WO2021170104A1 - Eh 550 mpa grade quenched and tempered marine steel plate for high heat input welding and manufacturing method therefor - Google Patents

Eh 550 mpa grade quenched and tempered marine steel plate for high heat input welding and manufacturing method therefor Download PDF

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WO2021170104A1
WO2021170104A1 PCT/CN2021/078224 CN2021078224W WO2021170104A1 WO 2021170104 A1 WO2021170104 A1 WO 2021170104A1 CN 2021078224 W CN2021078224 W CN 2021078224W WO 2021170104 A1 WO2021170104 A1 WO 2021170104A1
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tempered
quenched
heat input
steel plate
steel sheet
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PCT/CN2021/078224
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French (fr)
Chinese (zh)
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王睿之
蒋晓放
王毓男
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宝山钢铁股份有限公司
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Priority to KR1020227030534A priority Critical patent/KR20220134014A/en
Publication of WO2021170104A1 publication Critical patent/WO2021170104A1/en

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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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
    • C21D8/0215—Rapid solidification; Thin strip casting
    • 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
    • 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
    • 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
    • C22C38/04—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—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
    • C22C38/50—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
    • C21D2211/008—Martensite

Definitions

  • the invention belongs to the field of marine engineering steel, and particularly relates to a large heat input welding EH550MPa grade quenched and tempered marine steel plate and a manufacturing method thereof.
  • the width of the welding heat-affected zone is generally only a few millimeters, the severe decrease in toughness of the coarse-grained zone of the heat-affected zone is likely to become the source of cracks, leaving hidden dangers for the safe use of offshore platforms.
  • Chinese patent CN 106191659 A discloses "a steel plate for marine engineering that can be welded with high heat input and its manufacturing method", and successfully developed a marine steel that can be welded with high heat input.
  • the deoxidation process in the smelting process is simple, and Ferrosilicon and metal manganese are the main components, no strong deoxidizer is added, and the impact energy at -60°C is greater than 90J after the welding thermal simulation of 100kj/cm and 200kj/cm line energy.
  • the steel plate involved in the invention has a yield strength of 440-460 MPa and a tensile strength of 560-580 MPa, which does not solve the problem of high-strength marine steel welding with high heat input.
  • Chinese patent CN201410300713.X discloses "a large heat input welding 550MPa grade steel plate and its manufacturing method", starting from the alloy design, using ultra-low carbon C-ultra-low Si-high Mn-Nb series low-alloy steel as the basis. Reduce the content of Al in steel as much as possible, optimize the TMCP process, and successfully develop a yield strength ⁇ 465MPa, tensile strength 550MPa ⁇ 650MPa, -60°C Charpy impact energy (single value) ⁇ 100J, and large heat input heat influence of welding Zone -40°C Charpy impact energy (single value) ⁇ 100J steel plate.
  • the yield strength of the steel plate of this invention is less than 550MPa, and Ca is used as a deoxidizer, and the smelting process is more complicated.
  • the purpose of the present invention is to provide a large heat input welding EH550MPa grade quenched and tempered marine steel plate and its manufacturing method. ) ⁇ 180J, welding heat input 50kj/cm, 100kj/cm, 150kj/cm heat affected zone -40°C Charpy impact energy (single value) ⁇ 80J.
  • the test requirement of Charpy impact energy is to take three samples, measure three times, and take the average of the individual values of the three measurements to evaluate the samples.
  • the -40°C Charpy impact energy (single value) ⁇ 180J of the quenched and tempered marine steel base material of the present invention means that the three measurements of the -40°C Charpy impact energy of the base material are all ⁇ 180J; the welding heat input is 50kj/cm, 100kj/cm, 150kj/cm heat-affected zone -40°C Charpy impact energy (single value) ⁇ 80J means: welding heat input 50kj/cm heat-affected zone -40°C Charpy impact energy three measurements of the single value ⁇ 80J, the heat-affected zone of welding heat input of 100kj/cm, the individual value of Charpy impact energy measured three times at -40°C is ⁇ 80J, the heat-affected zone of welding heat input of 150kj/cm, the individual value of Charpy impact energy
  • the present invention ensures that the alloy composition of the steel plate is within the scope of the present invention to ensure that the steel plate has sufficient strength, toughness and suitable base material structure; at the same time, in the smelting process, the selection of deoxidizer types and addition
  • the structure of the heat-affected zone welded by large heat input can improve the low-temperature impact performance of the EH550MPa quenched and tempered marine steel plate.
  • the EH550MPa grade refers to the yield strength of the quenched and tempered marine steel plate EH ⁇ 550MPa.
  • the high heat input welded EH550MPa grade quenched and tempered marine steel sheet according to the present invention has a composition mass percentage of: C 0.06 ⁇ 0.12%, Si, 0.02 ⁇ 0.06%, Mn 0.7 ⁇ 1.2%, Ti 0.006 ⁇ 0.012% , Al 0.002 ⁇ 0.010%, Cr 0.30 ⁇ 0.50%, Mo 0.3 ⁇ 0.4%, V 0.03 ⁇ 0.04%, N 0.0020 ⁇ 0.0030%, S 0.002 ⁇ 0.010%, P ⁇ 0.008%, the rest is Fe and unavoidable impurities;
  • the average size of Ti-containing oxides in the steel sheet is between 2 ⁇ m and 3 ⁇ m, and the density of this type of Ti-containing oxides is not less than 50/mm 2 .
  • the chemical composition of the quenched and tempered marine steel plate further contains more than one element among Cu ⁇ 0.3%, Ni ⁇ 1.9%, or B ⁇ 0.0015%, in terms of mass percentage.
  • [Ti]/[Al] 2 to 3 in the quenched and tempered marine steel sheet.
  • the hot-rolled base metal microstructure of the quenched and tempered marine steel sheet of the present invention is a tempered martensite structure to ensure sufficient strength and toughness.
  • C is an important element in the marine steel plate. Increasing the content of C in the steel plate can increase the strength of the marine steel plate, reduce production costs, and increase the strength level of the marine steel plate. In the present invention, the content of C is not less than 0.06%; At the same time, the increase of the C content in the steel plate will reduce the low temperature toughness and welding performance of the offshore steel plate. Therefore, the C content is not higher than 0.12%. Therefore, in order to achieve the desired effect, the C content in the present invention is 0.06 to 0.12%, preferably 0.06 to 0.09%.
  • Si can be dissolved in ferrite and austenite to increase the hardness and strength of the steel plate, and Si is an important deoxidizer in the smelting process.
  • Si content is too high, it will significantly reduce the plasticity and toughness of the steel plate, and in the process of welding with high heat input, it will promote the formation of Mahau Island (island martensite-austenite) and significantly reduce the welding with high heat input.
  • the present invention adopts a low-Si process, and the content of Si is in the range of 0.02-0.06%, preferably 0.02-0.04%.
  • Mn an important deoxidizer in the steelmaking process, can also react with S in steel to form MnS, eliminating the harmful effects of S in steel, and MnS has a large heat input on the small lath bainite in the heat affected zone of welding.
  • the formation of Mn plays an important role, so the lower limit of Mn is 0.7%. Too high Mn content will increase the temper brittleness sensitivity of the offshore steel sheet, so the upper limit of the Mn content is 1.2%. Therefore, the content of Mn in the present invention is 0.7 to 1.2%, preferably 0.8 to 1.0%.
  • Ti can be combined with nitrogen and oxygen to produce Ti-containing oxides and nitrides. These Ti-containing oxides and nitrides can promote the formation of small lath bainite in the heat-affected zone of large heat input welding within a suitable size range. , So as to improve the welding low temperature toughness of the offshore steel plate.
  • the content of Ti is not less than 0.006%. However, too high Ti will generate TiC, reduce the low-temperature toughness of the base material and the heat-affected zone, and also promote the formation of large-size TiN, forming crack initiation points. Therefore, the upper limit of the Ti content is 0.012%. Therefore, the content of Ti in the present invention is 0.006 to 0.012%, preferably 0.006 to 0.009%.
  • Al is the most important deoxidizing element in the steelmaking process. Too high Al is easy to form clustered alumina, which affects the purity of molten steel. Too low Al cannot guarantee the control of free oxygen content in molten steel. In addition, Al plays a role in refining and refining, so the content of Al in the steel sheet should be controlled between 0.002 and 0.010%, preferably 0.005 to 0.006%.
  • Cr can increase the hardenability of the steel plate and has the effect of secondary hardening. In the quenching and tempering process, it can improve the hardenability, so that the steel plate has better comprehensive mechanical properties after quenching and tempering.
  • the lower limit of Cr is 0.30%.
  • An increase in the Cr content increases the tendency of high-temperature tempering brittleness, so the upper limit of Cr is 0.50%. Therefore, in order to achieve the desired effect, the Cr content in the present invention is 0.30 to 0.50%, preferably 0.35 to 0.50%.
  • Mo can improve the hardenability of the marine steel plate and prevent temper brittleness.
  • Mo can make the steel plate deep and hardenable, and improve the tempering resistance or tempering stability of the steel plate, which is effective Eliminate residual stress and improve plasticity, so the lower limit of Mo is 0.3%. Too high Mo content will significantly increase the carbon equivalent of the steel sheet and affect the weldability of the steel sheet, so the upper limit of Mo is 0.4%.
  • V can refine the structure and grains of the steel plate, increase the strength and yield ratio of the steel plate in the quenched and tempered steel plate, refine the grains, reduce the overheating sensitivity, and increase the tempering stability, so the lower limit of V is 0.03%. If the content of V is too high, excessive VC will be generated, so the upper limit of V is 0.04%.
  • the upper limit of the P content is 0.008%.
  • N When the content of N is high, N will precipitate from the ferrite during quenching, which will increase the strength and hardness of the steel plate and decrease the ductility and toughness.
  • the N content range is controlled within 0.0020 to 0.0030%.
  • Cu can increase the strength and yield ratio of the steel sheet without adversely affecting the welding performance. However, if it is added excessively, it will cause hot brittleness. Therefore, the upper limit of Cu addition is 0.3%.
