WO2011099408A1 - Procédé de production de tôles d'acier épaisses - Google Patents

Procédé de production de tôles d'acier épaisses Download PDF

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Publication number
WO2011099408A1
WO2011099408A1 PCT/JP2011/052188 JP2011052188W WO2011099408A1 WO 2011099408 A1 WO2011099408 A1 WO 2011099408A1 JP 2011052188 W JP2011052188 W JP 2011052188W WO 2011099408 A1 WO2011099408 A1 WO 2011099408A1
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Prior art keywords
rolling
temperature
cooling
passes
steel plate
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PCT/JP2011/052188
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English (en)
Japanese (ja)
Inventor
清孝 中島
学 星野
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新日本製鐵株式会社
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Application filed by 新日本製鐵株式会社 filed Critical 新日本製鐵株式会社
Priority to CN201180005020.2A priority Critical patent/CN102666885B/zh
Priority to JP2011523636A priority patent/JP4874434B1/ja
Priority to BR112012020436-0A priority patent/BR112012020436B1/pt
Publication of WO2011099408A1 publication Critical patent/WO2011099408A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • 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
    • C21D9/42—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for armour plate
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • 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
    • C21D2211/005—Ferrite
    • 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 method for producing a thick steel plate, and more particularly to a method for producing a thick steel plate for welded structure having high rolling productivity and excellent strength, elongation, and toughness.
  • Thick steel plates used for shipbuilding, construction, tanks, offshore structures, line pipes and other welded structures are required to have strength, elongation and toughness.
  • yield stress is 315 MPa to 550 MPa
  • plate thickness is 10 mm to 40 mm.
  • strength, elongation, and toughness are in a reciprocal relationship, and elongation and toughness decrease as the strength is increased.
  • Patent Document 1 describes a steel plate excellent in the arrestability of a brittle crack having a thickness of 40 mm or more.
  • Patent Document 2 describes a steel plate excellent in workability and a method for manufacturing the same, which defines the Vickers hardness in the steel plate.
  • the time between passes from the completion of the final five passes in finish rolling to the start before the final four passes is 30 seconds or more, and the time between each pass from the last four passes to the final pass is 15 seconds or less.
  • a method of manufacturing a steel material with little material variation is described.
  • Patent Document 4 rolling conditions are set so as to satisfy a predetermined relationship between rolling temperature and rolling reduction in each rolling pass, and the effect of refinement of recrystallized ⁇ grains and non-recrystallized rolling can be fully enjoyed.
  • a method for producing a steel sheet having a finer final structure and having excellent strength and toughness is described.
  • tandem rolling is performed within 5 seconds between passes by using two rolling mills, the recrystallization is promoted, and the cumulative reduction ratio in the non-recrystallized region is set to 70% or more.
  • a method for producing a steel sheet having excellent toughness is described.
  • Patent Documents 1 to 5 have the following problems.
  • the manufacturing method described in Patent Document 1 requires low-temperature rolling (CR) where the plate thickness is thick.
  • CR low-temperature rolling
  • the crystal grains can be made finer, and the low temperature toughness is improved.
  • low-temperature rolling after the high-temperature rolling is finished, a time for waiting for the temperature to decrease is generated, so that the rolling productivity is lowered.
  • the manufacturing method described in Patent Document 2 has low productivity because low temperature rolling is essential.
  • the target steel sheet is a high-strength steel having a yield stress of 600 MPa or more, the yield stress is 315 MPa to 550 MPa, and the thickness is 10 mm to 40 mm. Not applicable.
  • the time between passes was set to 30 seconds or longer as in the manufacturing method described in Patent Document 3, as a result of the study by the present inventors, it was found that the recrystallized ⁇ was coarsened.
  • the manufacturing method described in Patent Document 4 since the rolling temperature is controlled by the surface temperature, the material variation is large, and the time until recrystallization is not specified, so it is difficult to obtain finer recrystallized ⁇ grains. .
  • tandem rolling using two rolling mills is not practical because of great restrictions on facilities.
