WO2024027526A1 - 特厚Q500qE桥梁钢板及其生产方法 - Google Patents

特厚Q500qE桥梁钢板及其生产方法 Download PDF

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Publication number
WO2024027526A1
WO2024027526A1 PCT/CN2023/109002 CN2023109002W WO2024027526A1 WO 2024027526 A1 WO2024027526 A1 WO 2024027526A1 CN 2023109002 W CN2023109002 W CN 2023109002W WO 2024027526 A1 WO2024027526 A1 WO 2024027526A1
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stage
steel plate
controlled
heating
cooling
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PCT/CN2023/109002
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English (en)
French (fr)
Inventor
杨浩
曲锦波
镇凡
陆春洁
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江苏省沙钢钢铁研究院有限公司
江苏沙钢钢铁有限公司
江苏沙钢集团有限公司
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Publication of WO2024027526A1 publication Critical patent/WO2024027526A1/zh

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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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/58—Roll-force control; Roll-gap control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master 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
    • C22C38/42—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
    • C22C38/48—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
    • C22C38/58—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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention relates to the field of alloy technology, and specifically to an extra-thick Q500qE bridge steel plate and its production method.
  • the purpose of the present invention is to provide an extra thick Q500qE bridge steel plate and its production method.
  • the invention provides a production method of extra thick Q500qE bridge steel plate, which is characterized by:
  • the chemical composition of the steel plate includes, in terms of mass percentage: C: 0.05 ⁇ 0.07%, Si: 0.15 ⁇ 0.35%, Mn: 1.5 ⁇ 1.7%, Ni: 0.3 ⁇ 0.5%, Cr: 0.2 ⁇ 0.3%, Mo: 0.2 ⁇ 0.3%, Cu:0.15 ⁇ 0.25%, Nb: 0.04 ⁇ 0.05%, Ti: 0.01 ⁇ 0.02%, the rest is Fe and inevitable impurities, the impurities include P ⁇ 0.01%, S ⁇ 0.003%;
  • the production method includes the steps:
  • the slab is obtained by smelting and continuous casting
  • the slab is subjected to first-stage heating, second-stage heating and third-stage heating in sequence, wherein the second-stage heating temperature is controlled to 1180-1220°C, the first-stage heating temperature and the third-stage heating are The temperature is controlled to be lower than the heating temperature in the second stage.
  • the temperature of the slab is made uniform through heating in the first heating stage and the second heating stage.
  • the slab is heated from the surface to A gradually rising temperature gradient is formed to the center;
  • the heated slab is subjected to one-stage rolling to obtain a rolled steel plate with a maximum thickness of 150mm;
  • the rolled steel plate is sequentially subjected to first stage cooling, second stage cooling and third stage cooling, wherein the final cooling temperature of the third stage cooling is controlled to ⁇ 350°C, and the first stage cooling, second stage cooling and The cooling rates of stage cooling and third stage cooling increase sequentially.
  • the element symbol in the brackets is the mass percentage of the corresponding element, and the % element symbol means the mass percentage of the corresponding element multiplied by 100;
  • the slab is obtained by smelting and casting according to the above chemical composition ratio, which specifically includes:
  • the molten steel is smelted sequentially through the molten iron pre-desulfurization, converter smelting, LF refining, and RH vacuum refining processes.
  • the molten steel is continuously cast to obtain a slab with a thickness of 320 mm, and the slab is stacked. cool down.
  • the slab is sequentially subjected to first-stage heating, second-stage heating and third-stage heating, specifically including:
  • the slab is sequentially subjected to first-stage heating, second-stage heating and third-stage heating, wherein the first-stage heating temperature is controlled to 900-1100°C and the heating time is controlled to ⁇ 150 min; the second-stage heating temperature The heating temperature is controlled at 1180 ⁇ 1220°C, and the heating time is controlled at 180 ⁇ 240min; in the third stage, the heating temperature is controlled at 1140 ⁇ 1160°C, and the heating time is controlled at 30 ⁇ 60min.
  • the heated slab is subjected to one-stage rolling, which specifically includes:
  • the slab that has been heated in three stages is descaled and then rolled.
  • the rolling temperature is controlled at 980-1080°C.
  • the reduction in the remaining rolling passes is controlled to ⁇ 40mm.
  • the step of rolling the heated slab in one stage also includes:
  • the steel biting speed is controlled to 0.6m/s and the rolling speed is controlled to 1.2m/s.
  • the rolling steel plate is sequentially subjected to first-stage cooling, second-stage cooling and third-stage cooling, specifically including:
  • the rolled steel plate is sequentially subjected to first-stage cooling, second-stage cooling and third-stage cooling, wherein the first-stage cooling rate is controlled to 0.3-1°C/s, and the final cooling temperature is controlled to 760-780°C;
  • the second stage cooling speed is controlled at 3 ⁇ 5°C/s, and the final cooling temperature is controlled at 560 ⁇ 600°C. Wait 20 ⁇ 40s after the second stage cooling is completed.
  • the third stage cooling speed is controlled at 5 ⁇ 8°C/s.
  • the final cooling temperature is controlled to ⁇ 350°C.
  • An extra-thick Q500qE bridge steel plate is manufactured using the above-mentioned extra-thick Q500qE bridge steel plate production method.
  • the microstructure of the steel plate is a dual-phase structure of bainite and martensite, wherein the amount of bainite is greater than the amount of martensite.
  • the lower yield strength of the steel plate is ⁇ 430MPa
  • the tensile strength is ⁇ 540MPa
  • the yield strength ratio is ⁇ 0.85
  • the -40°C impact energy is ⁇ 180J
  • the Z-direction tensile area shrinkage is ⁇ 50%
  • the chemical composition of the steel plate includes, in terms of mass percentage: C: 0.05 ⁇ 0.07%, Si: 0.15 ⁇ 0.35%, Mn: 1.5 ⁇ 1.7%, Ni: 0.3 ⁇ 0.5%, Cr: 0.2 ⁇ 0.3%, Mo: 0.2 ⁇ 0.3%, Cu: 0.15 ⁇ 0.25%, Nb: 0.04 ⁇ 0.05%, Ti: 0.01 ⁇ 0.02%, the rest is Fe and inevitable impurities, the impurities include P ⁇ 0.01% , S ⁇ 0.003%;
  • CE (%C)+(%Mn)/6+(%Cr+%Mo+%V)/5+(%Ni+%Cu)/15,
  • the element symbol in the brackets is the mass percentage of the corresponding element, and the % element symbol means the mass percentage of the corresponding element multiplied by 100;
  • the maximum thickness of the steel plate produced by the steel plate is 150mm, the lower yield strength is ⁇ 430MPa, the tensile strength is ⁇ 540MPa, the yield ratio is ⁇ 0.85, the -40°C impact energy is ⁇ 180J, and the Z-direction tensile area shrinkage is ⁇ 50%, meeting the requirements of GB/ T 2970-2016 standard requires level II and above flaw detection.
