WO2014041802A1 - Tôle d'acier laminée à chaud et procédé pour la fabriquer - Google Patents

Tôle d'acier laminée à chaud et procédé pour la fabriquer Download PDF

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WO2014041802A1
WO2014041802A1 PCT/JP2013/005388 JP2013005388W WO2014041802A1 WO 2014041802 A1 WO2014041802 A1 WO 2014041802A1 JP 2013005388 W JP2013005388 W JP 2013005388W WO 2014041802 A1 WO2014041802 A1 WO 2014041802A1
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cooling
temperature
less
steel sheet
hot
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PCT/JP2013/005388
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English (en)
Japanese (ja)
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力 上
聡太 後藤
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Ｊｆｅスチール株式会社
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Priority to EP13837646.2A priority Critical patent/EP2871254B1/fr
Priority to IN772DEN2015 priority patent/IN2015DN00772A/en
Priority to US14/428,217 priority patent/US20150232970A1/en
Priority to KR1020157007700A priority patent/KR101702794B1/ko
Priority to CN201380047480.0A priority patent/CN104619876B/zh
Priority to JP2014510588A priority patent/JP5605527B2/ja
Priority to BR112015005419-6A priority patent/BR112015005419B1/pt
Publication of WO2014041802A1 publication Critical patent/WO2014041802A1/fr

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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
    • C22C38/58—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
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • 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
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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    • 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
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
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    • 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
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    • 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
    • C21D8/0247—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
    • 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
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1222—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
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1261—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
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    • 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
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
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    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the present invention relates to a low-yield-ratio high-strength hot-rolled steel sheet suitable as a material for spiral steel pipes or ERW steel pipes used for line pipes and a method for producing the same.
  • it relates to ensuring a low yield ratio and excellent low temperature toughness while preventing a decrease in yield strength after pipe making.
  • spiral steel pipes that are formed by spirally winding a steel sheet can be used to efficiently produce large-diameter steel pipes, and in recent years have come to be widely used as line pipes for transporting crude oil and natural gas.
  • pipelines for long-distance transportation are required to have high transportation efficiency and have a high pressure, and there are many oil wells and gas wells in cold regions, and they often pass through cold regions.
  • the line pipe used is required to have high strength and high toughness.
  • the line pipe is required to have a low yield ratio. The yield ratio of the spiral steel pipe in the longitudinal direction of the pipe hardly changes depending on the pipe making, and almost coincides with that of the hot-rolled steel sheet.
  • Patent Document 1 describes a method of manufacturing a hot-rolled steel sheet for a low-yield ratio high-tensile line pipe excellent in low-temperature toughness.
  • the technique described in Patent Document 1 contains, by weight, C: 0.03-0.12%, Si: 0.50% or less, Mn: 1.70% or less, Al: 0.070% or less, and Nb: 0.01-0.05%.
  • V 0.01 to 0.02%
  • Ti 0.01 to 0.20% of a steel slab containing at least one kind is heated to 1180 to 1300 ° C, then rough rolling finish temperature: 950 to 1050 ° C, finish rolling finish temperature : Hot rolled under conditions of 760 to 800 ° C, cooled at a cooling rate of 5 to 20 ° C / s, started air cooling until reaching 670 ° C, held for 5 to 20s, then 20 ° C / It is cooled at a cooling rate of s or higher and wound at a temperature of 500 ° C. or lower to form a hot rolled steel sheet.
  • Patent Document 1 the tensile strength of 60 kg / mm 2 or more (590 MPa or higher) in yield ratio of 85% or less, fracture appearance transition temperature: hot-rolled steel sheet having a -60 ° C. or less of the high toughness It can be manufactured.
  • Patent Document 2 describes a method for producing a hot-rolled steel sheet for a high-strength, low-yield ratio pipe.
  • Patent Document 2 contains C: 0.02 to 0.12%, Si: 0.1 to 1.5%, Mn: 2.0% or less, Al: 0.01 to 0.10%, and Mo + Cr: 0.1 to 1.5%
  • the steel to be heated is heated to 1000-1300 ° C, the hot rolling is finished in the range of 750-950 ° C, cooled to the coiling temperature at a cooling rate of 10-50 ° C / s, and in the range of 480-600 ° C. It is a manufacturing method of the hot-rolled steel plate wound up.
  • Patent Document 2 without quenching from the austenite temperature range, it is mainly composed of ferrite, has a martensite with an area ratio of 1 to 20%, has a yield ratio of 85% or less, In addition, it is said that a hot-rolled steel sheet with a small decrease in yield strength after pipe making can be obtained.
  • Patent Document 3 describes a method for producing a low yield ratio electric resistance welded steel pipe excellent in low temperature toughness.
  • Patent Document 3 includes, in mass%, C: 0.01 to 0.09%, Si: 0.50% or less, Mn: 2.5% or less, Al: 0.01 to 0.10%, Nb: 0.005 to 0.10% In addition, one or more of Mo: 0.5% or less, Cu: 0.5% or less, Ni: 0.5% or less, Cr: 0.5% or less, Mn, Si, P, Cr, Ni, Mo A slab with a composition containing Mneq that satisfies the content relation of 2.0 or more is hot-rolled, cooled to 500 to 650 ° C at a cooling rate of 5 ° C / s or more, and this temperature range.
