WO2021052314A1 - 耐火耐候钢板/带及其制造方法 - Google Patents

耐火耐候钢板/带及其制造方法 Download PDF

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WO2021052314A1
WO2021052314A1 PCT/CN2020/115284 CN2020115284W WO2021052314A1 WO 2021052314 A1 WO2021052314 A1 WO 2021052314A1 CN 2020115284 W CN2020115284 W CN 2020115284W WO 2021052314 A1 WO2021052314 A1 WO 2021052314A1
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resistant
strip
steel
fire
weather
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PCT/CN2020/115284
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English (en)
French (fr)
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吴建春
方园
范建勇
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宝山钢铁股份有限公司
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Priority claimed from CN201910888780.0A external-priority patent/CN112522640B/zh
Priority claimed from CN201910888779.8A external-priority patent/CN112522578B/zh
Application filed by 宝山钢铁股份有限公司 filed Critical 宝山钢铁股份有限公司
Priority to DE112020004462.9T priority Critical patent/DE112020004462T9/de
Publication of WO2021052314A1 publication Critical patent/WO2021052314A1/zh

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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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
    • 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
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/613—Gases; Liquefied or solidified normally gaseous material
    • 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
    • C21D8/021—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
    • 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
    • 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
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—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
    • C22C38/22—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
    • C22C38/18—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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • 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 belongs to a continuous casting process and product in the metallurgical industry, and is mainly used for thin strip steel products produced by a double-roll thin strip continuous casting process, and is particularly suitable for producing a fire-resistant and weather-resistant steel plate/strip product.
  • tin (Sn) and copper (Cu) are typical residual elements or harmful elements in steel. It is very difficult and very expensive to fully remove Sn and Cu during the steelmaking process. Once the steel contains Sn , Cu, basically can not be completely eliminated, only by diluting molten steel to reduce the content of Sn, Cu, these all cause the increase in the smelting cost of steel products.
  • Traditional thin strip steel is mostly produced by continuous rolling of cast billets with a thickness of 70-200mm through multiple passes.
  • the traditional hot rolling process is: continuous casting + billet reheating and heat preservation + rough rolling + finishing rolling + cooling + Coiling, that is, firstly obtain a cast slab with a thickness of about 200mm through continuous casting. After reheating and holding the cast slab, rough rolling and finishing rolling are performed to obtain a steel strip with a thickness generally greater than 2mm, and finally the steel strip is processed Laminar cooling and coiling complete the entire hot rolling production process. If you want to produce steel strips with a thickness of less than 1.5mm (inclusive), the difficulty is relatively large, and the hot-rolled steel strips are usually subjected to subsequent cold rolling and annealing to complete. In addition, the long process flow, high energy consumption, many units and equipment, and high capital construction costs result in high production costs.
  • the thin slab continuous casting and rolling process is: continuous casting + slab heat preservation and soaking + hot continuous rolling + cooling + coiling.
  • the main difference between this process and the traditional process is that the thickness of the cast slab in the thin slab process is greatly reduced to 50-90mm. Because the cast slab is thin, the cast slab only needs to undergo 1 to 2 passes of rough rolling (the thickness of the cast slab is 70-90mm When the thickness of the cast slab is 50mm, the thickness of the continuous casting slab in the traditional process must be repeatedly rolled to reduce the thickness to the required specifications before the finish rolling; and the thin slab casting process is not necessary to go through rough rolling (when the thickness of the cast slab is 50mm).
  • the billet directly enters the soaking furnace for soaking and heat preservation, or a small amount of temperature compensation, so the thin slab process greatly shortens the process flow, reduces energy consumption, reduces investment, and reduces production costs.
  • the faster cooling rate of thin slab continuous casting and rolling the strength of the steel will increase and the yield ratio will increase, thereby increasing the rolling load, so that the thickness specification of the hot-rolled product can be economically produced and the thickness specification is not too thin, generally ⁇ 1.5mm, see patents CN200610123458.1, CN200610035800.2 and CN200710031548.2, and these patents do not involve the elements Sn and Cu.
  • ESP all-headless thin slab continuous casting and rolling process
  • the flame cutting of slab and the heating furnace for heat preservation and soaking and slab transition are eliminated, and the length of the entire production line is greatly shortened to about 190 meters.
  • the thickness of the slab casted by the continuous casting machine is 90-110mm, and the width is 1100-1600mm.
  • the continuous casting slab passes through a section of induction heating roller table to keep the slab warm and soak, and then enters the rough rolling one by one. , Finish rolling, layer cooling, and coiling processes to obtain hot-rolled plates.
  • this process can obtain the thinnest hot-rolled sheet with a thickness of 0.8mm, which expands the specification range of the hot-rolled sheet.
  • its single production line output can reach 2.2 million tons/year.
  • the process has been rapidly developed and promoted.
  • the shorter process flow than thin slab continuous casting and rolling is the thin strip continuous casting and rolling process.
  • the thin strip continuous casting technology is a cutting-edge technology in the field of metallurgy and materials research. Its appearance has brought a revolution to the steel industry. It changes the production process of steel strip in the traditional metallurgical industry, integrating continuous casting, rolling, and even heat treatment into a whole, so that the produced thin strip will be formed into thin steel strip at one time after one online hot rolling.
  • the production process is simplified and the production cycle is shortened.
  • the length of the process line is only about 50m; the equipment investment is also reduced, and the product cost is significantly reduced. It is a low-carbon and environmentally friendly hot-rolled thin strip production process.
  • the twin-roll thin strip continuous casting process is a main form of the thin strip continuous casting process, and it is also the world's only industrialized thin strip continuous casting process.
  • the typical process flow of twin-roll thin strip continuous casting is shown in Figure 1.
  • the molten steel in the ladle 1 is directly poured into one by two through the ladle nozzle 2, the tundish 3, the immersion nozzle 4 and the distributor 5
  • the molten steel solidifies on the rotating circumferential surfaces of the crystallizing rollers 8a, 8b to form a solidified shell and gradually grow, and then the two A steel strip 11 with a thickness of 1-5mm is formed at the smallest gap (nip point) of the crystallizing roller.
  • the steel strip is fed into the rolling mill 13 through the guide plate 9 and guided to the pinch roller 12 to be rolled into a thin strip of 0.7-2.5mm, and then cooled
  • the device 14 is cooled, and after being cut by the flying shear device 16, it is finally sent to the coiler 19 to be wound into a roll.
  • Fire-resistant and weather-resistant steel requires good high-temperature performance, but it is different from heat-resistant steel that has been used for a long time at high temperatures.
  • Heat-resistant steel requires good high-temperature strength and high-temperature stability, and high-alloy steel is generally used.
  • the fire-resistant and weathering steel is loaded at room temperature, but it is required to maintain a high yield strength under high temperature conditions for a short time (usually 1-3h) in the event of a fire, which can win precious time for the safe evacuation of personnel, so it belongs to low alloy
  • its composition design should not add too many expensive alloying elements.
  • the Japanese steel structure safety design code stipulates that 2/3 of the yield strength of steel at room temperature is equivalent to the long-term allowable stress value of the material. When a fire occurs, if the yield point of the fire-resistant and weathering steel can still maintain this value, the building will not Will collapse. Therefore, it is required that the yield strength of refractory and weathering steel at a certain high temperature is not less than 2/3 of the room temperature yield strength. In order to improve the seismic resistance of steel structures, it is always desirable to increase the ability of steel to absorb seismic energy as much as possible. If the steel yield ratio ( ⁇ s / ⁇ b ) is high, local stress concentration and local large deformation will occur when an earthquake occurs. At this time, the steel structure can only absorb less energy, so a low yield ratio is beneficial to increase The energy absorbed by a building structure during an earthquake generally requires the yield ratio of earthquake-resistant, fire-resistant and weathering steel to be ⁇ 0.8.
  • the tests show that: The yield strength ( ⁇ s ) drops sharply in the range of 500-600°C, and ⁇ s drops below 50 MPa at 700°C or above. If the temperature to ensure the strength is set at 700°C, a large amount of alloying elements must be added, which makes it difficult to ensure good solderability and greatly increases the cost. If the temperature to ensure the strength is set at a lower 500°C, then the thickness of the refractory coating can only be slightly reduced, which does not conform to the original intention of using refractory and weathering steel. Therefore, the refractory temperature of the refractory and weathering steel is set to 600°C.
  • the performance indexes of fire-resistant and weather-resistant steel are determined as follows:
  • the thin strip continuous casting process is used to produce this high-strength refractory and weather-resistant steel sheet/strip. Due to the sub-rapid solidification characteristics of the thin strip continuous casting process itself, a certain thickness of fine-grained layer will naturally form on the surface of the strip, so that the produced steel grades have both Weather resistance; at the same time, it has certain manufacturing and cost advantages in thin specifications. Thin-gauge high-strength fire-resistant and weather-resistant steel plates/strips have a characteristic thickness of 1.2-2.0mm. Due to the thin thickness of the product, it is difficult to produce with the traditional continuous casting + hot continuous rolling production line, even if thin slab continuous casting and rolling production is used. The roll consumption of the rolls is also relatively large, and such a production process increases the production cost of thin-gauge high-strength fire-resistant and weather-resistant steel plates/strips.
  • thin strip continuous casting generally has the problems of uneven structure, low elongation, high yield ratio, and poor formability.
  • the cast strip has austenite crystals.
  • the grains have obvious non-uniformity, which will cause the final product structure obtained after austenite transformation to be uneven, resulting in unstable product properties, especially forming properties. Therefore, the use of thin strip continuous casting technology to produce high-strength refractory and weather-resistant steel plate/strip products also has certain difficulties and challenges, and requires breakthroughs in composition and technology.
  • the present invention is effective by adding an appropriate amount of B element and reasonable cooling measures after rolling. Improve the uniformity of the organization and achieve the purpose of reducing the yield ratio.
  • Chinese patent CN200610123458.1 discloses a method for producing 700MPa high-strength weathering steel based on the thin slab continuous casting and rolling process using Ti microalloying process.
  • the chemical composition of the weathering steel plate produced by this method is: C: 0.03-0.07%, Si :0.3-0.5%, Mn: 1.2-1.5, P: ⁇ 0.04%, S: ⁇ 0.008%, Al: 0.025-0.05%, Cr: 0.3-0.7%, Ni: 0.15-0.35%, Cu: 0.2-0.5 %, Ti: 0.08-0.14%, N: ⁇ 0.008%, the balance is Fe and unavoidable impurities.
  • the yield strength of the steel plate is ⁇ 700MPa, the tensile strength is ⁇ 775MPa, and the elongation is ⁇ 21%.
  • phosphorus is controlled in accordance with impurity elements, and the content is less than or equal to 0.04%, which is more relaxed than the traditional process of less than or equal to 0.025%.
  • Chinese patent CN200610035800.2 discloses a method for producing 700MPa grade VN microalloyed weathering steel based on the thin slab continuous casting and rolling process.
  • the chemical composition of the weathering steel plate produced by this method is: C: ⁇ 0.08%, Si: 0.25-0.75 %, Mn: 0.8-2, P: ⁇ 0.07-0.15%, S: ⁇ 0.04%, Cr: 0.3-1.25%, Ni: ⁇ 0.65%, Cu: 0.25-0.6%, V: 0.05-0.2%, N : 0.015-0.03%, the balance is Fe and unavoidable impurities.
  • the yield strength of the steel plate is ⁇ 700MPa, the tensile strength is ⁇ 785MPa, and the elongation is ⁇ 21%.
  • phosphorus is controlled in accordance with the elements that improve weather resistance, the content is 0.07-0.15%; the content of copper is 0.25-0.6%, and the lower limit and upper limit are respectively higher than the lower limit and upper limit of 0.2% and upper limit of copper content in the traditional process. 0.55%.
  • Cida patent CN1633509A mentions a method for producing copper-containing carbon steel products produced by thin strip continuous casting. The patent emphasizes the need to perform annealing, tempering and other heat treatment processes for this strip steel in the range of 400-700°C to make the copper element in the Precipitation or recrystallization in the strip.
  • US2008264525/CN200580009354.1 mentions a method for manufacturing high-copper and low-alloy thin strip. Its technical feature is that the strip steel is cooled to below 1080°C in a non-oxidizing atmosphere before entering the rolling mill to prevent "Hot brittleness" occurs in strip steel.
  • the above-mentioned patents all relate to the weather resistance of steel, but none of the content relates to the function of fire resistance.
  • the present invention is a steel grade specifically proposed for fire resistance and weather resistance.
  • the purpose of the present invention is to provide a fire-resistant and weather-resistant steel plate/belt and a manufacturing method thereof.
  • the produced fire-resistant and weather-resistant steel plate/belt can ensure that the steel maintains a high level of strength at high temperatures, and can also reduce the quality of the building and increase the safety of the building.
  • the fire-resistant and weather-resistant steel plate/belt produced on the basis of fire-resistant performance will naturally form a fine-grained layer with a certain thickness on the surface of the strip, making the product both weather-resistant performance.
  • the product has excellent seismic performance and excellent fire resistance. It is an ideal material in the field of seismic and fire-resistant steel. It can be widely used in some industries and fields such as construction steel, tower masts, construction machinery, and industrial structures that have fire-resistant and seismic requirements. Especially in places with high fire safety requirements such as high-rise buildings, large public buildings, and high-end residential buildings.