  • Ni can strengthen ferrite and refine pearlite, increase strength without reducing toughness. However, from a cost point of view, there is no need to add too much, so the upper limit is 1.9%.
  • B The main function is to increase the hardenability of steel, thereby saving other expensive alloys and reducing costs.
  • B has the effect of promoting temper brittleness, so the upper limit of B content is set at 0.0015%. Therefore, in order to achieve the desired effect, the content of B in the present invention is B ⁇ 0.0015%, preferably B ⁇ 0.0010%.
  • the three elements of Si, Al, and Ti are simultaneously controlled in the range interval, because these three elements are all deoxidizing elements, and different composition combinations will have a greater impact on the types of oxides in the steel.
  • excessive Si content will generate a large amount of Si-containing oxides in the steel sheet.
  • Such oxides are very easy to form chains in the steel sheet, which will significantly reduce the impact toughness.
  • the content of Si is too high, it will increase the formation of brittle phases of Martensite (island martensite-austenite) in the steel sheet and reduce local toughness.
  • the content of Al is too high, large-size Al 2 O 3 oxides will be formed.
  • This hard oxide will form the starting point of cracks in the steel plate, increasing the number of cracks during the impact process and reducing the impact toughness. If the content of Ti is too high, the formation of TiC will be promoted, and TiC will generate local brittle zones and reduce the impact toughness. At the same time, the Ti content should not be too low. Too low Ti content cannot reduce the oxygen content in the steel plate to an appropriate level. Too high oxygen content in the steel plate will increase the oxides in the steel plate and reduce the impact toughness.
  • the Ti content is controlled.
  • the manufacturing method of the high heat input welding EH550MPa grade quenched and tempered marine steel plate of the present invention includes the following steps:
  • the deoxidizer is added during the deoxidation process of the molten steel.
  • the type and order of the deoxidizer are Si ⁇ Mn ⁇ Al ⁇ Ti; and Fe 2 O 3 is added to the furnace.
  • Powder and Al are used to precisely control the initial oxygen content before adding Ti in the molten steel.
  • the amount of Fe 2 O 3 powder added makes the oxygen content of the molten steel 0.004 to 0.01% by mass, and Ti is added to deoxidize within this range;
  • the average size of Ti-containing oxides in the steel sheet is between 2 ⁇ m and 3 ⁇ m, and the density of this type of Ti-containing oxides is not less than 50/mm 2 ;
  • the holding time is 260-280 min. If the holding time is insufficient, the temperature will be uneven and the internal temperature of the steel ingot will not meet the requirements. If the holding time is too long, it will result in a waste of energy.
  • the rolled steel plate After the rolled steel plate is air-cooled to room temperature, it is heated to 910 ⁇ 930°C once, kept for 40 ⁇ 50 minutes, quenched to room temperature after being discharged, heated to 650 ⁇ 680°C for the second time, kept kept for 115 ⁇ 130 minutes, and cooled to room temperature after discharge.
  • the adopted smelting process is Si ⁇ Mn ⁇ Al ⁇ Ti, and Ti is added under the condition of suitable liquid steel oxygen content.
  • Si and Mn are used for deoxidation first to reduce the free oxygen content in the steel plate.
  • the deoxidation products of Si and Mn easily form low-melting-point oxides. These low-melting-point oxides float up and dissolve into the slag for removal.
  • the oxides of molten steel are not increased.
  • Al deoxidation is used. Al has a strong deoxidation effect and can control the free oxygen content in the molten steel to a low level.
  • Ti is added to control the oxide.
  • the key point of the oxide control process of the present invention is to control the oxygen content before adding Ti to an appropriate range through the addition of Al, so that the oxides generated under the condition of the oxygen content in the steel sheet can resist large heat input after welding.
  • the structure of the heat-affected zone plays an inducing role, inducing the formation of fine lath bainite structure in the heat-affected zone, thereby improving the low-temperature toughness of the heat-affected zone of large heat input welding.
  • the content of Al in the steel plate should be controlled between 0.002% and 0.010%. Too high Al is easy to form clustered alumina, which affects the purity of molten steel. Too low Al cannot guarantee the control of free oxygen content in molten steel.
  • [Ti]/[Al] in the steel plate should be controlled at an appropriate ratio. If [Ti]/[Al] is too large, it will cause the formation of Ti oxides larger than 5 ⁇ m in the molten steel, which will affect the low temperature toughness. If [Ti]/[Al] is too small, the quantity and size of Al 2 O 3 in the molten steel will increase significantly, and it cannot guarantee that a sufficient amount of Ti-containing oxide Al 2 O 3 -Ti 3 O 5 -MnS is generated in the molten steel. Therefore, [Ti]/[Al] should be controlled to 2 ⁇ 3.
  • the starting point of the crack is formed when the oxide density of a specific size is insufficient, and the structure of the heat-affected zone cannot be changed sufficiently and the low-temperature toughness can be improved. Therefore, the oxygen content before adding Ti is controlled at 0.0040-0.01%.
  • the present invention studies the inclusions in the heat-affected zone, and determines the appropriate composition, size and quantity of the inclusions.
  • the composition of inclusions is analyzed by Zeiss EVO18 scanning electron microscope SEM-EDS, and the size and density of inclusions are detected and analyzed by automatic inclusion analyzer.
  • the automatic inclusion analyzer uses SEM and EDS to collect data, uses analysis software to automatically detect and analyze inclusions, and can accurately identify the composition, size, quantity and other information of inclusions in the steel plate.
  • This system inclusions in steel sheet analysis found that the average size of the inclusions in the steel sheet containing Ti and the inclusion of this type of embodiment a density of 50 / mm 2 is not smaller than between 2 ⁇ m ⁇ 3 ⁇ m, low temperature impact Toughness is higher.
  • the type of such titanium-containing inclusions must be Al 2 O 3 -Ti 3 O 5 -MnS composite oxide.
  • This kind of MnS oxide precipitated on the surface of Al 2 O 3 -Ti 3 O 5 as the core plays an important role in the formation of fine lath bainite in the heat-affected zone. It is generally believed that the formation of Al 2 O 3 -Ti 3 O 5 -MnS composite oxide is attributed to the local saturation of Mn and S around the Al 2 O 3 -Ti 3 O 5 oxide.
  • due to the relatively high solubility of MnS in molten steel Generally, it will not precipitate in molten steel.
  • the heating temperature before rolling is 1100 ⁇ 1200°C
  • the heat preservation is at least 250min to ensure complete austenitization
  • the rough rolling opening temperature is 1000 ⁇ 1100°C
  • the cumulative reduction rate is greater than 30%
  • Rolling in this temperature range can recrystallize and refine the austenite grains.
  • the reduction ratio is less than 30%, there are more coarse austenite grains remaining, which affect the strength and toughness of the base metal.
  • the finish rolling opening temperature is 800-900°C, and it can be rolled in the two-phase zone.
  • the dislocations formed during the rolling can be used as the core of ferrite nucleation to improve the strength and toughness of the base material.
  • the cumulative reduction rate is greater than 30%. When the reduction rate is less than 30%, fewer dislocations are formed, and sufficient acicular ferrite nucleation cannot be induced.
  • Quenching and tempering heat treatment process after the rolled steel plate is air-cooled to room temperature, it is heated to 910-930°C at one time, kept for 40-50 minutes, and then quenched to room temperature with water.
  • This quenching process can transform the marine steel sheet of the present invention into martensite at a minimum cooling rate. Reheat it to 650 ⁇ 680°C, keep it for 115 ⁇ 130min, and cool it out to room temperature.
  • the quenched steel is mainly martensite. Martensite is in a metastable state at room temperature and has a tendency to transform into a stable state of ferrite and cementite. Tempering treatment is required to eliminate internal stress and prevent deformation And cracking.
  • Tempering at 650 ⁇ 680°C and holding for 115 ⁇ 130min can make the supersaturated carbon in the martensite structure of the marine steel plate after quenching precipitate, and the main structure of the base metal is transformed into tempered martensite, so that the quenched and tempered marine
  • the base metal structure of steel plate has high strength and toughness.
  • composition range of EH550 required by classification societies is: C ⁇ 0.18, Mn0.9 ⁇ 1.6, Si ⁇ 0.5, S ⁇ 0.035, P ⁇ 0.035, Al ⁇ 0.015.
  • the order of deoxidation is very critical. It must be carried out in the order of Si ⁇ Mn ⁇ Al ⁇ Ti, and the mass percentage of oxygen before adding Ti to the molten steel is 0.0040-0.01%. Under such deoxidation process conditions, it is possible to generate micron-level composite oxides with a density of not less than 50 pcs/mm2, an average size of 2 ⁇ m to 3 ⁇ m, and a type of Al 2 O 3 -Ti 3 O 5 -MnS. The change of the deoxidation sequence will lead to the change of the type of oxides in the steel plate, leading to the formation of brittle phases in the heat-affected zone, and affecting the impact toughness.
  • the present invention optimizes the composition design of the high-strength marine steel plate.
  • the refining process by controlling the free oxygen in the appropriate steel plate, and optimizing the deoxidizing alloy and alloy adding sequence, adjusting the deoxidizing alloy Al/Ti ratio, and achieving the control of Al 2 size, composition and number density of the target O 3 -Ti 3 O 5 -MnS oxide of the Al 2 O 3 -Ti 3 O 5 -MnS oxide can induce HAZ during solidification and phase transformation
  • the volume of the small lath bainite increases the low-temperature toughness of the heat-affected zone of the offshore steel plate after high heat input welding.
  • the invention avoids the use of strong deoxidizers such as Ca, Mg, Re, etc., simplifies the smelting process, and avoids the shortcomings of difficult storage and difficulty in adding the deoxidizer using the strong deoxidizer process.
  • the alloy composition is adjusted during the refining process, and the deoxidizing alloy is added in the order of Si ⁇ Mn ⁇ Al for deoxidation. While ensuring the alloy composition, Fe 2 O 3 powder is added to adjust the oxygen content in the steel sheet. , And then add ferro-titanium, the composition of ferro-titanium is Ti 69.8%.
