WO2016119500A1 - 一种具有高止裂性能的钢板及其制造方法 - Google Patents

一种具有高止裂性能的钢板及其制造方法 Download PDF

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WO2016119500A1
WO2016119500A1 PCT/CN2015/093745 CN2015093745W WO2016119500A1 WO 2016119500 A1 WO2016119500 A1 WO 2016119500A1 CN 2015093745 W CN2015093745 W CN 2015093745W WO 2016119500 A1 WO2016119500 A1 WO 2016119500A1
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steel sheet
high crack
property according
crack arresting
arresting property
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French (fr)
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李冰
张才毅
高珊
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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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
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C21D2201/00—Treatment for obtaining particular effects
    • C21D2201/05—Grain orientation
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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

Definitions

  • the present invention relates to a steel sheet and a method of manufacturing the same, and more particularly to an alloy steel sheet and a method of manufacturing the same.
  • Japanese Patent Publication No. CN101307412A published on November 19, 2008, entitled "Stainless steel crack propagation stop characteristic and steel sheet having excellent toughness at the center portion of the thickness” and a method for producing the same, discloses a steel sheet.
  • the mass percentage (wt.%) of each chemical element in the steel sheet is: C: 0.01-0.06, Si: 0.01-0.8, Mn: 1.0-1.8, Cr: 0.05-0.5, Ni: 0.20-0.8, Mo : 0.05-0.5, Cu: 0.05-0.08, Alt: 0.01-0.08, Nb: 0.02-0.08, Ti: 0.005-0.03, B: 0.00003-0.0003, Ca: 0.0005-0.0030, N: 0.003-0.008, REM: 0.0050 -0.030; and the steel sheet is composed of a ferrite-based structure, and the orientation of the two crystals is in the region of the entire thickness of the portion of the outermost layer of the steel sheet corresponding to the thickness of 1%.
  • Crystal grains enclosed have an average equivalent circle diameter of 8 mm or less and satisfy the relationship of the following formula (1): 1-(A2 - A1) / 100 ⁇ 0.8, wherein A1: crystal grains having a crystal orientation difference of 55 or more The proportion (area%) in the population, A2: the proportion (area%) of the crystal grains having a crystal orientation difference of less than 15° in the whole.
  • the mass percentage (wt.%) of each chemical element of the steel sheet is: C: 0.01-0.30, Si: ⁇ 0.5, Mn: ⁇ 2.0, Cr: ⁇ 0.5, Ni: ⁇ 1.0, Mo: ⁇ 0.5, Cu : ⁇ 0.9, V: ⁇ 0.1, Alt: 0.001-0.1, Nb: 0.005-0.05, Ti: 0.005-0.02, B: 0.0003-0.003, Ca: 0.0003-0.005, N: 0.001-0.008, Mg: 0.0003-0.005 ;REM: 0.0003-0.005; the balance is Fe and other unavoidable impurities.
  • the technical solution of the above patent document adopts ultra-low carbon and repeated phase change means to obtain surface ultrafine crystal.
  • Japanese Patent Publication No. JP2002-241891A published on August 28, 2002, entitled "Structural steel having excellent brittle crack propagation stop characteristics and fatigue crack propagation characteristics after plastic deformation, and a method for producing the same"
  • the steel plate in the Japanese patent document adopts a chemical element composition design of ultra-low carbon, high Ni and no Al, and through the controlled rolling process, the (211) surface texture parallel to the rolling plane is developed, and (100) The crystal texture is
  • the object of the present invention is to provide a steel sheet having high crack arresting property, which has high strength and good low temperature impact toughness, and has a yield strength of ⁇ 400 MPa, and a -40 °C Charpy V-notch impact energy ⁇ 64 J.
  • it compared with the steel plate in the prior art, it has excellent crack arresting performance, and its non-plastic transition temperature (NDTT, Nil-Ductility Transition Temperature) ⁇ -70 ° C, which is particularly suitable for use in ships, offshore engineering structures, etc. Manufacturing field.
  • the present invention proposes a steel sheet having high crack arresting property, wherein the chemical element mass percentage content is:
  • the balance is Fe and other unavoidable impurities.
  • C is the most basic strengthening element.
  • a gap solid solution can be formed to function as a solid solution strengthening, and C can also be combined with a forming element of a strong carbide to form a carbide precipitate, thereby functioning as a precipitation strengthening.
  • C can also improve the hardenability of steel.
  • C which is too high in content will adversely affect the ductility, toughness, crack arrestability and weldability of the steel sheet, and also reduce the solid solution of microalloying elements such as Nb and V. Affect the precipitation enhancement effect.
  • the content of the C element in the steel sheet having high crack arresting property according to the present invention is controlled to be between 0.04 and 0.12%.
  • Si acts as a reducing agent and a deoxidizer to eliminate the adverse effects of FeO inclusions on steel.
  • Si exists in a solid solution state in ferrite or austenite, which can increase the hardness and strength of ferrite or austenite and reduce the austenite phase region.
  • the present invention controls Si to 0.10% ⁇ Si ⁇ 0.30%.
  • Mn is one of the most basic alloying elements for low-alloy high-strength steels.
  • the strength of the steel sheet is increased by solid solution strengthening of Mn to compensate for the loss of strength of the steel sheet due to a decrease in the C content in the steel sheet.
  • Mn is also an element that expands the ⁇ phase region, which can reduce the ⁇ phase temperature of steel. Degree, help to obtain fine phase change products in the steel plate to improve the toughness and crack arrest performance of the steel plate.
  • the mass percentage of Mn in the steel sheet having high crack arresting property of the present invention is from 0.60 to 1.90%.
  • Chromium is one of the important elements for improving the hardenability of steel sheets. For steel plates with extra-thickness specifications, it is necessary to increase the hardenability of the steel sheet by adding more Cr elements to compensate for the strength loss caused by the thickness, and to improve the strength of the steel sheet while improving the performance of the steel sheet in the thickness direction. Uniformity. Cr can also inhibit the transformation of pro-eutectoid ferrite and pearlite, which is beneficial to obtain acicular ferrite structure.
  • the content of Cr in the technical solution of the present invention should be limited to a range of 0.01% to 0.40%.