  • the invention utilizes the residual Sn, Cu and other elements in the scrap steel to smelt molten steel, and selectively adds Mo/Nb/Cr and other microalloy elements and B elements to the steel; during the smelting process, the alkalinity of the slag and the steel are controlled. Type of inclusions and melting point, free oxygen content in molten steel, and acid-soluble aluminum Als content; then double-roll thin strip continuous casting is performed to cast a 1.5-3mm thick strip.
  • the strip After the strip exits the crystallizing roller, it directly enters a In the lower airtight chamber of a non-oxidizing atmosphere, it enters the online rolling mill for hot rolling under airtight conditions; the rolled steel strip adopts gas atomization cooling method to cool the strip steel, and the gas atomization cooling method can effectively reduce
  • the thickness of the oxide scale on the surface of the strip can improve the temperature uniformity of the strip and improve the surface quality of the strip.
  • the final produced steel coil can be used directly as a hot-rolled plate/strip, or it can be used as a finished plate/strip after trimming and flattening.
  • the material of the invention has low yield ratio, excellent seismic performance and excellent fire resistance, and is an ideal material in the field of seismic and fire-resistant steel.
  • the fire-resistant and weather-resistant steel sheet/strip of the present invention has the following chemical composition weight percentages: C: 0.02-0.06%, Si: 0.1-0.55%, Mn: 0.4-1.7%, P ⁇ 0.03%, S ⁇ 0.007% , Cr: 0.30-0.80%, Mo: 0.20-0.60%, N: 0.004-0.010%, Als ⁇ 0.001%, B: 0.001-0.006%, optional Nb: 0.01-0.08%, total oxygen [O] T :0.007-0.020%, the balance is Fe and other unavoidable impurities, and at the same time meet:
  • Pcm ⁇ 0.27%, Pcm C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B.
  • the fire-resistant and weather-resistant steel sheet or steel strip of the present invention is a thin-gauge fire-resistant and weather-resistant steel sheet or steel strip; preferably, its thickness is 0.8-2.5 mm, preferably 1.2-2.0 mm.
  • Pcm 0.25%. In some embodiments, 0.14% ⁇ Pcm ⁇ 0.25%.
  • the fire-resistant and weather-resistant steel sheet/strip of the present invention has room temperature yield strength ⁇ 345MPa, tensile strength ⁇ 490MPa, elongation ⁇ 17%; yield ratio ⁇ s / ⁇ b ⁇ 0.8, preferably ⁇ 0.75; 600°C high temperature yield strength ⁇ 232MPa , ⁇ s,600°C / ⁇ s,20°C ⁇ 0.67; relative corrosion rate ⁇ 60%.
  • the weight percentage of the chemical composition of the fire-resistant and weather-resistant steel sheet or steel strip of the present invention is: C: 0.02-0.06%, Si: 0.1-0.55%, Mn: 0.4-1.7%, P ⁇ 0.03%, S ⁇ 0.007%, Cr: 0.30-0.80%, Mo: 0.20-0.60%, N: 0.004-0.010%, Als ⁇ 0.001%, B: 0.001-0.006%, total oxygen [O]T: 0.007-0.020%, remaining
  • the room temperature yield strength of the fire-resistant and weather-resistant steel sheet/belt is ⁇ 345MPa, the tensile strength is ⁇ 490MPa, and the elongation is ⁇ 17%; the yield ratio ⁇ s / ⁇ b ⁇ 0.8, preferably ⁇ 0.75; °C high temperature yield strength ⁇ 232MPa, ⁇ s, 600°C / ⁇ s, 20°C ⁇ 0.67; relative corrosion rate ⁇ 60%.
  • the room-temperature yield strength of these fire-resistant and weather-resistant steel plates or steel strips is 345-370 MPa, the tensile strength is 490-530 MPa, and the elongation is 19-27%; the yield strength ratio ⁇ s / ⁇ b is 0.66-0.72; 600°C high temperature yield strength is 235-260MPa, ⁇ s, 600°C / ⁇ s, 20°C is 0.68-0.74; relative corrosion rate is ⁇ 60%.
  • the room temperature yield strength of the fire-resistant and weather-resistant steel sheet/belt is ⁇ 345MPa, the tensile strength is ⁇ 490MPa, and the elongation is ⁇ 17%; the yield ratio ⁇ s / ⁇ b ⁇ 0.8, preferably ⁇ 0.75; °C high temperature yield strength ⁇ 232MPa, ⁇ s, 600°C / ⁇ s, 20°C ⁇ 0.67; relative corrosion rate ⁇ 60%.
  • the room-temperature yield strength of these fire-resistant and weather-resistant steel plates or steel strips is 345-370 MPa, the tensile strength is 490-530 MPa, and the elongation is 19-27%; the yield strength ratio ⁇ s / ⁇ b is 0.66-0.72; 600°C high temperature yield strength is 235-260MPa, ⁇ s, 600°C / ⁇ s, 20°C is 0.68-0.74; relative corrosion rate is ⁇ 60%.
  • the room temperature yield strength of the fire-resistant and weather-resistant steel sheet/belt is ⁇ 410MPa, the tensile strength is ⁇ 590MPa, and the elongation is ⁇ 17%; the yield ratio ⁇ s / ⁇ b ⁇ 0.8, preferably ⁇ 0.75; °C high temperature yield strength ⁇ 275MPa, ⁇ s, 600°C / ⁇ s, 20°C ⁇ 0.67; relative corrosion rate ⁇ 60%.
  • the room-temperature yield strength of these fire-resistant and weather-resistant steel plates or steel strips is 410-450 MPa, the tensile strength is 590-630 MPa, and the elongation is 18-28%; the yield strength ratio ⁇ s / ⁇ b is 0.67-0.73; 600°C high temperature yield strength is 275-310MPa, ⁇ s, 600°C / ⁇ s, 20°C is 0.67-0.72; relative corrosion rate is ⁇ 60%.
  • the room temperature yield strength of the fire-resistant and weather-resistant steel sheet/belt is ⁇ 345MPa, the tensile strength is ⁇ 490MPa, and the elongation is ⁇ 17%; the yield ratio ⁇ s / ⁇ b ⁇ 0.8, preferably ⁇ 0.75; °C high temperature yield strength ⁇ 232MPa, ⁇ s, 600°C / ⁇ s, 20°C ⁇ 0.67; relative corrosion rate ⁇ 60%.
  • the room-temperature yield strength of these fire-resistant and weather-resistant steel plates or steel strips is 345-370 MPa, the tensile strength is 490-530 MPa, and the elongation is 19-27%; the yield strength ratio ⁇ s / ⁇ b is 0.66-0.72; 600°C high temperature yield strength is 235-260MPa, ⁇ s, 600°C / ⁇ s, 20°C is 0.68-0.74; relative corrosion rate is ⁇ 60%.
  • the room-temperature yield strength of these fire-resistant and weather-resistant steel plates or steel strips is 410-450 MPa, the tensile strength is 590-630 MPa, and the elongation is 18-28%; the yield strength ratio ⁇ s / ⁇ b is 0.67-0.73; 600°C high temperature yield strength is 275-310MPa, ⁇ s, 600°C / ⁇ s, 20°C is 0.67-0.72; relative corrosion rate is ⁇ 60%.
  • the average corrosion rate of the fire-resistant and weather-resistant steel sheet/belt of the present invention is less than or equal to 0.3000 mg/cm 2 ⁇ h.
  • the microstructure of the refractory and weathering steel plate/belt of the present invention is a mixed microstructure of massive ferrite+pearlite+acicular ferrite, or a mixed microstructure of massive ferrite+pearlite+lower bainite.
  • C is the most economical and basic strengthening element in steel. It improves the strength of steel through solid solution strengthening and precipitation strengthening. C is an essential element for the precipitation of cementite during austenite transformation. Therefore, the level of C content determines the strength level of steel to a large extent, that is, a higher C content corresponds to a higher strength level.
  • the interstitial solid solution and precipitation of C have great harm to the plasticity and toughness of steel, and the excessively high C content is detrimental to the welding performance, so the C content cannot be too high, and the strength of the steel can be compensated by adding alloy elements appropriately .
  • casting in the peritectic reaction zone is prone to slab surface cracks, and breakout accidents may occur in severe cases.
  • Si plays a solid solution strengthening effect in steel, and the addition of Si to steel can improve steel purity and deoxidation, but excessive Si content will lead to deterioration of weldability and toughness of the welding heat-affected zone. Therefore, the range of Si content used in the present invention is 0.1-0.55%.
  • Mn is one of the cheapest alloying elements. It can improve the hardenability of steel and has a considerable solid solubility in steel. It can improve the strength of steel through solid solution strengthening, and at the same time, it can basically improve the plasticity and toughness of steel. No damage, it is the most important strengthening element to increase the strength of steel, and it can also play a role in deoxidizing steel. However, excessive Mn content will cause deterioration of weldability and toughness of the welding heat-affected zone. Therefore, the range of Mn content used in the present invention is 0.4-1.7%.
  • P High content of P is easy to segregate in grain boundaries, increase the cold brittleness of steel, deteriorate welding performance, reduce plasticity, and deteriorate cold bending performance.
  • the solidification and cooling rate of the cast strip is extremely fast, which can effectively inhibit the segregation of P, thereby effectively avoiding the disadvantages of P and giving full play to the advantages of P. Therefore, in the present invention, a higher P content than the traditional production process is adopted, the content of P element is appropriately relaxed, and the dephosphorization process is eliminated in the steelmaking process. In actual operation, there is no need to deliberately perform the dephosphorization process, and no additional process is required. Add phosphorus, the range of P content is less than or equal to 0.03%.
  • S Under normal circumstances, S is a harmful element in steel, causing steel to produce hot brittleness, reducing the ductility and toughness of steel, and causing cracks during rolling. S also reduces welding performance and corrosion resistance. Therefore, in the present invention, S is also controlled as an impurity element, and its content range is ⁇ 0.007%; in some embodiments, the S content is ⁇ 0.0067%. And, Mn/S ⁇ 250. In some embodiments, Mn/S>250.
  • N Similar to the C element, the N element can improve the strength of the steel through interstitial solid solution.
  • the present invention uses the effect of N and B in the steel to generate the precipitated phase of BN, which requires a certain amount of N in the steel.
  • the interstitial solid solution of N has great harm to the plasticity and toughness of steel.
  • the existence of free N will increase the yield ratio of steel, so the N content cannot be too high.
  • the range of N content used in the present invention is 0.004-0.010%.
  • Cr not only an element that improves the hardenability of steel, but also can effectively improve the high-temperature oxidation resistance and creep resistance of steel. Adding Cr to fire-resistant and weathering steel is used to improve the high-temperature strength and creep strength of steel Another main function is to improve the weather resistance of steel, which can significantly improve the corrosion resistance of steel. However, if its content is too high, it will seriously deteriorate the welding performance. In the present invention, the Cr content is limited to 0.30-0.80%.
  • Nb Among refractory steels, Nb mainly relies on the precipitation strengthening of NbC in ferrite to increase the high-temperature strength of steel. At the same time, in the thin strip continuous casting process, due to its unique rapid solidification and rapid cooling characteristics, the added alloying element Nb can exist in the steel strip in a solid solution state, and the Nb element in the steel can be dissolved. Play the role of solid solution strengthening. In the present invention, when Nb is added, the content of Nb is designed to be in the range of 0.01-0.08%.
  • Mo solid dissolves in ferrite and strengthens the ferrite matrix. Mo diffuses slowly in ferrite at high temperatures, so it can significantly improve the high temperature strength and creep strength of steel. Studies have shown that solid-solution Mo is easy to segregate on the grain boundaries, which can improve the high-temperature strength of steel; Mo can also increase the stability of undercooled austenite, and the volume fraction of bainite in the steel increases after adding Mo; The bainite structure with high dislocation density makes the refractory and weathering steel obtain good high temperature performance. Mo precipitates in the steel to form carbides to improve its high-temperature strength.
  • the first view is that in addition to the strengthening effect of Nb and Mo alone, Mo can also be enriched at the NbC/matrix interface. Prevents the coarsening of NbC particles, thereby further improving the high-temperature strength of steel;
  • the second view is that Mo reduces the driving force for the precipitation of NbC, hinders the diffusion and nucleation process of NbC, thereby delaying the precipitation of NbC, and Mo in steel Promotes the bainite transformation, leading to an increase in its dislocation density and an increase in the nucleation site of NbC. These have resulted in a better precipitation strengthening effect, thereby increasing the high temperature strength of the steel.
  • Excessive Mo will increase the raw material smelting cost of steel. Therefore, in the present invention, the Mo content is limited to 0.20-0.60%.
  • Cu It mainly plays a solid solution and precipitation strengthening effect in steel. Cu is also an element that improves weather resistance. Because Cu is an element that is easy to segregate, the Cu content is generally strictly controlled in the traditional process. Using the rapid solidification effect of thin strip continuous casting, the present invention increases the upper limit of Cu to 0.60%. The increase of Cu content can make full use of scrap steel in a certain sense. It can be used without screening during the preparation of scrap steel, which can increase the smelting operation rate and reduce costs, promote the recycling of steel, and achieve the purpose of sustainable development; it can also achieve the purpose of inferior quality mines. Effective use of copper in resources (such as high copper mines).
