WO2020108615A1 - 一种热轧钢板及其制造方法 - Google Patents

一种热轧钢板及其制造方法 Download PDF

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WO2020108615A1
WO2020108615A1 PCT/CN2019/121964 CN2019121964W WO2020108615A1 WO 2020108615 A1 WO2020108615 A1 WO 2020108615A1 CN 2019121964 W CN2019121964 W CN 2019121964W WO 2020108615 A1 WO2020108615 A1 WO 2020108615A1
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hot
steel plate
rolled steel
steel sheet
temperature
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English (en)
French (fr)
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王双成
孙全社
周亮
王俊凯
王金涛
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • 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
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/20—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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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

Definitions

  • the invention relates to steel for enamel, in particular to a hot-rolled steel plate with excellent double-sided enamel performance and high-strength performance after enamel and a manufacturing method thereof.
  • the hot-rolled steel plate has excellent double-sided enamel performance and high-strength enamel performance Performance, the yield strength can still reach more than 400MPa after two high-temperature sintering in the temperature range of 780 ⁇ 920°C, and it can be mainly used in some enamel steel assembled storage tanks such as sewage treatment tanks, biogas fermentation tanks, fresh water storage tanks, etc. Manufacturing materials.
  • hot-rolled steel plates for high-strength double-sided enamel are mainly used for substrates of enamel steel for assembling tanks.
  • Such enamel assembling tanks can be used in large-scale water treatment facilities, chemical facilities, environmental protection facilities and other fields, such as urban garbage seepage and life Assembled tanks for sewage treatment, industrial sewage treatment, fresh water storage, etc.; also used as anaerobic fermentation assembling tanks, enameled steel plate biogas digesters, assembled enameled steel plate grain silo assembly tanks, etc.
  • the volume of assembled tanks is large, ranging from hundreds of cubic meters to tens of thousands of cubic meters.
  • the processing technology of the enamel steel plate for assembling the tank mainly includes: firstly bending the steel plate with a certain arc, and then removing the oxide scale and rust on the surface of the steel plate by pickling or shot blasting; then using wet primer and firing, the primer
  • the firing temperature is usually 840 ⁇ 920°C.
  • the firing temperature and holding time are adjusted according to the thickness of the steel plate. For a 6mm thick steel plate, the firing time is about 10 ⁇ 12min; another wet glaze and firing are performed.
  • the firing temperature of glaze is generally 780 ⁇ 850°C.
  • the firing temperature and holding time of top glaze are adjusted according to the thickness of steel plate. For 6mm thick steel plate, the firing time is 9 ⁇ 11min.
  • the steel plate used for this kind of application must first have a good coating enameling adaptability, which mainly means that the steel plate does not show scale explosion defects after double-sided enamel; at the same time, the steel plate still needs to have after two high temperature (780 ⁇ 920°C) sintering High yield strength to ensure the safety performance of large structural parts.
  • the scale explosion defect of the steel plate after enamel is mainly caused by hydrogen, which mainly enters the steel plate during the process of acid washing (metal dissolves in acid to produce hydrogen) and sintering (hydrogen of crystalline water contained in clay reacts with metal to generate hydrogen) of.
  • the steel plate After double-sided enamel, the steel plate is more prone to scale explosion than single-sided enamel.
  • the reason is that the hydrogen stored in the steel plate after double-sided enamel is more difficult to escape.
  • the enamel products are cooled in the air until the enamel solidifies, the hydrogen cannot escape In the steel plate, it reaches a supersaturated state, and then a certain pressure is formed. When the pressure is increased to cause the porcelain layer to fall off, scale explosion defects are formed.
  • t represents the calculated thickness (mm) of the steel plate of the assembled tank shell
  • H represents the design height (mm) of the liquid from the highest liquid level on the top to the bottom of a certain steel plate of the shell
  • D represents the diameter of the tank (mm)
  • S represents the vertical distance between the columns of the bolts (mm)
  • ⁇ represents the storage density (kg/m 3 )