  • Patent Document 3 it has a structure containing bainitic ferrite as a main phase and containing 3% or more martensite and, if necessary, 1% or more retained austenite, and has a fracture surface transition temperature of It is said that ERW steel pipes with excellent low temperature toughness and high plastic deformation absorption ability can be manufactured at -50 ° C or lower.
  • Patent Document 4 describes a low yield ratio high toughness thick steel plate.
  • JP 63-227715 A Japanese Patent Laid-Open No. 10-176239 JP 2006-299413 JP JP 2010-59472 A
  • the technique described in Patent Document 3 has a problem that it has not yet been able to stably secure excellent low-temperature toughness, which is a recent cold region specification, with a fracture surface transition temperature vTrs of ⁇ 80 ° C. or lower.
  • the thick steel plate obtained by the technique described in Patent Document 4 can only secure a toughness of about ⁇ 30 to ⁇ 41 ° C. at the fracture surface transition temperature vTrs at the latest. There is a problem that can not be dealt with. In recent years, high strength and thick steel pipe materials have been demanded from the requirement of transporting crude oil and the like with high efficiency.
  • the internal cooling rate will be too slow to form the desired inner layer structure. Can not be.
  • the surface hardness can be made uniform, but the maximum hardness of the cross section exceeds 300 points at HV0.5. Due to this increase in hardness, not only the problem of the pipe shape after pipe making, but also the problems of the steel pipe characteristics and the inability to make pipes become obvious.
  • the present invention solves the problems of the prior art, and does not require complex heat treatment, and without extensive modification of equipment, and is suitable for steel pipe materials, particularly for spiral steel pipes.
  • An object of the present invention is to provide a high yield hot-rolled steel sheet having a low yield ratio and excellent in low temperature toughness that can be prevented from lowering.
  • an object is to provide a low yield ratio high strength hot-rolled steel sheet having excellent low-temperature toughness having a thickness of 8 mm or more (more preferably 10 mm or more) and 50 mm or less (more preferably 25 mm or less).
  • high strength refers to the case where the yield strength in the 30-degree direction from the rolling direction is 480 MPa or more and the tensile strength in the sheet width direction is 600 MPa or more, and “excellent in low temperature toughness” When the fracture surface transition temperature vTrs of the Charpy impact test is -80 ° C or less, and “low yield ratio” indicates a continuous yield type stress-strain curve and the yield ratio is 85% or less, Each shall be said.
  • the “steel plate” includes a steel plate and a steel strip.
  • the present inventors diligently studied various factors affecting steel pipe strength after pipe making and steel pipe toughness.
  • the decrease in strength due to pipe making is caused by the decrease in yield strength due to the Bauschinger effect on the inner surface of the tube where compressive stress acts and the disappearance of yield elongation on the outer surface side where tensile stress acts. I found out. Therefore, as a result of further research, the inventors have made a structure in which the structure of the steel sheet has fine bainitic ferrite as a main phase, and hard massive martensite is finely dispersed in the bainitic ferrite.
  • the surface structure of the steel sheet is tempered martensite phase single phase or tempered. It was also found that a mixed phase of martensite and tempered bainite is effective.
  • the present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows.
  • the steel material is, in mass%, C: 0.03-0.10%, Si: 0.01-0.50% , Mn: 1.4 to 2.2%, P: 0.025% or less, S: 0.005% or less, Al: 0.005 to 0.10%, Nb: 0.02 to 0.10%, Ti: 0.001 to 0.030%, Mo: 0.01 to 0.50%, Cr: A steel material having a composition comprising 0.01 to 0.50%, Ni: 0.01 to 0.50%, the balance being Fe and inevitable impurities, and the hot rolling step, heating the steel material to a heating temperature of 1050 to 1300 ° C, The heated steel material is subjected to rough rolling to form a sheet bar, and the sheet bar is subjected to a finish rolling at a temperature range of 930 ° C.
  • the cooling process is started immediately after finishing rolling, and the surface temperature is equal to or lower than the martensite transformation start temperature (Ms point) at an average cooling rate of 100 ° C./s or higher.
  • Ms point martensite transformation start temperature
  • the tertiary cooling that cools to a cooling stop temperature in the temperature range of 600 to 450 ° C at a cooling rate of 30 ° C / s, and the average from the cooling stop temperature of the tertiary cooling to the coiling temperature at the center temperature of the plate thickness And cooling at a cooling rate of 2 ° C./s or less, or quaternary cooling in which the liquid is retained for 20 seconds or more in the temperature range from the cooling stop temperature of the tertiary cooling to the coiling temperature.
  • a method for producing a hot-rolled steel sheet characterized by a step of winding at a surface temperature and a winding temperature: 450 ° C. or higher.
  • a method for producing a hot-rolled steel sheet characterized by having a composition satisfying a Moeq defined in the range of 1.4 to 2.2%.
  • yield strength in the direction of 30 degrees from the rolling direction is 480 MPa or more
  • tensile strength in the plate width direction is 600 MPa or more
  • fracture surface transition temperature vTrs of Charpy impact test is -80 ° C or less
  • yield ratio A low yield ratio high strength hot-rolled steel sheet having an excellent low temperature toughness of 85% or less is obtained.