  • Table 1 lists the chemical components of the examples and comparative examples of the present invention.
  • the Al content in the comparative example is 0.045% and 0.051%, and one or two of the Ti/Al ratio and the Ti-containing oxide density in the size range of 2 to 3 ⁇ m do not meet the requirements of the present invention.
  • Table 2 shows the manufacturing process of the steel plates of the examples and comparative examples of the present invention.
  • Table 3 lists the comparison of the strength, low-temperature toughness and low-temperature toughness of the heat-affected zone of the base materials in the examples and comparative examples.
  • the yield strength, tensile strength and reduction of area of the base metal are the average of the two measured values.
  • the -40°C Charpy impact energy of the base metal and the -40°C Charpy impact energy of the heat-affected zone are the average of the three measured values. .
  • the tensile test is carried out in accordance with GB/T 228.1-2010 Metallic Material Tensile Test Part 1: The test standard of the room temperature tensile test method to test the yield strength, tensile strength, and reduction of area of the base material; SCL233200kN normal temperature tensile test Tensile testing machine; test conditions: 25°C, 2mm/min before yielding, humidity 56%, and 20mm/min after yielding.
  • the impact test is in accordance with the GB/T 229-2007 Charpy Pendulum Impact Test Method for Metallic Materials, using an instrumented impact testing machine (SCL112), and the impact energy is 60 (J).
  • the yield strength and tensile strength of the base material of the examples are slightly higher than those of the comparative examples.
  • the Charpy impact energy of the heat-affected zone at -40°C of the examples are all above 80j.
  • the Charpy impact energy at -40°C is relatively low. Therefore, after the embodiments are subjected to the oxide control process and composition design, the low-temperature toughness of the heat-affected zone is significantly improved, which meets the requirements of marine steel plates for welding with large heat input.
  • the present invention adopts optimized composition design to control the appropriate Ti/Al ratio in the steel sheet, optimize the deoxidation alloy and deoxidation sequence in the refining process, and control the size and composition suitable for Ti-containing oxides by adding Fe 2 O 3 powder And the number density, the small lath bainite structure is induced in the heat-affected zone, and finally the EH550 high-strength marine steel plate for welding with large heat input is manufactured.

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Abstract

Disclosed are an EH 550 MPa grade quenched and tempered marine steel plate for high heat input welding and a manufacturing method therefor. The mass percentages of the components of the steel plate are as follows: 0.06-0.12% of C, 0.02-0.06% of Si, 0.7-1.2% of Mn, 0.006-0.012% of Ti, 0.002-0.010% of Al, 0.30-0.50% of Cr, 0.3-0.4% of Mo, 0.03-0.04% of V, 0.0020-0.0030% of N, 0.002-0.010% of S, and P ≤ 0.008%, with the balance being Fe and unavoidable impurities, wherein the average size of a Ti-containing oxide in the steel plate is between 2 and 3 μm, and the density of this oxide is not less than 50 per mm2. The quenched and tempered marine steel plate has a yield strength EH ≥ 550 MPa and a tensile strength ≥ 670 MPa. The parent metal has a -40°C Charpy impact work (single value) ≥ 180 J, and a -40°C Charpy impact work (single value) ≥ 80 J in a heat-affected zone at weld heat inputs of 50 kj/cm, 100 kj/cm and 150 kj/cm.

Description

一种大热输入焊接EH550MPa级调质海工钢板及其制造方法Large heat input welding EH550MPa grade quenched and tempered marine steel plate and manufacturing method thereof 技术领域Technical field
本发明属于海洋工程用钢领域，特别涉及一种大热输入焊接EH550MPa级调质海工钢板及其制造方法。The invention belongs to the field of marine engineering steel, and particularly relates to a large heat input welding EH550MPa grade quenched and tempered marine steel plate and a manufacturing method thereof.
背景技术Background technique
海洋油气已经成为当今世界的重要能源，随着全球油气勘探和开发利用技术的发展，对海洋油气工程装备的需求越来越大，如自升式钻井平台、半潜式钻井平台，钻井船等。这些海洋油气工程装备制造所需的钢材强度等级、韧性等级及厚度、尺寸精度和焊接性能要求不断提高。Offshore oil and gas has become an important energy source in the world today. With the development of global oil and gas exploration and development and utilization technologies, there is an increasing demand for offshore oil and gas engineering equipment, such as jack-up drilling platforms, semi-submersible drilling platforms, and drilling ships. . The steel strength grade, toughness grade and thickness, dimensional accuracy and welding performance requirements for the manufacturing of these offshore oil and gas engineering equipment are continuously increasing.
海工钢焊接部位多，服役周期长，作业环境恶劣，对焊接性能要求高。采用大热输入焊接技术，能够缩短海洋平台的制造周期，降低制造成本，对海洋平台制造技术的提高有着重要的意义。但是由于海工钢板强度级别高，合金含量高于普通船板，所以焊接难度大，经过大热输入焊接后，热影响区的冷却速度会比较缓慢，热影响区晶粒将急剧增大，组织将会显著粗化，焊接热影响区的韧性会明显下降。与母材相比，热影响区韧性损失严重时可高达80％。虽然焊接热影响区宽度一般只有几毫米，但热影响区粗晶区的韧性严重下降很可能成为裂纹的开裂源，为海洋平台的安全使用留下隐患。There are many welding parts of offshore steel, long service period, harsh working environment, and high requirements for welding performance. The use of large heat input welding technology can shorten the manufacturing cycle of the offshore platform and reduce the manufacturing cost, which is of great significance to the improvement of the manufacturing technology of the offshore platform. However, due to the high strength level of marine steel plates and higher alloy content than ordinary ship plates, welding is difficult. After welding with large heat input, the cooling rate of the heat-affected zone will be relatively slow, and the grains of the heat-affected zone will increase sharply. It will be significantly coarsened, and the toughness of the welding heat-affected zone will be significantly reduced. Compared with the base metal, the toughness loss of the heat-affected zone can be as high as 80% when it is severe. Although the width of the welding heat-affected zone is generally only a few millimeters, the severe decrease in toughness of the coarse-grained zone of the heat-affected zone is likely to become the source of cracks, leaving hidden dangers for the safe use of offshore platforms.
中国专利CN 106191659 A公开的“一种可大线能量焊接的海洋工程用钢板及其制造方法”，成功的开发出一种可大线能量焊接的海工钢，冶炼工序中脱氧工艺简单，以硅铁和金属锰为主，不添加强脱氧剂，经过100kj/cm，200kj/cm线能量的焊接热模拟后-60℃冲击功大于90J。但该发明涉及的钢板屈服强度440～460MPa，抗拉强度560～580MPa，没有解决高强度级别的海工钢大线能量焊接问题。Chinese patent CN 106191659 A discloses "a steel plate for marine engineering that can be welded with high heat input and its manufacturing method", and successfully developed a marine steel that can be welded with high heat input. The deoxidation process in the smelting process is simple, and Ferrosilicon and metal manganese are the main components, no strong deoxidizer is added, and the impact energy at -60°C is greater than 90J after the welding thermal simulation of 100kj/cm and 200kj/cm line energy. However, the steel plate involved in the invention has a yield strength of 440-460 MPa and a tensile strength of 560-580 MPa, which does not solve the problem of high-strength marine steel welding with high heat input.
中国专利CN201410300713.X公开的“一种可大热输入焊接550MPa级钢板及其制造方法”，从合金设计入手，采用超低碳C-超低Si-高Mn-Nb 系低合金钢作为基础，尽可能减少钢中Al的含量，优化TMCP工艺，成功开发出一种屈服强度≥465MPa、抗拉强度550MPa～650MPa，-60℃夏比冲击功(单个值)≥100J，焊接大热输入热影响区-40℃夏比冲击功(单个值)≥100J的钢板。但该发明的钢板屈服强度低于550MPa，且使用Ca为脱氧剂，冶炼工序较为复杂。Chinese patent CN201410300713.X discloses "a large heat input welding 550MPa grade steel plate and its manufacturing method", starting from the alloy design, using ultra-low carbon C-ultra-low Si-high Mn-Nb series low-alloy steel as the basis. Reduce the content of Al in steel as much as possible, optimize the TMCP process, and successfully develop a yield strength ≥465MPa, tensile strength 550MPa～650MPa, -60℃ Charpy impact energy (single value) ≥100J, and large heat input heat influence of welding Zone -40℃ Charpy impact energy (single value) ≥100J steel plate. However, the yield strength of the steel plate of this invention is less than 550MPa, and Ca is used as a deoxidizer, and the smelting process is more complicated.
发明内容Summary of the invention
本发明的目的是提供一种大热输入焊接EH550MPa级调质海工钢板及其制造方法，该钢板屈服强度EH≥550MPa、抗拉强度≥670MPa，母材-40℃夏比冲击功(单个值)≥180J，焊接热输入50kj/cm，100kj/cm，150kj/cm的热影响区-40℃夏比冲击功(单个值)≥80J。The purpose of the present invention is to provide a large heat input welding EH550MPa grade quenched and tempered marine steel plate and its manufacturing method. )≥180J, welding heat input 50kj/cm, 100kj/cm, 150kj/cm heat affected zone -40℃ Charpy impact energy (single value) ≥80J.