  • Nickel is an element that improves the low temperature toughness of materials. Adding an appropriate amount of Ni can reduce the stacking fault energy of the crystal, facilitate the slip motion of the dislocation, improve the impact toughness of the material, and especially improve the impact toughness of the central portion of the extra-thick plate. At the same time, the addition of Ni element in the technical solution can also improve the crack arrest performance of the steel sheet. In addition, Ni can also enhance the hardenability of Mo. However, if the Ni content is too high, the slab surface tends to form a high-viscosity iron oxide scale, which is difficult to remove in the subsequent manufacturing process, thereby affecting the surface quality and fatigue properties of the steel sheet.
  • the Ni content in the steel sheet having high crack arresting property according to the present invention needs to be controlled to be 0.10% to 0.70%.
  • Mo is an element that improves the hardenability of a steel sheet, and its effect is second only to the Mn element. Mo can not only effectively increase the strength of the steel sheet, but also inhibit the transformation of the pro-eutectoid ferrite and pearlite to help the steel sheet obtain the acicular ferrite structure. However, as the Mo content increases, the yield strength of the steel sheet gradually increases, while the plasticity of the steel sheet gradually decreases. For the steel sheet having high crack arresting property of the present invention, the mass percentage content of Mo should be set to 0.001% to 0.40%.
  • Cu can appropriately improve the hardenability of the steel sheet, and Cu can also improve the atmospheric corrosion resistance of the steel sheet.
  • the addition of an excessively high amount of Cu element to the steel deteriorates the weldability of the steel sheet, so the content of the Cu element in the steel sheet having high crack arresting property according to the present invention is controlled to be 0.001% to 0.50%.
  • Al is an element added to steel for deoxidation. After the deoxidation is complete, Al lowers the steel plate The content of O in the steel to improve the aging properties of the steel sheet. In addition, the addition of an appropriate amount of Al is also advantageous for refining the grains, thereby improving the toughness of the steel. Therefore, the content of the Al element in the steel sheet having high crack arresting property in the present invention is limited to 0.01 to 0.06%.
  • Nb is one of the most effective elements for increasing the recrystallization termination temperature. Nb can effectively reduce the rolling mill load and has a significant effect on grain refinement.
  • the rolling deformation is completed in the recrystallization and non-recrystallization rolling stages, and at this stage, Nb is precipitated by strain to inhibit the recovery and recrystallization of the deformed austenite, thereby refining The effect of grain size.
  • the Nb having a too high content cannot be dissolved, and the Nb is not advantageous.
  • Nb is also an expensive metal element, and adding more Nb will increase the manufacturing cost accordingly. Therefore, the Nb content in the steel sheet having high crack arresting property of the present invention should be controlled to be 0.01% to 0.06%.
  • Titanium is a strong solid N element. Since the Ti/N ratio is 3.42, a certain amount of N element can be fixed by using a small amount of Ti. For example, Ti of about 0.02 wt.% can fix N in a steel having a mass percentage of 60 ppm or less. In the slab continuous casting, the added Ti can form a fine high-temperature stable TiN precipitation phase with N. Such fine TiN particles can effectively hinder the growth of austenite grains during reheating of the slab, and contribute to the improvement of the solid solubility of Nb in austenite.
  • the addition of an appropriate Ti content is advantageous for the formation of stable TiN particles, which acts to suppress grain growth in the heat-affected zone during welding to improve the impact toughness of the weld heat affected zone.
  • N The nitride formed by N and alloying elements is a non-metallic inclusion, and more importantly, the N element reduces the role of the alloying element.
  • N also has a beneficial effect, and TiN formed with Ti can prevent the growth of austenite grains when the slab is heated.
  • its side effects are greater, so the technical solution limits the N content to ⁇ 0.007%.
  • the form of sulfide can be controlled by Ca treatment, the anisotropy of the steel sheet can be improved, and the low temperature toughness of the steel sheet can be improved.
  • the Ca content is less than 0.0001 wt.%, it does not produce any effect, and when the Ca content is more than 0.0045.wt%, many CaO, CaS are generated, and large inclusions are formed, which damages the toughness of the steel sheet. It even affects the welding performance of the steel sheet. Therefore, in the steel sheet having high crack arresting property of the present invention, it is necessary to set the Ca content to 0.0001% to 0.0045%.
  • Phosphorus, sulfur: P and S are inevitable harmful impurity elements in steel, they are easily formed in steel Defects such as segregation and inclusions deteriorate the weldability, impact toughness and anti-HIC performance of the steel sheet. For this reason, it is necessary to control P ⁇ 0.015 wt.% in the steel sheet having high crack arresting property of the present invention, and to control S to ⁇ 0.0040 wt.%.
  • the inclusion treatment of the S can be spheroidized and evenly distributed by the Ca treatment inclusion modification technique, reducing the influence on the toughness and corrosivity of the steel sheet.
  • Ca and S also need to satisfy: 1.0 ⁇ Ca / S ⁇ 2.0 in order to obtain a good sulfide treatment effect, thereby improving the crack arrest performance of the steel sheet.
  • the steel plate with high crack arresting property of the present invention does not add alloying elements such as V, Zr and W, and adopts low C, Ni-Cr-Mo alloying and Nb, Ti micro. Alloyed component system.
  • the steel sheet having high crack arresting property of the present invention has an average effective crystal grain size d ⁇ 7 ⁇ m and a grain orientation difference of ⁇ 15°.
  • a small angle grain boundary (grain orientation difference ⁇ 15°) does not effectively prevent crack propagation and thus has no effect on the toughness of the steel. This is because, in the small angle region, the grain boundary energy E increases with orientation, and when the orientation difference is ⁇ 15°, the grain boundary can reach the maximum value and remains unchanged. Only at large angle grain boundaries where the grain orientation difference is ⁇ 15°, the cleavage crack can undergo a significant transition, which consumes more energy. Therefore, the structural unit with a grain orientation difference of ⁇ 15° can be used as an effective crystal grain for controlling the cleavage crack propagation, and the higher the ratio of the large-angle grain boundary, the better the crack growth resistance is prevented.
  • the smaller the effective grain size obtained the stronger the ability to prevent crack propagation, that is, the better the crack arrest performance.
  • the inventors of the present technical solution have found that when the average effective grain size d ⁇ 7 ⁇ m, the crack arresting property is excellent, and conversely, the crack arresting property is rapidly lowered.
  • the steel material consists of a myriad of crystal grains.
  • the growth direction may be different, that is, the grain orientation is different (substructures with uniform grain orientation form a grain), different crystals
  • the difference in orientation between the particles is the difference in grain orientation. This difference in orientation is determined by setting a coordinate system. After determining the orientation of different crystal grains, the difference can be calculated.