  • Sn It is also one of the main residual elements in scrap steel. It is recognized as a harmful element in steel. Because Sn is an element that is easy to segregate, a small amount of Sn will be enriched at the grain boundary, resulting in cracks and other defects. The content of Sn element in the process is strictly controlled. Due to the characteristics of rapid solidification of thin strip continuous casting, the segregation of elements in the dendrites is greatly reduced, which can greatly increase the amount of solid solution of the elements. Therefore, under the conditions of the thin strip continuous casting process, the range of Sn elements can be expanded, so it can greatly Reduce steelmaking costs.
  • Figure 2 is the relationship between the Sn element and the average heat flux. It can be seen from Fig.
  • FIG. 3 shows the relationship between Sn content and surface roughness. Because the cracks on the surface of the cast strip are usually produced at the uneven wrinkles on the surface of the cast strip, the surface roughness is used to characterize the occurrence of surface cracks. If the roughness is large, the probability of occurrence of cracks is high. It can be seen from Fig. 3 that the increase of Sn content does not adversely affect the surface quality of the cast strip under the conditions of rapid solidification. From the results of Fig. 2 and Fig. 3, it can be seen that Sn has no adverse effect on the solidification and surface quality of the cast strip. Therefore, in the present invention, the requirements for Sn content can be further relaxed, and the design Sn content range is 0.005-0.04%.
  • B The significant effect of B in steel is: a very small amount of boron can double the hardenability of steel, and B can preferentially precipitate coarse BN particles in high-temperature austenite, thereby inhibiting the precipitation of fine AlN and weakening the fineness
  • the pinning effect of AlN on the grain boundary improves the growth ability of grains, thereby coarsening and homogenizing the austenite grains, which is beneficial to recrystallization after rolling.
  • the austenite grains are coarsened and homogenized, it is beneficial to Reduce the product yield ratio ⁇ s / ⁇ b , reduce the fluctuation range of yield strength, and improve the seismic performance; in addition, the combination of B and N can effectively prevent the appearance of the low melting point phase B 2 O 3 at the grain boundary.
  • B is a lively and easily segregated element, which is easy to segregate in the grain boundary.
  • the B content is generally controlled very strictly, generally around 0.001-0.003%; while in the thin strip continuous casting process, solidification and cooling The speed is faster, which can effectively inhibit the segregation of B and solid-solve more B content, so the B content can be appropriately relaxed; it can also be controlled by a reasonable process to generate coarse BN particles, inhibit the precipitation of fine AlN, and achieve nitrogen fixation effect.
  • Pcm ⁇ 0.27%, Pcm C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B.
  • the manufacturing method of the fire-resistant and weather-resistant steel plate/belt of the present invention includes the following steps:
  • the MnO/SiO 2 (mass ratio) in the -SiO 2 -Al 2 O 3 ternary inclusions is controlled to be 0.5-2, preferably 1 to 1.8;
  • the free oxygen [O] Free content in the molten steel is: 0.0005 to 0.005% ;In the composition of molten steel, Mn/S ⁇ 250;
  • the continuous casting adopts double-roll thin strip continuous casting to form a 1.5-3mm thick cast strip at the smallest gap between the two crystallizing rolls; the diameter of the crystallizing roll is between 500-1500mm, preferably 800mm; the inside of the crystallizing roll is cooled by water.
  • the casting speed of the machine is 60-150m/min; the continuous casting flow adopts a two-stage molten steel distribution flow system, that is, the tundish + flow distributor;
  • the temperature of the casting belt is between 1420 and 1480 °C, and it enters the lower closed chamber directly.
  • the lower closed chamber is filled with non-oxidizing gas.
  • the oxygen concentration in the lower closed chamber is controlled at ⁇ 5%.
  • the casting belt at the exit of the lower closed chamber The temperature is between 1150-1300°C;
  • the cast strip is sent to the rolling mill via pinch rolls in the lower enclosed chamber and rolled into a strip steel with a thickness of 0.8-2.5mm.
  • the rolling temperature is 1100-1250°C, and the hot rolling reduction rate is controlled to 10-50%.
  • the hot rolling The rolling reduction rate is 30-50%, and the thickness of the strip after rolling is 0.8-2.5mm, preferably 1.2-2.0mm;
  • the cooling rate of gas atomization cooling is 20-100°C/s
  • the cooled hot-rolled strip is cut by the cutting head to remove the poor quality head, it is directly coiled into a coil, and the coiling temperature of the hot-rolled strip is controlled to be 500-680°C.
  • step g) subsequent processing the steel coil is used directly as a hot-rolled plate/strip, or used as a finished plate/strip after trimming and flattening.
  • the smelting raw material can be 100% scrap steel without pre-screening, and the molten steel smelting adopts electric furnace steelmaking; or, the smelting adopts converter steelmaking, and the scrap steel is added to the converter at a ratio of more than 20% of the smelting raw material, and No need to pre-screen; then enter LF furnace, VD/VOD furnace or RH furnace for refining.
  • the non-oxidizing gas in step c) includes CO 2 gas obtained by sublimation of N 2 , Ar or dry ice.
  • the gas-water ratio of the gas atomization cooling in step e) is 15:1-10:1, the air pressure is 0.5-0.8 MPa, and the water pressure is 1.0-1.5 MPa.
  • air-water ratio refers to the flow ratio of compressed air and water, and the unit of flow is m 3 /h.
  • the winding in step f) adopts a double-winding machine or a Carrosel winding.
  • MnO-SiO 2 -Al 2 O 3 ternary inclusions As shown in the shaded area in Figure 4, MnO-SiO 2 -Al 2 O 3 ternary inclusions
  • the MnO/SiO 2 in the composition is controlled at 0.5-2, preferably 1-1.8.
  • oxygen (O) in the steel is an essential element for the formation of oxidized inclusions.
  • the present invention requires the formation of low melting point ternary inclusions of MnO-SiO 2 -Al 2 O 3 ,
  • the required free oxygen [O] Free range in molten steel is: 0.0005-0.005%.
  • converter steelmaking to provide molten steel requires manufacturers to have the conditions to provide molten iron. Under normal circumstances, blast furnace ironmaking or non-blast furnace ironmaking equipment is required, which belongs to the current long-process steel production mode. However, today with increasingly rich scrap steel resources, the country is advocating to increase the converter scrap ratio, so as to achieve the purpose of energy saving, consumption reduction and cost reduction.
  • the average level of converter scrap ratio in the past was about 8%. Now and in the future, the target of converter scrap ratio It is 15-25%.
  • the scrap ratio of the converter of the present invention can reach more than 20%.
  • Scrap steel As the main raw material.
  • Traditional processes such as die casting or thick plate continuous casting have a solidification and cooling rate of only 10 -1 -10°C/s. These residual elements in the scrap will solidify Grain boundary segregation occurs during the process, which deteriorates the performance and quality of the steel. In severe cases, cracks and fractures occur directly. Therefore, in the traditional process, these harmful elements must be strictly controlled.
  • some pre-screening is required.
  • some special treatments are required in the steelmaking process, such as adding some concentrates for dilution, etc., which undoubtedly increase the cost of production operations. Due to the need to control the composition of steel, there are certain quality requirements for the used scrap raw materials.
  • the scrap steel needs to be pre-screened and classified.
  • some domestic electric furnace steel plants will choose to add refined materials such as purchased sponge iron and iron carbide to the raw material composition to dilute the harmful elements that are difficult to remove in the scrap and improve the quality of molten steel.
  • Some domestic steel mills that have both blast furnaces and electric furnaces use self-produced molten iron into the electric furnace as raw materials to improve the production efficiency of the electric furnace, thereby greatly shortening the tapping time of the electric furnace, and the hot metal blending ratio in the electric furnace can reach 30-50% .
  • twin-roll thin strip continuous casting technology is a typical sub-rapid solidification process.
  • the solidification cooling rate is as high as 10 2 -10 4 °C/s.
  • Some harmful residual elements in the scrap such as Cu, Sn, P, etc., can be maximized
  • the ground solid dissolves into the steel matrix without producing grain boundary segregation, so 100% all scrap steel smelting can be realized without pre-screening, which greatly reduces the cost of raw materials.
  • These residual elements can also play a role of solid solution strengthening, thereby producing ultra-thin hot-rolled strip steel with excellent properties. Realize the comprehensive utilization of low-quality scrap steel resources, which has the effect of "turning harm into profit” and "waste utilization" for these harmful residual elements in the scrap steel.
  • the temperature of the casting belt is 1420-1480°C, and it enters the lower closed chamber directly.
  • the lower closed chamber is protected by non-oxidizing gas to protect the strip from oxidation. It can be N 2 , Ar can also be other non-oxidizing gases, such as CO 2 gas obtained by sublimation of dry ice, etc.
  • the oxygen concentration in the lower enclosed chamber is controlled to ⁇ 5%.
  • the lower airtight chamber protects the cast strip from oxidation to the entrance of the rolling mill.
  • the temperature of the casting strip at the outlet of the lower closed chamber is between 1150-1300°C.
  • thermodynamic equations of boron and nitrogen, aluminum and nitrogen in ⁇ -Fe in steel are as follows:
  • the initial precipitation temperature of BN in steel is about 1280°C, and the precipitation of BN tends to be balanced at 980°C, while the precipitation of AlN has just begun (the precipitation temperature of AlN is about 980°C).
  • the precipitation of BN has priority over AlN.
  • the invention completes the combination of B and N in the lower closed chamber to generate coarse BN particles, thereby inhibiting the precipitation of fine AlN, weakening the pinning effect of fine AlN on grain boundaries, improving the growth ability of grains, and thereby coarsening austenite
  • the grains make the austenite grains more uniform, which is beneficial to reduce the yield ratio ⁇ s / ⁇ b of the product , reduce the fluctuation range of the yield strength, and improve the seismic performance; in addition, the combination of B and N can effectively prevent the low melting point of the grain boundary The appearance of phase B 2 O 3.
  • the strip steel after the online hot rolling is cooled after rolling, and the strip steel is cooled by the gas atomization cooling method.
  • the gas atomization cooling method can effectively reduce the thickness of the surface oxide scale of the strip steel, improve the temperature uniformity of the strip, and increase the strip Surface quality of steel.
  • the gas-water ratio of gas atomization cooling is 15:1 ⁇ 10:1, the air pressure is 0.5 ⁇ 0.8MPa, and the water pressure is 1.0 ⁇ 1.5MPa.
  • high-pressure water mist is sprayed on the surface of the steel strip. On the one hand, it can reduce the temperature of the steel strip. On the other hand, the water mist will form a dense gas film covering the surface of the steel strip, which can prevent the strip from being oxidized.
  • This cooling method can avoid the problems caused by traditional spray or laminar cooling, uniformly reduce the surface temperature of the strip, and improve the uniformity of the strip temperature, thereby achieving the effect of homogenizing the internal microstructure and improving the yield ratio of the material; at the same time; Uniform cooling can improve the shape quality and performance stability of the strip steel; effectively reduce the thickness of the oxide scale on the surface of the strip steel.
  • the cooling rate of gas atomization cooling is in the range of 20-100°C/s.
  • the cooled hot-rolled strip is cut by the cutting head to remove the poor quality head, it is directly coiled into a coil, and the coiling temperature of the hot-rolled strip is controlled to 500-680°C to make the high-temperature austenite after rolling
  • the structure transforms into a mixed microstructure of massive ferrite + pearlite + acicular ferrite, or a mixed microstructure of massive ferrite + pearlite + lower bainite, as shown in Figure 6.
  • the coiling machine adopts double coiling form, and can also adopt Carrosel coiling form to ensure the continuous production of strip steel.
  • the present invention eliminates the need for complex processes such as slab heating and multi-pass repeated hot rolling. Through double-roll thin strip continuous casting + one online hot rolling process, the production process is shorter, the efficiency is higher, and the investment cost of the production line is reduced. The production cost is greatly reduced.
  • the present invention omits many complicated intermediate steps in the traditional production process. Compared with the traditional production process, the energy consumption and CO 2 emission of production are greatly reduced, and it is a green and environmentally friendly product.
  • the present invention adopts a thin strip continuous casting process to produce hot-rolled refractory and weathering steel. Due to the sub-rapid solidification characteristics of the thin strip continuous casting process itself, a fine-grained layer with a certain thickness is naturally formed on the surface of the strip, so that the produced steel has both Weather resistance; at the same time, the thickness of the cast strip itself is relatively thin.
  • the thin gauge products can be directly supplied to the market to achieve the purpose of supplying thin gauge hot rolled plates, which can significantly improve the cost performance of the plate and strip.
  • the present invention adopts the addition of a small amount of B element to preferentially precipitate coarse BN particles in high-temperature austenite, thereby inhibiting the precipitation of fine AlN, weakening the pinning effect of fine AlN on grain boundaries, improving the growth ability of grains, and thus Refining and homogenizing the austenite grains is conducive to improving the formability of the product and reducing the yield ratio of the material.
  • a low yield ratio is conducive to improving the energy absorption of the building structure during an earthquake and improving the seismic performance of the material.
  • the smelting of the present invention adopts electric furnace steel smelting, and the raw materials smelted can be smelted with 100% scrap steel in a true sense without pre-screening, which greatly reduces the cost of raw materials; if the smelting is through converter steel smelting, scrap accounts for 20% of the raw materials
  • the above ratio is added to the converter without pre-screening, which maximizes the scrap ratio of the converter and greatly reduces the smelting cost and energy consumption.