  • the microstructure of the steel plate is a dual-phase structure of bainite and martensite, wherein the amount of bainite is greater than the amount of martensite.
  • the beneficial effects of the present invention are: the production method used in the present invention directly rolls the slab after heating before three-stage rolling, and performs three-stage cooling treatment on the steel plate after rolling, so that the maximum thickness can reach 150mm.
  • Q500qE steel plate the steel plate can meet the Z-direction tensile performance requirements of Z35 level and the flaw detection requirements of level II or above in GB/T 2970-2016 standard.
  • the production process is simple, the efficiency is high and the production cost is low.
  • Figure 1 is a schematic diagram of the steps of the production method of extra thick Q500qE bridge steel plates in one embodiment of the present invention.
  • Figure 2 is a picture of the metallographic structure of the extra thick Q500qE bridge steel plate in Embodiment 1 of the present invention.
  • This embodiment provides an extra-thick Q500qE bridge steel plate and its production method.
  • This production method directly rolls the continuous casting billet to obtain a steel plate with a maximum thickness of 150mm. Compared with the existing extra-thick bridge steel, it has a lower The compression ratio, no low-temperature controlled rolling, and no heat treatment make the steel plate have high strength and high toughness.
  • the production method is simple and the steel plate has excellent performance.
  • the steel plate produced by this method can be used as a bridge steel plate of Q500qE grade.
  • the chemical composition of the steel plate provided by this embodiment includes, in terms of mass percentage: C: 0.05 ⁇ 0.07%, Si: 0.15 ⁇ 0.35%, Mn: 1.5 ⁇ 1.7%, Ni: 0.3 ⁇ 0.5%, Cr: 0.2 ⁇ 0.3%, Mo: 0.2 ⁇ 0.3%, Cu: 0.15 ⁇ 0.25%, Nb: 0.04 ⁇ 0.05%, Ti: 0.01 ⁇ 0.02%, the rest is Fe and inevitable impurities, including P ⁇ 0.01% and S ⁇ 0.003%.
  • the C content can significantly affect the organizational structure of the steel, thereby effectively ensuring the strength of the steel plate.
  • the C content plays an important role in the hardenability of the steel plate and increasing the yield-strength ratio of the steel plate. , however, an excessively high C content will significantly deteriorate the low-temperature toughness of the steel plate. Therefore, in this embodiment, the C content is controlled to 0.05 to 0.07%.
  • Si As a deoxidizing element, it improves the strength of materials through solid solution strengthening. Si can be dissolved in ferrite and austenite to increase the hardness and strength of steel. Si can also inhibit the transformation of pearlite, but it is A high Si content can easily lead to an increase in the M/A (martensite/austenite) content and deteriorate the low-temperature toughness of the steel plate. Therefore, in this embodiment, the Si content is controlled to 0.15 to 0.35%.
  • Mn It is a solid solution strengthening element that can improve the hardenability of the steel plate, thereby increasing its strength, and Mn Can promote the formation of acicular ferrite. At the same time, Mn is also a good deoxidizer and desulfurizer, which can be combined with the harmful element S to reduce the thermal brittleness of the steel plate. However, too much Mn will aggravate the segregation of P, Sb, Sn and other elements, deteriorate the low-temperature toughness of the core of the steel plate, and the expansion during the rolling process will lead to improper flaw detection of the steel plate. Therefore, in the present invention, the Mn content is controlled to 1.40% to 1.60%.
  • Ni P and Ni alloy-based deposition behavior will occur at the crack tip of steel, and chemical deposition will occur on the crack surface at the tail end of the crack tip.
  • NiP deposits induce crack closure and generate residual compressive stress near the crack tip, effectively reducing
  • the growth rate of fatigue cracks improves the low-temperature toughness of the material through the stress release at the crack tip.
  • Ni can effectively improve the hardenability of steel, but adding too much Ni will result in higher alloy costs. Therefore, in this embodiment, the Ni content is controlled to 0.1 to 0.2%.
  • Cr It has a solid solution strengthening effect similar to Mn and can effectively improve the hardenability of steel.
  • the price of Cr alloy is higher than that of Mn, and too high Cr content affects the stability of supercooled austenite. Therefore, in this embodiment, the Cr content is controlled to 0.1 to 0.2%.
  • Mo It can significantly increase the hardenability of steel, and can improve the strength of steel plates when combined with accelerated cooling after rolling.
  • Mo is a precious alloy element, and adding too much can easily lead to high costs. Therefore, in this embodiment, 0.08 to 0.16 is added. %.
  • the Cu It can improve the strength and corrosion resistance of the steel plate, and has relatively little adverse effect on low-temperature toughness. However, when the Cu content is too high, copper embrittlement may easily occur and affect the surface quality of the steel plate. Therefore, in this embodiment, the Cu content is controlled within 0.15 ⁇ 0.25%.
  • Nb It is a micro-alloy strengthening element. It has precipitation strengthening and fine grain strengthening effects. It can increase the strength of steel and improve low-temperature toughness. However, when the Nb content is too high, a large number of large-sized M/A will easily form in the welding heat-affected zone, thus deteriorating Therefore, in this embodiment, the Nb content is controlled to 0.04% to 0.05%.
  • Ti It is a microalloy strengthening element with precipitation strengthening and grain refinement strengthening effects. Ti nitrides and oxides can inhibit the growth of austenite grains and refine the austenite. In this embodiment, the Ti content is controlled In 0.010 ⁇ 0.020%.
  • P and S are residual impurity elements that are detrimental to the low-temperature toughness of steel, so the P content is controlled to ⁇ 0.015% and the S content is ⁇ 0.005%.
  • the chemical composition of the steel plate also meets the following requirements: carbon equivalent CE ⁇ 0.485 to ensure that the steel plate has good weldability.
  • the element symbol in brackets is the mass percentage of the corresponding element
  • the % element symbol means the mass percentage of the corresponding element multiplied by 100.
  • the element symbol in brackets is the mass percentage of the corresponding element
  • the % element symbol means the mass percentage of the corresponding element multiplied by 100.
  • the production method of extra thick Q500qE bridge steel plate includes the steps:
  • the slab is obtained by smelting and continuous casting.
  • the slab is heated in the first stage, the second stage and the third stage in sequence.