  • the low yield ratio high-strength hot-rolled steel sheet of this invention can be manufactured easily and cheaply, without performing special heat processing.
  • the present invention has a remarkable industrial effect.
  • a line pipe laid by the reel barge method and an ERW steel pipe for a line pipe that requires earthquake resistance can be easily and inexpensively manufactured.
  • the low-yield ratio high-strength hot-rolled steel sheet according to the present invention is used as a raw material, there is also an effect that a high-strength spiral steel pipe pile serving as a building member and a port member having excellent earthquake resistance can be manufactured.
  • the spiral steel pipe using such a hot-rolled steel sheet has a low yield ratio in the longitudinal direction of the pipe, it has an effect that it can also be applied to high-value-added high-strength steel pipe piles.
  • C 0.03-0.10% C precipitates as a carbide and contributes to an increase in the strength of the steel sheet through precipitation strengthening. It is also an element that contributes to improving the toughness of the steel sheet through grain refinement. Further, C has an action of forming a solid solution in the steel, stabilizing austenite, and promoting the formation of untransformed austenite. In order to obtain these effects, a content of 0.03% or more is required. On the other hand, if the content exceeds 0.10%, the tendency to form coarse cementite at the grain boundaries becomes strong, and the toughness decreases.
  • C is limited to the range of 0.03-0.10%.
  • the content is 0.04 to 0.09%.
  • Si: 0.01-0.50% Si contributes to increasing the strength of the steel sheet through solid solution strengthening. Moreover, it contributes to yield ratio reduction through formation of a hard second phase (for example, martensite). In order to obtain these effects, a content of 0.01% or more is required. On the other hand, if the content exceeds 0.50%, the generation of oxide scale containing firelite becomes remarkable, and the appearance of the steel sheet deteriorates. For this reason, Si was limited to the range of 0.01 to 0.50%. Note that the content is preferably 0.20 to 0.40%.
  • Mn 1.4-2.2% Mn dissolves to improve the hardenability of the steel and promote the formation of martensite. Further, it is an element that lowers the bainitic ferrite transformation start temperature and contributes to improvement of steel sheet toughness through refinement of the structure. In order to obtain these effects, a content of 1.4% or more is required. On the other hand, the content exceeding 2.2% lowers the toughness of the weld heat affected zone. For this reason, Mn was limited to the range of 1.4 to 2.2%. From the viewpoint of stable production of massive martensite, it is preferably 1.6 to 2.0%. P: 0.025% or less P dissolves and contributes to an increase in steel sheet strength, but at the same time lowers toughness.
  • P is reduced as an impurity as much as possible.
  • P is limited to 0.025% or less.
  • P is 0.015% or less. Since excessive reduction raises the refining cost, it is preferable to make it about 0.001% or more.
  • S: 0.005% or less S forms coarse sulfide inclusions such as MnS in the steel and causes cracks such as slabs. Moreover, the ductility of a steel plate is reduced. Such a phenomenon becomes remarkable when the content exceeds 0.005%. For this reason, S was limited to 0.005% or less. In addition, Preferably it is 0.004% or less.
  • Al acts as a deoxidizer. Further, it is an element effective for fixing N that causes strain aging. In order to obtain these effects, a content of 0.005% or more is required. On the other hand, if the content exceeds 0.10%, the amount of oxide in the steel increases and the toughness of the base metal and the bath contact portion decreases. Further, when a steel material such as a slab or a steel plate is heated in a heating furnace, a nitride layer is easily formed on the surface layer, which may increase the yield ratio.
  • Nb 0.02 to 0.10% Nb is a solid solution in steel or precipitated as carbonitride, and suppresses the austenite grain size and suppresses the recrystallization of austenite grains. Is possible. It is also an element that precipitates finely as carbide or carbonitride and contributes to an increase in the strength of the steel sheet.
  • the content is preferably 0.03 to 0.07%.
  • Ti: 0.001 to 0.030% Ti fixes N as nitride and contributes to prevention of slab cracking. Moreover, it has the effect
  • Mo 0.01-0.50% Mo contributes to improving hardenability, attracts C in bainitic ferrite to untransformed austenite, and promotes martensite formation by improving the hardenability of untransformed austenite. Furthermore, it is an element that contributes to an increase in steel sheet strength by solid solution in steel and solid solution strengthening. In order to obtain these effects, a content of 0.01% or more is required. On the other hand, if the content exceeds 0.50%, martensite is formed more than necessary, and the toughness of the steel sheet is lowered. In addition, Mo is an expensive element, and a large amount thereof causes an increase in material cost. For this reason, Mo is limited to the range of 0.01 to 0.50%. Note that the content is preferably 0.10 to 0.40%.
  • Cr 0.01-0.50% Cr delays the ⁇ ⁇ ⁇ transformation, contributes to improving hardenability, and has an action of promoting martensite formation. In order to acquire such an effect, 0.01% or more of content is required. On the other hand, if it exceeds 0.50%, defects tend to occur frequently in the weld. For this reason, Cr is limited to the range of 0.01 to 0.50%. Note that the content is preferably 0.20 to 0.45%.