  • R el represents the yield strength of the enamel steel plate (kg/m 3 )
  • d represents the bolt diameter (mm);
  • ⁇ represents the partial coefficient.
  • the yield strength of the steel plate is proportional to the height of the liquid level in the tank and the diameter of the tank, that is, the higher the yield strength of the steel plate, the more the tank diameter can be designed. Bigger, higher.
  • the yield strength of the steel plate is inversely proportional to the thickness of the steel plate, that is, when the yield strength of the steel plate is increased, its thickness can be appropriately thinned, thereby reducing manufacturing costs and saving resources.
  • the maximum thickness of steel plates is generally controlled at 13 mm or less.
  • the existing patent literature on hot-rolled double-sided enamel steel reports that the composition generally uses extremely low S and N elements, and controls the ratio of Ti and C elements to form a finely dispersed TiC precipitate phase as a hydrogen storage trap. Realize the anti-scaling performance of the steel plate after double-sided enamel. However, after sintering of this type of steel plate at high temperature (780 ⁇ 920°C), the dislocation density decreased significantly, and the grains were coarsened obviously. At the same time, the TiC precipitated phases will grow together with the increase of the sintering temperature and the holding time.
  • the object of the present invention is to provide a hot-rolled steel plate with excellent double-sided enameling performance and high-strength performance after enameling and a manufacturing method thereof, the steel plate does not suffer from scale explosion defects after double-sided enameling and has good adhesion to the porcelain layer ; After two high-temperature sintering in the temperature range of 780 ⁇ 920 °C, the yield strength of the steel plate can still reach more than 400MPa; it can meet the requirements of some large-scale water treatment facilities, chemical facilities, environmental protection facilities and other engineering structural parts for enamel steel. demand.
  • the hot-rolled steel plate of the present invention adopts a composition system of high C-Mn-Ti and low S-micro Nb alloy, and adopts a strict hot rolling controlled rolling process to obtain a fine structure of ferrite + pearlite, which fully exerts the function of fine grain strengthening And pearlite tissue strengthening effect.
  • a large number of 5-25 nm TiC and NbC precipitation phases formed in the matrix fully exert the precipitation strengthening effect.
  • TiC, NbC, Ti 4 C 2 S 2 and other second-phase particles formed in the matrix are used as hydrogen storage traps, so that the steel sheet can obtain excellent anti-scaling performance.
  • the hot-rolled steel sheet of the present invention having excellent double-sided coating and high-strength performance after lining has a weight percentage of C: 0.13 to 0.20%, Si: 0.15 to 0.50%, and Mn: 1.0 ⁇ 2.3%, P ⁇ 0.03%, S: 0.01 ⁇ 0.03%, Al: 0.006 ⁇ 0.08%, N ⁇ 0.006%, Cr: 0.03 ⁇ 0.10%, Ti: 0.15 ⁇ 0.25%, Nb: 0.02 ⁇ 0.12%, Cu : 0.02 ⁇ 0.10%, the rest is Fe and inevitable impurities; and at the same time satisfy the following relationship:
  • %S, %Ti, %Nb, %C and %Mn in the above formulas respectively represent the weight percentage of the corresponding elements in the steel plate
  • the value substituted by Mn is the value before the percent sign.
  • the content of S in Example 1 is 0.016%.
  • the substituted value should be 0.016 instead of 0.00016.
  • the substitution of other elements can be deduced by analogy.
  • composition design of the double-sided enamel steel of the present invention is the composition design of the double-sided enamel steel of the present invention:
  • the carbon content in the invention is limited to 0.13-0.20%;
  • Silicon element plays a role of solid solution strengthening in steel. Silicon can also improve the resistance to high temperature deformation and improve the softening resistance of the steel plate during the high temperature enamel firing process. However, when the silicon content is too high, the plasticity of the steel becomes poor, which may also affect the adhesion between the steel plate and the enamel, so the silicon content in the present invention is limited to 0.15 to 0.50%;
  • Manganese can improve the strength of the steel plate, and is an important element to ensure that the steel plate still has high strength after two high temperature sintering. Manganese also plays a deoxidizing role with aluminum and silicon elements in steel. The deoxidizing effect of manganese can promote the effective function of titanium element. Manganese has the effect of expanding the austenite phase area and lowering the Ac3 point temperature, which is detrimental to the enamel performance of the steel plate, because the austenite phase has a stronger ability to dissolve hydrogen than the ferrite phase, and it is more likely to cause scale explosion defects after cooling. ; In addition, excessively high manganese element will seriously reduce the plasticity of the steel, so it should not be added excessively. The manganese content of the present invention is controlled at 1.0-2.3%.
