US20150147222A1 - Ni-containing steel plate - Google Patents

Ni-containing steel plate Download PDF

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US20150147222A1
US20150147222A1 US14/406,405 US201314406405A US2015147222A1 US 20150147222 A1 US20150147222 A1 US 20150147222A1 US 201314406405 A US201314406405 A US 201314406405A US 2015147222 A1 US2015147222 A1 US 2015147222A1
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steel plate
temperature
toughness
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Shinichi Miura
Yukio Shimbo
Nobuyuki Ishikawa
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JFE Steel Corp
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JFE Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • 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
    • C22C38/002—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
    • C22C38/02—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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

Definitions

  • the present invention relates to an Ni-containing steel plate with excellent low-temperature toughness, in particular to a steel plate which is suitable for use as members such as storage tanks for liquefied natural gas.
  • Ni steel considerations on various properties such as mechanical properties and weldability have been made.
  • Steel and Iron by Furukimi Osamu, Suzuki Shigeharu, Nakano Yashifumi, 69(1982)5, S492 (NPL 1) discloses that low-temperature toughness is improved by reducing the amount of impurity elements such as P and S.
  • NPL 2 discloses that low-temperature toughness is improved by stabilizing retained austenite.
  • Ni is an expensive metal, it is desired to reduce Ni content.
  • PTL 1 discloses that mechanical properties of a steel plate can be improved by predetermining the chemical composition of the steel plate, defining the amount, aspect ratio, and average equivalent circular diameter of austenite contained in the steel plate, and manufacturing the steel plate with a method to satisfy such definitions.
  • PTL 2 discloses that toughness of the heat-affected zone of a steel plate can be improved when the steel plate has a predetermined chemical composition and the Fe content obtained by an extraction residue method after a heat-cycle simulation test is more than a predetermined value.
  • PTL 3 discloses that a brittle crack-arrest property of steel can be improved when the steel has a predetermined chemical composition, with certain textures developed.
  • NPL 1 Steel and iron by Furukimi Osamu, Suzuki Shigeharu, Nakano Yoshifumi, 69(1982)5, S492
  • NPL 2 Handbook of Metal, 4 th revised edition, edited by The Japan Institute of Metals and Materials, Maruzen, p 800-802
  • the present invention has been developed in view of such situation, and an object thereof is to provide an Ni-containing steel plate which is low in cost and has excellent low-temperature toughness.
  • the inventors of the present invention as a result of intense investigation for providing an Ni-containing steel plate with excellent low-temperature toughness, discovered, that by containing C, Si, Mn, P, S, Al, and Ni as essential elements of a steel, and setting the amount of retained austenite contained in the steel after performing sub-zero treatment were cooling is performed until reaching liquid nitrogen temperature to be less than 1.7%, and setting the average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more to 5 ⁇ m or less by equivalent circle diameter, excellent low-temperature toughness can be achieved even when the Ni content is reduced compared to conventional 9% Ni steel.
  • Ni content in steel is reduced to be smaller than that of 9% Ni Steel, even if retained austenite is stable at room temperature, it will be unstable at ⁇ 165° C. where LNG tanks are used. Further, it is considered that toughness decreases when retained austenite exists at ⁇ 165° C., because the retained austenite is transformed into martensite phase due to deformation induced transformation, at the tip of a crack formed in the steel material when the LNG tank fractures. Under the situation, by reducing the amount of retained austenite remaining after sub-zero treatment corresponding to ⁇ 165° C. where LNG tanks are used, and forming a fine microstructure as described above, it is assumed that low-temperature toughness can be improved even if the Ni content in steel is reduced to be smaller than that of conventional 9% Ni steel.
  • the present invention is based on the above discoveries and it provides the following (1) to (4).
  • An Ni-containing steel plate having, a chemical composition containing by mass % C: 0.01% to 0.15%, Si: 0.02% to 0.20%, Mn: 0.45% to 2.00%, P: 0.020% or less, S: 0.005% or less, Al: 0.005% to 0.100%, Ni: 5.0% to 8.0%, and the balance being Fe and incidental impurities, wherein
  • the steel plate has a microstructure containing less than 1.7% by volume fraction of retained austenite when cooled to liquid nitrogen temperature, and having an average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more of 5 ⁇ m or less by equivalent circle diameter.
  • Ni-containing steel plate according to any one of aspects (1) to (3), wherein the chemical composition further contains by mass % at least one element selected from Ca: 0.0050% or less and REM: 0.0050% or less.
  • an Ni-containing steel plate containing less Ni content compared to 9% Ni steel but having low-temperature toughness equivalent to that of 9% Ni steel can be easily manufactured, and an industrially remarkable effect is provided.