  • the present invention improves the low productivity due to the necessity of low temperature rolling, and can be applied to a thick steel plate having a yield stress of 315 MPa to 550 MPa and a plate thickness of 10 mm to 40 mm. It is an object of the present invention to provide a method for producing a thick steel plate for welded structure that does not require special equipment, has small material variations, and is excellent in strength, elongation, and toughness. Specifically, the structure can be refined only by high-temperature rolling without performing low-temperature rolling.Furthermore, by applying accelerated cooling in which the cooling rate is changed stepwise, the ferrite is secured while the second phase is secured. It is an object of the present invention to provide a method for producing a thick steel plate that can be hardened.
  • the present inventors diligently studied a method for producing a thick steel plate. As a result, even when rolling at a high temperature of about 850 to 950 ° C., called the ⁇ recrystallization temperature range, the production conditions that can refine the structure by utilizing the refining by ⁇ recrystallization have been found and rolled production A thick steel plate manufacturing method that achieves both high temperature and low temperature toughness has been realized.
  • the reduction ratio per pass is determined in the conventional manufacturing method after the hot rolling (hereinafter also referred to as “rear rolling”.
  • the former stage of hot rolling is also referred to as “previous rolling” hereinafter).
  • the time between passes is optimized in comparison with. When the rolling reduction per pass is increased, the number of passes is reduced, so that productivity is increased.
  • the rolling reaction force is increased, so that the reduction rate is suppressed to less than 10%.
  • the reduction rate is set to 10 to 25% and the time between passes is set to 3 to 25 seconds. It has been found that it is possible to refine the structure by utilizing the refinement by. Further, the accelerated cooling after rolling is divided into two stages with different cooling rates, the cooling rate in the first half cooling (hereinafter also referred to as “pre-stage cooling”) is slow, and the latter half cooling (hereinafter also referred to as “second stage cooling”).
  • the present invention has been made on the basis of the above-mentioned findings and further considered the component composition of steel excellent in productivity, strength, elongation, and toughness, and the gist thereof is as follows.
  • a pre-stage cooling is performed from 750 ° C. or more at a sheet thickness center temperature of 630 to 700 ° C.
  • the plate thickness is 10 to 40 mm
  • the yield stress is 315 to 550 MPa
  • the microstructure is a soft phase ferrite, hard phase pearlite, bainite, martensite, or a mixture of two or more types
  • the center of the thickness A thick steel plate having a ferrite area ratio of 70 to 95%, an average Vickers hardness of the hard phase of 250 to 500, and an average crystal grain size of 5 to 20 ⁇ m Method.
  • the method for producing a thick steel plate for welded structure according to the present invention has a short temperature waiting time because no low temperature rolling is performed, and has a large rolling reduction, so that the number of passes is small and the rolling productivity is high.
  • the refinement by recrystallization of ⁇ is utilized to refine the structure by high-temperature rolling in the ⁇ recrystallization temperature range, and further, accelerated cooling after rolling is performed at the first stage with slow cooling. Further, as a two-stage cooling in which the subsequent stage is rapidly cooled, a thick steel plate for welded structure excellent in strength, elongation, and toughness can be produced by hardening the second phase while securing ferrite.
  • molten steel adjusted to a desired component composition is melted by a known melting method using a converter or the like, and is made into a steel slab by a known casting method such as continuous casting.
  • a known casting method such as continuous casting.
  • the steel slab is heated to a temperature of 1000 to 1200 ° C.
  • the heating temperature of the steel slab is less than 1000 ° C., solutionization becomes insufficient.
  • the heating temperature exceeds 1200 ° C., the austenite grains become coarse, and it becomes difficult to refine in the subsequent rolling process, and furthermore, there is a time to wait for the temperature to drop before the start of high temperature rolling. Low.
  • a preferable heating temperature range is 1050 to 1150 ° C.
  • the first stage of hot rolling (first stage rolling) is performed at a sheet thickness center temperature of 950 to 1200 ° C., a cumulative reduction ratio of 50 to 95%, and the number of passes of 4 to 16.
  • the plate thickness center temperature exceeds 1200 ° C.
  • the recrystallized ⁇ grains cannot be made fine.
  • the productivity is lowered.
  • a preferred thickness center temperature is 1000 to 1150 ° C.
  • the cumulative rolling reduction is less than 50%, recrystallization does not proceed sufficiently and the recrystallized ⁇ grains cannot be made fine.
  • the cumulative rolling reduction exceeds 95%, the rolling load increases and productivity decreases.