夏比冲击功的检测要求是取三个试样，测量三次，取三次测得的单个值的平均值来评价试样。本发明的调质海工钢板母材-40℃夏比冲击功(单个值)≥180J是指母材-40℃夏比冲击功三次测量的单个值均≥180J；焊接热输入50kj/cm，100kj/cm，150kj/cm的热影响区-40℃夏比冲击功(单个值)≥80J是指：焊接热输入50kj/cm的热影响区-40℃夏比冲击功三次测量的单个值均≥80J，焊接热输入100kj/cm的热影响区-40℃夏比冲击功三次测量的单个值均≥80J，焊接热输入150kj/cm的热影响区-40℃夏比冲击功三次测量的单个值均≥80J。The test requirement of Charpy impact energy is to take three samples, measure three times, and take the average of the individual values of the three measurements to evaluate the samples. The -40°C Charpy impact energy (single value) ≥180J of the quenched and tempered marine steel base material of the present invention means that the three measurements of the -40°C Charpy impact energy of the base material are all ≥180J; the welding heat input is 50kj/cm, 100kj/cm, 150kj/cm heat-affected zone -40℃ Charpy impact energy (single value) ≥ 80J means: welding heat input 50kj/cm heat-affected zone -40℃ Charpy impact energy three measurements of the single value ≥80J, the heat-affected zone of welding heat input of 100kj/cm, the individual value of Charpy impact energy measured three times at -40℃ is ≥80J, the heat-affected zone of welding heat input of 150kj/cm, the individual value of Charpy impact energy measured for three times at -40℃ The values are all ≥80J.
为达到上述目的，本发明的技术方案是：To achieve the above objective, the technical solution of the present invention is:
本发明通过优化合金成分设计，确保钢板的合金成分在本发明的范围内，以保证钢板有足够的强度、韧性和合适的母材组织；同时在冶炼过程中，对脱氧剂种类的选择，添加顺序的优化、钢液中氧含量的控制和几种脱氧剂的添加比例控制，通过脱氧工艺的优化，控制钢板中生成成分合适尺寸适宜的含Ti氧化物，通过合适的含Ti氧化物来影响大热输入焊接热影响区的组织，从而提高EH550MPa级调质海工钢板的低温冲击性能，其中，EH550MPa级是指调质海工钢板的屈服强度EH≥550MPa。By optimizing the alloy composition design, the present invention ensures that the alloy composition of the steel plate is within the scope of the present invention to ensure that the steel plate has sufficient strength, toughness and suitable base material structure; at the same time, in the smelting process, the selection of deoxidizer types and addition The optimization of the sequence, the control of the oxygen content in the molten steel, and the control of the addition ratio of several deoxidizers, through the optimization of the deoxidation process, control the generation of Ti-containing oxides with appropriate components and sizes in the steel plate, which is affected by the appropriate Ti-containing oxides The structure of the heat-affected zone welded by large heat input can improve the low-temperature impact performance of the EH550MPa quenched and tempered marine steel plate. Among them, the EH550MPa grade refers to the yield strength of the quenched and tempered marine steel plate EH≥550MPa.
具体的，本发明所述的大热输入焊接EH550MPa级调质海工钢板，其成分质量百分比为：C 0.06～0.12％，Si，0.02～0.06％，Mn 0.7～1.2％，Ti 0.006～0.012％，Al 0.002～0.010％，Cr 0.30～0.50％，Mo 0.3～0.4％，V  0.03～0.04％，N 0.0020～0.0030％，S 0.002～0.010％，P≤0.008％，其余为Fe和不可避免杂质；其中，钢板中含Ti氧化物的平均尺寸在2μm～3μm之间，且此种类型的含Ti氧化物密度为不小于50个/mm 2。 Specifically, the high heat input welded EH550MPa grade quenched and tempered marine steel sheet according to the present invention has a composition mass percentage of: C 0.06～0.12%, Si, 0.02～0.06%, Mn 0.7～1.2%, Ti 0.006～0.012% , Al 0.002～0.010%, Cr 0.30～0.50%, Mo 0.3～0.4%, V 0.03～0.04%, N 0.0020～0.0030%, S 0.002～0.010%, P≤0.008%, the rest is Fe and unavoidable impurities; Among them, the average size of Ti-containing oxides in the steel sheet is between 2 μm and 3 μm, and the density of this type of Ti-containing oxides is not less than 50/mm 2 .
进一步，所述调质海工钢板的化学成分还含有Cu≤0.3％、Ni≤1.9％或B≤0.0015％中一种以上元素，以质量百分比计。Further, the chemical composition of the quenched and tempered marine steel plate further contains more than one element among Cu≤0.3%, Ni≤1.9%, or B≤0.0015%, in terms of mass percentage.
优选的，所述调质海工钢板中[Ti]/[Al]＝2～3。Preferably, [Ti]/[Al]=2 to 3 in the quenched and tempered marine steel sheet.
本发明所述调质海工钢板热轧态的母材显微组织为回火马氏体组织，以保证足够的强度和韧性。The hot-rolled base metal microstructure of the quenched and tempered marine steel sheet of the present invention is a tempered martensite structure to ensure sufficient strength and toughness.
在本发明钢板的成分设计中：In the composition design of the steel plate of the present invention:
C是海工钢板中重要的元素，增加钢板中C的含量，能够提高海工钢板的强度且降低生产成本，增加海工钢板的强度级别，本发明中，C的含量不低于0.06％；同时，钢板中C含量的增加，会降低海工钢板的低温韧性和焊接性能，所以，C含量不高于0.12％。因此，为了达到预期的效果，本发明中C含量为0.06～0.12％，优选为0.06～0.09％。C is an important element in the marine steel plate. Increasing the content of C in the steel plate can increase the strength of the marine steel plate, reduce production costs, and increase the strength level of the marine steel plate. In the present invention, the content of C is not less than 0.06%; At the same time, the increase of the C content in the steel plate will reduce the low temperature toughness and welding performance of the offshore steel plate. Therefore, the C content is not higher than 0.12%. Therefore, in order to achieve the desired effect, the C content in the present invention is 0.06 to 0.12%, preferably 0.06 to 0.09%.
Si，能溶于铁素体和奥氏体中提高钢板的硬度和强度，而且Si元素是冶炼过程中重要的脱氧剂。但Si的含量过高，会显著降低钢板的塑性和韧性，而且在大热输入焊接过程中，会促进马奥岛(岛状马氏体-奥氏体)的生成，显著降低大热输入焊接热影响区的低温韧性。本发明采用低Si工艺，Si的含量范围为0.02～0.06％，优选为0.02～0.04％。Si can be dissolved in ferrite and austenite to increase the hardness and strength of the steel plate, and Si is an important deoxidizer in the smelting process. However, if the Si content is too high, it will significantly reduce the plasticity and toughness of the steel plate, and in the process of welding with high heat input, it will promote the formation of Mahau Island (island martensite-austenite) and significantly reduce the welding with high heat input. Low temperature toughness of the heat-affected zone. The present invention adopts a low-Si process, and the content of Si is in the range of 0.02-0.06%, preferably 0.02-0.04%.
Mn，是炼钢过程中重要的脱氧剂，也可与钢中的S反应，生成MnS，消除S在钢中的有害影响，且MnS对大热输入焊接热影响区的细小板条贝氏体的生成起着重要的作用，所以Mn的下限为0.7％。Mn的含量过高，会增加海工钢板的回火脆性敏感性，所以Mn含量的上限为1.2％。因此，Mn在本发明中的含量为0.7～1.2％，优选为0.8～1.0％。Mn, an important deoxidizer in the steelmaking process, can also react with S in steel to form MnS, eliminating the harmful effects of S in steel, and MnS has a large heat input on the small lath bainite in the heat affected zone of welding. The formation of Mn plays an important role, so the lower limit of Mn is 0.7%. Too high Mn content will increase the temper brittleness sensitivity of the offshore steel sheet, so the upper limit of the Mn content is 1.2%. Therefore, the content of Mn in the present invention is 0.7 to 1.2%, preferably 0.8 to 1.0%.
Ti，可以与氮、氧结合，生成含Ti氧化物和氮化物，这些含Ti的氧化物和氮化物在合适的尺寸范围内能够促进大热输入焊接热影响区的细小板条贝氏体生成，从而提高海工钢板的焊接低温韧性。Ti的含量不低于0.006％。但过高的Ti，会生成TiC，降低母材和热影响区的低温韧性，也会促进大尺寸TiN的生成，形成裂纹起裂点，所以，Ti含量的上限为0.012％。因此，Ti在本发明中的含量为0.006～0.012％，优选为 0.006～0.009％。Ti can be combined with nitrogen and oxygen to produce Ti-containing oxides and nitrides. These Ti-containing oxides and nitrides can promote the formation of small lath bainite in the heat-affected zone of large heat input welding within a suitable size range. , So as to improve the welding low temperature toughness of the offshore steel plate. The content of Ti is not less than 0.006%. However, too high Ti will generate TiC, reduce the low-temperature toughness of the base material and the heat-affected zone, and also promote the formation of large-size TiN, forming crack initiation points. Therefore, the upper limit of the Ti content is 0.012%. Therefore, the content of Ti in the present invention is 0.006 to 0.012%, preferably 0.006 to 0.009%.
Al，是炼钢过程中最重要的脱氧元素，过高的Al容易形成簇状氧化铝，影响钢液的纯净度，过低的Al不能保证钢液中的自由氧含量控制。且Al起到一定的细化精炼的作用，所以钢板中Al的含量要控制在0.002～0.010％之间，优选为0.005～0.006％。Al is the most important deoxidizing element in the steelmaking process. Too high Al is easy to form clustered alumina, which affects the purity of molten steel. Too low Al cannot guarantee the control of free oxygen content in molten steel. In addition, Al plays a role in refining and refining, so the content of Al in the steel sheet should be controlled between 0.002 and 0.010%, preferably 0.005 to 0.006%.
Cr，能够增加钢板的淬透性并有二次硬化的作用，在调质工艺中，可以提高淬透性，使钢板经淬火回火后具有较好的综合力学性能。Cr的下限为0.30％。Cr含量的增加，会使高温回火脆性的倾向增大，所以Cr的上限为0.50％。因此，为了达到预期的效果，本发明中Cr含量为0.30～0.50％，优选为0.35～0.50％。Cr can increase the hardenability of the steel plate and has the effect of secondary hardening. In the quenching and tempering process, it can improve the hardenability, so that the steel plate has better comprehensive mechanical properties after quenching and tempering. The lower limit of Cr is 0.30%. An increase in the Cr content increases the tendency of high-temperature tempering brittleness, so the upper limit of Cr is 0.50%. Therefore, in order to achieve the desired effect, the Cr content in the present invention is 0.30 to 0.50%, preferably 0.35 to 0.50%.