  • Ni-containing steel plate according to the present invention will be explained in detail and separately based on chemical composition, microstructure, and manufacturing method.
  • C is an important element for solid solution strengthening of steel. If C content is less than 0.01%, sufficient strength cannot be obtained. On the other hand, adding C in an amount exceeding 0.15% would cause deterioration of weldability and workability. Therefore, C content is set to be in the range of 0.01% to 0.15%. Preferably, the range is from 0.03% to 0.10%.
  • Si is an effective element as a deoxidizer in molten steel and an effective element for solid solution strengthening. If Si content is less than 0.02%, deoxidizing effect cannot be sufficiently obtained. On the other hand, adding Si in an amount exceeding 0.20% would cause problems such as reduction in ductility and toughness, and an increase of inclusions. Therefore, Si content is set to be in the range of 0.02% to 0.20% and preferably in the range of 0.03% to 0.10%.
  • Mn is an effective element from the viewpoint of ensuring quench hardenability and enhancing strength. If Mn content is less than 0.45%, the effect thereof cannot be sufficiently obtained. On the other hand, adding Mn in an amount exceeding 2.00% would cause deterioration of weldability. Therefore, Mn content is set to be in the range of 0.45% to 2.00%, and preferably in the range of 0.55% to 1.00%.
  • the upper limit of P content is set to be 0.020%.
  • High S content in steel causes precipitation as MnS, and this, as an inclusion, becomes the fracture generation origin of high tensile strength steel and leads to deterioration of toughness.
  • the upper limit of S content is set to be 0.005%.
  • Al is an effective element as a deoxidizer in molten steel and an effective element for improving low-temperature toughness. If Al content is less than 0.005%, these effects cannot be sufficiently obtained. On the other hand, if the content thereof exceeds 0.100%, weldability will decrease. Therefore, Al content is set to be in the range of 0.005% to 0.100%, and preferably in the range of 0.020% to 0.050%.
  • Ni is an important element for the present invention, and it is an element that enhances quench hardenability and improves toughness of ferrite matrix. If Ni content is less than 5.0%, these effects cannot be sufficiently exhibited. On the other hand, if the content thereof exceeds 8.0%, costs will increase. Therefore, Ni content is set to be in a range of 5.0% to 8.0%. In addition, from the viewpoint of further reducing costs, it is desirable for Ni content to be in the range of 5.0% to 7.5%.
  • Cr enhances quench hardenability and provides an effect of improving low-temperature toughness by refining martensite phase.
  • the content thereof exceeds 1.00%, it would cause deterioration of weldability and an increase in manufacturing costs. Therefore, when containing Cr, the content thereof is set to be in the range of 1.00% or less. In order to effectively exhibit the above effect, it is preferable for the Cr content to be 0.05% or more, and more preferably in the range of 0.10% to 0.75%.
  • Mo enhances quench hardenability and provides an effect of improving low-temperature toughness by refining martensite phase.
  • the content thereof exceeds 1.000%, it would cause deterioration of weldability and an increase in manufacturing costs. Therefore, when containing Mo, the content thereof is set to be in the range of 1.000% or less. In order to effectively exhibit the above effects, it is preferable for the content thereof to be 0.005% or more, and more preferably in the range of 0.010% to 0.500%.
  • Cu is an element that enhances quench hardenability. However, if the content thereof exceeds 1.00%, it would cause reduction of hot workability and an increase in costs. Therefore, when containing Cu, the content thereof is set to be in the range of 1.00% or less. In order to effectively exhibit the above effect, it is preferable for the content thereof to be 0.05% or more.
  • V is an element that precipitates as carbonitride, has an effect of refining microstructures, and is useful for improving toughness. However, if the content thereof exceeds 0.100% it would cause deterioration of weldability. Therefore, when containing V, the content thereof is set to be in the range of 0.100% or less. In order to effectively exhibit the above effects, it is preferable for the content thereof to be 0.005% or more.
  • Nb is an element that precipitates as carbonitride, has an effect of refining microstructures, and is useful for improving toughness. However, if the content thereof exceeds 0.100%, it would cause deterioration of weldability. Therefore, when containing Nb, the content thereof is set to he in the range of 0.100% or less. In order to effectively exhibit the above effects, it is preferable for the content thereof to be 0.005% or more.
  • Ti has an effect of improving toughness by fixing solute N, which is harmful to toughness, as TiN.
  • the content thereof exceeds 0.100%, it would cause precipitation of a coarse carbonitride, and deteriorate toughness. Therefore, when containing Ti, the content thereof is set to be in the range of 0.100% or less. In order to effectively exhibit the above effect, it is preferable for the content thereof to be 0.005% or more, and more preferably in the range of 0.010% to 0.050%.