  • the present invention uses scrap steel containing Cu and Sn to "turn harm into benefits" for Cu and Sn in the steel, and realize the full use of existing scrap steel or low-quality low-quality mineral resources (high tin ore, high copper ore) Utilize, promote the recycling of scrap steel, reduce production costs, and realize the sustainable development of the steel industry.
  • the present invention adopts the strip steel gas atomization cooling method after rolling, which can avoid the problems caused by traditional spraying or laminar cooling, make the surface temperature of the strip uniformly drop, improve the uniformity of the strip temperature, and achieve uniform internal microcosmic The effect of the structure; at the same time, uniform cooling can improve the shape quality and performance stability of the strip steel; effectively reduce the thickness of the oxide scale on the surface of the strip steel.
  • the precipitation of alloying elements occurs during the cooling process of the traditional slab.
  • the utilization of alloying elements is often reduced due to insufficient re-dissolution of the alloy elements.
  • the high-temperature cast strip is directly hot-rolled, and the added alloy elements mainly exist in a solid solution state, which can improve the alloy utilization rate.
  • the present invention uses a hot-rolled steel strip Carrousel coiler, which effectively shortens the length of the production line; at the same time, co-coiling can greatly improve the control accuracy of the coiling temperature and improve the stability of product performance.
  • the most obvious feature of the present invention which is different from the existing thin strip continuous casting technology is the diameter of the crystallizing roll and its corresponding flow distribution method.
  • the technical feature of EUROSTRIP is ⁇ 1500mm large diameter crystallizing roller, large crystallizing roller, large molten steel capacity in molten pool, easy flow distribution, high cost of crystallizing roller manufacturing and operation and maintenance.
  • the technical feature of CASTRIP is the ⁇ 500mm small diameter crystallizing roller, the crystallizing roller is small, the molten steel volume is small, and the flow distribution is very difficult, but the cost of manufacturing and operation and maintenance of the casting machine is low.
  • CASTRIP adopts a three-stage molten steel distribution flow system (tundish + transition bag + flow distributor).
  • the use of a three-stage flow distribution system directly leads to an increase in the cost of refractory materials; more importantly, the three-stage flow distribution system makes the path of molten steel flow longer and the temperature drop of molten steel is also greater.
  • the tapping temperature needs to be greatly increased. The increase in the tapping temperature will cause problems such as increased steelmaking costs, increased energy consumption, and shortened life of refractory materials.
  • the molten steel flowing out of the distributor forms different distribution patterns along the roller surface and the two end surfaces, and flows in two paths without interfering with each other. Due to the use of a two-stage flow distribution system, compared with a three-stage flow system, the cost of refractory materials is greatly reduced; the shortening of the molten steel flow path reduces the temperature drop of the molten steel, which can lower the tapping temperature, compared with the three-stage flow system , The tapping temperature can be reduced by 30-50°C.
  • the lowering of the tapping temperature can effectively reduce the cost of steelmaking, save energy and extend the life of refractory materials.
  • the invention is matched with a crystallizing roller with a roller diameter of ⁇ 800mm and adopts a two-stage molten steel distribution system, which not only realizes the requirement of stable molten steel distribution, but also realizes the goals of simple structure, convenient operation and low processing cost.
  • Figure 1 is a schematic diagram of the layout of the twin-roll thin strip continuous casting process
  • Figure 2 is a schematic diagram of the relationship between Sn content and average heat flux
  • Figure 3 is a schematic diagram of the relationship between the Sn content and the surface roughness of the cast strip
  • Figure 4 is a ternary phase diagram of MnO-SiO 2 -Al 2 O 3 (shaded area: low melting point area);
  • Figure 5 is a schematic diagram of the thermodynamic curves of the precipitation of BN and AlN;
  • Figure 6 is the microstructure of the steel in Example 1 of the present invention.
  • Fig. 7 is the microstructure of the steel of Example 15 of the present invention.
  • the molten steel in accordance with the chemical composition design of the present invention is directly poured in a large ladle 1, through a ladle nozzle 2, a tundish 3, an immersion nozzle 4, and a distributor 5, which is rotated by two relative to each other and can quickly
  • the molten steel solidifies on the rotating circumferential surface of the crystallizing rollers 8a, 8b, and then forms a solidified shell and gradually grows on the two crystallizing rollers
  • a 1.5-3mm thick cast belt 11 is formed at the smallest gap (nip point).
  • the diameter of the crystallizing roller of the present invention is between 500-1500mm, and the inside is cooled by water; depending on the thickness of the casting strip, the casting speed of the casting machine is in the range of 60-150m/min.
  • the temperature of the casting belt is between 1420 and 1480 °C, and it directly enters the lower closed chamber 10, and the lower closed chamber 10 protects the strip with non-oxidizing gas to realize the anti-oxidation of the strip.
  • the atmosphere for anti-oxidation protection can be N 2 , Ar, or other non-oxidizing gases, such as CO 2 gas obtained by sublimation of dry ice, etc.
  • the oxygen concentration in the lower closed chamber 10 is controlled to be less than 5%.
  • the lower airtight chamber 10 protects the cast strip 11 from oxidation to the entrance of the rolling mill 13.
  • the temperature of the cast strip at the outlet of the lower closed chamber 10 is between 1150-1300°C.
  • the cast strip is sent to the hot rolling mill 13 through the swinging guide plate 9, the pinch roll 12, and the roller table 15.
  • the gas atomization rapid cooling device 14 adopts gas atomization cooling Way to cool the strip steel to improve the temperature uniformity of the strip steel.
  • the cutting head falls into the flying shear pit 18 along the flying shear guide plate 17, and the hot-rolled strip after the cutting head enters the coiler 19 for coiling.
  • the steel coil is removed from the coiler, it is naturally cooled to room temperature.
  • the final produced steel coil can be used directly as a hot-rolled plate/strip, or it can be used as a finished plate/strip after trimming and flattening.
  • Examples are used to further illustrate the method of the present invention.
  • the chemical composition of the embodiment of the present invention is shown in Table 1, and the composition balance is Fe and other unavoidable impurities.
  • the process parameters are shown in Table 2, and the mechanical properties of the finally obtained hot-rolled strip are shown in Table 3.
  • the corrosion resistance test of the steel in the example was carried out: ordinary carbon steel Q345B was used as a comparative sample, and the 72h cycle infiltration corrosion test method (TB/T2375-1993) was used for the 72h cycle infiltration corrosion test.
  • the average corrosion rate is obtained by calculating the corrosion weight loss per unit area of the sample, and then the relative corrosion rate of the steel type is obtained.
  • the test results are shown in Table 4.
  • Table 3 show that the present invention uses the thin strip continuous casting process to produce thin-gauge fire-resistant and weather-resistant steel plates/strips according to the designed steel grade composition, with room temperature yield strength ⁇ 345MPa, tensile strength ⁇ 490MPa, and elongation ⁇ 17%; Strength ratio ⁇ s / ⁇ b ⁇ 0.8; 600°C high temperature yield strength ⁇ 232MPa, ⁇ s, 600°C / ⁇ s, 20°C ⁇ 0.67; cold working bending performance is qualified.
  • the comparison results of corrosion resistance in Table 4 also show that the relative corrosion rate of the inventive steel is ⁇ 60%. It meets and exceeds the performance requirements of fire-resistant and weather-resistant steel.
  • Table 1 The chemical composition of the example steel (wt.%)
  • Example 1 0.2506 51.12
  • Example 2 0.2758 56.26
  • Example 3 0.2848 58.10
  • Example 4 0.2766 56.43
  • Example 5 0.2668
  • Example 6 0.2724 55.57
  • Example 7 0.2905 59.26
  • Example 8 0.2876 58.67
  • Example 9 0.2862 58.38
  • Example 10 0.2797 57.06
  • Example 11 0.2657 54.20
  • Example 12 0.2558 52.18
  • Example 13 0.2908 59.32
  • Example 14 0.2839 57.92
  • Examples 14-28 are examples containing Nb, the chemical composition of which is shown in Table 5, and the balance of the composition is Fe and other unavoidable impurities.
  • the process parameters are shown in Table 6, and the mechanical properties of the finally obtained hot-rolled strip are shown in Table 7.
  • the corrosion resistance test of the steel in the example was carried out: ordinary carbon steel Q345B was used as a comparative sample, and the 72h cycle infiltration corrosion test method (TB/T2375-1993) was used for the 72h cycle infiltration corrosion test.
  • the average corrosion rate is obtained by calculating the corrosion weight loss per unit area of the sample, and then the relative corrosion rate of the steel type is obtained.
  • the test results are shown in Table 8.
  • the high-strength fire-resistant and weather-resistant steel plate/belt produced by the thin strip continuous casting process technology according to the steel grade composition design range provided by the present invention has room temperature yield strength ⁇ 410MPa, tensile strength ⁇ 590MPa, and elongation ⁇ 17 %; Yield strength ratio ⁇ s / ⁇ b ⁇ 0.8; 600°C high temperature yield strength can be ⁇ 275MPa, ⁇ s, 600°C / ⁇ s, 20°C ⁇ 0.67; cold working bending performance is qualified.
  • the comparison results of corrosion resistance in Table 8 also show that the relative corrosion rate of the steel of the present invention is less than or equal to 60%. It meets and exceeds the performance requirements of fire-resistant and weather-resistant steel. At the same time, it can realize the supply of thin-gauge hot-rolled products. The production cost is also greatly reduced, the material yield ratio is low, the seismic performance is excellent, and the fire resistance is excellent. It is a seismic and fire-resistant steel Ideal material for the field.