Mo，能够提高海工钢板的淬透性，防止回火脆性，在调质海工钢板中，Mo能使钢板淬深，淬透，提高钢板的抗回火性或回火稳定性，有效的消除残余应力，提高塑性，所以，Mo的下限为0.3％。Mo含量过高，会显著提高钢板的碳当量，影响钢板的焊接性，所以Mo的上限为0.4％。Mo can improve the hardenability of the marine steel plate and prevent temper brittleness. In the quenched and tempered marine steel plate, Mo can make the steel plate deep and hardenable, and improve the tempering resistance or tempering stability of the steel plate, which is effective Eliminate residual stress and improve plasticity, so the lower limit of Mo is 0.3%. Too high Mo content will significantly increase the carbon equivalent of the steel sheet and affect the weldability of the steel sheet, so the upper limit of Mo is 0.4%.
V，能够细化钢板的组织和晶粒，在调质钢板中提高钢板的强度和屈强比，细化晶粒，降低过热敏感性，增加回火稳定性，所以V的下限为0.03％。V的含量过高，会生成过量的VC，所以V的上限为0.04％。V can refine the structure and grains of the steel plate, increase the strength and yield ratio of the steel plate in the quenched and tempered steel plate, refine the grains, reduce the overheating sensitivity, and increase the tempering stability, so the lower limit of V is 0.03%. If the content of V is too high, excessive VC will be generated, so the upper limit of V is 0.04%.
S，会与钢板中的Mn生成MnS，MnS会在钢板中含Ti氧化物上析出，促进细小板条贝氏体的生成，所以S的含量下限为0.002％。S的含量过高，会在铸坯的中心产生偏析，影响厚板的Z向性能，所以，S的含量上限为0.010％。S will form MnS with Mn in the steel sheet. MnS will precipitate on Ti-containing oxides in the steel sheet to promote the formation of fine lath bainite, so the lower limit of the S content is 0.002%. If the content of S is too high, segregation will occur in the center of the slab and affect the Z-direction performance of the thick plate. Therefore, the upper limit of the content of S is 0.010%.
P，有很强的固溶强化作用，可使钢板的强度、硬度显著提高，但会剧烈降低钢板的低温韧性，所以，P含量的上限为0.008％。P has a strong solid solution strengthening effect, which can significantly increase the strength and hardness of the steel sheet, but it will drastically reduce the low temperature toughness of the steel sheet. Therefore, the upper limit of the P content is 0.008%.
N，含量较高时，在淬火时，N会从铁素体中析出，使钢板的强度硬度升高，塑性韧性下降，N的含量范围控制在0.0020～0.0030％。When the content of N is high, N will precipitate from the ferrite during quenching, which will increase the strength and hardness of the steel plate and decrease the ductility and toughness. The N content range is controlled within 0.0020 to 0.0030%.
Cu，能够提高钢板的强度和屈强比，且对焊接性能没有不利影响，但如果加入过量，会导致热脆性，所以，Cu的加入上限为0.3％。Cu can increase the strength and yield ratio of the steel sheet without adversely affecting the welding performance. However, if it is added excessively, it will cause hot brittleness. Therefore, the upper limit of Cu addition is 0.3%.
Ni，能强化铁素体并细化珠光体，提高强度并不降低韧性。但从成本角度考虑，也无需加入过多，所以其上限为1.9％。Ni can strengthen ferrite and refine pearlite, increase strength without reducing toughness. However, from a cost point of view, there is no need to add too much, so the upper limit is 1.9%.
B，主要作用是增加钢的淬透性，从而节约其它价格昂贵的合金，降 低成本，但B有促进回火脆性作用，所以B含量的上限设定为0.0015％。因此，为了达到预期的效果，本发明中B含量为B≤0.0015％，优选为B≤0.0010％。B. The main function is to increase the hardenability of steel, thereby saving other expensive alloys and reducing costs. However, B has the effect of promoting temper brittleness, so the upper limit of B content is set at 0.0015%. Therefore, in order to achieve the desired effect, the content of B in the present invention is B≦0.0015%, preferably B≦0.0010%.
本发明成分设计中，同时控制Si，Al，Ti三种元素在范围区间，因为这三种元素都是脱氧元素，不同的成分组合，会对钢中氧化物的种类造成较大的影响。在Al的含量较低的情况下，Si的含量过高会使钢板中生成大量含Si的氧化物，这类氧化物极易在钢板中形成链状，会显著的降低冲击韧性。同时，Si的含量过高，会增加钢板中脆性相马奥岛(岛状马氏体-奥氏体)的生成，降低局部韧性。Al的含量过高，会形成大尺寸的Al 2O 3氧化物，这种硬质氧化物在钢板中会形成裂纹起点，在冲击过程中增加裂纹数量，降低冲击韧性。Ti的含量过高，会促进TiC的生成，TiC会生成局部脆性区，降低冲击韧性。同时，Ti的含量不能太低，过低的Ti含量无法将钢板中的氧含量降低到一个合适的水平，钢板中的氧含量过高，将会增加钢板中的氧化物，降低冲击韧性。 In the composition design of the present invention, the three elements of Si, Al, and Ti are simultaneously controlled in the range interval, because these three elements are all deoxidizing elements, and different composition combinations will have a greater impact on the types of oxides in the steel. In the case of low Al content, excessive Si content will generate a large amount of Si-containing oxides in the steel sheet. Such oxides are very easy to form chains in the steel sheet, which will significantly reduce the impact toughness. At the same time, if the content of Si is too high, it will increase the formation of brittle phases of Martensite (island martensite-austenite) in the steel sheet and reduce local toughness. If the content of Al is too high, large-size Al 2 O 3 oxides will be formed. This hard oxide will form the starting point of cracks in the steel plate, increasing the number of cracks during the impact process and reducing the impact toughness. If the content of Ti is too high, the formation of TiC will be promoted, and TiC will generate local brittle zones and reduce the impact toughness. At the same time, the Ti content should not be too low. Too low Ti content cannot reduce the oxygen content in the steel plate to an appropriate level. Too high oxygen content in the steel plate will increase the oxides in the steel plate and reduce the impact toughness.
在控制Si含量的前提下，控制Ti的含量。钢板中Ti与Al的质量百分比为[Ti]/[Al]＝2～3，目的是控制钢板中生成Al 2O 3-Ti 3O 5-MnS类型的氧化物。当[Ti]/[Al]的质量百分比比值＜2时，钢液中会生成更多数量单独的Al 2O 3，单独的Al 2O 3也会作为析出核心，促进MnS析出，生成Al 2O 3-MnS的氧化物，这种类型的氧化物无法作为形核核心而促进细小板条贝氏体的生成，因为虽然这种类型的氧化物表面也有MnS析出，但不能在氧化物周围的基体中形成贫锰区，从而无法诱导热影响区细小板条贝氏体的生成。当[Ti]/[Al]的质量百分比比值＞3.0时，在生成TiC的同时，也会生成大尺寸的TiN，这些大尺寸的TiN在钢液中析出，极易形成裂纹的起裂点。同时，当Ti/N比不在2.0～3.0范围内时，会导致Al 2O 3-Ti 3O 5-MnS类型的氧化物数量不够多，不足以形成足够的细小板条贝氏体，从而无法提高热影响区低温韧性。 Under the premise of controlling the Si content, the Ti content is controlled. The mass percentage of Ti and Al in the steel sheet is [Ti]/[Al]=2 to 3, and the purpose is to control the formation of Al 2 O 3 -Ti 3 O 5 -MnS type oxides in the steel sheet. When the mass percentage ratio of [Ti]/[Al] is less than 2, a larger amount of separate Al 2 O 3 will be generated in the molten steel, and the separate Al 2 O 3 will also serve as the precipitation core to promote the precipitation of MnS and form Al 2 O 3 -MnS oxide, this type of oxide cannot be used as a nucleation core to promote the formation of fine lath bainite, because although this type of oxide also has MnS precipitated on the surface, it cannot be around the oxide A manganese-poor zone is formed in the matrix, so that the formation of fine lath bainite in the heat-affected zone cannot be induced. When the mass percentage ratio of [Ti]/[Al] is greater than 3.0, large-size TiN will also be generated when TiC is generated. These large-size TiN will precipitate in molten steel and easily form crack initiation points. At the same time, when the Ti/N ratio is not within the range of 2.0 to 3.0, the amount of Al 2 O 3 -Ti 3 O 5 -MnS type oxides will not be large enough to form enough fine lath bainite, and thus cannot Improve the low temperature toughness of the heat-affected zone.
本发明所述的大热输入焊接EH550MPa级调质海工钢板的制造方法，包括如下步骤：The manufacturing method of the high heat input welding EH550MPa grade quenched and tempered marine steel plate of the present invention includes the following steps:
1)冶炼、精炼和铸造1) Smelting, refining and casting
按上述成分冶炼、精炼和连铸成板坯；其中，在钢液脱氧过程中加 入脱氧剂，脱氧剂种类和添加顺序是Si→Mn→Al→Ti；并通过向炉内添加Fe 2O 3粉和Al来精确控制钢液中加Ti前的初始氧含量，Fe 2O 3粉的添加量使钢液的氧含量质量百分比为0.004～0.01％，在此范围内加入Ti进行脱氧； Smelting, refining and continuous casting into slabs according to the above composition; among them, the deoxidizer is added during the deoxidation process of the molten steel. The type and order of the deoxidizer are Si→Mn→Al→Ti; and Fe 2 O 3 is added to the furnace. Powder and Al are used to precisely control the initial oxygen content before adding Ti in the molten steel. The amount of Fe 2 O 3 powder added makes the oxygen content of the molten steel 0.004 to 0.01% by mass, and Ti is added to deoxidize within this range;
钢板中含Ti氧化物的平均尺寸在2μm～3μm之间，且此种类型的含Ti氧化物的密度为不小于50个/mm 2； The average size of Ti-containing oxides in the steel sheet is between 2 μm and 3 μm, and the density of this type of Ti-containing oxides is not less than 50/mm 2 ;
2)轧制2) Rolling
将板坯加热到1100～1200℃，保温至少250min；粗轧开轧温度1000～1100℃，累计压下率大于30％；精轧开轧温度800～900℃，累计压下率大于30％；可选地，保温时间为260-280min，若保温时间不足，会导致温度不均匀，钢锭的内部温度达不到要求，若保温时间过长，则会导致能源的浪费。Heat the slab to 1100～1200℃ for at least 250min; the rough rolling opening temperature is 1000～1100℃, the cumulative reduction rate is greater than 30%; the finishing rolling temperature 800～900℃, the cumulative reduction rate is greater than 30%; Optionally, the holding time is 260-280 min. If the holding time is insufficient, the temperature will be uneven and the internal temperature of the steel ingot will not meet the requirements. If the holding time is too long, it will result in a waste of energy.