  • the general grain orientation difference can be directly measured by EBSD and other methods. This technical terminology is well known to those skilled in the art, and thus is only briefly described herein and will not be described again.
  • the average effective grain size of the above-mentioned steel sheet having high crack arrestability needs to be obtained mainly by rational composition design and subsequent process control.
  • the steel sheet having high crack arresting property according to the present invention further contains B, which satisfies: 0 ⁇ B ⁇ 0.0025 wt.%.
  • the B element mainly serves to improve the hardenability of the steel sheet to ensure the mechanical properties of the steel sheet.
  • the B content is less than 0.0025 wt.%, the effect that can be achieved is optimal.
  • the premise that B can function is that it must be dissolved in steel, and the addition of Mo and Ti contributes to the improvement of the hardenability of B.
  • too high a C content will lower the hardenability of B, and based on this, in the case where B is added, the content of C should be kept at a low level.
  • C and Mn also satisfy: 0.10 wt% ⁇ C + Mn / 6 ⁇ 0.50 wt%.
  • Cr, Mo, B, C and Mn also satisfy: 0.9 wt% ⁇ (Cr + Mo + B) / (C + Mn / 6) ⁇ 3.3 wt%.
  • Ni, Nb, Ti, Al, C and Mn also satisfy: 0.9 wt% ⁇ (Ni + Nb + Ti + Al) / (C + Mn /6) ⁇ 2.2 wt%.
  • the above-mentioned added alloying elements are controlled under the premise of the defined mass percentage content, and further defining that these elements satisfy the above relationship is to ensure the balance of the alloying element content, so as to further ensure that the steel sheet obtains good strength and toughness matching, thereby The steel plate provides better crack arrest performance.
  • microstructure of the steel sheet having high crack arresting property according to the present invention is acicular ferrite + polygonal ferrite.
  • the microstructure is defined as ferrite + acicular ferrite, on the one hand, because the acicular ferrite itself has good crack arresting property, and on the other hand, because the two-phase structure has a lower
  • the yield ratio is sufficient to absorb energy and improve the crack arrest performance.
  • the comparative example (area ratio) of the above acicular ferrite is ⁇ 90%.
  • acicular ferrite ⁇ 90% is beneficial to further prevent crack propagation and improve the crack arrest performance of the steel.
  • the present invention also provides the above-described method for producing a steel sheet having high crack arresting properties, which comprises the steps of: smelting, refining, casting, slab heating, controlled rolling, and controlled cooling.
  • the heating temperature T 1120+420 C Nb +190 C Ti ⁇ 20, wherein the temperature unit is °C, C Nb is the content of Nb, the unit is wt.%, and C Ti is the content of Ti, and the unit is wt.%.
  • the purpose of setting the reheating temperature of the steel sheet slab is to ensure sufficient solid solution of microalloying elements such as Nb, V, Ti, etc., and to ensure precipitation of carbonitrides in the subsequent rolling process to prevent recrystallized grains. Growing up, thus playing the role of refining the grains.
  • the rolling temperature is Ar3+200°C to Ar3+350°C
  • the finishing rolling temperature is Ar3+40°C. ⁇ Ar3 + 100 ° C.
  • Ar3 is the temperature at which the austenite changes to a ferrite equilibrium phase transition
  • the arc rolling temperature is controlled to Ar3+200°C to Ar3+350°C in order to ensure that the steel sheet starts rolling in the recrystallization zone to fully recrystallize.
  • the precipitation of the nitride further effects the precipitation precipitation strengthening.
  • the cumulative reduction ratio is 60 to 99% in the controlled rolling step.
  • the cumulative reduction ratio in the controlled rolling step is limited to 60 to 99% in order to sufficiently deform the steel sheet, to refine the grain in the steel, and in particular to ensure sufficient deformation of the core portion of the steel sheet to obtain a uniform structure.
  • the cooling temperature is Ar3 + 15 ° C to Ar 3 + 50 ° C
  • the final cooling temperature is 250 to 450 ° C. .
  • the reason for setting the cooling temperature is to rapidly cool the steel sheet under the condition of complete austenitizing to obtain the microstructure required for the steel sheet, and the reason for setting the final cooling temperature is as follows:
  • the final cooling temperature range is lower than the phase transition end temperature of the acicular ferrite, which can cause the steel sheet to undergo a sufficient phase transformation, thereby obtaining more than 90% of acicular ferrite, thereby giving the steel sheet good strength and crack arresting performance.
  • the cooling rate is 10 to 30 ° C/s.
  • the cooling rate is obtained.
  • the control is 10 to 30 ° C / s.
  • the steel plate with high crack arresting property of the invention has high strength and good low temperature impact toughness, and its yield strength is ⁇ 400Mpa, and the -40°C Charpy V-notch impact energy is ⁇ 64J.
  • the steel sheet having high crack arresting property according to the present invention has excellent crack arresting performance and has a plasticity-free transition temperature (NDTT) ⁇ -70 ° C as compared with the steel sheet of the same thickness in the prior art.
  • NDTT plasticity-free transition temperature
  • the technical solution described in the present invention is capable of producing a steel sheet having a high crack arresting property of thickness ⁇ 90 mm, and is particularly suitable for production in the field of marine and offshore engineering structures.
  • the reduction rate is 60 to 99%;
  • the opening temperature is Ar3 + 15 ° C ⁇ Ar3 + 50 ° C
  • the final cooling temperature is 250 ⁇ 450 ° C
  • the cooling rate is 10 ⁇ 30 ° C / s
  • Table 1 lists the mass percentage contents of the respective chemical elements in the steel sheets of Examples A1 to A8.
  • Ceq C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15.
  • Table 2 lists the process parameters of the method for producing the steel sheets in Examples A1 to A8.
  • Table 3 lists the relationship and average effective grain size parameters satisfied by the relevant chemical elements in the steel sheets of Examples A1 - A8.
  • the finished board in the above embodiment is subjected to rod stretching ( ⁇ 10 mm) or plate stretching, Charpy V-notch impact, and NDTT performance test (Nil-Ductility Transition Temperature, NDTT performance is an important index for measuring the crack arrestability of the steel sheet)
  • the mechanical properties obtained are shown in Table 4.
  • Table 4 lists the mechanical properties of the steel sheets having high crack arresting properties in Examples A1 to A8 of the present invention.
  • NDTT is Nil-Ductility Transition Temperature.