  • Example 15 0.2938 59.93
  • Example 16 0.2764 56.39
  • Example 17 0.2833 57.79
  • Example 18 0.2793 56.98
  • Example 19 0.2843 58.00
  • Example 20 0.2916 59.49
  • Example 21 0.2783 56.77
  • Example 22 0.2776 56.63
  • Example 23 0.2852 58.18
  • Example 24 0.2797 57.06
  • Example 25 0.2869 58.53
  • Example 26 0.2747 56.04
  • Example 27 0.2838 57.89
  • Example 28 0.2793 56.98

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Abstract

耐火耐候钢板/带及其制造方法，其化学成分重量百分比为：C 0.02-0.06％，Si 0.1-0.55％，Mn 0.4-1.7％，P≤0.03％，S≤0.007％，Cr 0.30-0.80％，Mo 0.20-0.60％，N 0.004-0.010％，Als<0.001％，B：0.001-0.006％，任选的Nb：0.01-0.08％，总氧[O] T：0.007-0.020％，余Fe和其他不可避免杂质，且，含有Cu 0.10-0.60％或Sn 0.005-0.04％中一种或两种元素；Mn/S≥250；Pcm≤0.27％。本发明利用废钢中残余的Sn、Cu等元素进行冶炼，并选择地添加Mo/Cr等微合金元素和B元素；冶炼控制渣的碱度、钢中夹杂物类型及熔点、钢水中的游离氧含量、酸溶铝Als含量；采用双辊薄带连铸浇铸，铸带在线热轧，轧后冷却采用气雾化冷却方式。

Description

耐火耐候钢板/带及其制造方法 技术领域
本发明属于冶金行业连铸工艺和产品，主要用于双辊薄带连铸工艺生产的薄带钢产品，尤其适用于生产一种耐火耐候钢板/带产品。
背景技术
在传统钢铁生产流程中，锡(Sn)、铜(Cu)是钢中典型的残余元素或有害元素，炼钢过程中要充分地去除Sn、Cu非常困难而且也是非常昂贵，一旦钢中含有Sn、Cu，基本是无法彻底消除的，只能通过稀释钢水来降低Sn、Cu的含量，这些都造成钢铁产品冶炼成本的升高。
近年来，由于废钢的连续循环利用，废钢资源越来越多，电价也持续降低，国内基于废钢的短流程电炉炼钢日益兴起，导致钢中的Sn、Cu等残余元素的含量逐渐升高，钢中的Sn、Cu是易偏析元素，容易富集在晶界导致裂纹等缺陷发生，因此在传统的工艺中Sn、Cu元素的含量是被严格控制的，在普通结构用钢中，对Sn、Cu的含量均有明确的要求：Sn(wt％)≤0.005％；Cu(wt％)≤0.2％。
因此，如果能对钢(特别是废钢)中Sn、Cu等残余元素做到合理利用，“化害为利”，将对整个冶金界产生积极的影响；可以实现对现有废钢或低品质劣质矿资源(高锡矿、高铜矿)的有效利用，促进钢的循环利用，降低生产成本，实现钢铁业可持续发展。
传统的薄带钢大都是由厚达70-200mm的铸坯经过多道次连续轧制生产出来的，传统热轧工艺流程是：连铸+铸坯再加热保温+粗轧+精轧+冷却+卷取，即首先通过连铸得到厚度为200mm左右的铸坯，对铸坯进行再加热并保温后，再进行粗轧和精轧，得到厚度一般大于2mm的钢带，最后对钢带进行层流冷却和卷取，完成整个热轧生产过程。如果要生产厚度小于1.5mm(含)的钢带，则难度相对较大，通常要对热轧钢带进行后续冷轧以及退火来完成。且工艺流程长、能耗高、机组设备多、基建成本高，导致生产成本较高。
薄板坯连铸连轧工艺流程是：连铸+铸坯保温均热+热连轧+冷却+卷取。该工艺与传统工艺的主要区别是：薄板坯工艺的铸坯厚度大大减薄，为50-90mm，由于铸坯薄，铸坯只要经过1～2道次粗轧(铸坯厚度为70-90mm时)或者不需要经过粗轧(铸坯厚度为50mm时)，而传统工艺的连铸坯要经过反复多道次轧制，才能减薄到精轧前所需规格；而且薄板坯工艺的铸坯不经冷却，直接进入均热炉进行均热保温，或者少量补温，因此薄板坯工艺大大缩短了工艺流程，降低了能耗，减少了投资，从而降低了生产成本。但薄板坯连铸连轧由于较快的冷速会导致钢材强度提高，屈强比提高，从而增加轧制载荷，使得可经济地生产热轧产品的厚度规格也不可能太薄，一般为≥1.5mm，见专利CN200610123458.1，CN200610035800.2以及CN200710031548.2，且这些专利均未涉及元素Sn和Cu。
近年来兴起的一种全无头薄板坯连铸连轧工艺(简称：ESP)，是在上述半无头薄板坯连铸连轧工艺的基础上发展起来的一种改进工艺，ESP实现了板坯连铸的无头轧制，取消了板坯火焰切割和起保温均热、板坯过渡作用的加热炉，整条产线长度大大缩短到190米左右。连铸机连铸出来的板坯厚度在90-110mm，宽度在1100-1600mm，连铸出来的板坯通过一段感应加热辊道对板坯起到保温均热的作用，然后再依次进入粗轧、精轧、层冷、卷取工序得到热轧板。这种工艺由于实现了无头轧制，可以得到最薄0.8mm厚度的热轧板，拓展了热轧板的规格范围，再加上其单条产线产量可达220万t/年规模。目前该工艺得到了快速发展和推广，目前世界上已有多条ESP产线在运营生产。
比薄板坯连铸连轧更短的工艺流程是薄带连铸连轧工艺，薄带连铸技术是冶金及材料研究领域内的一项前沿技术，它的出现为钢铁工业带来一场革命，它改变了传统治金工业中钢带的生产过程，将连续铸造、轧制、甚至热处理等整合为一体，使生产的薄带坯经过一道次在线热轧就一次性形成薄钢带，大大简化了生产工序，缩短了生产周期，其工艺线长度仅50m左右；设备投资也相应减少，产品成本显著降低，是一种低碳环保的热轧薄带生产工艺。双辊薄带连铸工艺是薄带连铸工艺的一种主要形式，也是世界上唯一实现产业化的一种薄带连铸工艺。
双辊薄带连铸典型的工艺流程如图1所示，大包1中的熔融钢水通过大包长水口2、中间包3、浸入式水口4以及布流器5直接浇注在一个由两个相对转动并能够快速冷却的结晶辊8a、8b和侧封装置6a、6b围成的熔池7中，钢水在结晶辊8a、 8b旋转的周向表面凝固形成凝固壳并逐渐生长，进而在两结晶辊辊缝隙最小处(nip点)形成1-5mm厚的钢带11，钢带经由导板9导向夹送辊12送入轧机13中轧制成0.7-2.5mm的薄带钢，随后经过冷却装置14冷却，经飞剪装置16切头后，最后送入卷取机19卷取成卷。
近年来，随着国内外大型建筑、高层建筑不断涌现，为避免建筑物发生火灾时建筑钢材因为受热，强度急剧下降导致建筑物垮塌，给居民生命财产造成巨大损失，国际上对建筑用钢的防火工艺设计受到人们的广泛重视，建筑用钢的防火工艺设计已成为保证建筑安全的必要措施之一。普通建筑用钢受热时其强度和承载能力迅速降低，不能满足防火安全的要求。为了提高采用普通建筑用钢建造的建筑物抵抗火灾的能力，以前通常的做法是必须采取喷涂耐火涂层或覆盖防火板等措施，而现在大量使用耐火钢可减薄或省去耐火涂层或防火板，并能保证钢材在高温下保持较高的强度水平，还可缩短建造周期，减轻建筑物质量，增加建筑的安全性，降低建造成本,具有显著的经济效益和社会效益。同时，建筑用钢大多会裸露在空气中，服役年限也较长，因此，在耐火性能的基础上再兼具耐候性能，则衍生出一种全新的耐火耐候钢产品。在上述应用大背景下，目前耐火耐候钢板/带被越来越多地应用在一些有防火要求的建筑用钢、塔桅栏柱、工程机械、工业结构等行业和领域，特别在高层建筑、大型公共建筑、高档住宅等消防安全要求较高的地方被广泛应用。
耐火耐候钢要求具有良好的高温性能，但它又不同于长期在高温下服役的耐热钢，耐热钢要求具有良好的高温强度及高温稳定性，一般采用高合金钢。而耐火耐候钢是在常温下承载，只是要求在遇到火灾的短时(通常为1-3h)高温条件下能够保持较高的屈服强度，可以为人员安全撤离赢得宝贵时间，因而属于低合金结构用钢的范畴，其成分设计不宜添加过多的昂贵合金元素。
日本钢结构安全设计规范中规定：常温下钢材屈服强度的2/3相当于该材料的长期允许应力值，当发生火灾时，如果耐火耐候钢的屈服点仍然能保持此值，建筑物就不会倒塌。因此，要求耐火耐候钢在一定高温下其屈服强度不低于室温屈服强度的2/3。为提高钢结构的抗震性，总是希望尽量提高钢材吸收地震能量的能力。若钢的屈强比(σ s/σ b)较高，发生地震时就会产生局部应力集中和局部大变形，此时钢结构只能吸收较少的能量，因此低屈强比有利于提高建筑结构地震时吸收的能量，一般要求抗震耐火耐候钢的屈强比≤0.8。
耐火耐候钢研制的关键之一是设定希望它达到高温强度下的耐火温度。在欧洲的Creusot-Loire炼钢厂曾研究了耐900-1000℃高温的含Mo钢，但因成本太高未推广应用。为了确定与降低生产成本和减少耐火材料用量之间达到最佳配合的耐火温度，新日铁对抗拉强度为400-780MPa的几种典型钢进行了高温拉伸试验，试验表明：所有试验钢的屈服强度(σ s)在500-600℃范围内急剧下降，在700℃或700℃以上时σ s降至50MPa以下。如果把保证强度的温度定在700℃，则必须加入大量的合金元素，这就很难保证其良好的可焊性，也大大提高了成本。若将保证强度的温度定在较低的500℃，那么仅能使耐火涂层的厚度略微减少，这又不符合使用耐火耐候钢的初衷。因此，耐火耐候钢的耐火温度被设定为600℃。
综上所述并根据建筑用钢的一般要求，确定耐火耐候钢的性能指标如下：
(1)耐火性能：σ s,600℃≥(2/3)σ s,20℃；
(2)室温力学性能及其他质量指标满足普通建筑用钢标准的要求；
(3)抗震性：室温下σ s/σ b≤0.8，屈服强度波动范围尽量小；
(4)焊接性良好，等同或优于普通建筑用钢；
(5)耐候性：对比Q345B，采用标准TB/T 2375-1993测定，相对腐蚀率≤60％。
采用薄带连铸工艺来生产这种高强耐火耐候钢板/带，由于薄带连铸工艺本身的亚快速凝固特性，带钢表面会天然形成一定厚度的细晶层，使生产的钢种兼具耐候性能；同时，在薄规格使用场合具备一定的制造和成本优势。薄规格高强耐火耐候钢板/带产品规格特征厚度1.2-2.0mm，由于产品厚度较薄，假如采用传统的连铸+热连轧产线进行生产比较困难，即使采用薄板坯连铸连轧生产，轧辊的辊耗也较大，这样的生产流程增加了薄规格高强耐火耐候钢板/带的生产成本。
热轧带钢作为薄规格热轧板产品使用时，对带钢表面质量要求很高。一般要求带钢表面氧化皮的厚度越薄越好，这就需要在铸带后续的各个阶段控制氧化铁皮的生成，如在薄带连铸工艺中，在结晶辊直至轧机入口均采用密闭室装置防止铸带氧化，在密闭室装置内如美国专利US6920912添加氢气以及在美国专利US20060182989中控制氧气含量小于5％，均可以控制铸带表面的氧化皮厚度。但是在轧机至卷取这段输送过程如何控制氧化皮的厚度很少有关专利涉及，尤其是在采用层流冷却或喷淋冷却对带钢进行冷却的过程中，高温的带钢与冷却水接触，铸带表面的氧化皮厚度增长很快。同时，高温的带钢与冷却水接触还会带来很多问题： 其一，会在带钢表面形成水斑(锈斑)，影响表面质量；其二，层流冷却或喷淋冷却用的冷却水容易造成带钢表面局部冷却不均匀，造成带钢内部微观组织的不均匀，从而造成带钢性能的不均匀，影响产品质量；其三，带钢表面局部冷却不均匀，会造成板形的恶化，影响板形质量。
但是，薄带连铸由于其本身的快速凝固工艺特性，生产的钢种普遍存在组织不均匀、延伸率偏低、屈强比偏高、成型性不好的问题；同时铸带奥氏体晶粒具有明显不均匀性，会导致奥氏体相变后所获得的最终产品组织也不均匀，从而导致产品的性能特别是成形性能不稳定。因此采用薄带连铸工艺来生产高强耐火耐候钢板/带产品，同样具有一定难度和挑战，需要在成分和工艺上有突破，本发明通过添加适量的B元素以及合理的轧后冷却措施，有效改善组织均匀性，达到降低屈强比的目的。
中国专利CN200610123458.1公开了一种基于薄板坯连铸连轧流程采用Ti微合金化工艺生产700MPa级高强耐候钢的方法，该方法制造耐候钢板的化学成分为：C：0.03-0.07％，Si：0.3-0.5％，Mn：1.2-1.5，P：≤0.04％，S：≤0.008％，Al：0.025-0.05％，Cr：0.3-0.7％，Ni：0.15-0.35％，Cu：0.2-0.5％，Ti：0.08-0.14％，N：≤0.008％，余量为Fe和不可避免的杂质。钢板的屈服强度≥700MPa，抗拉强度≥775MPa，延伸率≥21％。在该专利中，磷是按照杂质元素来控制的，含量≤0.04％，较传统工艺的≤0.025％，有所放宽。
中国专利CN200610035800.2公开了一种基于薄板坯连铸连轧工艺生产700MPa级V-N微合金化耐候钢的方法，该方法制造耐候钢板的化学成分为：C：≤0.08％，Si：0.25-0.75％，Mn：0.8-2，P：≤0.07-0.15％，S：≤0.04％，Cr：0.3-1.25％，Ni：≤0.65％，Cu：0.25-0.6％，V：0.05-0.2％，N：0.015-0.03％，余量为Fe和不可避免的杂质。钢板的屈服强度≥700MPa，抗拉强度≥785MPa，延伸率≥21％。在该专利中，磷是按照提高耐候性的元素来控制的，含量为0.07-0.15％；铜的含量为0.25-0.6％，其下限和上限分别高于传统工艺的铜含量下限0.2％和上限0.55％。
中国专利CN1633509A提到了一种薄带连铸所生产含铜碳钢产品的方法，该专利强调要对这种的带钢在400-700℃范围内进行退火、回火等热处理工序使铜元素在带钢中沉淀或再结晶。US2008264525/CN200580009354.1中提到的一种高铜低合金薄带的制造方法，其技术特点是，在进入轧机前对所述的带钢在非氧化气氛中实 施冷却至低于1080℃以防止带钢发生“热脆”现象。
上述这些专利都涉及到了钢的耐候性，但内容均未涉及到耐火的作用，本发明是特别针对耐火耐候特性而提出的一个钢种。
发明内容