  • Phosphorus is an element that seriously damages the toughness and plasticity of steel, but it is also an inevitable impurity element. In the present invention, phosphorus is controlled at ⁇ 0.03%
  • S Sulfur
  • MnS manganese
  • the content of sulfur in steel without titanium should be as low as possible.
  • sulfur preferentially forms the compound Ti 4 C 2 S 2 with the titanium element, which can play a certain role in hydrogen storage and improve the scale resistance of the steel plate. Therefore, the sulfur element in the present invention is limited to 0.01 to 0.03%;
  • Titanium Ti and nitrogen (N): Titanium is an element that forms strong carbonitrides, which is beneficial for fixing nitrogen in steel. The formed titanium nitride can make the austenite grains grow excessively and refine when the billet is heated. Original austenite grains.
  • Titanium can be combined with carbonization in the steel plate to form nano-scale TiC and micro-scale TiN second phase particles, both of which can be used as hydrogen storage traps to improve the scale resistance of the steel plate.
  • nano-scale TiC particles are the main contributors to precipitation strengthening, while micro-scale TiN particles do not play a role in precipitation strengthening.
  • titanium preferentially forms TiN with nitrogen, excessively high N content will reduce the amount of TiC precipitation, which in turn will reduce the strength properties of the steel sheet. Therefore, in the present invention, the nitrogen element content is limited to ⁇ 0.006%, more preferably ⁇ 0.005%.
  • titanium can also combine with carbon and sulfide to form Ti 4 C 2 S 2 precipitation phase in steel, and also can be used as a hydrogen storage trap to improve the resistance to scale explosion of enamel.
  • the content of titanium is too high, on the one hand, it will increase the cost, on the other hand, it will be detrimental to the mechanical properties of the steel plate, so the content of titanium in the present invention is limited to 0.15 to 0.25%;
  • Niobium is the most effective micro-alloying element for grain refinement.
  • niobium exists in the form of replacement solid solution atoms in steel, because its atoms are larger than iron atoms, they tend to segregate on the dislocations, which has a strong drag on the dislocations and inhibits the recrystallization nucleation. Therefore, it has a strong preventive effect on recrystallization. In the controlled rolling process, it has an extremely significant effect on retarding austenite recrystallization and grain refinement. With the proper addition of niobium, recrystallization will not occur during the rolling process.
  • niobium can form NbC, which can prevent dislocation pinning and migration of sub-grain boundaries, thereby greatly improving the strength of steel; at the same time, it can also serve as an irreversible hydrogen storage trap and play a role in resisting scale explosion.
  • Niobium is a precious alloy element, and excessive addition will increase the cost of steel grades. In the present invention, the content of niobium element is limited to 0.02 to 0.12%.
  • Aluminum is a strong deoxidizing element. In order to ensure that the oxygen content in the steel is as low as possible, the aluminum content in the present invention is controlled at 0.006 to 0.08%;
  • Copper (Cu) and chromium (Cr) Appropriate addition of copper and chromium elements is conducive to surface deposition, which in turn improves the adhesion between it and enamel, and improves resistance to scale explosion.
  • Part of the Cr in the steel replaces iron to form alloy cementite (Fe, Cr) 3C, which improves its stability, and part of it is dissolved in ferrite, which causes solid solution strengthening and improves the strength and hardness of ferrite; but too high copper
  • the content of chromium element will not only increase the cost, but also enhance the corrosion resistance of the steel plate, but it will not be conducive to the coating performance of the steel plate during the enamel process. Therefore, the content of copper and chromium in the present invention are limited to Cu: 0.02 ⁇ 0.10 %, Cr: 0.03 to 0.10%.