  • the steel sheets in the examples A1-A8 of the present case have high strength, the yield strength is ⁇ 412 MPa, the tensile strength is ⁇ 524 MPa, and the low temperature toughness is good, and the average value of the impact work is 276 J or more.
  • the elongation rate is over 24%.
  • the steel sheets in Examples A1 to A8 also had excellent crack arresting properties, and their plastic-free transition temperatures (NDTT) ⁇ -75 °C. Therefore, the steel plate with high crack arresting property according to the present invention can be applied to key parts such as ships and offshore engineering structures. Manufacturing and production of components.

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Abstract

一种具有高止裂性能的钢板及其制备方法。该钢板的化学元素含量（ｗｔ．％）为：０．０４％≤Ｃ≤０．１２％，０．１０％≤Ｓｉ≤０．３０％，０．６０％≤Ｍｎ≤１．９０％，Ｐ≤０．０１５％，Ｓ≤０．００４０％，０．０１％≤Ｃｒ≤０．４０％，０．１０％≤Ｎｉ≤０．７０％，０．００１％≤Ｍｏ≤０．４０％，０．００１％≤Ｃｕ≤０．５０％，０．０１％≤Ａｌ≤０．０６％，０．０１％≤Ｎｂ≤０．０６％，０．０１％≤Ｔｉ≤０．０６％，Ｎ≤０．００７％，０．０００１％≤Ｃａ≤０．００４５％，且１．０≤Ｃａ／Ｓ≤２．０，余量为Ｆｅ和其他不可避免的杂质。该钢板的制造方法，其包括以下步骤：冶炼、炉外精炼、铸造、板坯加热、控制轧制和控制冷却。

Description

一种具有高止裂性能的钢板及其制造方法 技术领域
本发明涉及一种钢板及其制造方法，尤其涉及一种合金钢板及其制造方法。
背景技术
近年来，对于船舶、海洋工程结构的安全性以及由于安全性而引起环境保护问题的意识正在逐步提高。对于大型焊接结构，例如船舶和海洋工程结构中的焊接结构，在发生事故时，尤其是在事故的碰撞过程中，这些焊接结构不可避免地会起裂，因这些结构所存在着裂缝、局部脆性区，或者由于结构的几何应力集中、具有焊接残余应力，因此这些结构都有可能发生裂纹起裂。由于船舶、海洋工程结构中的焊接结构数量很多，以使得在此类工程结构中进行100％的探伤检测是不可能的，此时，就需要考虑到在工程结构中有可能已经预先存在的疲劳裂纹。对于厚板来说，在焊缝处所产生的脆性裂纹通常是沿着焊缝传播的，并不发生偏转，即便是裂纹进入母材中也很难止住，同时塑性变形也降低了钢材的止裂能力。由此可知，虽然起裂韧性对于焊缝及焊接热影响区非常重要，但是更为重要的是基料能够止住从焊缝起裂而快速扩展的裂纹，即止裂韧性也是提高钢板使用安全性的重要指标之一。
为了提高船舶、海洋等工程结构的安全性和可靠性，出于避免因钢板脆性断裂而引发的结构断裂事故的目的，需要在确保结构的起裂韧性的前提下，来提高钢板的止裂性能。
公开号为CN101307412A，公开日为2008年11月19日，名称为“脆性龟裂传播停止特性和板厚中央部的韧性优异的钢板及其制造方法”的中国专利文献公开了一种钢板。该钢板中的各化学元素的质量百分含量(wt.％)为：C：0.01-0.06，Si：0.01-0.8，Mn：1.0-1.8，Cr：0.05-0.5，Ni：0.20-0.8，Mo：0.05-0.5，Cu：0.05-0.08，Alt：0.01-0.08，Nb：0.02-0.08，Ti：0.005-0.03，B：0.00003-0.0003，Ca：0.0005-0.0030，N：0.003-0.008，REM：0.0050-0.030；并且钢板中由铁素体为主体的组织构成，在钢板的除去表背面的各自最表层的相当于板厚1％的部分的板厚方向整体的区域中，由2个结晶的方位差为15°以上的大角晶界 所包围的晶粒的平均当量圆直径为8mm以下，并且满足下式(1)的关系：1-(A2-A1)/100≥0.8，其中，A1：结晶方位差为55°以上的晶粒在总体中所占的比例(面积％)，A2：结晶方位差低于15°的晶粒在总体中所占的比例(面积％)。
公开号为JP04-141517A，公开日为1992年5月15日，名称为“具有优异的脆性裂纹扩展停止特性且低温韧性的钢板的制造的方法”的日本专利文献记载了一种钢板。该钢板的各化学元素的质量百分含量(wt.％)为：C：0.01-0.30，Si：≤0.5，Mn：≤2.0，Cr：≤0.5，Ni：≤1.0，Mo：≤0.5，Cu：≤0.9，V：≤0.1，Alt：0.001-0.1，Nb：0.005-0.05，Ti：0.005-0.02，B：0.0003-0.003，Ca：0.0003-0.005，N：0.001-0.008，Mg：0.0003-0.005；REM：0.0003-0.005；余量为Fe和其他不可避免的杂质。上述专利文献的技术方案采用了超低碳及反复相变手段，以获得表面超细晶。
公开号为JP2002-241891A，公开日为2002年8月28日，名称为“具有优良的脆性裂纹扩展停止特性以及塑性变形后的疲劳裂纹扩展特性的结构钢及其制造方法”的日本专利文献涉及了一种钢板，其各化学元素的质量百分含量(wt.％)为：C：≤0.03，Si：≤0.5，Mn：1.0-2.0，Cr：≤0.5，Ni：≤2.0，Mo：≤0.5，Cu：0.7-2.0，V：0.005-0.2，Nb：0.005-0.20，Ti：0.005-0.20，B：0.0003-0.005，Ca：0.0005-0.003，N：0.003-0.008，REM：0.0050-0.030；余量为Fe和其他不可避免的杂质。该日本专利文献中的钢板采用了超低碳、高Ni且不含Al的化学元素成分设计，并通过控轧工艺，使得平行于轧制平面的(211)面织构发达，而令(100)晶面织构弱化。