  • a preferred cumulative rolling reduction is 60% to 90%. If the number of passes is less than 4, the recrystallized ⁇ grains cannot be made fine. When the number of passes exceeds 16, productivity decreases. A preferred number of passes is 5-14. Subsequently, a subsequent hot rolling (second-stage rolling) is performed at a sheet thickness center temperature of 850 to 950 ° C., a reduction ratio of 10 to 25% per pass, a time between passes of 3 to 25 seconds, and a pass number of 2 to 8 passes. When the plate thickness center temperature exceeds 950 ° C., the recrystallized ⁇ grains cannot be made fine. When the plate thickness center temperature is less than 850 ° C., the productivity is lowered. A preferred thickness center temperature is 870 to 930 ° C.
  • the rolling reduction per pass is less than 10%, the number of passes increases, so the productivity decreases. If the rolling reduction per pass exceeds 25%, the burden on the rolling mill becomes very large, which is difficult to realize.
  • a preferable rolling reduction per pass is 13 to 22%.
  • the time between passes is an important factor. When the rolling reduction per pass is in the range of 10 to 25% and the time between passes is less than 3 seconds, the process proceeds to the next pass within the incubation period required for nucleation of recrystallization or during the initial stage of recrystallization. Therefore, recrystallization does not proceed sufficiently.
  • the time between passes exceeds 25 seconds, the primary recrystallization is completed and the secondary recrystallization using the grain boundary energy as a driving force is started before proceeding to the next pass, so that the recrystallized ⁇ grains become coarse. . That is, if the time between passes is not in the range of 3 to 25 seconds, the refinement of the structure in high temperature rolling, which is the subject of the present invention, cannot be achieved. A preferred time between passes is 5 to 23 seconds. When the number of passes is less than 2, the recrystallized ⁇ grains cannot be made fine. When the number of passes exceeds 8, the productivity is lowered. A preferred number of passes is 3-7.
  • the former stage cooling is performed at a cooling rate of 0.5 to 8 ° C./s from a center thickness of 750 ° C. or more until the center thickness reaches a range of 630 to 700 ° C. Then, the latter stage cooling is performed to a temperature of 550 ° C. or less at a cooling rate of 10 to 50 ° C./s.
  • the plate thickness center temperature at the start of cooling is less than 750 ° C., the ferrite transformation proceeds, and it is difficult to obtain a ferrite fine grain structure.
  • the cooling rate in the pre-stage cooling is less than 0.5 ° C./s, a fine structure cannot be obtained, and when the cooling rate exceeds 8 ° C./s, a ferrite area ratio of 70% or more cannot be obtained.
  • the cooling rate in the latter stage cooling is less than 10 ° C./s, the hardness of the hard phase does not become 250 or more in average Vickers hardness, and when it exceeds 50 ° C./s, the hardness of the hard phase becomes 500 or less in average Vickers hardness. do not become.
  • the cooling stop temperature exceeds 550 ° C., the hardness of the hard phase does not exceed 250 in terms of average Vickers hardness.
  • the preferred accelerated cooling conditions are a plate thickness center temperature of 770 ° C.
  • the cooling stop temperature is 500 ° C. or lower.
  • the temperature distribution inside the steel sheet is calculated while measuring the surface temperature of the steel sheet from heating to rolling, and the rolling control is performed while predicting the rolling reaction force from the calculation result of the temperature distribution. It is carried out.
  • the steel plate center temperature can be easily obtained during rolling.
  • the accelerated cooling is controlled while predicting the temperature distribution inside the plate thickness.
  • tempering may be performed at 300 to 650 ° C. as necessary. When tempering at less than 300 ° C., the effect of tempering is difficult to obtain. When the tempering temperature exceeds 650 ° C., the amount of softening increases and it becomes difficult to ensure the strength.
  • a preferable tempering temperature is 400 to 600 ° C.
  • the production method of the present invention is applicable to the production of a steel plate having a plate thickness of 10 to 40 mm and a yield stress of 315 to 550 MPa.
  • the present invention is applicable to the production of yield stress 315 MPa class, 355 MPa class, or 390 MPa class steel sheets for hull structures.
  • Accelerated cooling cannot be applied to a steel plate having a thickness of less than 10 mm because the plate shape deteriorates.
  • low temperature rolling is essential in order to ensure toughness, and thus it is impossible to achieve both productivity.