本发明的目的在于提供一种耐火耐候钢板/带及其制造方法，生产出的耐火耐候钢板/带能保证钢材在高温下保持较高的强度水平，还可减轻建筑物质量，增加建筑的安全性，降低建造成本；同时，利用薄带连铸的工艺特性，生产出的耐火耐候钢板/带在耐火性能的基础上，带钢表面会天然形成一定厚度的细晶层，使产品兼具耐候性能。产品抗震性能优良，耐火性能优异，是抗震、防火用钢领域的理想用材，可广泛应用在一些有防火、抗震要求的建筑用钢、塔桅栏柱、工程机械、工业结构等行业和领域，特别在高层建筑、大型公共建筑、高档住宅等消防安全要求较高的地方。
为达到上述目的，本发明的技术方案是；
本发明利用废钢中残余的Sn、Cu等元素进行钢水的冶炼，并在钢中有选择地添加Mo/Nb/Cr等微合金元素和B元素；冶炼过程中通过控制渣的碱度、钢中夹杂物类型及熔点、钢水中的游离氧含量、酸溶铝Als含量；然后进行双辊薄带连铸浇铸出1.5-3mm厚的带钢，在带钢出结晶辊后，直接进入到一个有非氧化性气氛的下密闭室中，并在密闭情况下进入到在线轧机进行热轧；轧制后的带钢采用气雾化冷却方式对带钢进行冷却，气雾化冷却方式可以有效减小带钢表面氧化皮厚度，改善带钢温度均匀性，提高带钢表面质量。最后生产的钢卷可以直接作为热轧板/带使用，也可以经过切边-平整后作为精整板/带使用。本发明的材料屈强比低，抗震性能优良，耐火性能优异，是抗震、防火用钢领域的理想用材。
具体的，本发明所述耐火耐候钢板/带，其化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，任选的Nb：0.01-0.08％，总氧[O] T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：
含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素；
Mn/S≥250；
Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。
在一些实施方案中，本发明所述耐火耐候钢板或钢带为薄规格的耐火耐候钢板或钢带；优选地，其厚度为0.8-2.5mm，优选厚度为1.2-2.0mm。
在一些实施方案中，Pcm≤0.25％。在一些实施方案中，0.14％≤Pcm≤0.25％。
本发明所述耐火耐候钢板/带的室温屈服强度≥345MPa，抗拉强度≥490MPa，延伸率≥17％；屈强比σ s/σ b≤0.8，优选≤0.75；600℃高温屈服强度≥232MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％。
在一些实施方案中，本发明所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素，Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。优选地，这些实施方案中，所述耐火耐候钢板/带的室温屈服强度≥345MPa，抗拉强度≥490MPa，延伸率≥17％；屈强比σ s/σ b≤0.8，优选≤0.75；600℃高温屈服强度≥232MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％。在这些耐火耐候钢板或钢带的一些实施方案中，这些耐火耐候钢板或钢带的室温屈服强度为345-370MPa，抗拉强度为490-530MPa，延伸率为19-27％；屈强比σ s/σ b为0.66-0.72；600℃高温屈服强度为235-260MPa，σ s,600℃/σ s,20℃为0.68-0.74；相对腐蚀率≤60％。
在一些实施方案中，本发明所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，Cu：0.10-0.60％，任选的Sn：0.005-0.04％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。优选地，这些实施方案中，所述耐火耐候钢板/带的室温屈服强度≥345MPa，抗拉强度≥490MPa，延伸率≥17％；屈强比σ s/σ b≤0.8，优选≤0.75；600℃高温屈服强度≥232MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％。在这些耐火耐候钢板或钢带的一些实施方案中，这些耐火耐候钢板或钢 带的室温屈服强度为345-370MPa，抗拉强度为490-530MPa，延伸率为19-27％；屈强比σ s/σ b为0.66-0.72；600℃高温屈服强度为235-260MPa，σ s,600℃/σ s,20℃为0.68-0.74；相对腐蚀率≤60％。
在一些实施方案中，本发明所述耐火耐候钢板或钢带为高强耐火耐候钢板或钢带；优选地，其化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Cu：0.10-0.60％，Mo：0.20-0.60％，Nb：0.01-0.08％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O] T：0.007-0.020％；余量为Fe和不可避免杂质；且，同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。优选地，这些实施方案中，所述耐火耐候钢板/带的室温屈服强度≥410MPa，抗拉强度≥590MPa，延伸率≥17％；屈强比σ s/σ b≤0.8，优选≤0.75；600℃高温屈服强度≥275MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％。在这些耐火耐候钢板或钢带的一些实施方案中，这些耐火耐候钢板或钢带的室温屈服强度为410-450MPa，抗拉强度为590-630MPa，延伸率为18-28％；屈强比σ s/σ b为0.67-0.73；600℃高温屈服强度为275-310MPa，σ s,600℃/σ s,20℃为0.67-0.72；相对腐蚀率≤60％。
在一些实施方案中，本发明所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Cu：0.10-0.60％，Als<0.001％，B：0.001-0.006％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可避免杂质，其中，所述耐火耐候钢板或钢带含有Nb：0.01-0.08％，或不含有Nb但含Sn：0.005-0.04％或同时也不含有Sn，且同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。优选地，这些实施方案中，所述耐火耐候钢板/带的室温屈服强度≥345MPa，抗拉强度≥490MPa，延伸率≥17％；屈强比σ s/σ b≤0.8，优选≤0.75；600℃高温屈服强度≥232MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％。在这些耐火耐候钢板或钢带的一些实施方案中，这些耐火耐候钢板或钢带的室温屈服强度为345-370MPa，抗拉强度为490-530MPa，延伸率为19-27％；屈强比σ s/σ b为0.66-0.72；600℃高温屈服强度为235-260MPa，σ s,600℃/σ s,20℃为0.68-0.74；相对腐蚀率≤60％。在这些耐火耐候钢板或钢带的一些实施方案中，这些耐火耐候钢板或钢带的室温屈服强度为410-450MPa，抗拉强度为590-630MPa， 延伸率为18-28％；屈强比σ s/σ b为0.67-0.73；600℃高温屈服强度为275-310MPa，σ s,600℃/σ s,20℃为0.67-0.72；相对腐蚀率≤60％。
优选地，在上述任一实施方案中，Mn/S＞250。
优选地，本发明所述耐火耐候钢板/带的平均腐蚀速率≤0.3000mg/cm 2·h。
本发明所述耐火耐候钢板/带的显微组织为块状铁素体+珠光体+针状铁素体混合微观组织，或块状铁素体+珠光体+下贝氏体混合微观组织。
在本发明耐火耐候钢板/带的成分设计中：
C：C是钢中最经济、最基本的强化元素，通过固溶强化和析出强化来提高钢的强度。C是奥氏体转变过程中析出渗碳体必不可少的元素，因此C含量的高低在很大程度上决定钢的强度级别，即较高的C含量对应较高的强度级别。但是，由于C的间隙固溶和析出对钢的塑性和韧性有较大危害，而且，过高的C含量对焊接性能不利，因此C含量不能过高，钢的强度通过适当添加合金元素来弥补。同时，对常规板坯连铸来说，在包晶反应区浇铸易产生铸坯表面裂纹，严重时会发生漏钢事故。对薄带连铸来说也同样如此，在包晶反应区浇铸铸带坯易发生表面裂纹，严重时会发生断带。因此，Fe-C合金的薄带连铸同样需要避开包晶反应区。故本发明采用的C含量范围是0.02-0.06％。
Si：Si在钢中起固溶强化作用，且钢中加Si能提高钢质纯净度和脱氧，但Si含量过高会导致可焊性和焊接热影响区韧性恶化。故本发明采用的Si含量范围是0.1-0.55％。
Mn：Mn是价格最便宜的合金元素之一，它能提高钢的淬透性，在钢中具有相当大的固溶度，通过固溶强化提高钢的强度，同时对钢的塑性和韧性基本无损害，是提高钢的强度最主要的强化元素，还可以在钢中起到脱氧的作用。但Mn含量过高会导致可焊性和焊接热影响区韧性恶化。故本发明采用的Mn含量范围是0.4-1.7％。
P：高含量的P容易在晶界偏析，增加钢的冷脆性，使焊接性能变坏，降低塑性，使冷弯性能变坏。在薄带连铸工艺中，铸带的凝固和冷却速率极快，可有效抑制P的偏析，从而可有效避免P的劣势，充分发挥P的优势。故在本发明中，采用较传统工艺生产时高的P含量，适当放宽P元素的含量，炼钢工序中取消脱磷工序，在实际操作中，不需要刻意进行脱磷工序，也不需要额外添加磷，P含量的范围 ≤0.03％。
S：在通常情况下S是钢中有害元素，使钢产生热脆性，降低钢的延展性和韧性，在轧制时造成裂纹。S还会降低焊接性能和耐腐蚀性。故在本发明中，S也作为杂质元素来控制，其含量范围是≤0.007％；在一些实施方案中，S含量≤0.0067％。且，Mn/S≥250。在一些实施方案中，Mn/S＞250。
Als：为控制钢中的夹杂物，本发明要求不能用Al脱氧，耐材的使用中，也应尽量避免Al的额外引入，严格控制酸溶铝Als的含量：<0.001％。
N：与C元素类似，N元素可通过间隙固溶提高钢的强度，本发明要利用钢中的N跟B作用生成BN的析出相，需要钢中有一定的N含量。但是，N的间隙固溶对钢的塑性和韧性有较大危害，自由N的存在会提高钢的屈强比，因此N含量也不能过高。本发明采用的N含量范围是0.004-0.010％。
Cr：不仅是提高钢的淬透性的元素，还可以有效提高钢的高温抗氧化性和抗蠕变性能，在耐火耐候钢中添加Cr，一是用于提高钢的高温强度和蠕变强度，另一个主要作用是提高钢的耐侯性，可以显著提高钢的耐腐蚀性能。但是其含量太高会严重恶化焊接性能，本发明中将Cr含量限定在0.30-0.80％。
Nb：耐火钢中，Nb主要依靠NbC在铁素体中的析出强化来提高钢的高温强度。同时在薄带连铸工艺中，由于其独特的快速凝固和快速冷却特性，可以使添加的合金元素Nb更多地以固溶态存在于钢带中，固溶于钢中的Nb元素，可以起到固溶强化的作用。本发明中，添加Nb时，设计Nb的含量范围在0.01-0.08％。
Mo：固溶于铁素体中，强化了铁素体基体，高温下Mo在铁素体中扩散速度较慢，因而可显著提高钢的高温强度与蠕变强度。研究表明，固溶的Mo容易在晶界上偏聚，起到提高钢的高温强度的作用；Mo还可增加过冷奥氏体的稳定性，加Mo后钢中贝氏体体积分数增加；高位错密度的贝氏体组织使耐火耐候钢获得了良好的高温性能。Mo在钢中析出形成碳化物提高了其高温强度。有研究表明，Nb、Mo复合添加后可产生更好的沉淀强化效果：第1种观点认为复合添加时除了单独添加Nb、Mo的强化作用外，Mo还能在NbC/基体界面上富集，阻止了NbC颗粒的粗化，从而进一步提高了钢的高温强度；第2种观点认为Mo降低了NbC的析出驱动力，阻碍NbC的扩散成核过程，从而延迟了NbC的沉淀析出，钢中Mo促进了贝氏体相变，导致其位错密度增加,增加了NbC的成核位置。这些都造成了更 佳的沉淀强化效果，进而提高了钢的高温强度。过高的Mo会增加钢的原料冶炼成本。故本发明中将Mo含量限定在0.20-0.60％。
Cu：在钢中主要起固溶和沉淀强化作用，Cu还是提高耐候性的元素，由于Cu是易偏析元素，传统工艺流程中一般对Cu含量有较严格的控制。运用薄带连铸的快速凝固效应，本发明将Cu的上限提高到0.60％。Cu含量的提高，在一定意义上可以充分利用废钢，可以在废钢原料准备时不加筛选，提高冶炼作业率和降低成本，促进钢的循环利用，实现可持续发展的目的；还可实现劣质矿资源(如高铜矿)中铜的有效利用。
Sn：也是废钢中的主要残余元素之一，它被公认为钢中的有害元素，因为Sn是易偏析元素，少量的Sn就会在晶界富集，导致是裂纹等缺陷发生，因此在传统的工艺中Sn元素的含量是被严格控制的。薄带连铸由于快速凝固的特点，元素在枝晶间的偏析大大减小，可以大大提高元素的固溶量，因此在薄带连铸工艺条件下，Sn元素的范围可以扩大，因此可以大大降低炼钢成本。图2是Sn元素与平均热流密度的关系。由图2可见，当Sn加入量小于0.04％时，对热流密度的影响不大，即对薄带凝固过程没有影响。图3是Sn含量与表面粗糙度的关系。因为铸带表面的裂纹通常都是在铸带表面凹凸不平的皱褶处产生，用表面粗糙度来表征表面裂纹发生情况。如果粗糙度大，则裂纹发生的概率高。由图3可知，Sn含量的增加，在快速凝固条件下并没有对铸带的表面质量产生不良的影响。由图2和图3的结果可知，Sn没有对铸带的凝固和表面质量产生不良影响。故在本发明中，对Sn含量的要求可进一步放宽，设计Sn的含量范围在0.005-0.04％。
B：B在钢中的显著作用是：极微量的硼就可以使钢的淬透性成倍增加，B可以在高温奥氏体中优先析出粗大的BN颗粒从而抑制细小AlN的析出，减弱细小AlN对晶界的钉扎作用，提高晶粒的生长能力，从而粗化和均匀化奥氏体晶粒，有利于轧制后的再结晶，奥氏体晶粒粗化均匀化以后，有利于降低产品屈强比σ s/σ b，减小屈服强度的波动范围，提高抗震性能；另外B与N的结合可以有效防止晶界低熔点相B 2O 3的出现。