  • the second stage heating temperature is controlled at 1180 ⁇ 1220°C
  • the first stage heating temperature and the third stage heating temperature are controlled at low
  • the slab is heated to a uniform temperature in the first and second heating stages, and in the third heating stage, the slab forms a gradually rising temperature gradient from the surface to the core.
  • S4 The rolled steel plate is subjected to the first stage of cooling, the second stage of cooling and the third stage of cooling in sequence.
  • the final cooling temperature of the third stage of cooling is controlled to ⁇ 350°C.
  • the cooling rates of the three stages of cooling increase sequentially.
  • step S1 it includes the following steps in sequence:
  • KR desulfurization is performed on the molten iron to control the sulfur content in the molten iron. After removing the desulfurization slag, the molten iron is mixed into the converter for converter smelting.
  • pre-desulfurized molten iron and scrap steel are used as raw materials for converter smelting to obtain molten steel.
  • ferrosilicon alloy, metallic manganese and carbon powder are sequentially added to the molten steel to deoxidize and alloy the molten steel.
  • the molten steel is refined until it meets the predetermined requirements and then vacuumed for cyclic degassing.
  • the molten steel is evacuated and subjected to cyclic degassing to remove inclusions for further refining.
  • the molten steel is formed into a slab with a thickness of 320mm through continuous casting. After obtaining the slab, the slabs are stacked and slowly cooled.
  • the thickness of the slab is controlled to 320mm, and with the subsequent rolling process, a steel plate with a maximum thickness of 150mm can be obtained.
  • the steel plate can also be obtained according to the most required steel plate thickness and rolling process.
  • the slab thickness obtained by continuous casting is adjusted according to the manufacturing process parameters.
  • step S2 it specifically includes:
  • the slab is heated in the first stage, the second stage and the third stage in sequence.
  • the heating temperature in the first stage is controlled to 900 ⁇ 1100°C, and the heating time is controlled to ⁇ 150min (that is, the residence time of the slab in the heating furnace Controlled to ⁇ 150min);
  • the second stage heating temperature is controlled to 1180 ⁇ 1220°C, and the heating time is controlled to 180 ⁇ 240min (that is, the residence time of the slab in the heating furnace is controlled to 180 ⁇ 240min);
  • the third stage heating temperature is controlled to 1140 ⁇ 1160°C, and the heating time is controlled to 30 ⁇ 60min (that is, the residence time of the slab in the heating furnace is controlled to 30 ⁇ 60min).
  • Heating the slab to a uniform temperature suitable for rolling before rolling can improve the plasticity of the steel, reduce the deformation resistance, and make the steel easy to deform, so that a larger reduction can be used during the slab rolling process. Moreover, heating can improve the internal structure and properties of the slab, and uneven structures and non-metallic inclusions can be homogenized through the diffusion effect of high-temperature heating.
  • a relatively low heating temperature is set to prevent the slab from heating up too quickly and causing thermal stress to cause cracks on the slab surface.
  • long-term heating is performed to coordinate with the subsequent second-stage heating process. Ensure that the overall temperature of the slab is uniform and can reach the set heating temperature.
  • a higher heating temperature is set and heat preservation is performed for a long time to ensure that the inside of the slab is fully heated and the temperature at the center and surface of the steel plate is uniform.
  • the maximum heating time is limited to prevent the slab surface from excessive growth of grains and oxidation or melting of grain boundaries due to long-term heating under high temperature conditions, thereby avoiding surface overburning and oxide scale sticking that may be caused by the above situation.
  • a lower heating temperature and a shorter heating time are set compared to the second-stage heating process, thereby forming a gradually increasing temperature gradient from the surface to the center in the thickness direction of the slab to facilitate the heating process.
  • the deformation phase penetrates into the center of the slab.
  • step S3 it specifically includes:
  • the slab that has been heated in three stages is descaled and then rolled.
  • the rolling temperature is controlled to 980 ⁇ 1080°C
  • the steel biting speed is controlled to 0.6m/s
  • the rolling speed is controlled to 1.2m/s.
  • the reduction of the other rolling passes is controlled to ⁇ 40mm, and finally a steel plate with a maximum thickness of 150mm is obtained.
  • Descaling refers to removing the primary oxide scale on the surface of the slab through descaling equipment to prepare the slab for rolling.
  • high-temperature, one-stage, large-reduction rolling is used.
  • the rolling temperature is controlled at 980 ⁇ 1080°C.
  • single-pass large-reduction rolling is performed. Except for the last pass, the reduction in other passes is ⁇ 40mm to ensure that the deformation can be transferred to the slab.
  • the core is penetrated to avoid defects such as loose core and micro-cracks after rolling to ensure that the steel plate meets the flaw detection requirements.
  • the continuous casting billet is heated directly and then rolled.
  • the process steps are simpler, the required man-hours are reduced, and the production consumption is reduced.
  • one-stage high-temperature and large-pressure rolling is used, without the need for multi-stage low-temperature controlled rolling.
  • the rolling process is simple and the rolling efficiency is high. Compared with the traditional low-temperature controlled rolling process, the rolling efficiency can be increased by more than 50%. .
  • a steel plate with a maximum thickness of 150mm is obtained by direct rolling of a continuous cast billet with a thickness of 320mm, breaking through the compression ratio limitation of traditional continuous cast billet production of extra-thick plates.
  • step S4 it specifically includes:
  • the rolled steel plate is subjected to the first stage of cooling, the second stage of cooling and the third stage of cooling in sequence.
  • the cooling speed of the first stage is controlled to 0.3 ⁇ 1°C/s, and the final cooling temperature is controlled to 760 ⁇ 780°C;
  • the cooling speed in the first stage is controlled at 3 ⁇ 5°C/s, and the final cooling temperature is controlled at 560 ⁇ 600°C. Wait 20 ⁇ 40s after the second stage of cooling.
  • the cooling speed in the third stage is controlled at 5 ⁇ 8°C/s, and the final cooling temperature is controlled at 560 ⁇ 600°C.
  • Cold temperature control is ⁇ 350°C.
  • the structure of the rolled steel plate is controlled through a three-stage cooling method to ensure that it obtains good strength and toughness.
  • a slow cooling rate is used to prevent the steel plate from forming an excessively coarse side lath ferrite structure near the surface when it is cooled at around 1000°C, which will affect the low-temperature toughness of the steel plate, and prepare the near-surface structure for the next stage.
  • the cooling rate is increased to 3 ⁇ 5°C/s, and the structure of the steel plate from the near surface layer to 1/4 of the thickness is regulated, so that the steel plate structure in this range will be phased first.