  • B is an element that enhances quench hardenability when added to steel by a small amount. However, if the content thereof exceeds 0.0030%, it would cause deterioration of toughness. Therefore, when containing B, the content thereof is set to be in the range of 0.0030% or less. In order to effectively exhibit the above effect, it is preferable for the content thereof to be 0.0003% or more.
  • Ca is an element that fixes S and inhibits generation of MnS which becomes the cause of reduction in toughness.
  • the content thereof exceeds 0.0050%, it would cause an increase in the amount of inclusions existing in steel and lead to deterioration of toughness rather than providing the above effect. Therefore, when containing Ca, the content thereof is set to be in the range of 0.0050% or less. In order to effectively exhibit the above effect, it is preferable for the content thereof to be 0.0005% or more.
  • REM Radar Earth Metal
  • the balance other than the components described above includes Fe and incidental impurities.
  • the Ni-containing steel plate of the present invention has the above chemical composition, and also has a microstructure containing less than 1.7% of retained austenite when cooled to liquid nitrogen temperature, and having an average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more of 5 ⁇ m or less by equivalent circle diameter.
  • the microstructure at ⁇ 165° C. where LNG tanks are used is important. Therefore, the microstructure after sub-zero treatment where the steel plate is held at liquid nitrogen temperature, is defined. If the amount of retained austenite remaining after sub-zero treatment is 1.7% or more by volume fraction, sufficient low-temperature toughness cannot be obtained. Some reports have been made that retained austenite improves low temperature toughness. However, for the Ni-containing steel plate of the present invention, retained austenite has a harmful effect on toughness.
  • the Ni content is smaller than the Ni content in conventional 9% Ni steel, even if retained austenite exists at ⁇ 165° C., it is unstable, and if the steel structure undergoes plastic deformation at the tip of a crack, the retained austenite transforms into martensite by plasticity-induced martensite phase transformation. Therefore, the amount of retained austenite when the steel plate is cooled to liquid nitrogen temperature is set to be less than 1.7% by volume fraction. This amount is preferably 1.0% or less, and more preferably 0.5% or less.
  • the average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more exceeds 5 ⁇ m by equivalent circle diameter, sufficient low-temperature toughness cannot be obtained. Therefore, the average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more is set to be 5 ⁇ m or less by equivalent circle diameter, and preferably 3 ⁇ m or less by equivalent circle diameter.
  • manufacturing condition for manufacturing the steel plate of the present invention having the above described chemical composition and the above microstructure will be described.
  • the following manufacturing condition is merely an example of a condition for manufacturing the Ni-containing steel plate of the present invention, and as long as the Ni-containing steel plate of the present invention can be obtained, manufacturing condition for the present invention is not limited to the following manufacturing condition.
  • a slab or a steel billet having the above described chemical composition at a temperature range of 900° C. to 1100° C. for 10 hours or less, and then to subject it to hot rolling at a temperature range of 870° C. or lower so that the cumulative rolling reduction ratio is 40% or more and 70% or less and the finisher delivery temperature is between 700° C. and 820° C., and then to subject the obtained hot rolled steel plate to direct quenching treatment where quenching is immediately performed until reaching a temperature of 200° C. or lower at a cooling rate of 5° C./s or more, and then to heat the steel plate to a temperature range of 500° C. to 650° C. at a heating rate of 0.05° C./s to 1.0° C./s, and then to subject the steel plate to tempering by holding the temperature at the same temperature range for 10 minutes or more and 60 minutes or less.
  • Heating Temperature 900° C. to 1100° C., Heating duration: 10 hours or less
  • the heating temperature is lower than 900° C.
  • coarse AlN which precipitates during the stage of casting of the steel slab does not dissolve, and toughness decreases. Further, the following rolling conditions cannot be substantially satisfied. If the heating temperature exceeds 1100° C, austenite becomes coarse grains and toughness will decrease. If the heating duration exceeds 10 hours, austenite grains become coarse and toughness decreases. Therefore, the heating temperature is set to be between 900° C. and 1100° C., and the heating duration is 10 hours or less.
  • Rolling Reduction Ratio Cumulative Rolling Reduction Ratio of 40% or more and 70% or less at 870° C. or lower
  • the rolling reduction ratio in the non-recrystallized region of austenite at 870° C. or lower is less than 40%, refinement of martensite phase will not be sufficient, and toughness decreases.
  • the rolling reduction ratio is set to be 40% or more and 70% or less at 870° C. or lower.
  • Finisher delivery temperature 700° C. to 820° C.