发明内容
本发明的目的在于提供一种具有高止裂性能的钢板，其具有较高的强度和较好的低温冲击韧性，其屈服强度≥400Mpa，-40℃夏比V型缺口冲击功≥64J。另外，较之于现有技术中的钢板，其具备了优良的止裂性能，其无塑性转变温度(NDTT，Nil-Ductility Transition Temperature)≤-70℃，特别适合应用于船舶、海洋工程结构等制造领域。
为了实现上述目的，本发明提出了一种具有高止裂性能的钢板，其化学元素质量百分比含量为：
0.04％≤C≤0.12％；
0.10％≤Si≤0.30％；
0.60％≤Mn≤1.90％；
P≤0.015％；
S≤0.0040％；
0.01％≤Cr≤0.40％；
0.10％≤Ni≤0.70％；
0.001％≤Mo≤0.40％；
0.001％≤Cu≤0.50％；
0.01％≤Al≤0.06％；
0.01％≤Nb≤0.06％；
0.01％≤Ti≤0.06％；
N≤0.007％；
0.0001％≤Ca≤0.0045％；且1.0≤Ca/S≤2.0；
余量为Fe和其他不可避免的杂质。
本技术方案中的各化学元素的设计原理为：
碳：C是最基本的强化元素。C溶解于钢中可以形成间隙固溶体，以起到固溶强化的作用，另外，C还可以与强碳化物的形成元素结合而生成碳化物析出，起到了沉淀强化的作用。与此同时，C还能够提高钢的淬透性。不过，对于本技术方案来说，含量太高的C对于钢板的延性、韧性、止裂性能和焊接性能均会产生不利影响，并且还会降低Nb、V等微合金化元素的固溶，从而影响析出强化效果。鉴于此，本发明所述的具有高止裂性能的钢板中的C元素的含量控制在0.04～0.12％之间。
硅：Si作为还原剂和脱氧剂，可以消除FeO夹杂对钢的不良影响。Si以固溶态存在于铁素体或奥氏体中，可以提高铁素体或奥氏体的硬度和强度，缩小奥氏体相区。但随着硅含量的增加，会降低钢的焊接性能。因此，本发明将Si控制在0.10％≤Si≤0.30％。
锰：Mn对于低合金高强钢种来说是最基本的合金元素之一。通过Mn的固溶强化作用来提高钢板的强度，以补偿钢板中由于C含量的降低而引起钢板强度的损失。Mn还是扩大γ相区的元素，其可以降低钢的γ→α相变温 度，有助于在钢板中获得细小的相变产物，用以提高钢板的韧性及止裂性能。可是，当Mn含量过高时，对于特厚钢板而言，容易在钢板中心位置产生偏析，从而降低钢板中心部位的低温韧性。因此，本发明的具有高止裂性能的钢板中的Mn的质量百分比含量为0.60～1.90％。
铬：Cr是提高钢板的淬透性的重要元素之一。对于特厚规格的钢板来说，需要通过添加较多的Cr元素来提高钢板的淬透性以弥补厚度带来的强度损失，在提高钢板强度的同时，并改善钢板在厚度方向上的性能的均匀性。Cr还可以抑制先共析铁素体及珠光体的转变，有利于获得针状铁素体组织。一旦含量过高的Cr和Mn同时加入钢板中，就会导致低熔点的Cr-Mn复合氧化物的形成，这样会使得钢板在热加工过程中形成表面裂纹，并且还会严重恶化钢板的焊接性能。为此，本发明的技术方案中的Cr的含量应该限定在0.01％～0.40％范围之间。
镍：Ni是提高材料的低温韧性的元素。加入适量的Ni能够降低晶体的层错能，有利于位错的滑移运动，改善材料的冲击韧性，尤其能够改善特厚板中心部位的冲击韧性。同时，本技术方案添加Ni元素还可以提高钢板的止裂性能。此外，Ni还可以提升Mo的淬透性效果。不过，如果Ni含量太高的话，板坯表面容易生成黏性较高的氧化铁皮，在后序的加工制造过程中难以去除，从而影响钢板的表面质量和疲劳性能。另外，当Ni含量太高时，不利于特厚钢板的焊接性能。鉴于此，本发明所述的具有高止裂性能的钢板中的Ni含量需要控制为0.10％～0.70％。
钼：Mo是提高钢板的淬透性的元素，其作用仅次于Mn元素。Mo不仅能够有效地提高钢板的强度，还能够抑制先共析铁素体及珠光体的转变，以有助于钢板获得针状铁素体组织。但是，随着Mo含量的增加，钢板的屈服强度逐渐提高，而钢板的塑性却会逐渐降低。对于本发明的具有高止裂性能的钢板来说，Mo的质量百分比含量应当设定为0.001％～0.40％。
铜：Cu能够适当地提高钢板的淬透性，并且Cu还可以提高钢板的抗大气腐蚀能力。然而，向钢中添加含量过高的Cu元素会恶化钢板的焊接性能，所以将本发明所述的具有高止裂性能的钢板中的Cu元素的含量控制为0.001％～0.50％。
铝：Al是为了脱氧而加入钢中的元素。在脱氧完全后，Al降低了钢板 中的O的含量，以改善钢板的时效性能。此外，添加适量的Al还有利于细化晶粒，从而改善钢材的强韧性能。因此，将本发明中的具有高止裂性能的钢板中的Al元素的含量限定为0.01～0.06％。
铌：在微合金钢中，Nb是提高再结晶终止温度最有效的元素之一。Nb能够有效地降低轧机载荷，对晶粒细化的作用十分明显。对于本发明所述的钢板而言，轧制变形在再结晶及非再结晶轧制阶段完成，在此阶段Nb通过应变诱导析出以阻碍形变奥氏体的回复、再结晶，从而起到细化晶粒尺寸的效果。但是受到C含量的限制及加热温度的影响，含量太高的Nb无法固溶，同样也不能发挥Nb的有利作用。同时，Nb还是一种昂贵的金属元素，添加较多的Nb也会相应地增加生产制造成本。因而，在本发明的具有高止裂性能的钢板中的Nb含量应当控制在0.01％～0.06％。
钛：Ti是较强的固N元素。由于Ti/N比为3.42，因此，利用很少量的Ti就可以固定一定含量的N元素，例如，0.02wt.％左右的Ti就可以固定钢中质量百分比含量为60ppm以下的N。在板坯连铸时，所加入的Ti可以和N形成细小的高温稳定的TiN析出相。这种细小的TiN粒子能够有效地阻碍板坯再加热时的奥氏体晶粒的长大，有助于提高Nb在奥氏体中的固溶度。对于特厚钢板而言，添加适当的Ti含量，有利于形成稳定的TiN粒子，在焊接时起到抑制热影响区晶粒长大的作用，以改善焊接热影响区的冲击韧性。基于本发明的技术方案，需要将钢板中的Ti含量限定在0.01％～0.06％范围之间。