3)调质热处理3) Quenched and tempered heat treatment
轧制钢板空冷到室温后，一次加热到910～930℃，保温40～50分钟，出炉淬火到室温，二次加热到650～680℃，保温115～130分钟，出炉空冷至室温。After the rolled steel plate is air-cooled to room temperature, it is heated to 910～930℃ once, kept for 40～50 minutes, quenched to room temperature after being discharged, heated to 650～680℃ for the second time, kept kept for 115～130 minutes, and cooled to room temperature after discharge.
在本发明的制造方法中，采用的冶炼工艺是Si→Mn→Al→Ti，在合适的钢液氧含量条件下加入Ti。在脱氧过程中，先使用Si、Mn进行脱氧，将钢板中的自由氧含量降低，Si、Mn的脱氧产物容易形成低熔点的氧化物，这些低熔点的氧化物上浮溶解到渣中去除，能在显著降低钢液自由氧含量的条件下不增加钢液的氧化物。之后再使用Al脱氧，Al有很强的脱氧作用，能将钢液中的自由氧含量控制在一个较低的水平，最后加入Ti进行氧化物的控制。加入Ti后，一部分自由氧与Ti结合，生成Ti的氧化物，一部分Ti与氧化铝复合在一起生成Al 2O 3-Ti 3O 5复合的氧化物，还有一部分的过量Ti将溶解在钢板中，形成自由钛。本发明的氧化物控制工艺的关键点就是通过Al的加入将加Ti前的氧含量控制在一个合适的范围，使在该钢板中氧含量的条件下生成的氧化物能对大热输入焊接后热影响区的组织起到诱导的作用，诱导热影响区生成细小板条贝氏体组织，从而提高大热输入焊接热影响区的低温韧性。 In the manufacturing method of the present invention, the adopted smelting process is Si→Mn→Al→Ti, and Ti is added under the condition of suitable liquid steel oxygen content. In the deoxidation process, Si and Mn are used for deoxidation first to reduce the free oxygen content in the steel plate. The deoxidation products of Si and Mn easily form low-melting-point oxides. These low-melting-point oxides float up and dissolve into the slag for removal. Under the condition of significantly reducing the free oxygen content of molten steel, the oxides of molten steel are not increased. After that, Al deoxidation is used. Al has a strong deoxidation effect and can control the free oxygen content in the molten steel to a low level. Finally, Ti is added to control the oxide. After adding Ti, part of the free oxygen combines with Ti to form Ti oxides, part of Ti is compounded with alumina to form Al 2 O 3 -Ti 3 O 5 composite oxides, and part of the excess Ti will dissolve in the steel plate. In, free titanium is formed. The key point of the oxide control process of the present invention is to control the oxygen content before adding Ti to an appropriate range through the addition of Al, so that the oxides generated under the condition of the oxygen content in the steel sheet can resist large heat input after welding. The structure of the heat-affected zone plays an inducing role, inducing the formation of fine lath bainite structure in the heat-affected zone, thereby improving the low-temperature toughness of the heat-affected zone of large heat input welding.
钢板中Al的含量要控制在0.002～0.010％之间，过高的Al容易形成簇 状氧化铝，影响钢液的纯净度，过低的Al，不能保证钢液中的自由氧含量控制。The content of Al in the steel plate should be controlled between 0.002% and 0.010%. Too high Al is easy to form clustered alumina, which affects the purity of molten steel. Too low Al cannot guarantee the control of free oxygen content in molten steel.
钢板中[Ti]/[Al]要控制在一个合适比值。如果[Ti]/[Al]过大，将会导致钢液中生成大于5μm的Ti的氧化物，影响低温韧性。[Ti]/[Al]过小，钢液中的Al 2O 3数量尺寸都会显著增加，不能保证钢液中生成足够量的含Ti氧化物Al 2O 3-Ti 3O 5-MnS。所以，[Ti]/[Al]要控制为2～3。 [Ti]/[Al] in the steel plate should be controlled at an appropriate ratio. If [Ti]/[Al] is too large, it will cause the formation of Ti oxides larger than 5μm in the molten steel, which will affect the low temperature toughness. If [Ti]/[Al] is too small, the quantity and size of Al 2 O 3 in the molten steel will increase significantly, and it cannot guarantee that a sufficient amount of Ti-containing oxide Al 2 O 3 -Ti 3 O 5 -MnS is generated in the molten steel. Therefore, [Ti]/[Al] should be controlled to 2～3.
通过研究发现，当钢液中的氧含量过低时，低于0.0040％时，钢液中无法生成足够数量的含Ti氧化物，更多的Ti与钢板中的N结合，在钢液温度较高时生成TiN，尺寸较大，这种类型的氧化物不能充分起到诱导大热输入热影响区细小板条贝氏体组织的作用。当钢液中的氧含量过高时，高于0.01％时，钢液中大于5μm的氧化物占比较大，且2μm～3μm尺寸范围的氧化物密度较小，大尺寸的氧化物容易在冲击时形成裂纹起点，特定尺寸的氧化物密度不足也不能充分的改变热影响区的组织、起到提高低温韧性的作用，所以，加Ti前的氧含量控制在0.0040～0.01％。Through research, it is found that when the oxygen content in the molten steel is too low, below 0.0040%, a sufficient amount of Ti-containing oxides cannot be generated in the molten steel, and more Ti combines with the N in the steel plate, and the temperature of the molten steel is lower TiN is formed when it is high, and the size is larger. This type of oxide cannot fully induce the small lath bainite structure in the heat-affected zone with large heat input. When the oxygen content in the molten steel is too high, higher than 0.01%, the oxides larger than 5μm in the molten steel account for a relatively large proportion, and the density of oxides in the size range of 2μm to 3μm is small, and large-sized oxides are likely to be impacted. The starting point of the crack is formed when the oxide density of a specific size is insufficient, and the structure of the heat-affected zone cannot be changed sufficiently and the low-temperature toughness can be improved. Therefore, the oxygen content before adding Ti is controlled at 0.0040-0.01%.
本发明研究了热影响区夹杂物，确定了夹杂物的合适成分、尺寸和数量。夹杂物的成分采用蔡司的EVO18扫描电子显微镜SEM-EDS进行分析，夹杂物的尺寸和密度采用夹杂物自动分析仪进行检测分析。夹杂物自动分析仪是采用SEM和EDS来采集数据，利用分析软件对夹杂物进行自动检测、分析，能够准确的识别出钢板中的夹杂物成分、尺寸、数量等信息。利用该系统对钢板中的夹杂物进行分析发现，钢板中含Ti夹杂物的平均尺寸在2μm～3μm之间且此种类型的夹杂物密度为不小于50个/mm 2的实施例，低温冲击韧性较高。同时，这种含钛的夹杂物类型必须为Al 2O 3-Ti 3O 5-MnS复合氧化物。这种以Al 2O 3-Ti 3O 5为核心表面析出MnS的氧化物对热影响区细小板条贝氏体的生成有着重要的作用。一般认为Al 2O 3-Ti 3O 5-MnS复合氧化物的形成归功于Al 2O 3-Ti 3O 5氧化物周围Mn和S元素的局部饱和，但由于MnS在钢液中的溶解度较大，一般不会在钢液中析出，但在凝固和冷却过程中MnS的溶解度降低且S元素易于偏析，所以极易在先期生成的Al 2O 3-Ti 3O 5氧化物表面析出，这种类型的Al 2O 3-Ti 3O 5-MnS复合氧化物可以作为细小板条贝氏体形核的核心，在Al 2O 3-Ti 3O 5-MnS复合氧化物与钢板基体界面附近形成贫锰区，促进细小 板条贝氏体的生成。对热影响区的氧化物利用ESD进行分析发现，尺寸在2μm～3μm之间的Al 2O 3-Ti 3O 5-MnS复合氧化物，很好的诱导了热影响区的细小板条贝氏体的生成。 The present invention studies the inclusions in the heat-affected zone, and determines the appropriate composition, size and quantity of the inclusions. The composition of inclusions is analyzed by Zeiss EVO18 scanning electron microscope SEM-EDS, and the size and density of inclusions are detected and analyzed by automatic inclusion analyzer. The automatic inclusion analyzer uses SEM and EDS to collect data, uses analysis software to automatically detect and analyze inclusions, and can accurately identify the composition, size, quantity and other information of inclusions in the steel plate. Using this system inclusions in steel sheet analysis found that the average size of the inclusions in the steel sheet containing Ti and the inclusion of this type of embodiment a density of 50 / mm 2 is not smaller than between 2μm ~ 3μm, low temperature impact Toughness is higher. At the same time, the type of such titanium-containing inclusions must be Al 2 O 3 -Ti 3 O 5 -MnS composite oxide. This kind of MnS oxide precipitated on the surface of Al 2 O 3 -Ti 3 O 5 as the core plays an important role in the formation of fine lath bainite in the heat-affected zone. It is generally believed that the formation of Al 2 O 3 -Ti 3 O 5 -MnS composite oxide is attributed to the local saturation of Mn and S around the Al 2 O 3 -Ti 3 O 5 oxide. However, due to the relatively high solubility of MnS in molten steel Generally, it will not precipitate in molten steel. However, during solidification and cooling, the solubility of MnS decreases and the element S is easy to segregate, so it is very easy to precipitate on the surface of the Al 2 O 3 -Ti 3 O 5 oxides formed in the early stage. Various types of Al 2 O 3 -Ti 3 O 5 -MnS composite oxides can be used as the core of fine lath bainite nucleation, which is formed near the interface between Al 2 O 3 -Ti 3 O 5 -MnS composite oxide and the steel substrate. The manganese-poor zone promotes the formation of small lath bainite. Analyzing the oxides in the heat-affected zone by ESD, it is found that the Al 2 O 3 -Ti 3 O 5 -MnS composite oxide with a size between 2 μm and 3 μm can induce the small laths in the heat-affected zone. The generation of the body.