  • the cooling rate is further increased compared to the second stage cooling process to regulate the structure within the range of 1/4 to 1/2 of the thickness of the steel plate. Since this range is close to the center of the steel plate, the cooling and heat dissipation effect is relatively large. Compared with the surface layer of the steel plate, it is significantly weakened. In order to ensure the cooling effect of the core of the steel plate, the cooling amplitude needs to be further increased, so the cooling rate is increased to 5 ⁇ 8°C/s. In addition, thanks to the phase change that has occurred in the near-surface layer during the second stage of cooling, although the cooling intensity in the third stage is enhanced, it does not have a significant impact on the near-surface layer structure.
  • the steel plate is cooled through a three-stage cooling method, and a larger cooling rate is used in the second and third stages of cooling, and the temperature of the final cooling stage is controlled to ⁇ 350°C, which effectively improves the structure of the extra-thick steel plate.
  • a dual-phase structure composed mainly of bainite and a small amount of martensite is obtained.
  • the steel plate structure is further strengthened by high-strength martensite, thereby regulating its strength and toughness.
  • This embodiment also provides an extra-thick Q500qE bridge steel plate, which is manufactured by the above-mentioned extra-thick Q500qE bridge steel plate production method.
  • the chemical composition of the steel plate includes: C: 0.05 ⁇ 0.07%, Si: 0.15 ⁇ 0.35%, Mn: 1.5 ⁇ 1.7%, Ni: 0.3 ⁇ 0.5%, Cr: 0.2 ⁇ 0.3%, Mo: 0.2 ⁇ 0.3 %, Cu: 0.15 ⁇ 0.25%, Nb: 0.04 ⁇ 0.05%, Ti: 0.01 ⁇ 0.02%, the rest is Fe and inevitable impurities, the impurities include P ⁇ 0.01%, S ⁇ 0.003%.
  • the lower yield strength of the steel plate is ⁇ 430MPa
  • the tensile strength is ⁇ 540MPa
  • the yield-to-strength ratio is ⁇ 0.85
  • the impact energy at -40°C is ⁇ 180J
  • the Z-direction tensile area shrinkage is ⁇ 50%, meeting Grade II or above in the GB/T 2970-2016 standard. Detection requirements.
  • the production method used in the present invention directly rolls the slab after heating before three-stage rolling, and performs three-stage cooling treatment on the steel plate after rolling, so that Q500qE with a maximum thickness of 150mm can be obtained
  • Steel plate the steel plate can meet the Z-direction tensile performance requirements of Z35 level and the flaw detection requirements of level II or above in GB/T 2970-2016 standard.
  • the production process is simple, the efficiency is high and the production cost is low.
  • ordinary continuous casting billets can be used to produce extra-thick steel plates, without the need for mold casting or preparation of composite billets;
  • high-temperature one-stage high-pressure rolling is used, without the need for mold casting or composite billet preparation.
  • Multi-stage low-temperature controlled rolling has a simple rolling process and high rolling efficiency; thirdly, there is no need for heat treatment such as tempering, normalizing, normalizing and rapid cooling after rolling, so there are fewer production processes, a short production cycle, and low production costs.