  • accelerated cooling is not necessary, and therefore it is not necessary to apply the present invention.
  • the component composition of the thick steel plate to which the production method of the present invention is applied is as follows in consideration of strength, elongation, toughness, weld heat affected zone (HAZ) toughness, weldability, and the like.
  • C is added by 0.04% or more in order to ensure the strength and toughness of the base material. If the C content exceeds 0.16%, it becomes difficult to ensure good HAZ toughness, so the C content is set to 0.16% or less. In order to ensure the strength of the base material, the lower limit of the C content may be limited to 0.06% or 0.08%. In order to improve HAZ toughness, the upper limit of the C content may be limited to 0.15% or 0.14%.
  • Si is effective as a deoxidizing element and a strengthening element, 0.01% or more is added. If the Si content exceeds 0.5%, the HAZ toughness is greatly deteriorated, so the Si addition amount is 0.5% or less. In order to ensure deoxidation, the lower limit of the Si content may be limited to 0.05% or 0.10%. In order to improve HAZ toughness, the upper limit of the Si content may be limited to 0.40% or 0.34%. Mn is added in an amount of 0.2% or more in order to ensure the strength and toughness of the base material. If the Mn content exceeds 2.5%, the center segregation becomes prominent, and the toughness of the base material and the HAZ where the center segregation has occurred deteriorates, so the Mn content is 2.5% or less.
  • the lower limit of the Mn content may be limited to 0.6% or 0.8%.
  • the upper limit of the Mn content may be limited to 2.0%, 1.8%, or 1.6%.
  • P is an impurity element.
  • the P content In order to ensure the HAZ toughness stably, it is necessary to reduce the P content to 0.03% or less. In order to improve the HAZ toughness, the P content may be 0.02% or less or 0.015% or less.
  • S is an impurity element. In order to stably ensure the characteristics of the base material and the HAZ toughness, the S content needs to be reduced to 0.02% or less.
  • the S content may be 0.01% or less or 0.008% or less.
  • Al is an element necessary for deoxidation and reducing O which is an impurity element.
  • Mn and Si also contribute to deoxidation.
  • the Al content is less than 0.001%, O cannot be stably reduced.
  • the Al content exceeds 0.10%, alumina-based coarse oxides and clusters thereof are formed, and the base material and the HAZ toughness are impaired. Therefore, the Al content is 0.10% or less. .
  • the lower limit of the Al content may be 0.01% or 0.015%.
  • the upper limit of the Al content may be 0.08% or 0.06%.
  • Nb contributes to the improvement of the strength and toughness of the base material by adding 0.003% or more. However, if the Nb content exceeds 0.02%, the HAZ toughness and weldability deteriorate, so the Nb content is set to 0.02% or less. In order to further exhibit the effect of refining by Nb, the lower limit of the Nb content may be 0.005%. In order to improve HAZ toughness and weldability, the upper limit of the Nb content may be 0.015% or 0.012%. When Ti is added, TiN is formed and suppresses an increase in the austenite grain size when the steel slab is heated.
  • the crystal grain size after transformation also increases and the toughness decreases.
  • the Ti content exceeds 0.05%, TiC is formed and the HAZ toughness decreases, so the Ti content is set to 0.05% or less.
  • the upper limit of the Ti content may be 0.03% or 0.02%.
  • N forms TiN and suppresses an increase in the austenite grain size when the steel slab is heated, so 0.001% or more is added. If the N content exceeds 0.008%, the steel material becomes brittle, so the N content is set to 0.008% or less.
  • optional elements that can be added as needed include Cu: 0.03-1.5%, Ni: 0.03-2.0%, Cr: 0% by mass. 0.03 to 1.5%, Mo: 0.01 to 1.0%, V: 0.03 to 0.2%, B: 0.0002 to 0.005% May be.
  • the strength and toughness of the base material can be improved.
  • upper limit of Cu content is 1.0%, 0.5% or 0.3%
  • upper limit of Ni content is 1.0%, 0.5% or 0.3%
  • the upper limit of the Cr content is 1.0%, 0.5%, or 0.3%
  • the upper limit of the Mo content is 0.3%, 0.2%, or 0.1%.