  • Ni 0.01-0.50% Ni contributes to improving hardenability and promotes martensite formation. In addition, it is an element that further contributes to improved toughness. In order to obtain these effects, a content of 0.01% or more is required.
  • the content is 0.30 to 0.45%.
  • Moeq is an index representing the hardenability of untransformed austenite remaining in the steel sheet after passing through the cooling step.
  • Moeq is less than 1.4%, the hardenability of untransformed austenite is insufficient, and it transforms into pearlite or the like during the subsequent winding process.
  • Moeq exceeds 2.2%, martensite is generated more than necessary, and the toughness decreases.
  • Moeq is preferably limited to a range of 1.4 to 2.2%. If Moeq is 1.5% or more, the yield ratio is low and the deformability is further improved. For this reason, Moeq is more preferably 1.5% or more.
  • One or more selected from Cu: 0.50% or less, V: 0.10% or less, B: 0.0005% or less Cu, V, and B are all elements that contribute to increasing the strength of the steel sheet, and can be selected and contained as necessary.
  • V and Cu contribute to increasing the strength of the steel sheet through solid solution strengthening or precipitation strengthening.
  • B segregates at the grain boundaries and contributes to increasing the strength of the steel sheet through improving hardenability.
  • Ca 0.0005 to 0.0050% Ca is an element that contributes to the control of the morphology of sulfides in which coarse sulfides are spherical sulfides, and can be contained as required.
  • the low yield ratio high strength hot-rolled steel sheet of the present invention has the above-described composition, and further includes a sheet thickness direction surface side layer (hereinafter sometimes simply referred to as a surface layer) and a sheet thickness direction inner surface side layer (hereinafter simply referred to as a surface layer). (Sometimes referred to as the inner layer).
  • a sheet thickness direction surface side layer herein refers to a region having a depth of less than 1.5 mm in the plate thickness direction from the front and back surfaces of the steel sheet.
  • the “thickness direction inner surface side layer (inner layer)” refers to a region having a depth of 1.5 mm or more in the thickness direction inward from the front and back surfaces of the steel plate.
  • the plate thickness direction surface side layer (surface layer) exhibits a tempered martensite phase single phase structure or a mixed structure of a tempered martensite phase and a tempered bainite phase.
  • tissue By setting it as such a structure
  • the hot-rolled steel sheet is subjected to non-uniform cooling history, for example, cooling that passes through the transition boiling region, the hardness increases locally, and hardness unevenness occurs.
  • a problem can be avoided by making the surface layer a tempered martensite phase single phase structure or a mixed structure of a tempered martensite phase and a tempered bainite phase.
  • the mixing ratio of the tempered martensite phase and the tempered bainite phase is not particularly limited, but the tempered martensite phase is 60 to 100% in area ratio and the tempered bainite phase is changed.
  • the area ratio is preferably 0 to 40% from the viewpoint of temper softening treatment.
  • the above structure is 50% or more of the cumulative reduction rate in the temperature range of 930 ° C. or less in finish rolling, and the surface temperature is 100 ° C./s or more at the surface temperature in the cooling step after finish rolling.
  • the tertiary cooling is performed at the temperature at the center of the plate thickness at an average cooling rate of 5 to 30 ° C / s to the cooling stop temperature in the temperature range of 600 to 450 ° C, and further cooling of the tertiary cooling. Cool from the stop temperature to the coiling temperature at the center of the plate thickness at an average cooling rate of 2 ° C / s or stay for 20s or more in the temperature range from the cooling stop temperature to the coiling temperature of the tertiary cooling. Can be obtained by sequentially performing the quaternary cooling. In addition, the tissue and the area ratio can be observed, measured, identified and calculated by the method described in Examples described later.
  • the hardness at a position of 0.5 mm in the thickness direction from the steel sheet surface is 95% or less of the maximum hardness in the thickness direction. That is, it is important from the viewpoint of ensuring the workability of the hot-rolled steel sheet and the pipe shape after pipe forming that the hardness at the position 0.5 mm from the steel sheet surface in the thickness direction does not become the maximum hardness in the thickness direction. is there.
  • the maximum hardness in the plate thickness direction is preferably Vickers hardness HV0.5 and 165 points or more. Moreover, it is preferably 300 points or less, more preferably 280 points or less.
  • the hardness is cooled to a temperature below the martensitic transformation start temperature (Ms point) at an average cooling rate of 100 ° C./s or higher at the surface temperature in the manufacturing conditions, particularly in the cooling step after finishing rolling. It can be obtained by performing primary cooling and secondary cooling that retains at a surface temperature of 600 ° C. or more for 1 s or more after completion of the primary cooling. Moreover, hardness can be measured by the method as described in the Example mentioned later.
  • the thickness direction inner surface side layer is composed of a main phase and a second phase in which a bulk martensite having an aspect ratio of less than 5.0 is dispersed as a second phase with a bainitic ferrite phase as a main phase.
  • the main phase refers to a phase having an occupied area of 50% or more in area ratio.
  • Bainitic ferrite is preferably 85% or more in area ratio, and more preferably 88.3% or more.