  • the continuous casting billet with a thickness of 320mm is prepared through the steps of molten iron pre-desulfurization, converter smelting, LF refining, RH vacuum refining, continuous casting, and slab stacking and slow cooling.
  • the steel plate is rolled at high temperature in one stage and under large pressure. After the slab is released from the furnace, it is rolled immediately after rough descaling.
  • the rolling temperature is 1006 ⁇ 1038°C
  • the steel biting speed is 0.6m/s
  • the rolling speed is 1.2m/s.
  • the secondary reductions are 43mm, 45mm, 45mm, and 37mm
  • the finished product thickness is 150mm.
  • the first stage cooling rate is 0.3°C/s and the cooling end temperature is 774°C.
  • the second stage cooling rate is 4.5°C/s and the cooling end temperature is 572°C.
  • the second stage cooling is completed and the waiting time is 20s; the third stage The stage cooling rate is 7.2°C/s, and the cooling end temperature is 328°C.

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Abstract

一种特厚Q500qE桥梁钢板及其生产方法，所述生产方法在进行三阶段轧制前加热后直接对板坯进行轧制处理，并在轧后对钢板进行三阶段冷却处理，可获得最大厚度达150mm的Q500qE钢板，钢板能够满足Z35级别的Z向拉伸性能要求及GB/T 2970-2016标准中Ⅱ级以上探伤要求。如此设置，生产工艺简单，效率高，生产成本低。

Description

特厚Q500qE桥梁钢板及其生产方法 技术领域
本发明涉及合金技术领域，具体地涉及一种特厚Q500qE桥梁钢板及其生产方法。
背景技术
随着我国社会经济的不断发展，大跨度、重载荷的特大桥梁工程也越来越多。随着跨度增加、载荷增大，对特厚规格桥梁钢的需求也越来越大，且对钢板的性能要求也越来越高，如更高的强度、更好的韧性、更少的心部缺陷、更优良的抗层状撕裂性能等。特厚规格桥梁钢相比于普通规格桥梁钢，因成品厚度增加，压缩比变小，造成钢板心部变形不足，板坯中心缺陷无法轧合而出现探伤不合格及抗层状撕裂能力差等问题。此外，钢板厚度增加后，冷却渗透能力变差，无法有效通过轧后在线冷却对钢板的强、韧性进行调控。
现有的特厚桥梁钢生产方式较为复杂且厚度依然较薄，如专利号为CN107557690B、CN102041438B的专利采用模铸方式制造坯料，专利号为CN107460278B、CN107287527B的专利采用复合坯方式获得大厚度坯料，专利号为CN104988435B、CN103540848B的专利虽然采用连铸坯生产特厚板，但可生产的钢板最大厚度规格仅120mm。因此，如何通过较为简单的生产工艺生产获得特厚桥梁钢是业界亟待解决的问题。
发明内容
本发明的目的在于提供一种特厚Q500qE桥梁钢板及其生产方法。
本发明提供一种特厚Q500qE桥梁钢板生产方法，其特征在于：
所述钢板的化学成分以质量百分比计包括：C:0.05～0.07％、Si:0.15～0.35％、Mn:1.5～1.7％、Ni:0.3～0.5％、Cr:0.2～0.3％、Mo:0.2～0.3％、Cu:0.15～0.25％、 Nb:0.04～0.05％、Ti:0.01～0.02％，其余为Fe和不可避免的杂质，所述杂质包括P≤0.01％、S≤0.003％；
所述生产方法包括步骤：
按照上述化学成分配比，冶炼、连铸得到板坯；
将所述板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，其中，所述第二阶段加热温度控制为1180～1220℃，所述第一阶段加热温度和第三阶段加热温度控制为低于所述第二阶段加热温度，经所述第一加热阶段和所述第二加热阶段加热使所述板坯温度均匀，在所述第三加热阶段使所述板坯自表面至心部形成逐渐上升的温度梯度；
将加热后所述板坯进行一阶段轧制，得到最大厚度为150mm的轧制态钢板；
将所述轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，其中，所述第三阶段冷却终冷温度控制为≤350℃，所述第一阶段冷却、第二阶段冷却和第三阶段冷却冷速依次增加。
作为本发明的进一步改进，所述钢板的化学成分还满足：碳当量CE≤0.485，冷裂纹敏感指数Pcm≤0.24，其中，碳当量CE的计算公式为：
CE＝(％C)+(％Mn)/6+(％Cr+％Mo+％V)/5+(％Ni+％Cu)/15，
冷裂纹敏感指数Pcm的计算公式为：
Pcm＝(％C)+(％Si)/30+(％Mn+％Cu+％Cr)/20+(％Ni)/60+(％Mo)/15+(％V)/10+5(％B)，
其中，括号内元素符号为相应元素的质量百分数，％元素符号表示相应元素的质量百分数乘以100；
作为本发明的进一步改进，所述按照上述化学成分配比，冶炼铸造得到板坯，具体包括：
按照上述化学成分配比，依次通过铁水预脱硫、转炉冶炼、LF精炼、RH真空精炼工序冶炼得到钢水，将所述钢水进行连铸得到厚度为320mm的板坯，并将所述板坯堆垛冷却。
作为本发明的进一步改进，所述将所述板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，具体包括：
所述将所述板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，其中，第一阶段加热温度控制为900～1100℃，加热时间控制为≥150min；第二阶段加热温度控制为1180～1220℃，加热时间控制为180～240min；第三阶段加热温度控制为1140～1160℃，加热时间控制为30～60min。
作为本发明的进一步改进，所述将加热后所述板坯进行一阶段轧制，具体包括：
将经过三阶段加热的所述板坯除鳞后进行轧制，在轧制过程中，轧制温度控制为980～1080℃，除末道次外，其余轧制道次压下量控制为≥40mm。
作为本发明的进一步改进，所述将加热后所述板坯进行一阶段轧制，还包括：
在轧制过程中，将咬钢速度控制为0.6m/s，轧制速度控制为1.2m/s。
作为本发明的进一步改进，所述将所述轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，具体包括：