  • the upper limit of the amount may be limited to 0.1%, 0.07% or 0.05%, and the upper limit of the B content may be limited to 0.003%, 0.002 or 0.001%. If the content of these elements is too large, the HAZ toughness and weldability deteriorate, so the upper limit of the content is specified as described above. Furthermore, as other selective elements, one or two of mass%, Ca: 0.0005 to 0.01%, Mg: 0.0005 to 0.01%, REM: 0.0005 to 0.01% You may contain the above. By adding these elements, the HAZ toughness is improved. These selective elements can be intentionally added to improve the strength and toughness of the base material. However, it is not necessary to add any of these selective elements in order to reduce alloy costs.
  • the steel plate produced by the method for producing a thick steel plate for welded structure of the present invention has a carbon equivalent calculated by the above formula (A) of 0.2 to 0.5%.
  • the carbon equivalent is obtained by substituting its content. If the carbon equivalent is less than 0.2%, the strength required for the steel sheet produced by the production method of the present invention cannot be satisfied. If the carbon equivalent exceeds 0.5%, the elongation, toughness, and weldability required for the steel sheet produced by the production method of the present invention cannot be satisfied. In order to ensure strength, the lower limit of the carbon equivalent may be limited to 0.25%, 0.28%, or 0.30%. In order to improve HAZ toughness and weldability, the lower limit of the carbon equivalent may be limited to 0.43%, 0.4%, or 0.38%.
  • the microstructure of the steel sheet produced by the method for producing a thick steel sheet for welded structure of the present invention is a mixed structure of soft phase ferrite, hard phase pearlite, bainite, and martensite.
  • the ferrite area ratio in the central portion of the thickness of the steel sheet produced by the method for producing a steel sheet for welded structure of the present invention is 70 to 95%
  • the Vickers hardness of the hard phase is 250 to 500 on average
  • the particle size is 5 to 20 ⁇ m.
  • the component composition of the molten steel was adjusted in the steel making process, and then a steel slab was produced by continuous casting. Next, this steel slab was reheated and further subjected to thick plate rolling to obtain a thick steel plate having a thickness of 10 to 40 mm. Subsequently, the thick steel plate was cooled with water. Test No. In the case of 25 steel plates, air cooling was performed instead of water cooling (comparative example). Thereafter, heat treatment was performed as necessary to produce a thick steel plate having a yield strength of 315 MPa to 550 MPa. Tables 1 and 2 show the composition of each thick steel plate. The underline in Table 1 indicates that the content is outside the scope of the present invention.
  • the brackets in Table 2 indicate the analytical value of the amount contained as an inevitable impurity.
  • the microstructure phase fraction was defined as the average value of the area ratios of the respective phases with respect to the entire visual field region obtained by imaging the microstructure at a plate thickness center position at a magnification of 500 times with an optical microscope.
  • the average crystal grain size is determined by measuring an area of 500 ⁇ m ⁇ 500 ⁇ m at a pitch of 1 ⁇ m by an EBSP (Electron Back Scattering Pattern) method, and defining a boundary where the crystal orientation difference from adjacent grains is 15 ° or more as a grain boundary. The average value of the crystal grain size was taken.
  • the Vickers hardness was measured in accordance with JIS Z 2244 (2009), the hard phase was measured at 20 points with a test load of 10 gf, and the average value was obtained.
  • the yield stress and elongation were the total thickness, and the Charpy fracture surface transition temperature (vTrs) was tested using a test specimen taken from the center of the plate thickness, and the results were used as representative values for each steel plate.
  • the tensile test was carried out in accordance with “Metal Material Tensile Test Method” of JIS Z 2241 (1998), and two of them were tested and measured, and the average value was obtained.
  • the tensile test piece was a JIS Z 2201 (1998) No. 1B test piece.
  • the Charpy fracture surface transition temperature (vTrs) is based on JIS Z 2242 (2005) “Charpy impact test method for metal materials” using 2 mm V notch Charpy impact test specimens, and 3 each for 5 temperatures each. The temperature at the time of 50% brittle fracture surface ratio was measured. These measurement results of each thick steel plate are shown in Tables 3 to 8 together with the production method.
  • the temperature and cooling rate in the manufacturing method are values at the center position of the plate thickness, and were obtained from the measured surface temperature by heat conduction analysis using a known differential method. In this example, the total elongation of 20% or more, the fracture surface transition temperature of ⁇ 60 ° C. or less, and the rolling time of 200 s or less were defined as good.