  • finisher delivery temperature is lower than 700° C., it results in ⁇ - ⁇ dual phase rolling so that bainite phase forms, and therefore a desired strength cannot be satisfied.
  • finisher delivery temperature exceeds 820° C., it becomes substantially difficult to perform sufficient rolling reduction in the non-recrystallized region of austenite, a fine microstructure cannot be obtained, and toughness decreases. Therefore, the finisher delivery temperature is set to be in the range of 700° C. to 820° C.
  • Cooling direct quenching is started immediately after rolling is finished. If cooling is not immediately started, bainite phase will generate, and. therefore a desired strength cannot be satisfied. Therefore, cooling is started immediately after rolling is finished.
  • “immediately” refers to a point in time within 120 seconds after the completion of rolling.
  • Cooling Rate 5° C./s or more
  • the cooling rate is set to be 5° C./s or more.
  • the cooling rate is 10° C./s or more.
  • Cooling Stop Temperature 200° C. or lower
  • the cooling stop temperature is set to be 200° C. or lower.
  • Tempering Heating Rate 0.05° C./s to 1.0° C./s
  • the tempering heating rate is set to be in the range of 0.05° C./s to 1.0° C./s.
  • Tempering temperature 500° C. to 650° C.
  • the tempering temperature is set to be in the range of 500° C. to 650° C.
  • Tempering Holding Time 10 minutes or more and 60 minutes or less
  • the tempering holding time is set to be 10 minutes or more and 60 minutes or less. Cooling, after tempering may be performed by either water cooling or air cooling. However, if the cooling rate is too fast, the temperature difference between the surface and the inside of the steel plate becomes large and causes formation of strains inside the steel plate and low temperature toughness decreases. Therefore, the cooling rate is preferably 5° C./s or less.
  • the dual phase heat treatment heating rate is set to be in the range of 0.1° C./s to 1.5° C./s.
  • the dual phase heat treatment temperature is lower than 650° C.
  • sufficient austenite reverse transformation does not occur, and refining effect of the microstructure cannot be obtained, and therefore a toughness improving effect cannot be obtained.
  • the amount of austenite reverse transformation is small, C easily concentrates in austenite, and retained austenite increases.
  • the dual phase heat treatment temperature exceeds 800° C.
  • reverse transformation austenite becomes coarse and toughness decreases.
  • the microstructure after cooling becomes coarse, toughness decreases. Further, manufacturing costs increase. Therefore, the dual phase heat treatment temperature is set to be in the range of 650° C. to 800° C.
  • the dual phase heat treatment temperature is preferably in the range of 720° C. to 780° C.
  • Dual Phase Heat Treatment Holding Time 10 minutes or more and 60 minutes or less
  • the dual phase heat treatment holding time is less than 10 minutes, sufficient austenite reverse transformation does not occur and toughness improving effect caused by refinement of the microstructure cannot be sufficiently obtained.
  • the dual phase heat treatment holding time exceeds 60 minutes, austenite grains become coarse and toughness decreases. Further, since the microstructure generated after cooling also becomes coarse, toughness decreases. Since C concentrates in austenite, retained austenite increases. Manufacturing costs increase as well. Therefore, the dual phase heat treatment holding time is set to be 10 minutes or more and 60 minutes or less.
  • Cooling Rate after Dual Phase Heat Treatment 5° C./s or more
  • the cooling rate is set to be 5° C./s or more.
  • the cooling rate is 10° C./s or more.
  • Cooling Stop Temperature after Dual Phase Heat Treatment 200° C. or lower
  • the cooling stop temperature exceeds 200° C.
  • transformation to martensite phase will not occur uniformly in the steel plate, and a desirable strength and toughness cannot be obtained. Further, C concentrates in austenite and tends to remain as retained austenite. Therefore, the cooling stop temperature is set to be 200° C. or lower.
  • tempering is conducted in the manner previously described. That is, the steel is heated to a temperature range of 500° C. to 650° C. at a heating rate of 0.05° C./s to 1.0° C./s, and then subjected to tempering by holding the temperature at the same temperature range for 10 minutes or more and 60 minutes or less.
  • Molten steels with the chemical compositions shown in table I were obtained by steelmaking in a vacuum melting, furnace and made into small-sized steel ingots (150 kg). These steels were heated in the conditions shown in table 2, subjected to hot rolling until reaching a plate thickness of 7 mm to 50 mm, and then subjected to quenching just after the rolling. Some of the steel plates were then subjected to tempering treatment. Regarding the rest of the steel plates, after quenching, they were subjected to dual phase heat treatment and then to tempering treatment.
  • TS tensile strength
  • YS yield strength
  • V-notch test specimens were collected in accordance with JIS Z2202 (1998) standard, and subjected to a Charpy impact test with 3 specimens per each temperature for each steel plate in accordance with JIS Z2242 (1998) standard, and absorbed energy at ⁇ 196° C. was measured to evaluate base material toughness.
  • Steel plates with an average value of absorbed energy (vE. 196 ) of 3 specimens of 150 J or more are considered as having excellent base material toughness.