将所述轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，其中，第一阶段冷却速度控制为0.3～1℃/s，终冷温度控制为760～780℃；第二阶段冷却速度控制为3～5℃/s，，终冷温度控制为560～600℃，在第二阶段冷却结束后等待20～40s；第三阶段冷却速度控制为5～8℃/s，终冷温度控制为≤350℃。
一种特厚Q500qE桥梁钢板，其采用上述的特厚Q500qE桥梁钢板生产方法制造得到。
作为本发明的进一步改进，所述钢板微观组织为贝氏体加马氏体的双相组织，其中，所述贝氏体数量多于所述马氏体数量。
作为本发明的进一步改进，所述钢板下屈服强度≥430MPa，抗拉强度≥540MPa，屈强比≤0.85，-40℃冲击功≥180J、Z向拉伸断面收缩率≥50％，满足GB/T 2970-2016标准中Ⅱ级以上探伤要求。
一种特厚Q500qE桥梁钢板，所述钢板的化学成分以质量百分比计包括：C:0.05～0.07％、Si:0.15～0.35％、Mn:1.5～1.7％、Ni:0.3～0.5％、Cr:0.2～0.3％、Mo:0.2～0.3％、Cu:0.15～0.25％、Nb:0.04～0.05％、Ti:0.01～0.02％，其余为Fe和不可避免的杂质，所述杂质包括P≤0.01％、S≤0.003％；
并且，所述钢板碳当量CE≤0.485，冷裂纹敏感指数Pcm≤0.24，其中，碳当量 CE的计算公式为：
CE＝(％C)+(％Mn)/6+(％Cr+％Mo+％V)/5+(％Ni+％Cu)/15，
冷裂纹敏感指数Pcm的计算公式为：
Pcm＝(％C)+(％Si)/30+(％Mn+％Cu+％Cr)/20+(％Ni)/60+(％Mo)/15+(％V)/10+5(％B)，
其中，括号内元素符号为相应元素的质量百分数，％元素符号表示相应元素的质量百分数乘以100；
所述钢板所制钢板最大厚度150mm，下屈服强度≥430MPa，抗拉强度≥540MPa，屈强比≤0.85，-40℃冲击功≥180J、Z向拉伸断面收缩率≥50％，满足GB/T 2970-2016标准中Ⅱ级以上探伤要求。
作为本发明的进一步改进，所述钢板微观组织为贝氏体加马氏体的双相组织，其中，所述贝氏体数量多于所述马氏体数量。
本发明的有益效果是：本发明所使用的生产方法，进行三阶段轧制前加热后直接对板坯进行轧制处理，并在轧后对钢板进行三阶段冷却处理，可获得最大厚度达150mm的Q500qE钢板，钢板能够满足Z35级别的Z向拉伸性能要求及GB/T 2970-2016标准中Ⅱ级以上探伤要求。其生产工艺简单，效率高，生产成本低。第一，在生产过程中，采用普通连铸坯即可生产得到特厚规格钢板，无需模铸、无需制备复合坯；第二，在轧制过程中采用高温一阶段大压下轧制，无需多阶段低温控轧，轧制工艺简单，轧制效率高；第三，轧后无需进行调质、正火、正火快冷等热处理，生产工序少，生产周期短，生产成本低。
附图说明
图1是本发明一实施方式中的特厚Q500qE桥梁钢板生产方法步骤示意图。
图2是本发明实施例一中的特厚Q500qE桥梁钢板金相组织图片。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚，下面将结合本发明具体实施方 式及相应的附图对本发明技术方案进行清楚、完整地描述。显然，所描述的实施方式仅是本发明一部分实施方式，而不是全部的实施方式。基于本发明中的实施方式，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施方式，都属于本发明保护的范围。
下面详细描述本发明的实施方式，实施方式的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施方式是示例性的，仅用于解释本发明，而不能理解为对本发明的限制。
本实施方式提供一种特厚Q500qE桥梁钢板及其生产方法，本生产方法直接对连铸坯进行轧制得到最大厚度为150mm的钢板，其相比于现有的特厚规格桥梁钢，在低压缩比、无低温控轧、无热处理的情况下使钢板具备高强度和高韧性，生产方法简单，钢板性能优异，通过本方法生产得到的钢板能够作为Q500qE牌号的桥梁钢板使用。
本实施方式提供的钢板的化学成分以质量百分比计包括：C:0.05～0.07％、Si:0.15～0.35％、Mn:1.5～1.7％、Ni:0.3～0.5％、Cr:0.2～0.3％、Mo:0.2～0.3％、Cu:0.15～0.25％、Nb:0.04～0.05％、Ti:0.01～0.02％，其余为Fe和不可避免的杂质，杂质包括P≤0.01％、S≤0.003％。
具体地，钢板的化学成分的设计原理说明如下：
C：其为强化元素，C含量的多少能显著影响钢材的组织结构，从而可以有效地保证钢板的强度，同时，C含量对钢板的淬透性、增加钢板的屈强比都有重要的作用，但是过高的C含量会显著恶化钢板的低温韧性，因此，在本实施方式中，将C含量控制为0.05～0.07％。
Si：其作为脱氧元素，通过固溶强化提高材料的强度，Si能溶于铁素体和奥氏体中提高钢的硬度和强度，并且Si还能起到抑制珠光体转变的作用，但过高的Si含量易导致M/A(马氏体/奥氏体)含量增加，恶化钢板低温韧性，因此，在本实施方式中，将Si含量控制为0.15～0.35％。
Mn：其为固溶强化元素，可以提高钢板的淬透性，从而提高其强度，并且Mn 能够促进针状铁素体形成。同时Mn也是良好的脱氧剂和脱硫剂，其可以与有害元素S结合以降低钢板的热脆性。但过多的Mn会加剧P、Sb、Sn等元素的偏析，劣化钢板心部低温韧性，在轧制过程中的延展会导致钢板探伤不合。因此，在本发明中，将Mn含量控制为1.40～1.60％。
Ni：在钢材裂纹尖端处会产生以P、Ni合金为主的沉积行为，在裂纹尖端尾部裂纹面上产生化学沉积，NiP沉积物诱导裂纹闭合和在裂尖附近产生残余压应力，有效地降低疲劳裂纹的扩展速率，通过裂纹尖端的应力释放，提高材料的低温韧性。同时，Ni能够有效改善钢材的淬透性，但添加过多的Ni会造成合金成本较高，因此，在本实施方式中，将Ni含量控制为0.1～0.2％。
Cr：其具有和Mn相近的固溶强化作用，可以有效提高钢材的淬透性。但Cr合金价格高于Mn，且过高Cr含量影响过冷奥氏体稳定性，因此，在本实施方式中，将Cr含量控制为0.1～0.2％。
Mo：其可显著增加钢的淬透性，配合轧后加速冷却可提高钢板强度，但Mo属于贵重合金元素，添加过多易造成成本过高，因此，在本实施方式中，添加0.08～0.16％。
Cu：其可提高钢板强度及耐腐蚀性能，且对低温韧性的不利影响相对较小，但Cu含量过高时易发生铜脆影响钢板表面质量，因此，在本实施方式中，Cu含量控制在0.15～0.25％。
Nb：其属于微合金强化元素，具有析出强化和细晶强化作用，可提高钢强度，改善低温韧性，但Nb含量过高时，焊接热影响区易形成大量大尺寸的M/A，从而恶化钢板的焊接性能，因此，在本实施方式中，将Nb含量控制为0.04～0.05％。
Ti：其属于微合金强化元素，具有析出强化和细晶强化作用，Ti的氮化物与氧化物能够抑制奥氏体晶粒长大而细化奥氏体，在本实施方式中，Ti含量控制在0.010～0.020％。
P、S：为残存杂质元素，对钢的低温韧性不利，因此控制P含量≤0.015％、S含量≤0.005％。
进一步的，钢板的化学成分还满足：碳当量CE≤0.485，以确保钢板具有良好的焊接性，根据B/T1591-2018标准，碳当量CE的计算公式为：
CE＝(％C)+(％Mn)/6+(％Cr+％Mo+％V)/5+(％Ni+％Cu)/15。
其中，括号内元素符号为相应元素的质量百分数，％元素符号表示相应元素的质量百分数乘以100。