  • Reference numeral 13 is an example of the present invention that satisfies all the conditions of the present invention, and is good in strength, elongation, toughness, and productivity.
  • Test NO. 14 ⁇ NO. 37 is a comparative example in which the underlined condition is out of the scope of the present invention.
  • Test NO. No. 14 had a large number of rolling passes in the former stage and the latter stage, and the end temperature of the latter stage rolling was low, so the rolling time was long and the productivity was low.
  • Test NO. Nos. 23, 31, and 32 have a long inter-pass rolling time, so that the ferrite area ratio is small, the average crystal grain size is large, the hardness, the elongation, and the toughness are low. No. 32 had a long rolling time and low productivity.
  • the end temperature of the pre-stage cooling was low, so the hardness and strength of the hard phase were low.
  • Test NO. In No. 37 the end temperature of the pre-cooling was high, so the ferrite area ratio was small, the average crystal grain size was large, and the hardness, elongation, and toughness of the hard phase were low. From the above examples, according to the production method of the present invention, the refinement by recrystallization of ⁇ is utilized, the structure is refined by high-temperature rolling in the ⁇ recrystallization temperature region, and accelerated cooling after rolling is further performed.
  • the method for producing a thick steel plate according to the present invention has a low temperature waiting time because there is no low-temperature rolling process, and has a large rolling reduction, so that the number of passes is small and rolling productivity is high.
  • the present invention by utilizing the refinement by recrystallization of ⁇ , the structure is refined even in high temperature rolling in the ⁇ recrystallization temperature range.
  • As the second stage cooling by securing the ferrite and hardening the second phase, it is possible to provide a method for manufacturing a steel plate for welded structure with excellent strength, elongation, and toughness. It can be applied to the production of thick steel plates used for welded structures such as marine structures and line pipes, and has great industrial applicability.

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

Abstract

L'invention divulgue un procédé de production de tôles d'acier épaisses, comprenant les étapes suivantes : une pièce d'acier qui présente une composition de composant spécifique est chauffée entre 1000 °C et 1200 °C ; ensuite, alors que la température au centre de l'épaisseur de la tôle est comprise entre 950 °C et 1200 °C, un laminage initial est exécuté pendant 4 à 16 passes à un taux de réduction de laminage cumulé qui est compris entre 50 % et 95 % ; après quoi, alors que la température au centre de l'épaisseur de la tôle est comprise entre 850 °C et 950 °C, un laminage subséquent est exécuté pendant 2 à 8 passes, chaque passe étant réalisée à un taux de réduction de laminage qui est compris entre 10 % et 25 %, la durée des passes étant comprise entre 3 secondes et 25 secondes ; ensuite, il est procédé à un refroidissement initial au cours duquel la température au centre de l'épaisseur de la tôle est abaissée à partir de 750 °C, ou plus, jusqu'à une température comprise entre 630 °C et 700 °C à une vitesse de refroidissement comprise entre 0,5 °C/s et 8 °C/s ; et enfin il est procédé à un refroidissement subséquent au cours duquel la température est abaissée à 550 °C, ou moins, à une vitesse de refroidissement comprise entre 10 °C/s et 50 °C/s. La tôle d'acier épaisse produite est caractérisée en ce qu'elle présente une épaisseur de tôle qui est comprise entre 10 mm et 40 mm, et une limite d'élasticité comprise entre 315 MPa et 550 MPa, en ce qu'elle présente une microstructure qui est une structure mixte composée d'un ou de plusieurs des composants suivants : une ferrite en phase douce, une perlite en phase dure, une bainite et une martensite, et en ce qu'elle présente un rapport de surface de ferrite dans la partie centrale de la tôle d'acier qui est compris entre 70 % et 95 %, une dureté Vickers moyenne de la phase dure comprise entre 250 et 500, et un diamètre moyen de particule cristalline compris entre 5 µm et 20 μm.
PCT/JP2011/052188 2010-02-15 2011-01-27 Procédé de production de tôles d'acier épaisses WO2011099408A1 (fr)

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CN201180005020.2A CN102666885B (zh) 2010-02-15 2011-01-27 厚钢板的制造方法
JP2011523636A JP4874434B1 (ja) 2010-02-15 2011-01-27 厚鋼板の製造方法
BR112012020436-0A BR112012020436B1 (pt) 2010-02-15 2011-01-27 Método de produção de chapa de aço.