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  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
US14/406,405 2012-07-23 2013-07-18 Ni-containing steel plate Abandoned US20150147222A1 (en)

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JP2012-162335 2012-07-23
JP2012162335A JP5594329B2 (ja) 2012-07-23 2012-07-23 低温靱性に優れたＮｉ含有厚鋼板
PCT/JP2013/004399 WO2014017057A1 (ja) 2012-07-23 2013-07-18 Ni含有厚鋼板

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US20210332465A1 (en) * 2020-04-27 2021-10-28 Questek Innovations Llc Auto-tempering steels for additive manufacturing
JP2022505860A (ja) * 2018-10-26 2022-01-14 ポスコ 極低温靭性及び延性に優れた圧力容器用鋼板及びその製造方法
US11279993B2 (en) * 2018-12-27 2022-03-22 Nippon Steel Corporation Nickel-containing steel plate
US11434557B2 (en) 2017-11-17 2022-09-06 Posco Low-temperature steel plate having excellent impact toughness, and method for manufacturing same
US11608549B2 (en) 2017-11-17 2023-03-21 Posco Co., Ltd Cryogenic steel plate and method for manufacturing same

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CN103864585B (zh) * 2014-03-19 2015-11-25 中国科学技术大学 一种制备3,4,5-三甲氧基甲苯的方法
JP6196929B2 (ja) 2014-04-08 2017-09-13 株式会社神戸製鋼所 極低温でのｈａｚ靱性に優れた厚鋼板
WO2019037749A1 (zh) * 2017-08-23 2019-02-28 宝山钢铁股份有限公司 一种低温压力容器用钢及其制造方法
EP3674426B1 (en) * 2017-08-25 2022-04-20 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Method for production of ni-containing steel plate
US20220154303A1 (en) * 2019-03-13 2022-05-19 Jfe Steel Corporation Steel plate and method for manufacturing the same
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
KR102200225B1 (ko) * 2019-09-03 2021-01-07 주식회사 포스코 극저온 횡팽창이 우수한 압력용기용 강판 및 그 제조 방법
US20230203631A1 (en) * 2020-04-15 2023-06-29 Nippon Steel Corporation Steel material
WO2022118592A1 (ja) * 2020-12-03 2022-06-09 Ｊｆｅスチール株式会社 鋼板
JP7078203B1 (ja) * 2020-12-03 2022-05-31 Ｊｆｅスチール株式会社 鋼板
KR102427046B1 (ko) * 2020-12-10 2022-07-28 주식회사 포스코 극저온 인성이 우수한 압력용기용 강판 및 이의 제조방법

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Publication number Priority date Publication date Assignee Title
US11434557B2 (en) 2017-11-17 2022-09-06 Posco Low-temperature steel plate having excellent impact toughness, and method for manufacturing same
US11608549B2 (en) 2017-11-17 2023-03-21 Posco Co., Ltd Cryogenic steel plate and method for manufacturing same
JP2022505860A (ja) * 2018-10-26 2022-01-14 ポスコ 極低温靭性及び延性に優れた圧力容器用鋼板及びその製造方法
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US11279993B2 (en) * 2018-12-27 2022-03-22 Nippon Steel Corporation Nickel-containing steel plate
US20210332465A1 (en) * 2020-04-27 2021-10-28 Questek Innovations Llc Auto-tempering steels for additive manufacturing
EP3903971A1 (en) * 2020-04-27 2021-11-03 Questek Innovations LLC Auto-tempering steels for additive manufacturing
US11780014B2 (en) * 2020-04-27 2023-10-10 Questek Innovations Llc Auto-tempering steels for additive manufacturing

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KR101702480B1 (ko) 2017-02-03
WO2014017057A1 (ja) 2014-01-30
JP5594329B2 (ja) 2014-09-24
EP2876179B1 (en) 2017-10-11
WO2014017057A8 (ja) 2014-12-11
KR20150023724A (ko) 2015-03-05
CN104487602A (zh) 2015-04-01
EP2876179A4 (en) 2016-02-17
CN104487602B (zh) 2016-09-28
EP2876179A1 (en) 2015-05-27
JP2014019936A (ja) 2014-02-03
IN2014DN10853A (zh) 2015-09-11

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