B是活泼易偏析元素，容易在晶界偏聚，传统工艺生产含B钢时，B含量一般控制的非常严格，一般在0.001-0.003％左右；而在薄带连铸工艺中，凝固和冷却速率较快，可有效抑制B的偏析，固溶更多的B含量，因此B的含量可以适当放宽； 还可以通过合理的工艺控制生成粗大的BN颗粒，抑制细小的AlN析出，起到固氮的作用。还有研究表明，B在和Nb、Mo复合添加时，会得到更好的效果，会减小C原子的偏聚倾向，避免了晶界Fe 23(C,B) 6的析出，因此可以添加更多的B。故在本发明中，采用较传统工艺更高的B含量，范围是0.001-0.006％。
为保证本发明钢种的焊接性能，上述元素设计时，应满足如下关系式：
Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。
本发明所述的耐火耐候钢板/带的制造方法，其包括如下步骤：
a)冶炼
按照上述化学成分要求进行冶炼，炼钢过程造渣的碱度a＝CaO/SiO 2(质量比)控制在a<1.5，优选a<1.2，或a＝0.7-1.0；钢水中获得低熔点MnO-SiO 2-Al 2O 3三元夹杂物中的MnO/SiO 2(质量比)控制在0.5～2，优选为1～1.8；钢水中的自由氧[O] Free含量为：0.0005-0.005％；钢水成分中，Mn/S≥250；
b)连铸
连铸采用双辊薄带连铸，在两结晶辊辊缝隙最小处形成1.5-3mm厚的铸带；结晶辊直径在500-1500mm之间，优选直径为800mm；结晶辊内部通水冷却，铸机的浇铸速度为60-150m/min；连铸布流采用两级钢水分配布流系统，即中间包+布流器；
c)下密闭室保护
铸带出结晶辊后，铸带温度在1420-1480℃，直接进入到下密闭室内，下密闭室内通非氧化性气体，下密闭室内的氧浓度控制在<5％，下密闭室出口铸带的温度在1150-1300℃；
d)在线热轧
铸带在下密闭室内经夹送辊送至轧机，轧制成0.8-2.5mm厚度的带钢，轧制温度为1100-1250℃，控制热轧压下率为10-50％，优选地，热轧压下率30-50％，轧后带钢厚度为0.8-2.5mm，优选厚度为1.2-2.0mm；
e)轧后冷却
对轧后带钢进行冷却，采用气雾化冷却方式对带钢进行冷却，气雾化冷却的冷却速率为20-100℃/s；
f)带钢卷取
冷却后的热轧带钢经切头剪切除质量较差的头部后，直接进行卷取成卷，控制热轧带的卷取温度为500-680℃。
进一步，还包括步骤g)后续处理，钢卷直接作为热轧板/带使用，或经过切边-平整后作为精整板/带使用。
优选的，步骤a)中，冶炼原料可选用100％全废钢，无需预筛选，钢水冶炼采用电炉炼钢；或者，冶炼采用转炉炼钢，废钢按占冶炼原料20％以上的比例加入转炉，且无需预筛选；然后再进入LF炉、VD/VOD炉或RH炉精炼。
优选的，步骤c)所述非氧化性气体包括N 2、Ar或干冰升华得到的CO 2气体。
优选的，步骤e)所述气雾化冷却的气水比为15：1～10：1，气压0.5～0.8MPa，水压1.0～1.5MPa。本文中，气水比指压缩空气和水的流量比，流量的单位为m 3/h。
在一些实施方案中，所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素，Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B；优选地，其制造方法中的步骤f)的卷取温度为580-680℃。
在一些实施方案中，所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Cu：0.10-0.60％，Mo：0.20-0.60％，Nb：0.01-0.08％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O] T：0.007-0.020％；余量为Fe和不可避免杂质；且，同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B；优选地，其制造方法中的步骤f)的卷取温度为500-600℃。
优选的，步骤f)卷取采用双卷取机形式，或采用卡罗塞尔卷取形式。
在本发明制造方法中：
为提高薄带连铸钢水的可浇铸性，炼钢过程造渣的碱度a＝CaO/SiO 2控制在a<1.5，优选a<1.2，或a＝0.7-1.0。
为提高薄带连铸钢水的可浇铸性，需要获得低熔点MnO-SiO 2-Al 2O 3三元夹杂 物，如图4的阴影区域，MnO-SiO 2-Al 2O 3三元夹杂物中的MnO/SiO 2控制在0.5～2，优选在1～1.8。
为提高薄带连铸钢水的可浇铸性，钢中的氧(O)是形成氧化夹杂物的必要元素，本发明需要形成低熔点的MnO-SiO 2-Al 2O 3的三元夹杂物，要求钢水中的自由氧[O] Free范围为：0.0005-0.005％。
为提高薄带连铸钢水的可浇铸性，上述成分中，Mn和S的控制须满足如下关系式：Mn/S≥250。
现代钢铁生产企业为节省投资成本与生产成本，积极对现有生产工艺流程进行技术革新。针对现有热带钢生产工艺流程长、设备多且复杂的问题，许多生产厂家将连铸连轧技术与传统工艺紧密结合，以满足连铸连轧工艺的需求。
采用转炉炼钢提供钢水，则需要生产厂家具备有提供铁水的条件，一般情况下，需要有高炉炼铁或者非高炉炼铁设备，属于目前长流程钢铁生产模式。但是，在废钢资源日益丰富的今天，国家正在倡导提高转炉废钢比，从而可以达到节能降耗、降成本的目的，以前转炉废钢比的平均水平在8％左右，现在和今后转炉废钢比的目标是15-25％。本发明转炉废钢比已经可以达到20％以上。
采用电炉炼钢提供钢水，则以废钢为主要原料，传统工艺比如模铸或者厚板连铸，其凝固冷却速度仅有10 -1-10℃/s，废钢中的这些残余元素，会在凝固过程中发生晶界偏析，恶化钢的性能和质量，严重时直接发生开裂、断裂现象，所以在传统工艺中，要对这些有害元素严加控制，在废钢原料的选择上，需要进行一些预筛选，以及在炼钢过程中需要进行一些特殊处理，比如添加一些精料进行稀释等等，这无疑增加了生产作业成本。由于需要控制钢的成分，对采用的废钢原料有一定的质量要求，一般情况下，需要对废钢进行预筛选分类。有些国内电炉钢厂为了提高生产效率，会在原料组成里选择添加精料如外购海绵铁、碳化铁等来稀释废钢中难以脱除的有害元素，提高钢水的质量。有些国内同时拥有高炉和电炉的钢厂利用自产铁水兑入到电炉中作为电炉原料来提高电炉的生产效率，从而大大缩短电炉的出钢时间，电炉中的铁水勾兑比可达到30～50％。
而采用双辊薄带连铸技术，是典型的亚快速凝固过程，凝固冷却速度高达10 2-10 4℃/s，废钢中的一些有害残余元素，比如Cu、Sn、P等，可以最大限度地固溶到钢的基体中而不产生晶界偏析，因此可以实现100％全废钢冶炼，无需进行预 筛选，大大降低原料成本。这些残余元素还可以起到固溶强化的作用，从而生产出性能优良的超薄热轧带钢。实现劣质废钢资源的生产综合利用，对废钢中的这些有害残余元素起到“化害为利”，“废物利用”的效果。
铸带出结晶辊后，铸带温度在1420-1480℃，直接进入到下密闭室内，下密闭室通非氧化性气体保护带钢，实现对带钢的防氧化保护，防氧化保护的气氛可以是N 2，也可以是Ar，也可以是其他非氧化性气体，比如干冰升华得到的CO 2气体等，下密闭室内的氧浓度控制在<5％。下密闭室对铸带的防氧化保护到轧机入口。下密闭室出口铸带的温度在1150-1300℃。
铸带在下密闭过程中涉及到的BN析出相的理论基础：
钢中硼与氮、铝和氮在γ-Fe中的热力学方程如下：
BN＝B+N；Log[B][N]＝-13970/T+5.24  (1)
AlN＝Al+N；Log[Al][N]＝-6770/T+1.03  (2)
如图5所示，钢中BN的开始析出温度在1280℃左右，980℃时BN的析出趋于平衡，而此时AlN的析出才刚刚开始(AlN的析出温度在980℃左右)，从热力学上讲，BN的析出要优先于AlN。本发明在下密闭室内完成B与N的结合，生成粗大的BN颗粒，从而抑制了细小的AlN析出，减弱细小AlN对晶界的钉扎作用，提高晶粒的生长能力，从而粗化奥氏体晶粒，使奥氏体晶粒更加均匀，有利于降低产品屈强比σ s/σ b，减小屈服强度的波动范围，提高抗震性能；另外B与N的结合可以有效防止晶界低熔点相B 2O 3的出现。
对在线热轧后的带钢进行轧后冷却，采用气雾化冷却方式对带钢进行冷却，气雾化冷却方式可以有效减小带钢表面氧化皮厚度，改善带钢温度均匀性，提高带钢表面质量。气雾化冷却的气水比为15：1～10：1，气压0.5～0.8MPa，水压1.0～1.5MPa。气雾化后形成高压水雾喷射在钢带表面，一方面起到了降低钢带温度的作用，另一方面水雾会形成致密的气膜包覆在带钢表面，起到带钢防氧化的作用，从而有效控制了热轧带钢表面氧化皮的生长。该种冷却方式可以避免传统喷淋或者层流冷却带来的问题，使带钢表面温度均匀下降，提高带钢温度均匀性，从而达到均匀化内部微观组织和改善材料屈强比的效果；同时冷却均匀，可以提高带钢的板形质量和性能稳定性；有效减少带钢表面的氧化皮厚度。气雾化冷却的冷却速率范围为20-100℃/s。
冷却后的热轧带钢经切头剪切除质量较差的头部后，直接进行卷取成卷，控制热轧带的卷取温度为500-680℃，使轧后的高温奥氏体组织转变为块状铁素体+珠光体+针状铁素体混合微观组织，或块状铁素体+珠光体+下贝氏体混合微观组织，如图6所示。卷取机采用双卷取形式，也可以采用卡罗塞尔卷取形式，保证带钢的连续生产。
本发明的主要优点：
本发明利用薄带连铸技术生产的耐火耐候钢，迄今为止尚未见报导，归纳优点如下：
1.本发明省去了板坯加热、多道次反复热轧等复杂过程，通过双辊薄带连铸+一道次在线热轧工序，生产流程更短、效率更高，产线投资成本和生产成本大幅降低。
2.本发明省去了传统工艺生产中诸多复杂的中间步骤，与传统生产工艺相比，生产的能耗和CO 2排放大幅度降低，是一种绿色环保的产品。
3.本发明采用薄带连铸工艺生产热轧耐火耐候钢，由于薄带连铸工艺本身的亚快速凝固特性，带钢表面会天然形成一定厚度的细晶层，使生产的钢种兼具耐候性能；同时，铸带厚度本身较薄，通过在线热轧至期望产品厚度，薄规格产品可直接供给市场使用，达到薄规格热轧板供货的目的，可以显著提高板带材的性价比。
4.本发明采用添加微量的B元素，在高温奥氏体中优先析出粗大的BN颗粒从而抑制细小AlN的析出，减弱细小AlN对晶界的钉扎作用，提高晶粒的生长能力，从而粗化、均匀化奥氏体晶粒，有利于改善产品的成形性能，降低材料的屈强比，低屈强比有利于提高建筑结构地震时吸收能量，提高材料的抗震性能。
5.本发明冶炼采用通过电炉炼钢，冶炼的原料可以从真正意义上实现100％全废钢冶炼，无需进行预筛选，大大降低原料成本；如果冶炼通过转炉炼钢，废钢按占冶炼原料20％以上的比例加入转炉，且无需预筛选，最大限度提高转炉废钢比，大大降低冶炼成本和能耗。
6.本发明利用含Cu、Sn的废钢，对钢中的Cu、Sn做到“化害为利”，实现对现有废钢或低品质劣质矿资源(高锡矿、高铜矿)的充分利用，促进废钢的循环利用，降低生产成本，实现钢铁业可持续发展。
7.本发明采用轧后带钢气雾化冷却方式，可以避免传统喷淋或者层流冷却带 来的问题，使带钢表面温度均匀下降，提高带钢温度均匀性，从而达到均匀化内部微观组织的效果；同时冷却均匀，可以提高带钢的板形质量和性能稳定性；有效减少带钢表面的氧化皮厚度。
8.传统工艺板坯冷却过程中发生合金元素析出，板坯再加热时往往会由于合金元素回溶不充分而降低合金元素利用率。本发明薄带连铸工艺中，高温铸带直接热轧，所添加的合金元素主要以固溶态存在，可提高合金利用率。
9.本发明选用热轧钢带卡罗塞尔卷取机，有效缩短产线长度；同时同位卷取可以大大提高卷取温度的控制精度，提高产品性能的稳定性。
10.本发明区别于现有薄带连铸技术最明显的一个特征就是结晶辊的辊径及其相对应的布流方式。EUROSTRIP技术特征就是Φ1500mm大辊径结晶辊，结晶辊大、熔池钢水容量大，布流容易，结晶辊制造及运维成本高。CASTRIP技术特征就是Φ500mm小辊径结晶辊，结晶辊小、熔池钢水容量小，布流非常困难，但铸机设备制造与运维成本低。CASTRIP为解决小熔池的均匀布流问题，采用三级钢水分配布流系统(中间包+过渡包+布流器)。由于采用了三级布流系统，会直接导致耐材成本增加；更为主要的是，三级布流系统使钢水流动的路径变长，钢水的温降也较大，为了满足熔池钢液的温度，出钢温度需要大大提高。出钢温度的提高，会导致炼钢成本增加、能耗增加以及耐材寿命缩短等问题。
11.本发明结晶辊直径在500-1500mm优选Φ800mm辊径的结晶辊，采用两级钢水分配布流系统(中间包+布流器)。从布流器流出的钢水，沿辊面和两个端面形成不同的布流模式，且分两路流动，互不干扰。由于采用了两级布流系统，相比三级布流系统，耐材成本大幅度降低；钢水流动路径的缩短，使钢水温降减小，可以降低出钢温度，相比三级布流系统，出钢温度可降低30-50℃。出钢温度的降低，可有效降低炼钢成本、节约能耗以及延长耐材寿命。本发明配合优选Φ800mm辊径的结晶辊，采用两级钢水分配布流系统，既实现了钢水稳定布流的要求，又实现了结构简单、操作方便、加工成本低的目标。
附图说明
图1为双辊薄带连铸工艺的布置示意图；
图2为Sn含量与平均热流密度的关系示意图；
图3为Sn含量与铸带表面粗糙度的关系示意图；
图4为MnO-SiO 2-Al 2O 3三元相图(阴影区域：低熔点区)；
图5为BN、AlN析出的热力学曲线示意图；
图6为本发明实施例1钢的微观组织；
图7为本发明实施例15钢的微观组织。
具体实施方式
下面用实施例和附图对本发明作进一步阐述，但这些实施例绝非对本发明有任何限制。本领域技术人员在本说明书的启示下对本发明实施中所作的任何变动都将落在本发明权利要求保护范围内。
参见图1，将符合本发明化学成分设计的钢水经大包1，通过大包长水口2、中间包3、浸入式水口4以及布流器5直接浇注在一个由两个相对转动并能够快速冷却的结晶辊8a、8b和侧封板装置6a、6b围成的熔池7中，钢水在结晶辊8a、8b旋转的周向表面凝固，进而形成凝固壳并逐渐生长随后在两结晶辊辊缝隙最小处(nip点)形成1.5-3mm厚的铸带11。本发明所述的结晶辊直径在500-1500mm之间，内部通水冷却；根据铸带厚度不同，铸机的浇铸速度范围介于60-150m/min。