  • the main phase bainitic ferrite is a phase having a substructure with a high dislocation density, and includes acicular ferrite and acicular ferrite.
  • the bainitic ferrite does not include polygonal ferrite having a very low dislocation density or quasi (pseudo) polygonal ferrite with a substructure such as fine subgrains. In order to secure a desired high strength, it is necessary that fine carbonitride is precipitated in the bainitic ferrite as the main phase.
  • the bainitic ferrite as the main phase has an average particle size of 10 ⁇ m or less.
  • the average particle size exceeds 10 ⁇ m, the work hardening ability in a low strain region of less than 5% is insufficient, and the yield strength decreases due to bending during spiral pipe making.
  • the second phase in the inner layer is massive martensite with an area ratio of 1.4 to 15% and an aspect ratio of less than 5.0.
  • the massive martensite referred to in the present invention is martensite generated from untransformed austenite in the old ⁇ grain boundary or in the old ⁇ grain in the cooling process after rolling.
  • such massive martensite is dispersed between the old ⁇ grain boundaries or the bainitic ferrite grains as the main phase and the bainitic ferrite grains.
  • Martensite is harder than the main phase, and a large amount of movable dislocations can be introduced into the bainitic ferrite during processing, and the yield behavior can be a continuous yield type.
  • martensite has a higher tensile strength than bainitic ferrite, a low yield ratio can be achieved.
  • the martensite is a massive martensite having an aspect ratio of less than 5.0, more movable dislocations can be introduced into the surrounding bainitic ferrite, which is effective in improving the deformability.
  • the aspect ratio of martensite is 5.0 or more, it becomes rod-shaped martensite (non-aggregated martensite) and the desired low yield ratio cannot be achieved, but if the rod-shaped martensite is less than 30% in terms of the area ratio with respect to the total amount of martensite. acceptable.
  • the bulk martensite is preferably 70% or more in terms of the area ratio of the total amount of martensite.
  • an aspect ratio can be measured by the method as described in the Example mentioned later. In order to ensure such an effect, it is necessary to disperse massive martensite having an area ratio of 1.4% or more. If the bulk martensite is less than 1.4%, it becomes difficult to secure a desired low yield ratio.
  • lump martensite was limited to the range of 1.4 to 15%.
  • Preferably it is 10% or less.
  • a 2nd phase may contain the bainite etc. of about 7.0% or less by area ratio other than a block martensite.
  • the above structure is 50% or more of the cumulative reduction rate in the temperature range of 930 ° C. or less in finish rolling, and the surface temperature is 100 ° C./s or more at the surface temperature in the cooling step after finish rolling.
  • Primary cooling for cooling to a temperature equal to or lower than the martensite transformation start temperature (Ms point) at an average cooling rate, secondary cooling for retaining at a surface temperature of 600 ° C. or more for 1 s or more after completion of the primary cooling, After the completion of the secondary cooling, the tertiary cooling is performed at the temperature at the center of the plate thickness at an average cooling rate of 5 to 30 ° C / s to the cooling stop temperature in the temperature range of 600 to 450 ° C, and further cooling of the tertiary cooling.
  • Ms point martensite transformation start temperature
  • the size of the massive martensite is preferably 5.0 ⁇ m or less at maximum and 0.5 to 3.0 ⁇ m on average. When the bulk martensite size exceeds 3.0 ⁇ m on average, it becomes a starting point of brittle fracture or facilitates the propagation of cracks, and the low temperature toughness decreases.
  • the size of the massive martensite is preferably 5.0 ⁇ m or less at maximum and 0.5 to 3.0 ⁇ m on average. In addition, the size was defined as “diameter” of 1/2 of the sum of the long side length and the short side length.
  • the largest of them was regarded as the “maximum” of the size of the massive martensite, and the value obtained by arithmetically averaging the “diameter” of each obtained grain was designated as the “average” of the size of the massive martensite.
  • the number of martensite to be measured is 100 or more.
  • the above structure is 50% or more of the cumulative reduction rate in the temperature range of 930 ° C. or less in finish rolling, and the surface temperature is 100 ° C./s or more at the surface temperature in the cooling step after finish rolling.
  • the tertiary cooling is performed at the temperature at the center of the plate thickness at an average cooling rate of 5 to 30 ° C / s to the cooling stop temperature in the temperature range of 600 to 450 ° C, and further cooling of the tertiary cooling. Cool from the stop temperature to the coiling temperature at the center of the plate thickness at an average cooling rate of 2 ° C / s or stay for 20s or more in the temperature range from the cooling stop temperature to the coiling temperature of the tertiary cooling. Can be obtained by sequentially performing the quaternary cooling.
  • the preferable manufacturing method of the low yield ratio high-strength hot-rolled steel sheet of this invention is demonstrated.
  • the steel material having the above composition is subjected to a hot rolling process, a cooling process, and a winding process to obtain a hot rolled steel sheet.
  • a steel material such as a slab by a known melting method.
  • the obtained steel material is subjected to a hot rolling process.
  • a steel material having the above composition is heated to a heating temperature of 1050 to 1300 ° C., subjected to rough rolling to form a sheet bar, and the sheet bar is subjected to a cumulative reduction in a temperature range of 930 ° C. or less.