氮：N与合金元素生成的氮化物是非金属夹杂，更重要的是N元素会降低合金元素的作用。然而，N也有有益作用，其与Ti形成的TiN能够阻止板坯加热时奥氏体晶粒的长大。但总体而言，其副作用更大，因此本技术方案将N含量限制为≤0.007％。
钙：通过Ca处理可以控制硫化物的形态，改善钢板的各向异性，提高钢板的低温韧性。当Ca含量少于0.0001wt.％时，其不能产生任何效果，而当Ca含量高于0.0045.wt％时，则会产生许多CaO、CaS，并形成大型夹杂物，对钢板的韧性造成损害，甚至于影响钢板的焊接性能。由此，在本发明的具有高止裂性能的钢板中需要将Ca含量设定为0.0001％～0.0045％。
磷、硫：P和S是钢中不可避免的有害杂质元素，它们极易在钢中形 成偏析、夹杂等缺陷，恶化钢板的焊接性能、冲击韧性和抗HIC性能。为此，需要控制本发明的具有高止裂性能的钢板中的P≤0.015wt.％，且将S控制为≤0.0040wt.％。对于S元素来说，可以通过Ca处理夹杂物改性技术来使得S的夹杂物形态球化且分布均匀，减少其对钢板的韧性和腐蚀性的影响。Ca和S还需要满足：1.0≤Ca/S≤2.0，以便获得良好的硫化物处理效果，从而提高钢板的止裂性能。
较之于现有技术中的钢板，本发明的具有高止裂性能的钢板中不添加V、Zr和W等合金元素，其采用了低C，Ni-Cr-Mo合金化及Nb、Ti微合金化的成分体系。
进一步地，本发明所述的具有高止裂性能的钢板的平均有效晶粒尺寸d≤7μm，晶粒取向差≥15°。
对于本技术方案来说，发明人发现，小角度晶界(晶粒取向差＜15°)不能有效阻止裂纹扩展，因此对钢的韧性没有影响。这是因为，在小角度区域，晶界能E是随取向增长的，当取向差≥15°后，晶界能达到最大值，并且保持不变。只有在晶粒取向差≥15°的大角度晶界处，解理裂纹才能发生显著的转折，从而会消耗更多的能量。因此，晶粒取向差≥15°的组织单元可以作为控制解理断裂裂纹扩展的有效晶粒，且大角度晶界比例越高，其阻止裂纹扩展能力越好。因此，获得的有效晶粒尺寸越小，阻止裂纹扩展的能力约强，即止裂性能越好。此外，本技术方案的发明人还发现，当平均有效晶粒尺寸d≤7μm时，其止裂性能非常优异，反之，则止裂韧性会迅速下降。
钢铁材料由无数个晶粒组成，每个晶粒在相变过程中，长大的方向可能不一样，也就是晶粒取向不一样(晶粒取向一致的亚结构构成一个晶粒)，不同晶粒之间的取向的差值就是晶粒取向差。这个取向差是通过设定一个坐标系，不同晶粒的取向确定后，就可以计算差值了，一般晶粒取向差是通过EBSD等方法直接可以测出来的。该技术术语是本领域内技术人员所熟知的，故本文仅在此做简单介绍而不再赘述。
上述具有高止裂性能的钢板的平均有效晶粒尺寸需要主要通过合理的成分设计和后序工艺控制来获得。
更进一步地，上述平均有效晶粒尺寸d＝10-Ceq-dA/20-2R-(Tn-Ar3)/70-(Tn-TE)/500-CR/20-FA/5；其中Ceq＝C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15，单位 为wt.％；dA表示原始奥氏体晶粒尺寸，单位为μm；R表示轧制过程中的累积压下率，单位为％；Tn表示开冷温度，单位为℃；Ar3表示钢在缓慢冷却时的开始相变温度，单位为℃；TE表示终冷温度，单位为℃；CR表示冷却速率，单位为℃/s；FA表示针状铁素体的相比例。
需要说明的是，本技术方案并不含有V元素，因此上述碳当量公式中，V元素的含量始终为0。
进一步地，本发明所述的具有高止裂性能的钢板还含有B，其满足：0＜B≤0.0025wt.％。
B元素主要是起到提高钢板的淬透性的作用，以保证钢板的力学性能。当B含量小于0.0025wt.％时，其能够达到的效果最佳。B能够发挥作用的前提是必须固溶于钢中，Mo、Ti的添加有助于提高B的淬透性效果。与此同时，C含量过高也会降低B的淬透性，基于此，在添加B的情况下，应当将C的含量控制在较低水平。为了进一步获得更好的淬透性效果，需要在本专利的具有高止裂性能的钢板中添加B，且控制其含量为：0＜B≤0.0025％。
进一步地，在本发明所述的具有高止裂性能的钢板中，C和Mn还满足：0.10wt％≤C+Mn/6≤0.50wt％。
进一步地，在本发明所述的具有高止裂性能的钢板中，Cr、Mo、B、C和Mn还满足：0.9wt％≤(Cr+Mo+B)/(C+Mn/6)≤3.3wt％。
进一步地，在本发明所述的具有高止裂性能的钢板中，Ni、Nb、Ti、Al、C和Mn还满足：0.9wt％≤(Ni+Nb+Ti+Al)/(C+Mn/6)≤2.2wt％。
将上述添加的合金元素控制在其限定的质量百分比含量的前提下，进一步限定这些元素满足以上关系式，是为了确保合金元素含量的平衡，以进一步保证钢板获得良好的强度和韧性匹配，从而为钢板提供更为优良的止裂性能。
进一步地，本发明所述的具有高止裂性能的钢板的微观组织为针状铁素体+多边形铁素体。
在本技术方案中，限定微观组织为铁素体+针状铁素体，一方面是由于针状铁素体本身具有良好的止裂性能，另一方面，也是由于双相组织具有较低的屈强比，足够的塑形变形有利于吸收能量，提高止裂性能。
更进一步地，上述针状铁素体的相比例(面积比)≥90％。
本技术方案限定针状铁素体≥90％有利于进一步阻止裂纹的扩展，提高钢种的止裂性能。
相应地，本发明还提供了上述具有高止裂性能的钢板的制造方法，其包括步骤：冶炼、炉外精炼、铸造、板坯加热、控制轧制和控制冷却。
进一步地，在本发明所述的具有高止裂性能的钢板的制造方法中，在控制轧制步骤中，在开轧前先进行再加热，再加热温度T为＝1120+420CNb+190CTi±20，其中温度单位为℃，CNb为Nb的含量，其单位为wt.％，CTi为Ti的含量，单位为wt.％。
对于钢板板坯再加热温度进行设定的目的是为了保证Nb、V、Ti等微合金元素的充分固溶，并且确保在随后的轧制过程中析出碳氮化物，以阻止再结晶晶粒的长大，从而起到细化晶粒的作用。