冷裂纹敏感指数Pcm≤0.24，以降低钢在焊接时产生裂纹的倾向，保证其焊接性。根据B/T1591-2018标准，冷裂纹敏感指数Pcm的计算公式为：
Pcm＝(％C)+(％Si)/30+(％Mn+％Cu+％Cr)/20+(％Ni)/60+(％Mo)/15+(％V)/10+5(％B)，
其中，括号内元素符号为相应元素的质量百分数，％元素符号表示相应元素的质量百分数乘以100。
如图1所示，所述特厚Q500qE桥梁钢板生产方法包括步骤：
S1：按照上述化学成分配比，冶炼、连铸得到板坯。
S2：将板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，其中，第二阶段加热温度控制为1180～1220℃，第一阶段加热温度和第三阶段加热温度控制为低于第二阶段加热温度，在第一加热阶段和第二加热阶段加热至板坯温度均匀，在第三加热阶段使板坯自表面至心部形成逐渐上升的温度梯度。
S3：将加热后板坯进行一阶段轧制，得到最大厚度为150mm的轧制态钢板。
S4：将轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，其中，第三阶段冷却终冷温度控制为≤350℃，第一阶段冷却、第二阶段冷却和第三阶段冷却冷速依次增加。
具体的，在步骤S1中，其依次包括以下工序：
铁水预脱硫、转炉冶炼、LF精炼、RH真空精炼、连铸和板坯堆垛缓冷。
在铁水预脱硫工序中，对铁水进行KR脱硫，控制铁水中硫含量，在扒除脱硫渣后将铁水兑入转炉进行转炉冶炼。
在转炉冶炼中，使用预脱硫后的铁水和废钢等为原料进行转炉冶炼得到钢水，在冶炼过程中，在钢水中依次加入硅铁合金、金属锰和碳粉等对钢水进行脱氧合金化。
将钢水精炼至满足预定要求后抽真空进行循环脱气处理。
将精炼后钢水抽真空进行循环脱气处理，去除夹杂物，进行进一步精炼。
精炼后将钢液通过连铸形成厚度为320mm的板坯，获得板坯后，将板坯堆垛缓冷。
在本实施方式中，将板坯厚度控制为320mm，配合后续的轧制工艺，可以获得最大厚度为150mm的钢板，在本发明的其他实施方式中，也可根据最所需的钢板厚度和轧制工艺参数而对连铸获得的板坯厚度进行调整。
在步骤S2中，其具体包括：
将板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，其中，第一阶段加热温度控制为900～1100℃，加热时间控制为≥150min(即将板坯在加热炉中停留时间控制为≥150min)；第二阶段加热温度控制为1180～1220℃，加热时间控制为180～240min(即将板坯在加热炉中停留时间控制为180～240min)；第三阶段加热温度控制为1140～1160℃，加热时间控制为30～60min(即将板坯在加热炉中停留时间控制为30～60min)。
在轧制前将板坯加热到均匀的、适合轧制的温度，能够提高钢的塑性，降低变形抗力，使钢容易变形，从而在板坯轧制过程中可以使用较大的压下量。并且，加热能改善板坯的内部组织和性能，不均匀组织和非金属夹杂物能够通过高温加热的扩散作用而均匀化。
在第一阶段加热过程中，设置一相对较低的加热温度，避免板坯升温速率过快而产生热应力导致板坯表面开裂，并且，进行长时间加热来配合后续第二阶段加热过程，以保证板坯整体温度均匀且能够达到所设置的加热温度。在第二阶段加热加热过程中，设置较高的加热温度且进行长时间保温，以保证板坯内部得到充分加热，使得钢板心部和表面处温度均匀。并且对最长加热时间进行限制，以避免板坯表面因在高温条件下长时间加热而使晶粒过分长大以及晶界氧化或融化，从而避免上述情况可能导致的表面过烧、氧化皮粘附等钢板表面质量问题。在第三阶段加热过程中，相对于第二阶段加热过程，设置一较低加热温度和较短加热时间，从而在板坯厚度方向形成自表面向心部逐渐增加的温度梯度，以有利于在后续轧制过程中使变形相板坯心部渗透。
在步骤S3中，其具体包括：
将经过三阶段加热的板坯除鳞后进行轧制，在轧制过程中，将轧制温度控制为980～1080℃，咬钢速度控制为0.6m/s，轧制速度控制为1.2m/s，除末道次外，其余轧制道次压下量控制为≥40mm，最终得到最大厚度为150mm的钢板。
除鳞即通过除鳞设备去除板坯表面一次氧化铁皮，为对板坯进行轧制处理而做准备。
在本实施方式中，为保证低压缩比条件下钢板具有良好的心部质量，采用高温、一阶段、大压下方式进行轧制。轧制温度控制为980～1080℃，利用高温下变形抗力小的特点进行单道次大压下轧制，除末道次外，其余道次压下量≥40mm，从而保证变形能够向板坯心部渗透，避免轧后出现心部疏松、微裂纹等缺陷，以保障钢板满足探伤要求。
本实施方式直接将连铸坯加热后进行轧制处理，无需在轧制处理之前进行开坯轧制，工艺步骤更加简单，缩减了所需的工时，降低了生产消耗。在轧制过程中，采用高温一阶段大压下轧制，无需多阶段低温控轧，轧制工艺简单，轧制效率高，较传统低温控轧工艺，轧制效率可提高50％以上。
并且，在本实施方式中，通过厚度为320mm的连铸坯直接轧制获得最大厚度为150mm的钢板，突破了传统连铸坯生产特厚板的压缩比限制。
在步骤S4中，其具体包括：
将轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，其中，第一阶段冷却速度控制为0.3～1℃/s，终冷温度控制为760～780℃；第二阶段冷却速度控制为3～5℃/s，，终冷温度控制为560～600℃，在第二阶段冷却结束后等待20～40s；第三阶段冷却速度控制为5～8℃/s，终冷温度控制为≤350℃。
将轧后的钢板通过三阶段的冷却方式对其组织进行调控，以保证其获得良好的强度和韧性。在第一阶段冷却过程中，采用慢冷速进行冷却，避免钢板在1000℃左右冷却时近表层形成过于粗大的侧板条铁素体组织而影响钢板低温韧性，并为下一阶段近表层组织调控作准备。在第二阶段冷却过程中，相对于第一阶段冷却过程增加冷却速度至3～5℃/s，对钢板近表层至厚度1/4范围内组织进行调控，使该范围内钢板组织先行发生相变，避免下一阶段强冷时近表层因冷却强度大出现过多对韧性 不利的马氏体硬相组织。在第三阶段冷却过程中，相对于第二阶段冷却过程进一步增加冷却速度，以对钢板厚度1/4至1/2范围内组织进行调控，由于该范围靠近于钢板心部，冷却散热效果相较于钢板表层明显减弱，为保证该钢板心部冷却效果需要进一步提高冷却幅度，因此将冷速提升至5～8℃/s。此外，得益于第二阶段冷却时近表层已发生相变，第三阶段冷却强度虽然增强但对近表层组织并未造成明显影响。
通过三阶段的冷却方式对钢板进行冷却，并在第二和第三阶段冷却过程中采用较大的冷却速度，以及控制终冷阶段温度为≤350℃，有效的对特厚钢板的组织进行了调控，获得以贝氏体为主加少量马氏体的双相组织，在贝氏体组织基础上，通过高强度的马氏体对钢板组织进行进一步强化，进而对其强、韧性进行调控。
本实施方式还提供一种特厚Q500qE桥梁钢板，其通过上述特厚Q500qE桥梁钢板生产方法制造得到。
钢板的化学成分以质量百分比计包括：C:0.05～0.07％、Si:0.15～0.35％、Mn:1.5～1.7％、Ni:0.3～0.5％、Cr:0.2～0.3％、Mo:0.2～0.3％、Cu:0.15～0.25％、Nb:0.04～0.05％、Ti:0.01～0.02％，其余为Fe和不可避免的杂质，杂质包括P≤0.01％、S≤0.003％。
并且，钢板的碳当量CE≤0.485，冷裂纹敏感指数Pcm≤0.24。
钢板下屈服强度≥430MPa，抗拉强度≥540MPa，屈强比≤0.85，-40℃冲击功≥180J、Z向拉伸断面收缩率≥50％，满足GB/T 2970-2016标准中Ⅱ级以上探伤要求。