  • Rate It is a process of applying hot rolling to 50% or more to obtain a hot-rolled steel sheet. Heating temperature: 1050-1300 ° C
  • the steel material used in the present invention essentially contains Nb and Ti as described above.
  • the heating temperature of the steel material is 1050 ° C. or higher. If it is less than 1050 degreeC, each element will remain undissolved and desired steel plate strength will not be obtained. On the other hand, when the temperature exceeds 1300 ° C., the crystal grains become coarse and the steel sheet toughness decreases. For this reason, the heating temperature of the steel material was limited to 1050-1300 ° C.
  • the steel material heated to the above heating temperature is subjected to rough rolling to form a sheet bar.
  • the conditions for rough rolling need not be particularly limited as long as a sheet bar having a desired size and shape can be secured.
  • Finish rolling is a rolling with a cumulative reduction ratio of 50% or more in a temperature range of 930 ° C. or lower. Cumulative rolling reduction in the temperature range below 930 ° C: 50% or more 50% cumulative rolling reduction in the temperature range below 930 ° C due to the refinement of bainitic ferrite and fine dispersion of massive martensite in the inner layer structure That's it. If the cumulative rolling reduction in the temperature range of 930 ° C or lower is less than 50%, the rolling amount is insufficient, and fine bainitic ferrite that is the main phase in the inner layer structure cannot be secured.
  • the cumulative rolling reduction in the temperature range of 930 ° C. or lower in finish rolling is limited to 50% or more.
  • the cumulative rolling reduction is preferably 80% or less. Even if the rolling reduction exceeds 80%, the effect is saturated, the occurrence of segregation becomes significant, and the Charpy impact test absorbed energy may be reduced.
  • the finish rolling temperature of finish rolling is preferably 850 to 760 ° C.
  • finishing temperature of finish rolling exceeds 850 ° C and becomes high, it is necessary to increase the reduction amount per pass in order to increase the cumulative reduction rate in the temperature range of 930 ° C or less to 50% or more. There may be an increase in load.
  • the temperature is lower than 760 ° C., ferrite is produced during rolling, which causes coarsening of the structure and precipitates, and may reduce the low temperature toughness and strength.
  • the obtained hot-rolled steel sheet is then subjected to a cooling step.
  • the cooling step starts cooling immediately after finishing rolling, and performs primary cooling to cool to a temperature below the martensitic transformation start temperature (Ms point) at an average cooling rate of 100 ° C./s or more at the surface temperature,
  • Ms point martensitic transformation start temperature
  • the secondary cooling is maintained for 1 s or more at a surface temperature of 600 ° C. or more, and after the completion of the secondary cooling, the temperature at the center of the plate thickness is 600 to 600 ° C. at an average cooling rate of 5 to 30 ° C./s.
  • the cooling rate in the primary cooling means the average of the temperature range of 600 to 450 ° C. at the surface temperature.
  • the upper limit of the average cooling rate of primary cooling is not limited. Depending on the capacity of the cooling device used, it is possible to cool at a higher rate.
  • Ms point martensitic transformation start temperature
  • tissue it is less than 10 second, Preferably it is less than 7 second. If it stays for a long time in the temperature range below Ms point, the area
  • Secondary cooling is followed by primary cooling, but in secondary cooling, it is not particularly cooled, and is retained for 1 s or more at a surface temperature of 600 ° C. or higher by reheating or heating from the inside.
  • the martensite phase and the bainite phase are tempered, and the surface layer structure becomes a tempered martensite phase single phase structure or a mixed structure of the tempered martensite phase and the tempered bainite phase.
  • the steel sheet surface temperature is less than 600 ° C. and the residence time is less than 1 s, the tempering of the surface layer structure becomes insufficient. For this reason, secondary cooling was set as the process which makes 1 s or more stay at the temperature of a steel plate surface temperature of 600 degreeC or more.
  • the method for raising the surface temperature of the steel sheet to a temperature of 600 ° C. or higher includes a method using heat in the thickness direction and a method using an external heating facility, but is not particularly limited.
  • a steel sheet surface layer structure is formed by primary cooling and secondary cooling, followed by tertiary cooling to form a steel sheet inner layer structure having bainitic ferrite as the main phase and massive martensite as the second phase.
  • the cooling rate of the tertiary cooling is an average cooling rate of 750 to 600 ° C., which is the polygonal ferrite formation temperature range, in the center of the plate thickness, and is in the range of 5 to 30 ° C./s.
  • the average cooling rate is less than 5 ° C./s, the structure of the inner layer becomes a structure mainly composed of polygonal ferrite, and it becomes difficult to secure a structure having a desired bainitic ferrite as a main phase.
  • the average cooling rate exceeds 30 ° C./s, the concentration of the alloy elements into untransformed austenite becomes insufficient, and the desired amount of massive martensite cannot be finely dispersed by the subsequent cooling.
  • the cooling rate at the central portion of the plate thickness is limited to 5 to 30 ° C./s, and preferably 5 to 25 ° C./s.
  • the temperature at the center of the plate thickness can be obtained by heat transfer calculation or the like based on the surface temperature of the steel plate, the temperature of the cooling water, the amount of water, and the like.