在铸带11出结晶辊8a、8b后，铸带温度在1420-1480℃，直接进入到下密闭室10内，下密闭室10通非氧化性气体保护带钢，实现对带钢的防氧化保护，防氧化保护的气氛可以是N 2，也可以是Ar，也可以是其他非氧化性气体，比如干冰升华得到的CO 2气体等，下密闭室10内的氧浓度控制在<5％。下密闭室10对铸带11的防氧化保护到轧机13入口。下密闭室10出口铸带的温度在1150-1300℃。然后通过摆动导板9、夹送辊12、辊道15将铸带送至热轧机13，热轧后形成0.8-2.5mm的热轧带，使用气雾化快速冷却装置14采用气雾化冷却方式对带钢进行冷却，改善带钢温度均匀性。经飞剪装置16切头之后，切头沿着飞剪导板17掉入飞剪坑18中，切头后的热轧带进入卷取机19进行卷取。将钢卷从卷取机上取下后，自然冷却至室温。最后生产的钢卷可以直接作为热轧板/带使用，也可以经过切边-平整后作为精整板/带使用。
通过实施例来进一步阐述本发明的方法。本发明实施例化学成分如表1所示，其成分余量为Fe和其它不可避免杂质。经本发明的制造方法，工艺参数见表2， 最终获得热轧带的力学性能见表3。
对实施例钢进行耐腐蚀性能测试：以普通碳钢Q345B为对比样品，按72h周期浸润腐蚀试验方法(TB/T2375-1993)进行72h周期浸润循环腐蚀实验。通过计算样品单位面积腐蚀失重量求得平均腐蚀速率，进而求得钢种的相对腐蚀率。测试结果见表4。
表3的结果显示，本发明利用薄带连铸工艺，按设计的钢种成分制造的薄规格耐火耐候钢板/带，室温屈服强度≥345MPa，抗拉强度≥490MPa，延伸率≥17％；屈强比σ s/σ b≤0.8；600℃高温屈服强度≥232MPa，σ s,600℃/σ s,20℃≥0.67；冷加工折弯性能合格。表4的耐腐蚀性能对比结果亦表明发明钢种的相对腐蚀率≤60％。达到并且超过了耐火耐候钢的性能要求，同时可以实现薄规格热轧产品的供货，生产成本也大幅度降低，材料屈强比低，抗震性能优良，耐火性能优异，是抗震、防火用钢领域的理想用材。
表1：实施例钢的化学成分(wt.％)
Figure PCTCN2020115284-appb-000001
表2：实施例的工艺参数
Figure PCTCN2020115284-appb-000002
表3：实施例钢的产品力学性能
Figure PCTCN2020115284-appb-000003
Figure PCTCN2020115284-appb-000004
表4：实施例钢的耐腐蚀性能测试结果
  平均腐蚀速率，mg/cm 2·h 相对腐蚀率，％
Q345B 0.4902 100
实施例1 0.2506 51.12
实施例2 0.2758 56.26
实施例3 0.2848 58.10
实施例4 0.2766 56.43
实施例5 0.2668 54.43
实施例6 0.2724 55.57
实施例7 0.2905 59.26
实施例8 0.2876 58.67
实施例9 0.2862 58.38
实施例10 0.2797 57.06
实施例11 0.2657 54.20
实施例12 0.2558 52.18
实施例13 0.2908 59.32
实施例14 0.2839 57.92
下述实施例14-28为含有Nb的实施例，其化学成分如表5所示，其成分余量为Fe和其它不可避免杂质。经本发明的生产方法，工艺参数见表6，最终获得热轧带的力学性能见表7。
对实施例钢进行耐腐蚀性能测试：以普通碳钢Q345B为对比样品，按72h周期浸润腐蚀试验方法(TB/T2375-1993)进行72h周期浸润循环腐蚀实验。通过计算样品单位面积腐蚀失重量求得平均腐蚀速率，进而求得钢种的相对腐蚀率。测试结果见表8。
由表7可知，利用薄带连铸工艺技术按本发明提供的钢种成分设计范围生产的高强耐火耐候钢板/带，其室温屈服强度可≥410MPa，抗拉强度可≥590MPa，延伸率≥17％；屈强比σ s/σ b≤0.8；600℃高温屈服强度可≥275MPa，σ s,600℃/σ s,20℃≥0.67；冷加工折弯性能合格。
表8的耐腐蚀性能对比结果亦表明本发明钢种的相对腐蚀率≤60％。达到并且超过了耐火耐候钢的性能要求，同时可以实现薄规格热轧产品的供货，生产成本也大幅度降低，材料屈强比低，抗震性能优良，耐火性能优异，是抗震、防火用钢领域的理想用材。
表5：实施例钢的化学成分(wt.％)
Figure PCTCN2020115284-appb-000005
Figure PCTCN2020115284-appb-000006
表6：实施例的工艺参数
Figure PCTCN2020115284-appb-000007
表7：实施例钢的产品力学性能
Figure PCTCN2020115284-appb-000008
Figure PCTCN2020115284-appb-000009
表8：实施例钢的耐腐蚀性能测试结果
  平均腐蚀速率，mg/cm 2·h 相对腐蚀率，％
Q345B 0.4902 100
实施例15 0.2938 59.93
实施例16 0.2764 56.39
实施例17 0.2833 57.79
实施例18 0.2793 56.98
实施例19 0.2843 58.00
实施例20 0.2916 59.49
实施例21 0.2783 56.77
实施例22 0.2776 56.63
实施例23 0.2852 58.18
实施例24 0.2797 57.06
实施例25 0.2869 58.53
实施例26 0.2747 56.04
实施例27 0.2838 57.89
实施例28 0.2793 56.98

Claims (15)

  1. 耐火耐候钢板/带，其化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，任选的Nb：0.01-0.08％，总氧[O] T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：
    含有Cu：0.10-0.60％和Sn：0.005-0.04％中的一种或两种元素；
    Mn/S≥250；
    Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。
  2. 如权利要求1所述的耐火耐候钢板/带，其特征在于，其化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：含有Cu：0.10-0.60％或Sn：0.005-0.04％中的一种或两种元素，Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。
  3. 如权利要求1所述的耐火耐候钢板/带，其特征在于，其化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，Cu：0.10-0.60％，任选的Sn：0.005-0.04％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可避免杂质，且同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。
  4. 如权利要求1所述的耐火耐候钢板/带，其特征在于，其化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Cu：0.10-0.60％，Mo：0.20-0.60％，Nb：0.01-0.08％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O] T：0.007-0.020％；余量为Fe和不可避免杂质；且同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B。
  5. 如权利要求1所述的耐火耐候钢板/带，其特征在于，所述耐火耐候钢板/带的显微组织为块状铁素体+珠光体+针状铁素体混合微观组织，或块状铁素体+珠光 体+下贝氏体混合微观组织。
  6. 如权利要求1-3中任一项所述的耐火耐候钢板/带，其特征在于，所述耐火耐候钢板/带的室温屈服强度≥345MPa，抗拉强度≥490MPa，延伸率≥17％；屈强比σ s/σ b≤0.8；600℃高温屈服强度≥232MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％。
  7. 如权利要求2或3所述的耐火耐候钢板/带，其特征在于，所述耐火耐候钢板或钢带的室温屈服强度为345-370MPa，抗拉强度为490-530MPa，延伸率为19-27％；屈强比σ s/σ b为0.66-0.72；600℃高温屈服强度为235-260MPa，σ s,600℃/σ s,20℃为0.68-0.74；相对腐蚀率≤60％。
  8. 如权利要求4所述的耐火耐候钢板/带，其特征在于，所述耐火耐候钢板/带的室温屈服强度≥410MPa，抗拉强度≥590MPa，延伸率≥17％；屈强比σ s/σ b≤0.8，优选≤0.75；600℃高温屈服强度≥275MPa，σ s,600℃/σ s,20℃≥0.67；相对腐蚀率≤60％；优选地，所述耐火耐候钢板或钢带的室温屈服强度为410-450MPa，抗拉强度为590-630MPa，延伸率为18-28％；屈强比σ s/σ b为0.67-0.73；600℃高温屈服强度为275-310MPa，σ s,600℃/σ s,20℃为0.67-0.72；相对腐蚀率≤60％。
  9. 如权利要求1-8中任一项所述的耐火耐候钢板/带的制造方法，其特征是，包括如下步骤：
    a)冶炼
    按照权利要求1所述化学成分要求进行冶炼，炼钢过程造渣的碱度a＝CaO/SiO 2控制在a<1.5，优选a<1.2，或a＝0.7-1.0；钢水中获得低熔点MnO-SiO 2-Al 2O 3三元夹杂物中的MnO/SiO 2控制在0.5～2，优选为1～1.8；钢水中的自由氧[O] Free含量为：0.0005-0.005％；钢水成分中，Mn/S≥250；
    b)连铸
    连铸采用双辊薄带连铸，在两结晶辊辊缝隙最小处形成1.5-3mm厚的铸带；结晶辊直径在500-1500mm之间，优选直径为800mm；结晶辊内部通水冷却，铸机的浇铸速度为60-150m/min；连铸布流采用两级钢水分配布流系统，即中间包+布流器；
    c)下密闭室保护
    连铸带出结晶辊后，铸带温度在1420-1480℃，直接进入到下密闭室内，下密闭室内通非氧化性气体，下密闭室内的氧浓度控制在<5％，下密闭室出口铸带的温 度在1150-1300℃；
    d)在线热轧
    铸带在下密闭室内经夹送辊送至轧机，轧制成0.8-2.5mm厚度的薄带钢，轧制温度为1100-1250℃，控制热轧压下率为10-50％，优选地，热轧压下率30-50％，轧后带钢厚度为0.8-2.5mm，优选厚度为1.2-2.0mm；
    e)轧后冷却
    对轧后带钢进行冷却，采用气雾化冷却方式对带钢进行冷却，气雾化冷却的冷却速率为20-100℃/s；
    f)带钢卷取
    冷却后的热轧带钢经切头剪切除质量较差的头部后，直接进行卷取成卷，控制热轧带的卷取温度为500-680℃。
  10. 如权利要求9所述的耐火耐候钢板/带的制造方法，其特征是，还包括步骤
    g)后续处理，钢卷直接作为热轧板/带使用，或经过切边-平整后作为精整板/带使用。
  11. 如权利要求9所述的耐火耐候钢板/带的制造方法，其特征是，步骤a)中，冶炼原料选用100％全废钢，无需预筛选，钢水冶炼采用电炉炼钢；或者，冶炼采用转炉炼钢，废钢按占冶炼原料20％以上的比例加入转炉，且无需预筛选；然后再进入LF炉、VD/VOD炉或RH炉精炼。
  12. 如权利要求9所述的耐火耐候钢板/带的制造方法，其特征是，步骤c)所述非氧化性气体为N 2、Ar或干冰升华得到的CO 2气体。
  13. 如权利要求9所述的耐火耐候钢板/带的制造方法，其特征是，步骤e)所述气雾化冷却的气水流量比为15：1～10：1，气压0.5～0.8MPa，水压1.0～1.5MPa，流量单位为m 3/h。
  14. 如权利要求9所述的耐火耐候钢板/带的制造方法，其特征是，步骤f)卷取采用双卷取机形式，或采用卡罗塞尔卷取形式。
  15. 如权利要求9所述的耐火耐候钢板/带的制造方法，其特征是，所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Mo：0.20-0.60％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O]T：0.007-0.020％，余量为Fe和其他不可 避免杂质，且同时满足：含有Cu：0.10-0.60％或Sn：0.005-0.04％中的一种或两种元素，Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B，所述制造方法中的步骤f)的卷取温度为580-680℃；或所述耐火耐候钢板或钢带的化学成分重量百分比为：C：0.02-0.06％，Si：0.1-0.55％，Mn：0.4-1.7％，P≤0.03％，S≤0.007％，Cr：0.30-0.80％，Cu：0.10-0.60％，Mo：0.20-0.60％，Nb：0.01-0.08％，N：0.004-0.010％，Als<0.001％，B：0.001-0.006％，总氧[O]T：0.007-0.020％；余量为Fe和不可避免杂质；且，同时满足：Mn/S≥250，以及Pcm≤0.27％，Pcm＝C+Si/30+Mn/20+Cu/20+Cr/20+Mo/15+5B，所述制造方法中的步骤f)的卷取温度为500-600℃。
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