综上所述，本发明所使用的生产方法，进行三阶段轧制前加热后直接对板坯进行轧制处理，并在轧后对钢板进行三阶段冷却处理，可获得最大厚度达150mm的Q500qE钢板，钢板能够满足满足Z35级别的Z向拉伸性能要求及GB/T 2970-2016标准中Ⅱ级以上探伤要求。其生产工艺简单，效率高，生产成本低。第一，在生产过程中，采用普通连铸坯即可生产得到特厚规格钢板，无需模铸、无需制备复合坯；第二，在轧制过程中采用高温一阶段大压下轧制，无需多阶段低温控轧，轧制工艺简单，轧制效率高；第三，轧后无需进行调质、正火、正火快冷等热处理，生产工序少，生产周期短，生产成本低。
以下通过1个实施例进一步对本发明的具体实施方式予以介绍。
实施例1
钢板的化学成分为C:0.058％、Si:0.28％、Mn 1.63％、P:0.008％、S:0.0026％、Ni:0.36％、Cr:0.24％、Mo:0.24％、Cu:0.20％、Nb:0.042％、Ti:0.014％，Ceq＝0.463，Pcm＝0.193，其余为Fe及不可避免杂质。
依次通过铁水预脱硫、转炉冶炼、LF精炼、RH真空精炼、连铸、板坯堆垛缓冷的步骤制备厚度320mm连铸坯。
板坯采用三阶段加热，第一阶段加热温度988～1093℃，停留时间t1＝180min，第二阶段加热温度1198～1210℃，停留时间t2＝204min，第三阶段加热温度1143～1156℃，停留时间t3＝36min。
钢板采用高温一阶段大压下轧制，板坯出炉后经粗除鳞后即进行轧制，轧制温度1006～1038℃，咬钢速度0.6m/s，轧制速度1.2m/s，道次压下量依次为43mm、45mm、45mm、37mm，成品厚度150mm。
钢板轧后采用三阶段冷却，第一阶段冷速0.3℃/s，冷却终止温度774℃；第二阶段冷速4.5℃/s，冷却终止温度572℃，第二阶段冷却结束等待20s；第三阶段冷速7.2℃/s，冷却终止温度328℃。
钢板各项性能见表1，典型组织见图2。
表1
应当理解，虽然本说明书按照实施方式加以描述，但并非每个实施方式仅包含一个独立的技术方案，说明书的这种叙述方式仅仅是为清楚起见，本领域技术人员应当将说明书作为一个整体，各实施方式中的技术方案也可以经适当组合，形成本领域技术人员可以理解的其他实施方式。
上文所列出的一系列的详细说明仅仅是针对本发明的可行性实施方式的具体说 明，并非用以限制本发明的保护范围，凡未脱离本发明技艺精神所作的等效实施方式或变更均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种特厚Q500qE桥梁钢板生产方法，其特征在于：
    所述钢板的化学成分以质量百分比计包括：C:0.05～0.07％、Si:0.15～0.35％、Mn:1.5～1.7％、Ni:0.3～0.5％、Cr:0.2～0.3％、Mo:0.2～0.3％、Cu:0.15～0.25％、Nb:0.04～0.05％、Ti:0.01～0.02％，其余为Fe和不可避免的杂质，所述杂质包括P≤0.01％、S≤0.003％；
    所述生产方法包括步骤：
    按照上述化学成分配比，冶炼、连铸得到板坯；
    将所述板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，其中，所述第二阶段加热温度控制为1180～1220℃，所述第一阶段加热温度和第三阶段加热温度控制为低于所述第二阶段加热温度，经所述第一加热阶段和所述第二加热阶段加热使所述板坯温度均匀，在所述第三加热阶段使所述板坯自表面至心部形成逐渐上升的温度梯度；
    将加热后所述板坯进行一阶段轧制，除末道次外，其余轧制道次压下量控制为≥40mm，得到最大厚度为150mm的轧制态钢板；
    将所述轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，其中，所述第三阶段冷却终冷温度控制为≤350℃，所述第一阶段冷却、第二阶段冷却和第三阶段冷却冷速依次增加。
  2. 根据权利要求1所述的特厚Q500qE桥梁钢板生产方法，其特征在于，所述钢板的化学成分还满足：碳当量CE≤0.485，冷裂纹敏感指数Pcm≤0.24，其中，碳当量CE的计算公式为：
    CE＝(％C)+(％Mn)/6+(％Cr+％Mo+％V)/5+(％Ni+％Cu)/15，
    冷裂纹敏感指数Pcm的计算公式为：
    Pcm＝(％C)+(％Si)/30+(％Mn+％Cu+％Cr)/20+(％Ni)/60+(％Mo)/15+(％V)/10+5(％B)，
    其中，括号内元素符号为相应元素的质量百分数，％元素符号表示相应元素的质量百分数乘以100；
  3. 根据权利要求1所述的特厚Q500qE桥梁钢板生产方法，其特征在于，所述按 照上述化学成分配比，冶炼铸造得到板坯，具体包括：
    按照上述化学成分配比，依次通过铁水预脱硫、转炉冶炼、LF精炼、RH真空精炼工序冶炼得到钢水，将所述钢水进行连铸得到厚度为320mm的板坯，并将所述板坯堆垛冷却。
  4. 根据权利要求1所述的特厚Q500qE桥梁钢板生产方法，其特征在于，所述将所述板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，具体包括：
    所述将所述板坯依次进行第一阶段加热、第二阶段加热和第三阶段加热，其中，第一阶段加热温度控制为900～1100℃，加热时间控制为≥150min；第二阶段加热温度控制为1180～1220℃，加热时间控制为180～240min；第三阶段加热温度控制为1140～1160℃，加热时间控制为30～60min。
  5. 根据权利要求1所述的特厚Q500qE桥梁钢板生产方法，其特征在于，所述将加热后所述板坯进行一阶段轧制，具体包括：
    将经过三阶段加热的所述板坯除鳞后进行轧制，在轧制过程中，轧制温度控制为980～1080℃，除末道次外，其余轧制道次压下量控制为≥40mm。
  6. 根据权利要求5所述的特厚Q500qE桥梁钢板生产方法，其特征在于，所述将加热后所述板坯进行一阶段轧制，还包括：
    在轧制过程中，将咬钢速度控制为0.6m/s，轧制速度控制为1.2m/s。
  7. 根据权利要求5所述的特厚Q500qE桥梁钢板生产方法，其特征在于，所述将所述轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，具体包括：
    将所述轧制态钢板依次进行第一阶段冷却、第二阶段冷却和第三阶段冷却，其中，第一阶段冷却速度控制为0.3～1℃/s，终冷温度控制为760～780℃；第二阶段冷却速度控制为3～5℃/s，，终冷温度控制为560～600℃，在第二阶段冷却结束后等待20～40s；第三阶段冷却速度控制为5～8℃/s，终冷温度控制为≤350℃。
  8. 一种特厚Q500qE桥梁钢板，其特征在于，采用权利要求1所述的特厚Q500qE桥梁钢板生产方法制造得到。
  9. 根据权利要求8所述的特厚Q500qE桥梁钢板，其特征在于，所述钢板微观组织为贝氏体加马氏体的双相组织，其中，所述贝氏体数量多于所述马氏体数量。
  10. 根据权利要求9所述的特厚Q500qE桥梁钢板，其特征在于，所述钢板下屈服强度≥430MPa，抗拉强度≥540MPa，屈强比≤0.85，-40℃冲击功≥180J、Z向拉伸断面收缩率≥50％，满足GB/T 2970-2016标准中Ⅱ级以上探伤要求。
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