perlite, et ０％～１％ d'une phase de mélange martensite-austénite, le diamètre particulaire moyen (diamètre) de l'ensemble des phases mesuré par diffraction d'électrons rétrodiffusés étant inférieur ou égal à ２０μｍ. Le total d'oxyde, sulfure et oxysulfure de diamètre de cercle équivalent (diamètre) supérieur ou égal à ２μｍ, compris dans la partie 1/4 de l'épaisseur, est inférieur ou égal à ５０／ｍｍ２. Le rapport （Ｍｎ（１／２）／Ｍｎ（１／４）） de la concentration en Mn （Ｍｎ（１／２）） en une position à 1/2 dans la direction de l'épaisseur de la tôle d'acier depuis sa surface (partie 1/2 de l'épaisseur), vis-à-vis de la concentration en Mn （Ｍｎ（１／４）） au niveau de la partie 1/4 de l'épaisseur, est compris entre ０,９０ et １,８０.
PCT/JP2018/035778 2017-10-03 2018-09-26 Tôle d'acier, et procédé de fabrication de celle-ci Ceased WO2019069771A1 (fr)

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KR20220146638A (ko) 2020-08-31 2022-11-01 닛폰세이테츠 가부시키가이샤 강판 및 그 제조 방법
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002212670A (ja) * 2000-05-09 2002-07-31 Nippon Steel Corp 溶接熱影響部のＣＴＯＤ特性に優れた４６０ＭＰａ以上の降伏強度を有する厚鋼板
JP2006257499A (ja) * 2005-03-17 2006-09-28 Sumitomo Metal Ind Ltd 高張力鋼板、溶接鋼管及びそれらの製造方法
WO2014038200A1 (fr) * 2012-09-06 2014-03-13 Ｊｆｅスチール株式会社 Acier à paroi épaisse, à résistance à la traction élevée, ayant d'excellentes caractéristiques ctod de la zone affectée par la chaleur de soudage et son procédé de fabrication
JP2015098642A (ja) * 2013-11-19 2015-05-28 新日鐵住金株式会社 鋼板

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5445720A (en) 1977-09-17 1979-04-11 Citizen Watch Co Ltd Rotor for pulse motor
JPS5846311A (ja) 1981-09-14 1983-03-17 Olympus Optical Co Ltd 顕微鏡写真撮影レンズ
JP6245352B2 (ja) * 2014-03-31 2017-12-13 Ｊｆｅスチール株式会社 高張力鋼板およびその製造方法
KR101726082B1 (ko) * 2015-12-04 2017-04-12 주식회사 포스코 취성균열전파 저항성 및 용접부 취성균열개시 저항성이 우수한 고강도 강재 및 그 제조방법

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002212670A (ja) * 2000-05-09 2002-07-31 Nippon Steel Corp 溶接熱影響部のＣＴＯＤ特性に優れた４６０ＭＰａ以上の降伏強度を有する厚鋼板
JP2006257499A (ja) * 2005-03-17 2006-09-28 Sumitomo Metal Ind Ltd 高張力鋼板、溶接鋼管及びそれらの製造方法
WO2014038200A1 (fr) * 2012-09-06 2014-03-13 Ｊｆｅスチール株式会社 Acier à paroi épaisse, à résistance à la traction élevée, ayant d'excellentes caractéristiques ctod de la zone affectée par la chaleur de soudage et son procédé de fabrication
JP2015098642A (ja) * 2013-11-19 2015-05-28 新日鐵住金株式会社 鋼板

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