本发明在轧制和热处理工艺中，轧制前的加热温度为1100～1200℃，保温至少250min，保证完全奥氏体化，粗轧开轧温度1000～1100℃，累计压下率大于30％，在此温度范围内轧制，可以发生再结晶，细化了奥氏体晶粒，当压下率小于30％时，残存的粗大奥氏体晶粒较多，影响母材强度和韧性。In the rolling and heat treatment process of the present invention, the heating temperature before rolling is 1100～1200℃, the heat preservation is at least 250min to ensure complete austenitization, the rough rolling opening temperature is 1000～1100℃, and the cumulative reduction rate is greater than 30% , Rolling in this temperature range can recrystallize and refine the austenite grains. When the reduction ratio is less than 30%, there are more coarse austenite grains remaining, which affect the strength and toughness of the base metal.
精轧开轧温度800～900℃，可以进行两相区轧制，轧制中形成的位错可以作为铁素体形核的核心，提高母材的强度和韧性。累计压下率大于30％，当压下率小于30％时，形成的位错较少，无法诱发足够的针状铁素体形核。The finish rolling opening temperature is 800-900℃, and it can be rolled in the two-phase zone. The dislocations formed during the rolling can be used as the core of ferrite nucleation to improve the strength and toughness of the base material. The cumulative reduction rate is greater than 30%. When the reduction rate is less than 30%, fewer dislocations are formed, and sufficient acicular ferrite nucleation cannot be induced.
调质热处理工艺，轧制钢板空冷到室温后，一次加热到910～930℃，保温40～50分钟，出炉水淬到室温。此淬火工艺可以使本发明的海工钢板以最小的冷却速度转变为马氏体。二次加热到650～680℃，保温115～130min，出炉空冷至室温。淬火后的钢以马氏体为主，马氏体在室温下处于亚稳定状态，有向铁素体加渗碳体的稳定状态转化的趋势，要进行回火处理，消除内应力，防止变形和开裂。在650～680℃回火，保温115～130min，可以使海工钢板淬火后的马氏体组织中的过饱和碳析出，母材的主要组织转变为回火马氏体，使调质海工钢板母材组织具有较高的强度和韧性。Quenching and tempering heat treatment process, after the rolled steel plate is air-cooled to room temperature, it is heated to 910-930°C at one time, kept for 40-50 minutes, and then quenched to room temperature with water. This quenching process can transform the marine steel sheet of the present invention into martensite at a minimum cooling rate. Reheat it to 650～680℃, keep it for 115～130min, and cool it out to room temperature. The quenched steel is mainly martensite. Martensite is in a metastable state at room temperature and has a tendency to transform into a stable state of ferrite and cementite. Tempering treatment is required to eliminate internal stress and prevent deformation And cracking. Tempering at 650～680℃ and holding for 115～130min can make the supersaturated carbon in the martensite structure of the marine steel plate after quenching precipitate, and the main structure of the base metal is transformed into tempered martensite, so that the quenched and tempered marine The base metal structure of steel plate has high strength and toughness.
船级社要求的EH550成分范围为：C≤0.18，Mn0.9～1.6，Si≤0.5，S≤0.035，P≤0.035，Al≥0.015.Nb＝0.02～0.05，V＝0.05～0.1，Ti≤0.02，Cu≤0.35，Cr≤0.2，Ni≤0.4，Mo≤0.08。The composition range of EH550 required by classification societies is: C≤0.18, Mn0.9～1.6, Si≤0.5, S≤0.035, P≤0.035, Al≥0.015. Nb＝0.02～0.05, V＝0.05～0.1, Ti≤ 0.02, Cu≤0.35, Cr≤0.2, Ni≤0.4, Mo≤0.08.
在冶炼过程中，脱氧顺序是非常关键的，必须按照Si→Mn→Al→Ti的顺序进行，且钢液中加Ti前的氧含量质量百分比为0.0040～0.01％。在这种脱氧工艺条件下，能够生成密度为不小于50个/mm2、平均尺寸在2μm～3μm之间且类型为Al 2O 3-Ti 3O 5-MnS的微米级复合氧化物。脱氧顺序的变化，会导致钢板中氧化物的类型变化，导致热影响区脆性相的生成，影响冲击韧性。 In the smelting process, the order of deoxidation is very critical. It must be carried out in the order of Si→Mn→Al→Ti, and the mass percentage of oxygen before adding Ti to the molten steel is 0.0040-0.01%. Under such deoxidation process conditions, it is possible to generate micron-level composite oxides with a density of not less than 50 pcs/mm2, an average size of 2 μm to 3 μm, and a type of Al 2 O 3 -Ti 3 O 5 -MnS. The change of the deoxidation sequence will lead to the change of the type of oxides in the steel plate, leading to the formation of brittle phases in the heat-affected zone, and affecting the impact toughness.
本发明的有益效果：The beneficial effects of the present invention:
本发明优化了高强度海工钢板的成分设计，在精炼的过程中，通过控制合适的钢板中自由氧，并优化脱氧合金和合金加入顺序，调整脱氧合金Al/Ti的比值，实现控制Al 2O 3-Ti 3O 5-MnS氧化物的尺寸、成分和数量密度的目标，使Al 2O 3-Ti 3O 5-MnS氧化物能在凝固和相变过程中诱导热影响区组织内的细小板条贝氏体的体积，增加了海工钢板大热输入焊接后热影响区的低温韧性。 The present invention optimizes the composition design of the high-strength marine steel plate. During the refining process, by controlling the free oxygen in the appropriate steel plate, and optimizing the deoxidizing alloy and alloy adding sequence, adjusting the deoxidizing alloy Al/Ti ratio, and achieving the control of Al 2 size, composition and number density of the target O 3 -Ti 3 O 5 -MnS oxide of the Al 2 O 3 -Ti 3 O 5 -MnS oxide can induce HAZ during solidification and phase transformation The volume of the small lath bainite increases the low-temperature toughness of the heat-affected zone of the offshore steel plate after high heat input welding.
本发明避免使用Ca、Mg、Re等强脱氧剂，简化冶炼工序，避免了采用强脱氧剂工艺的脱氧剂保管不易和加入困难等缺点。The invention avoids the use of strong deoxidizers such as Ca, Mg, Re, etc., simplifies the smelting process, and avoids the shortcomings of difficult storage and difficulty in adding the deoxidizer using the strong deoxidizer process.
具体实施方式Detailed ways
下面结合实施例对本发明做进一步说明。The present invention will be further described below in conjunction with the embodiments.
在本发明的实施例中，在精炼过程中调整合金成分，并按照Si→Mn→Al的顺序加入脱氧合金进行脱氧，在保证合金成分的同时，再加入Fe 2O 3粉调节钢板中氧含量，随后加入钛铁，钛铁的成分为Ti 69.8％。 In the embodiment of the present invention, the alloy composition is adjusted during the refining process, and the deoxidizing alloy is added in the order of Si→Mn→Al for deoxidation. While ensuring the alloy composition, Fe 2 O 3 powder is added to adjust the oxygen content in the steel sheet. , And then add ferro-titanium, the composition of ferro-titanium is Ti 69.8%.
表1中列出了本发明实施例和对比例的化学成分。对比例中的Al的含量为0.045％和0.051％，Ti/Al比值和2～3μm尺寸范围的含Ti氧化物密度中有一项或两项不满足本发明的要求。Table 1 lists the chemical components of the examples and comparative examples of the present invention. The Al content in the comparative example is 0.045% and 0.051%, and one or two of the Ti/Al ratio and the Ti-containing oxide density in the size range of 2 to 3 μm do not meet the requirements of the present invention.
表2为本发明实施例和对比例钢板的制造工艺。表3列出了实施例和对比例中母材的强度、低温韧性和热影响区的低温韧性对比。母材的屈服强度、抗拉强度和断面收缩率为两个检测值的平均值，母材-40℃夏比冲击功和热影响区-40℃夏比冲击功是三个检测值的平均值。Table 2 shows the manufacturing process of the steel plates of the examples and comparative examples of the present invention. Table 3 lists the comparison of the strength, low-temperature toughness and low-temperature toughness of the heat-affected zone of the base materials in the examples and comparative examples. The yield strength, tensile strength and reduction of area of the base metal are the average of the two measured values. The -40℃ Charpy impact energy of the base metal and the -40℃ Charpy impact energy of the heat-affected zone are the average of the three measured values. .
其中，拉伸实验按照GB/T 228.1-2010金属材料拉伸试验第1部分：室温拉伸试验方法的测试标准进行母材的屈服强度、抗拉强度、断面收缩率的测试；采用SCL233200kN常温拉伸试验机；试验条件：25℃，屈服前为2mm/min，湿度为56％，屈服后为20mm/min。冲击实验按照GB/T 229-2007金属材料夏比摆锤冲击试验方法，采用仪器化冲击试验机(SCL112)，打击能量为60(J)。Among them, the tensile test is carried out in accordance with GB/T 228.1-2010 Metallic Material Tensile Test Part 1: The test standard of the room temperature tensile test method to test the yield strength, tensile strength, and reduction of area of the base material; SCL233200kN normal temperature tensile test Tensile testing machine; test conditions: 25°C, 2mm/min before yielding, humidity 56%, and 20mm/min after yielding. The impact test is in accordance with the GB/T 229-2007 Charpy Pendulum Impact Test Method for Metallic Materials, using an instrumented impact testing machine (SCL112), and the impact energy is 60 (J).