进一步地，在本发明所述的具有高止裂性能的钢板的制造方法中，在控制轧制步骤中，开轧温度为Ar3+200℃～Ar3+350℃，终轧温度为Ar3+40℃～Ar3+100℃。
其中，Ar3为由奥氏体向铁素体平衡相变时的温度，将开轧温度控制为Ar3+200℃～Ar3+350℃是为了保障钢板在再结晶区开始轧制，以充分再结晶，细化晶粒，而将终轧温度控制为Ar3+40℃～Ar3+100℃的目的是为了使得钢板在奥氏体区获得反复大变形量的变形，以增加形核点，从而促进碳氮化物的析出，进而达到沉淀析出强化的作用。
进一步地，在本发明所述的具有高止裂性能的钢板的制造方法中，在控制轧制步骤中，累积压下率为60～99％。
将控轧步骤中的累积压下率限定为60～99％是为了使得钢板充分变形，钢中的晶粒细化，尤其是确保钢板心部的变形充分，以获得均一的组织。
更进一步地，在本发明所述的具有高止裂性能的钢板的制造方法中，在控制冷却步骤中，开冷温度为Ar3+15℃～Ar3+50℃，终冷温度为250～450℃。
在上述技术方案中，设定开冷温度的原因在于：令钢板在完全奥氏体化的条件下进行快速冷却，以获得所钢板所需要的微观组织，而设定终冷温度的原因在于：该终冷温度范围低于针状铁素体的相变结束温度，其能够使得钢板发生充分相变，从而获得90％以上的针状铁素体，从而令钢板具有良好的强度及止裂性能。
更进一步地，在本发明所述的具有高止裂性能的钢板的制造方法中，在控制冷却步骤中，冷却速度为10～30℃/s。
在上述控制冷却步骤中，为了避免钢中的先共析铁素体及珠光体的析出，为了获得更多的针状铁素体组织，以确保钢板具有良好的止裂性能，而将冷却速度控制为10～30℃/s。
本发明所述的具有高止裂性能的钢板具有较高的强度和较好的低温冲击韧性，其屈服强度≥400Mpa，-40℃夏比V型缺口冲击功≥64J。
另外，与现有技术中的同样厚度的钢板相比较，本发明所述的具有高止裂性能的钢板具备有优良的止裂性能，其无塑性转变温度(NDTT)≤-70℃。
此外，本发明所述的技术方案能够制造厚度≤90mm的具有高止裂性能的钢板，尤其适合用于船舶和海洋工程结构领域的生产制造。
具体实施方式
下面将结合具体的实施例对本发明所述的具有高止裂性能的钢板及其制造方法做进一步的解释和说明，然而，该解释和说明并不对本发明的技术方案构成不当限定。
按照下述步骤制造实施例A1-A8中的钢板：
1)冶炼；
2)炉外精炼：控制实施例A1-A8的钢板中的各化学元素的质量百分比如含量如表1和表3所示；
3)铸造；
4)板坯加热；
5)控制轧制：在开轧前先进行再加热，再加热温度T为＝1120+420CNb+190CTi±20，其中温度单位为℃，CNb为Nb的含量，其单位为wt.％，CTi为Ti的含量，单位为wt.％，开轧温度为Ar3+200℃～Ar3+350℃，而终轧温度为Ar3+40℃～Ar3+100℃，在轧制过程中的累积压下率为60～99％；
6)控制冷却：开冷温度为Ar3+15℃～Ar3+50℃，终冷温度为250～450℃，冷却速度为10～30℃/s；
7)最终获得具有高止裂性能的钢板，该钢板的平均有效晶粒尺寸d＝ 10-Ceq-dA/20-2R-(Tn-Ar3)/70-(Tn-TE)/500-CR/20-FA/5；其中Ceq＝C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15，单位为wt.％；dA表示原始奥氏体晶粒尺寸，单位为μm；R表示轧制过程中的累积压下率，单位为％；Tn表示开冷温度，单位为℃；Ar3表示钢在缓慢冷却时的开始相变温度，单位为℃；TE表示终冷温度，单位为℃；CR表示冷却速率，单位为℃/s；FA表示针状铁素体的相比例，并且钢板的微观组织为针状铁素体+多边形铁素体，其中，针状铁素体的相比例(面积比)≥90％。
上述制造方法所涉及各步骤中的具体工艺参数详细参见表2。
表1列出了实施例A1-A8的钢板中的各化学元素的质量百分比含量。
表1.(wt.％，余量为Fe和除了P和S以外的其他不可避免的杂质)
序号 C Si Mn P S Cr Ni Mo Cu Al Nb Ti N B Ca Ca/S Ceq*
A1 0.04 0.11 0.62 0.010 0.0023 0.21 0.11 0.23 0.10 0.020 0.015 0.010 0.0017 0 0.0035 1.5 0.25
A2 0.05 0.18 0.76 0.009 0.0015 0.02 0.21 0.30 0.12 0.025 0.011 0.030 0.0035 0 0.0020 1.3 0.26
A3 0.05 0.20 1.38 0.010 0.0021 0.11 0.26 0.31 0.001 0.011 0.058 0.012 0.0021 0 0.0027 1.3 0.38
A4 0.06 0.24 1.45 0.010 0.0019 0.28 0.40 0.03 0.34 0.059 0.011 0.013 0.0026 0 0.0024 1.3 0.41
A5 0.08 0.21 1.89 0.009 0.0020 0.32 0.52 0.33 0.48 0.012 0.011 0.059 0.0036 0.0010 0.0026 1.3 0.59
A6 0.10 0.25 1.56 0.008 0.0017 0.31 0.56 0.31 0.21 0.037 0.020 0.015 0.0022 0.0012 0.0020 1.2 0.54
A7 0.11 0.29 1.75 0.012 0.0024 0.34 0.68 0.35 0.15 0.039 0.031 0.018 0.0025 0.0015 0.0043 1.8 0.60
A8 0.12 0.23 1.62 0.011 0.0022 0.39 0.70 0.39 0.17 0.045 0.024 0.020 0.0024 0.0024 0.0025 1.1 0.60
*注：Ceq＝C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15。
表2列出了实施例A1-A8中的钢板的制造方法的工艺参数。
表2.