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JP2013177649A (ja) * 2012-02-28 2013-09-09 Nippon Steel & Sumitomo Metal Corp 低降伏比厚鋼板及びその製造方法
JP2013245360A (ja) * 2012-05-23 2013-12-09 Nippon Steel & Sumitomo Metal Corp Ｌｐｇタンク用鋼板
JP2014031546A (ja) * 2012-08-03 2014-02-20 Jfe Steel Corp 非調質低降伏比高張力厚鋼板およびその製造方法
WO2014132627A1 (fr) * 2013-02-28 2014-09-04 Ｊｆｅスチール株式会社 Tôle d'acier forte et procédé de production de tôle d'acier forte
WO2015075771A1 (fr) * 2013-11-19 2015-05-28 新日鐵住金株式会社 Tôle d'acier
EP2752499A4 (fr) * 2011-08-23 2015-07-15 Nippon Steel & Sumitomo Metal Corp Tube d'acier soudé par résistance électrique à paroi épaisse et procédé de fabrication de ce dernier
EP2813596A4 (fr) * 2011-02-15 2015-08-05 Jfe Steel Corp Tôle d'acier à haute résistance à la traction possédant une excellente ténacité à basse température dans des zones affectées thermiquement par la soudure, et son procédé de production
WO2015194619A1 (fr) * 2014-06-20 2015-12-23 株式会社神戸製鋼所 Plaque d'acier à haute résistance et procédé de production de cette dernière
EP2878695A4 (fr) * 2012-07-26 2015-12-30 Jfe Steel Corp Acier se prêtant à un traitement par nitrocarburation, pièce nitrocabrurée, et procédés de production dudit acier prêtant à un traitement par nitrocarburation et de ladite pièce nitrocabrurée
EP3018229A1 (fr) * 2013-07-04 2016-05-11 Nippon Steel & Sumitomo Metal Corporation Tube d'acier sans soudure pour un tube de canalisation utilisé dans un environnement acide
WO2017077967A1 (fr) * 2015-11-06 2017-05-11 株式会社神戸製鋼所 Élément en acier et tôle d'acier, et leurs procédés de production
EP3205443A1 (fr) * 2016-02-09 2017-08-16 Siemens Aktiengesellschaft Procede de fabrication d'une roue dentee, roue dentee et compresseur
JP2018104757A (ja) * 2016-12-26 2018-07-05 新日鐵住金株式会社 ラインパイプ用鋼材及びその製造方法
JP2021507099A (ja) * 2017-12-15 2021-02-22 ポスコＰｏｓｃｏ 引張強度及び低温衝撃靭性に優れた圧力容器用鋼板及びその製造方法
JP2023506255A (ja) * 2019-12-16 2023-02-15 ポスコホールディングス インコーポレーティッド 延性に優れた高強度鋼材及びその製造方法

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JP2003129134A (ja) * 2001-10-18 2003-05-08 Nippon Steel Corp 低温靱性に優れた高強度鋼板の製造方法
JP2004143500A (ja) * 2002-10-23 2004-05-20 Nippon Steel Corp 耐座屈特性に優れた高強度鋼管およびその製造方法
JP2004269924A (ja) * 2003-03-06 2004-09-30 Nippon Steel Corp 強度・靭性に優れた鋼板の高効率製造方法
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US9790579B2 (en) 2011-02-15 2017-10-17 Jfe Steel Corporation High tensile strength steel plate having excellent weld heat-affected zone low-temperature toughness and method for producing same
EP2813596A4 (fr) * 2011-02-15 2015-08-05 Jfe Steel Corp Tôle d'acier à haute résistance à la traction possédant une excellente ténacité à basse température dans des zones affectées thermiquement par la soudure, et son procédé de production
EP2752499A4 (fr) * 2011-08-23 2015-07-15 Nippon Steel & Sumitomo Metal Corp Tube d'acier soudé par résistance électrique à paroi épaisse et procédé de fabrication de ce dernier