  • the cooling stop temperature in the tertiary cooling is in the range of 600 to 450 ° C. If the cooling stop temperature is higher than the above-described temperature range, it is difficult to secure a structure of the inner layer whose main phase is desired bainitic ferrite.
  • FIG. 1 schematically shows the cooling in the temperature range from the cooling stop temperature of the tertiary cooling to the winding temperature as the fourth cooling at the plate thickness center temperature.
  • the fourth cooling is slow cooling as shown in FIG.
  • slow cooling is cooling from the cooling stop temperature of the above-mentioned tertiary cooling to the coiling temperature at the sheet thickness center temperature, an average cooling rate of 2 ° C / s or less, preferably 1.5 ° C / s or less?
  • the cooling is to be retained for 20 seconds or more in the temperature range from the cooling stop temperature of the above-described tertiary cooling to the coiling temperature.
  • the untransformed ⁇ remains between the bainitic ferrites, resulting in a rod-like shape, making it difficult to produce the desired massive martensite.
  • the hot rolled steel sheet is subjected to a winding process.
  • the winding process is a winding process at a surface temperature and a winding temperature of 450 ° C. or higher. If the coiling temperature is less than 450 ° C., the desired low yield ratio cannot be realized. For this reason, the coiling temperature was limited to 450 ° C. or higher. By setting it as the above-mentioned process, it can be made to retain for a predetermined time or more in the temperature range in which ferrite and austenite coexist.
  • a hot-rolled steel sheet manufactured by the above-described manufacturing method is used as a pipe-forming material, and is subjected to a normal pipe-making process to be a spiral steel pipe or an electric-welded steel pipe.
  • the pipe making process is not particularly limited, and any ordinary process can be applied.
  • the present invention will be described in more detail based on examples.
  • the molten steel having the composition shown in Table 1 was made into a slab (thickness: 220 mm) by a continuous casting method to obtain a steel material. Next, these steel materials are heated to the heating temperature shown in Table 2 and subjected to rough rolling to form a sheet bar, and then the sheet bar is subjected to finish rolling under the conditions shown in Table 2 to obtain a hot-rolled steel sheet (sheet thickness: A hot rolling process of 8 to 25 mm) was performed. Immediately after finishing rolling, the obtained hot-rolled steel sheet was subjected to a cooling process including primary cooling to quaternary cooling shown in Table 2. After the cooling step, a winding step of winding at a winding temperature shown in Table 2 and then allowing to cool was performed.
  • a test piece was collected and subjected to a structure observation, a tensile test, an impact test, and a hardness test.
  • the test method is as follows. (1) Microstructure observation From the obtained hot-rolled steel sheet, a microstructural specimen was taken so that the cross section in the rolling direction (L cross section) became the observation surface. The test piece was polished and subjected to Nital corrosion, and the structure was observed and imaged using an optical microscope (magnification: 500 times) or an electron microscope (magnification: 2000 times). The type of tissue, the tissue fraction (area ratio) of each phase, and the average particle diameter were measured from the obtained inner layer structure photograph using an image analyzer.
  • the average particle size of bainitic ferrite which is the main phase in the inner layer structure, was determined by a cutting method in accordance with JISG 0552.
  • the aspect ratio of the martensite grain is the ratio of the length in the longitudinal direction of each grain, that is, the direction in which the grain size is maximum (long side) and the length in the direction perpendicular to the length (short side), (long side). / (Short side). Martensite grains having an aspect ratio of less than 5.0 are defined as massive martensite. Martensite having an aspect ratio of 5.0 or more is referred to as “bar-shaped” martensite.
  • the size of the massive martensite is 1/2 the sum of the long side length and the short side length of each grain of the massive martensite, and the diameter of each obtained grain is arithmetically averaged.
  • the average size of martensite was used.
  • the largest value among the diameter of each grain of massive martensite was made into the maximum of the magnitude
  • the measured martensite grains were 100 or more.
  • Full thickness test pieces (width 38.1 mm; GL 50 mm) were collected and subjected to a tensile test in accordance with ASTM A 370 regulations to determine tensile properties (yield strength YS, tensile strength TS).
  • (3) Impact test V-notch test specimens were taken from the obtained hot-rolled steel sheet so that the longitudinal direction of the test specimen was perpendicular to the rolling direction, and the Charby impact test was conducted in accordance with ASTM 370 regulations.
  • the fracture surface transition temperature vTrs (° C.) was obtained.
  • a spiral steel pipe (outer diameter: 1067 mm ⁇ ) was manufactured by a spiral pipe making process using the obtained hot-rolled steel sheet as a pipe material.
  • From the obtained steel pipe take a tensile test piece (test piece specified in API) so that the tensile direction is the pipe circumferential direction, conduct a tensile test in accordance with the provisions of ASTMA 370, and obtain tensile properties (yield).
  • the yield strength in the direction of 30 degrees from the rolling direction was 480 MPa or more
  • the tensile strength in the sheet width direction was 600 MPa or more
  • the fracture surface transition temperature vTrs was ⁇ It has excellent toughness of 80 ° C or less and a low yield ratio high strength high toughness hot rolled steel sheet with a yield ratio of 85% or less.