从表中数据可以看出，实施例比对比例的母材屈服强度和抗拉强度都略高。在经过50kj/cm、100kj/cm、150kj/cm的热模拟试验后，实施例的 热影响区-40℃夏比冲击功都在80j以上。对比例经过三个热输入的热模拟后，-40℃夏比冲击功比较低。所以，实施例经过氧化物控制工艺和成分设计后，热影响区的低温韧性得到了明显的改善，符合大热输入焊接用海工钢板的要求。It can be seen from the data in the table that the yield strength and tensile strength of the base material of the examples are slightly higher than those of the comparative examples. After thermal simulation tests of 50kj/cm, 100kj/cm, and 150kj/cm, the Charpy impact energy of the heat-affected zone at -40°C of the examples are all above 80j. After thermal simulation of three heat inputs in the comparative example, the Charpy impact energy at -40°C is relatively low. Therefore, after the embodiments are subjected to the oxide control process and composition design, the low-temperature toughness of the heat-affected zone is significantly improved, which meets the requirements of marine steel plates for welding with large heat input.
本发明采用优化成分设计，控制钢板中合适的Ti/Al比，并优化精炼过程中的脱氧合金和脱氧顺序，并通过添加Fe 2O 3粉的方式来控制适合含Ti氧化物的尺寸、成分和数量密度，在热影响区诱导细小板条贝氏体组织，最终制造出可大热输入焊接用的EH550高强度海工钢板。 The present invention adopts optimized composition design to control the appropriate Ti/Al ratio in the steel sheet, optimize the deoxidation alloy and deoxidation sequence in the refining process, and control the size and composition suitable for Ti-containing oxides by adding Fe 2 O 3 powder And the number density, the small lath bainite structure is induced in the heat-affected zone, and finally the EH550 high-strength marine steel plate for welding with large heat input is manufactured.
Figure PCTCN2021078224-appb-000001
Figure PCTCN2021078224-appb-000001
Figure PCTCN2021078224-appb-000002
Figure PCTCN2021078224-appb-000002
Figure PCTCN2021078224-appb-000003
Figure PCTCN2021078224-appb-000003
Figure PCTCN2021078224-appb-000004
Figure PCTCN2021078224-appb-000004

Claims (9)

  1. 一种大热输入焊接EH550MPa级调质海工钢板，其成分质量百分比为：C 0.06～0.12％，Si 0.02～0.06％，Mn 0.7～1.2％，Ti 0.006～0.012％，Al 0.002～0.010％，Cr 0.30～0.50％，Mo 0.3～0.4％，V 0.03～0.04％，N 0.0020～0.0030％，S 0.002～0.010％，P≤0.008％，其余为Fe和不可避免杂质；其中，钢板中含Ti氧化物的平均尺寸在2μm～3μm之间且此种类型的含Ti氧化物的密度为不小于50个/mm 2。 A large heat input welded EH550MPa grade quenched and tempered marine steel plate, the composition mass percentage is: C 0.06～0.12%, Si 0.02～0.06%, Mn 0.7～1.2%, Ti 0.006～0.012%, Al 0.002～0.010%, Cr 0.30～0.50%, Mo 0.3～0.4%, V 0.03～0.04%, N 0.0020～0.0030%, S 0.002～0.010%, P≤0.008%, the rest is Fe and inevitable impurities; among them, the steel plate contains Ti oxidation The average size of the object is between 2 μm and 3 μm and the density of this type of Ti-containing oxide is not less than 50 pieces/mm 2 .
  2. 如权利要求1所述的大热输入焊接EH550MPa级调质海工钢板，其特征在于，还含有Cu≤0.3％、Ni≤1.9％或B≤0.0015％中一种以上元素，以质量百分比计。The high heat input welded EH550MPa grade quenched and tempered marine steel sheet according to claim 1, characterized in that it also contains more than one element among Cu≤0.3%, Ni≤1.9% or B≤0.0015%, calculated by mass percentage.
  3. 如权利要求1或2所述的大热输入焊接EH550MPa级调质海工钢板，其特征在于，钢中[Ti]/[Al]＝2～3。The high heat input welding EH550MPa grade quenched and tempered marine steel sheet according to claim 1 or 2, characterized in that [Ti]/[Al]=2～3 in the steel.
  4. 如权利要求1或2所述的大热输入焊接EH550MPa级调质海工钢板，其特征在于，所述调质海工钢板的显微组织为回火马氏体组织。The high heat input welding EH550MPa grade quenched and tempered marine steel sheet according to claim 1 or 2, wherein the microstructure of the quenched and tempered marine steel sheet is a tempered martensite structure.
  5. 如权利要求1或2所述的大热输入焊接EH550MPa级调质海工钢板，其特征在于，所述调质海工钢板的屈服强度EH≥550MPa、抗拉强度≥670MPa，母材-40℃夏比冲击功(单个值)≥180J，焊接热输入50kj/cm，100kj/cm，150kj/cm的热影响区-40℃夏比冲击功(单个值)≥80J。The high heat input welding EH550MPa grade quenched and tempered marine steel sheet according to claim 1 or 2, characterized in that the yield strength of the quenched and tempered marine steel sheet is EH≥550MPa, the tensile strength≥670MPa, and the base material is -40°C Charpy impact energy (single value) ≥ 180J, welding heat input 50kj/cm, 100kj/cm, 150kj/cm heat affected zone -40℃ Charpy impact energy (single value) ≥ 80J.
  6. 如权利要求1所述的大热输入焊接EH550MPa级调质海工钢板，其特征在于，所述含Ti氧化物为Al 2O 3-Ti 3O 5-MnS类型的复合氧化物。 The high heat input welding EH550MPa grade quenched and tempered marine steel sheet according to claim 1, wherein the Ti-containing oxide is an Al 2 O 3 -Ti 3 O 5 -MnS type composite oxide.
  7. 一种如权利要求1～6中任何一项所述的大热输入焊接EH550MPa级调质海工钢板的制造方法，其特征是，包括如下步骤：A method for manufacturing a large heat input welding EH550MPa grade quenched and tempered marine steel sheet according to any one of claims 1 to 6, characterized in that it comprises the following steps:
    1)冶炼、精炼和铸造1) Smelting, refining and casting
    按权利要求1至3任一项所述成分冶炼、精炼和连铸成板坯；其中，在钢液脱氧过程中加入脱氧剂，脱氧剂种类和添加顺序是Si→Mn→Al→Ti；并通过向炉内添加Fe 2O 3粉和Al来精确控制钢液中加Ti前的初始氧含量，Fe 2O 3粉的添加量使钢液的氧含量质量百分比为0.0040～0.01％，在此范围内加入Ti进行脱氧； Smelting, refining and continuous casting into slabs according to any one of claims 1 to 3; wherein, a deoxidizer is added during the deoxidation process of molten steel, and the type and order of the deoxidizer are Si→Mn→Al→Ti; and By adding Fe 2 O 3 powder and Al to the furnace to precisely control the initial oxygen content before adding Ti to the molten steel, the amount of Fe 2 O 3 powder added makes the oxygen content of the molten steel 0.0040～0.01% by mass. Add Ti within the range for deoxidation;
    钢板中含Ti氧化物的平均尺寸在2μm～3μm之间，且此种类型的含Ti氧化物的密度为不小于50个/mm 2； The average size of Ti-containing oxides in the steel sheet is between 2 μm and 3 μm, and the density of this type of Ti-containing oxides is not less than 50/mm 2 ;
    2)轧制2) Rolling
    将所述板坯加热到1100～1200℃，保温至少250min，粗轧开轧温度1000～1100℃，累计压下率大于30％；精轧开轧温度800～900℃，累计压下率大于30％；Heat the slab to 1100～1200℃, hold for at least 250min, rough rolling opening temperature 1000～1100℃, cumulative reduction rate greater than 30%; finishing rolling temperature 800～900℃, cumulative reduction rate greater than 30 %;
    3)调质热处理3) Quenched and tempered heat treatment
    轧制钢板空冷到室温后，一次加热到910～930℃，一次保温40～50分钟，出炉淬火到室温，二次加热到650～680℃，二次保温115～130分钟，出炉空冷至室温。After the rolled steel plate is air-cooled to room temperature, it is heated to 910-930°C once, held for 40-50 minutes once, quenched to room temperature once out, heated to 650-680°C for the second time, held for 115-130 minutes for the second time, and air-cooled to room temperature after leaving the furnace.
  8. 如权利要求7所述的大热输入焊接EH550MPa级调质海工钢板的制造方法，其特征是，所述调质海工钢板的显微组织为回火马氏体组织。The method for manufacturing a large heat input welding EH550MPa grade quenched and tempered marine steel sheet according to claim 7, wherein the microstructure of the quenched and tempered marine steel sheet is a tempered martensite structure.
  9. 如权利要求7或8所述的大热输入焊接EH550MPa级调质海工钢板的制造方法，其特征是，所述调质海工钢板的屈服强度EH≥550MPa、抗拉强度≥670MPa，母材-40℃夏比冲击功(单个值)≥180J，焊接热输入50kj/cm，100kj/cm，150kj/cm的热影响区-40℃夏比冲击功(单个值)≥80J。The manufacturing method of the high heat input welding EH550MPa grade quenched and tempered marine steel plate according to claim 7 or 8, characterized in that the yield strength of the quenched and tempered marine steel plate is EH ≥ 550 MPa, the tensile strength ≥ 670 MPa, and the base material -40℃ Charpy impact energy (single value) ≥ 180J, welding heat input 50kj/cm, 100kj/cm, 150kj/cm heat affected zone -40℃ Charpy impact energy (single value) ≥ 80J.
PCT/CN2021/078224 2020-02-28 2021-02-26 Eh 550 mpa grade quenched and tempered marine steel plate for high heat input welding and manufacturing method therefor WO2021170104A1 (en)

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