WO2013100106A1 (fr) * 2011-12-28 2013-07-04 新日鐵住金株式会社 Tuyau d'acier de haute résistance possédant une excellente ductilité et une ténacité à basse température, feuille d'acier de haute résistance, et procédé pour la production de feuille d'acier
JP2013177649A (ja) * 2012-02-28 2013-09-09 Nippon Steel & Sumitomo Metal Corp 低降伏比厚鋼板及びその製造方法
JP2013245360A (ja) * 2012-05-23 2013-12-09 Nippon Steel & Sumitomo Metal Corp Ｌｐｇタンク用鋼板
EP2878695A4 (fr) * 2012-07-26 2015-12-30 Jfe Steel Corp Acier se prêtant à un traitement par nitrocarburation, pièce nitrocabrurée, et procédés de production dudit acier prêtant à un traitement par nitrocarburation et de ladite pièce nitrocabrurée
US10125416B2 (en) 2012-07-26 2018-11-13 Jfe Steel Corporation Steel for nitrocarburizing and nitrocarburized component, and methods for producing said steel for nitrocarburizing and said nitrocarburized component
JP2014031546A (ja) * 2012-08-03 2014-02-20 Jfe Steel Corp 非調質低降伏比高張力厚鋼板およびその製造方法
JP5910792B2 (ja) * 2013-02-28 2016-04-27 Ｊｆｅスチール株式会社 厚鋼板及び厚鋼板の製造方法
US10041159B2 (en) 2013-02-28 2018-08-07 Jfe Steel Corporation Thick steel plate and production method for thick steel plate
EP2963138A4 (fr) * 2013-02-28 2016-03-23 Jfe Steel Corp Tôle d'acier forte et procédé de production de tôle d'acier forte
WO2014132627A1 (fr) * 2013-02-28 2014-09-04 Ｊｆｅスチール株式会社 Tôle d'acier forte et procédé de production de tôle d'acier forte
EP3018229A4 (fr) * 2013-07-04 2017-03-29 Nippon Steel & Sumitomo Metal Corporation Tube d'acier sans soudure pour un tube de canalisation utilisé dans un environnement acide
EP3018229A1 (fr) * 2013-07-04 2016-05-11 Nippon Steel & Sumitomo Metal Corporation Tube d'acier sans soudure pour un tube de canalisation utilisé dans un environnement acide
WO2015075771A1 (fr) * 2013-11-19 2015-05-28 新日鐵住金株式会社 Tôle d'acier
WO2015194619A1 (fr) * 2014-06-20 2015-12-23 株式会社神戸製鋼所 Plaque d'acier à haute résistance et procédé de production de cette dernière
JP2016008308A (ja) * 2014-06-20 2016-01-18 株式会社神戸製鋼所 高強度鋼板およびその製造方法
WO2017077967A1 (fr) * 2015-11-06 2017-05-11 株式会社神戸製鋼所 Élément en acier et tôle d'acier, et leurs procédés de production
JP2017088938A (ja) * 2015-11-06 2017-05-25 株式会社神戸製鋼所 鋼部材および鋼板ならびにこれらの製造方法
EP3205443A1 (fr) * 2016-02-09 2017-08-16 Siemens Aktiengesellschaft Procede de fabrication d'une roue dentee, roue dentee et compresseur
WO2017137209A1 (fr) * 2016-02-09 2017-08-17 Siemens Aktiengesellschaft Procédé de fabrication d'une roue dentée, roue dentée, compresseur à engrenage
JP2018104757A (ja) * 2016-12-26 2018-07-05 新日鐵住金株式会社 ラインパイプ用鋼材及びその製造方法
JP2021507099A (ja) * 2017-12-15 2021-02-22 ポスコＰｏｓｃｏ 引張強度及び低温衝撃靭性に優れた圧力容器用鋼板及びその製造方法
JP7161536B2 (ja) 2017-12-15 2022-10-26 ポスコ 引張強度及び低温衝撃靭性に優れた圧力容器用鋼板及びその製造方法
JP2023506255A (ja) * 2019-12-16 2023-02-15 ポスコホールディングス インコーポレーティッド 延性に優れた高強度鋼材及びその製造方法
JP7465351B2 (ja) 2019-12-16 2024-04-10 ポスコホールディングス インコーポレーティッド 延性に優れた高強度鋼板及びその製造方法

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BR112012020436B1 (pt) 2019-04-30
CN102666885A (zh) 2012-09-12

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