  • a hot-rolled steel sheet having the desired characteristics has not been obtained depending on whether the toughness is reduced or the low yield ratio is not ensured.
  • the steel sheet is suitable as a material for spiral steel pipes or ERW steel pipes.

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Abstract

L'invention concerne une tôle d'acier laminée à chaud ayant un rapport de rendement faible et une résistance élevée, qui a une excellente résistance aux basses températures et qui peut être employé en tant que matière première de tube d'acier. La présente invention a une composition comprenant 0,03-0,10% de C, 0,01-0,50% de Si, 1,4 -2,2% de Mn, pas plus de 0,025% de P, pas plus de 0,005% de S, 0,005-0,10% d'Al, 0,02-0,10% de Nb, 0,001-0,030% de Ti, 0,01-0,50% de Mo, 0,01-0,50% de Cr et 0,01-0,50% de Ni, Moeq se trouvant de préférence sur une plage de 1,4-2,2%, et les couches internes ayant une structure qui comprend du ferrite bainitique de granulométrie moyenne inférieure ou égale à 10 µm, comme phase principale et de la martensite massive ayant un rapport de surface de 1,4-15% et un facteur de forme inférieur à 5,0 en tant que seconde phase, la couche de surface comprenant une phase de martensite trempée ou une phase de martensite trempée et une phase de bainite trempée.
PCT/JP2013/005388 2012-09-13 2013-09-11 Tôle d'acier laminée à chaud et procédé pour la fabriquer WO2014041802A1 (fr)

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US14/428,217 US20150232970A1 (en) 2012-09-13 2013-09-11 Hot-rolled steel sheet and method for manufacturing the same
KR1020157007700A KR101702794B1 (ko) 2012-09-13 2013-09-11 열연 강판 및 그 제조 방법
CN201380047480.0A CN104619876B (zh) 2012-09-13 2013-09-11 热轧钢板及其制造方法
JP2014510588A JP5605527B2 (ja) 2012-09-13 2013-09-11 熱延鋼板およびその製造方法
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JP2018127646A (ja) * 2017-02-06 2018-08-16 Ｊｆｅスチール株式会社 高強度熱延鋼板およびその製造方法
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JP2022513269A (ja) * 2018-12-19 2022-02-07 ポスコ 脆性破壊抵抗性に優れた構造用鋼材及びその製造方法

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KR101830437B1 (ko) * 2016-04-25 2018-02-20 현대자동차주식회사 3층 구조를 갖는 고인성 열처리 강관 및 이의 제조방법
MX2019009803A (es) * 2017-02-17 2019-11-11 Jfe Steel Corp Lamina de acero laminada en caliente de alta resistencia y metodo para producir la misma.
US20200071801A1 (en) * 2017-04-28 2020-03-05 Nippon Steel Corporation High strength steel sheet and method of producing same
KR101999015B1 (ko) 2017-12-24 2019-07-10 주식회사 포스코 취성균열 전파 저항성이 우수한 구조용 강재 및 그 제조방법
JP7147960B2 (ja) * 2019-11-27 2022-10-05 Ｊｆｅスチール株式会社 鋼板およびその製造方法
WO2021123877A1 (fr) * 2019-12-17 2021-06-24 Arcelormittal Tôle d'acier laminée à chaud et son procédé de fabrication
CN113574199B (zh) * 2019-12-18 2022-11-29 Posco公司 热轧钢板及其制造方法
CN114107612B (zh) * 2021-11-30 2023-04-18 马鞍山钢铁股份有限公司 H型钢回火热处理设计方法、抗震耐火建筑结构用热轧h型钢及其回火热处理方法
WO2023162522A1 (fr) * 2022-02-24 2023-08-31 Ｊｆｅスチール株式会社 Tôle en acier, et procédé de fabrication de celle-ci

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CN111566249B (zh) * 2017-12-24 2022-05-13 株式会社Posco 高强度钢板及其制造方法
JP7096337B2 (ja) 2017-12-24 2022-07-05 ポスコ 高強度鋼板及びその製造方法
JP2022513269A (ja) * 2018-12-19 2022-02-07 ポスコ 脆性破壊抵抗性に優れた構造用鋼材及びその製造方法
JP7348947B2 (ja) 2018-12-19 2023-09-21 ポスコ カンパニー リミテッド 脆性破壊抵抗性に優れた構造用鋼材及びその製造方法
JP6690787B1 (ja) * 2019-03-29 2020-04-28 Ｊｆｅスチール株式会社 電縫鋼管およびその製造方法、並びに鋼管杭
WO2020202333A1 (fr) * 2019-03-29 2020-10-08 Ｊｆｅスチール株式会社 Tube d'acier soudé par résistance électrique ainsi que procédé de fabrication de celui-ci, et pieu tubulaire en acier

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IN2015DN00772A (fr) 2015-07-03
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KR101702794B1 (ko) 2017-02-03
KR20150038747A (ko) 2015-04-08
EP2871254B1 (fr) 2020-06-24
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JPWO2014041802A1 (ja) 2016-08-12
US20150232970A1 (en) 2015-08-20

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