Figure PCTCN2015093745-appb-000001
*注：1)板坯再加热温度T＝1120+420CNb+190CTi±20；2)开轧温度为Ar3+200℃～Ar3+350℃，3)终轧温度为Ar3+40℃～Ar3+100℃，4)开冷温度Tn为Ar3+15℃～Ar3+50℃。
表3列出了实施例A1-A8的钢板中的相关化学元素所满足的关系式和平均有效晶粒尺寸参数。
表3.
Figure PCTCN2015093745-appb-000002
*注：d＝10-Ceq-dA/20-2R-(Tn-Ar3)/70-(Tn-TE)/500-CR/20-FA/5，其中，FA为针状铁素体的相比例。
将上述实施例中的成品板进行棒状拉伸(Ф10mm)或板状拉伸、夏比V型缺口冲击、NDTT性能检验(Nil-Ductility Transition Temperature，NDTT性能是衡量钢板止裂性能的重要指标)，得到的各项力学性能结果如表4所示。
表4列出了本案实施例A1-A8中的具有高止裂性能的钢板的各项力学性能参数。
表4.
序号 屈服强度(MPa) 抗拉强度(MPa) 总延伸率(％) 冲击功均值,J(-40℃,纵向) NDTT*(℃)
A1 532 627 24 276 -90
A2 507 598 25 287 -95
A3 465 573 25 296 -85
A4 497 584 26 294 -90
A5 446 563 24 304 -85
A6 431 550 33 353 -80
A7 412 524 26 321 -80
A8 425 530 29 340 -75
*注：NDTT为无塑性转变温度(Nil-Ductility Transition Temperature)。
由表4可以看出，本案实施例A1-A8中的钢板具有较高的强度，其屈服强度≥412Mpa，抗拉强度≥524Mpa，并且具有良好的低温韧性，其冲击功均值达到276J以上，总延伸率达到24％以上。同时，实施例A1-A8中的钢板还具有优良的止裂性能，其无塑性转变温度(NDTT)≤-75℃。由此说明，本发明所述的具有高止裂性能的钢板能够适用于船舶、海洋工程结构等关键 构件的制造生产。
需要注意的是，以上列举的仅为本发明的具体实施例，显然本发明不限于以上实施例，随之有着许多的类似变化。本领域的技术人员如果从本发明公开的内容直接导出或联想到的所有变形，均应属于本发明的保护范围。

Claims (15)

  1. 一种具有高止裂性能的钢板，其特征在于，其化学元素质量百分比含量为：
    0.04％≤C≤0.12％,0.10％≤Si≤0.30％,0.60％≤Mn≤1.90％，P≤0.015％,S≤0.0040％，0.01％≤Cr≤0.40％,0.10％≤Ni≤0.70％,0.001％≤Mo≤0.40％,0.001％≤Cu≤0.50％，0.01％≤Al≤0.06％，0.01％≤Nb≤0.06％,0.01％≤Ti≤0.06％，N≤0.007％，0.0001％≤Ca≤0.0045％，且1.0≤Ca/S≤2.0，余量为Fe和其他不可避免的杂质。
  2. 如权利要求1所述的具有高止裂性能的钢板，其特征在于，所述钢板的平均有效晶粒尺寸d≤7μm，晶粒取向差≥15°。
  3. 如权利要求2所述的具有高止裂性能的钢板，其特征在于，所述平均有效晶粒尺寸d＝10-Ceq-dA/20-2R-(Tn-Ar3)/70-(Tn-TE)/500-CR/20-FA/5；其中Ceq＝C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15，单位为wt.％；dA表示原始奥氏体晶粒尺寸，单位为μm；R表示轧制过程中的累积压下率，单位为％；Tn表示开冷温度，单位为℃；Ar3表示钢在缓慢冷却时的开始相变温度，单位为℃；TE表示终冷温度，单位为℃；CR表示冷却速率，单位为℃/s；FA表示针状铁素体的相比例。
  4. 如权利要求1-3中任意一项所述的具有高止裂性能的钢板，其特征在于，还含有0＜B≤0.0025wt％。
  5. 如权利要求1-3中任意一项所述的具有高止裂性能的钢板，其特征在于，还满足：0.10wt％≤C+Mn/6≤0.50wt％。
  6. 如权利要求1-3中任意一项所述的具有高止裂性能的钢板，其特征在于，还满足：0.9wt％≤(Cr+Mo+B)/(C+Mn/6)≤3.3wt％。
  7. 如权利要求1-3中任意一项所述的具有高止裂性能的钢板，其特征在于，还满足：0.9wt％≤(Ni+Nb+Ti+Al)/(C+Mn/6)≤2.2wt％。
  8. 如权利要求1-3中任意一项所述的具有高止裂性能的钢板，其特征在于，其微观组织为针状铁素体+多边形铁素体。
  9. 如权利要求8所述的具有高止裂性能的钢板，其特征在于，所述针状铁素体的相比例≥90％。
  10. 一种如权利要求1-3中任意一项所述的具有高止裂性能的钢板的制造方法，其特征在于，包括步骤：冶炼、炉外精炼、铸造、板坯加热、控制轧制和控制冷却。
  11. 如权利要求10所述的具有高止裂性能的钢板的制造方法，其特征在于，在所述控制轧制步骤中，在开轧前先进行再加热，再加热温度T为＝1120+420CNb+190CTi±20，其中温度单位为℃，CNb为Nb的含量，其单位为wt.％，CTi为Ti的含量，单位为wt.％。
  12. 如权利要求10所述的具有高止裂性能的钢板的制造方法，其特征在于，在所述控制轧制步骤中，开轧温度为Ar3+200℃～Ar3+350℃，终轧温度为Ar3+40℃～Ar3+100℃。
  13. 如权利要求10所述的具有高止裂性能的钢板的制造方法，其特征在于，在所述控制轧制步骤中，累积压下率为60～99％。
  14. 如权利要求10所述的具有高止裂性能的钢板的制造方法，其特征在于，在所述控制冷却步骤中，开冷温度为Ar3+15℃～Ar3+50℃，终冷温度为250～450℃。
  15. 如权利要求10所述的具有高止裂性能的钢板的制造方法，其特征在于，在所述控制冷却步骤中，冷却速度10～30℃/s。
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