  • Vanadium (V) It is a strong carbon and nitride forming element, which can separate the second phase particles of VC alone, and can also precipitate (Ti, V)C in combination with Ti, which plays an anti-scaling role as an irreversible hydrogen storage trap; , Can also play a role in strengthening precipitation. Vanadium is also a more expensive alloy element, and excessive addition will increase the cost of steel grades. In the present invention, the element content is limited to V: 0.02 to 0.10%.
  • Controlling the elements of C, Nb, Ti, and Mn to satisfy this relationship can make the steel plate still have finely dispersed second phase particles after high temperature sintering, fully exert the precipitation strengthening effect, and at the same time, use these precipitation relative grain boundaries
  • the pinning effect avoids coarsening of ferrite grains and fully exerts the effect of fine grain strengthening.
  • a proper amount of C element remains to form a sufficient proportion of pearlite structure, which is evenly distributed in the ferrite matrix to play a further strengthening role. This relationship is determined based on the test results of FIG. 1 obtained by fully studying the relationship between the chemical composition of the steel plate and the strength properties after lining. It is one of the key innovations in the composition design of the present invention.
  • the microstructure of the hot-rolled steel sheet is ferrite + pearlite, the ferrite grain diameter is 8-20 ⁇ m, the proportion of pearlite per unit area is 3-20%, and it is measured under a transmission electron microscope.
  • Precipitation phases of TiC and NbC are dispersed and distributed in the matrix of hot rolled steel sheet from 5 to 25 nm.
  • the yield strength in the hot-rolled state is 556 to 654 MPa. After two high-temperature sinterings in the temperature range of 780 to 920°C, the yield strength is 435 to 476 MPa.
  • the manufacturing method of 400MPa grade hot-rolled double-sided enamel steel after lining in the present invention includes the following steps:
  • the cast billet After the cast billet is heated at a temperature of 1150-1260°C, it is rough-rolled into an intermediate billet with a roughing temperature greater than 1000°C; then it is finish-rolled at a temperature range of 800-1050°C and the final rolling temperature is 800-900°C
  • the coiling temperature is 550 ⁇ 680°C.
  • the final rolling temperature is 830-880°C.
  • the cooling rate of the laminar cooling is controlled at 6-15°C/s.
  • the coiling temperature is 580-640°C.
  • casting can be carried out by continuous casting or die casting to ensure uniform internal composition and good surface quality of the billet.
  • die casting the cast ingot needs to be rolled into a billet by a preliminary rolling machine.
  • Hot rolling and cooling After heating the cast billet at 1150 ⁇ 1260°C, rough rolling into intermediate billet, the rough rolling temperature is greater than 1000°C, and then finish rolling in the temperature range of 800 ⁇ 1050°C, the final rolling temperature is 800 ⁇ 900°C .
  • the continuous casting billet or steel billet is heated at a temperature of 1200 to 1260°C, on the one hand, a uniform austenite structure can be obtained, on the other hand, the titanium compound can be dissolved as much as possible, which is conducive to reprecipitation and formation in the next step Fine and dispersed titanium-containing precipitates.
  • laminar cooling control technology is adopted to perform water cooling at a cooling rate of 4 to 30°C/s.
  • the cooling process uses water cooling, and titanium and niobium will be precipitated in the form of compounds, evenly dispersed in the steel matrix in a finely dispersed state.
  • the ferrite structure in the steel is refined, and too high cooling rate is not conducive to the precipitation of titanium precipitates.
  • too high a cooling rate will also lead to phase transformation, which is not conducive to obtaining a mixed structure of ferrite and pearlite. Therefore, water cooling to a coiling temperature at a cooling rate of 4 to 30°C/s and then air cooling to room temperature can improve the strength of the steel plate on the one hand and the scale resistance of the steel plate on the other hand.
  • the coiling temperature is controlled at 550 ⁇ 680 °C, which is used as the coiling temperature in this temperature range, which is beneficial to obtain precipitates of appropriate size and be evenly distributed in the steel matrix. For improving the strength of the steel plate and hydrogen storage of the steel plate Performance is very important.
  • the present invention has the following beneficial effects:
  • the present invention creatively adopts high C-Mn-Ti and low S-micro Nb alloy composition systems, and controls the relationship between the elements to satisfy the relationship:
  • the present invention adopts a high content of C element, and uses Ti and Nb alloy elements to form a large amount of TiC and NbC precipitation phases in the matrix with Ti and Nb alloy elements and C in the matrix.
  • the excess C element forms an appropriate proportion of pearlite structure in the process of controlled rolling and cooling, which plays a role in strengthening the matrix.
  • the yield strength of the steel plate after high temperature sintering can still reach more than 400MPa. It can be widely used as the substrate of structural parts with high strength requirements and high coating and lining performance requirements in some large-scale water treatment facilities, chemical facilities, environmental protection facilities and other fields.
  • Figure 1 is the relationship between the chemical composition of the steel plate obtained by the experimental study and the yield strength performance after lining.
  • FIG. 2 is the metallographic structure of the hot-rolled steel sheet of Example A1 of the present invention, which is composed of ferrite and 12.5% pearlite, and the average ferrite grain diameter is 10 ⁇ m.
  • Fig. 3 shows the morphology of the precipitated phase in the matrix structure of the hot-rolled steel sheet of Example A1 of the present invention under a transmission electron microscope, which is mainly TiC and NbC precipitated phases with a diameter of 5 to 25 nm.
  • FIG. 4 is the metallographic microstructure of the hot-rolled steel sheet of Example A1 of the present invention after two high-temperature sintering, which is composed of fine ferrite and pearlite, and the average diameter of ferrite grains is about 8 ⁇ m.
  • the weight percentages of the chemical components of the double-sided enamel steel are: C: 0.14%, Si: 0.23%, Mn: 1.68%, S: 0.016%, Al: 0.036%, N: 0.005%, Cr: 0.055%, Ti: 0.19 %, Nb: 0.046%, Cu: 0.045%, and the rest are Fe and inevitable impurity elements.
  • the molten steel with the specific gravity of the above chemical composition is subjected to continuous casting after vacuum degassing.
  • the thickness of the continuous casting billet is 250mm.
  • the resulting continuous casting billet is heated at 1230°C. After 2 hours of heat preservation, it is rolled to a thickness of 10mm after 8 passes.
  • the exit temperature of rough rolling is 1060°C
  • the finish rolling open temperature is 1040°C
  • the final rolling temperature is 850°C
  • laminar water cooling the cooling rate is 10°C/s
  • the coiling temperature is 600°C.
  • Example A1 The steel plate of Example A1 was subjected to double-sided wet enamel treatment, enamel process: bottom enamel sintering (890°C ⁇ 11min)-air cooling-enamel glaze-sintering (800°C ⁇ 10min)-air cooling. After the enameled steel plate was allowed to stand for 48 hours, it was observed that no scale explosion occurred on both sides, and the hydraulic pressure head device was tested by the top pressure deformation test to verify that the adhesion between the steel plate and the enamel was excellent. After high temperature sintering, the yield strength of the steel plate is 451MPa, the tensile strength is 565MPa, and the elongation is 35%.
  • Fig. 2 shows the metallographic structure of the steel plate of Example A1, which is composed of ferrite + 12.5% pearlite.
  • Fig. 3 shows the morphology of the precipitated phase in the microstructure of the steel plate of Example A1, and a large amount of TiC and NbC precipitated phases are dispersed and distributed.
  • Figure 4 shows the microstructure of the steel plate of Example A1 after two high-temperature sintering. It can be seen that the ferrite grains are very fine after high-temperature sintering, with an average diameter of about 8 ⁇ m.
  • the thickness of the hot-rolled finished steel sheet processed with the above-mentioned components and process parameters is between 5 and 13 mm
  • the yield strength is 556 to 654 MPa
  • the temperature is twice between 780 and 920°C.
  • the yield strength is 435 ⁇ 476MPa.
  • the enamel steel plate finally obtained was observed on the surface after 48 hours, and there was no scale explosion on both sides. After the hydraulic pressure head device was pressed and deformed, the adhesion between the steel plate and the porcelain layer was excellent, which fully met the user's requirements.

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  • Heat Treatment Of Steel (AREA)

Abstract

一种热轧钢板及其制造方法，其成分重量百分比为：C 0.13～0.20％，Si 0.15～0.50％，Mn 1.0～2.3％，P≤0.03％，S 0.01～0.03％，Al 0.006～0.08％，N≤0.006％，Cr 0.03～0.10％，Ti 0.15～0.25％，Nb 0.02～0.12％，Cu：0.02～0.10％，其余为Fe和不可避免杂质。通过优化控轧及冷却工艺，所获得的钢板具备良好的双面涂搪性能及优良的抗鳞爆性能，且经780～920℃温度区间内共两次高温搪烧处理后，钢板仍具有400MPa以上的屈服强度。适用于制作有高强度要求的大型工程构件用双面搪瓷钢，可广泛应用于万立方米及以上超大容积的污水处理罐、沼气发酵罐、淡水存储罐等搪瓷钢拼装型储罐。

Description

一种热轧钢板及其制造方法 技术领域
本发明涉及搪瓷用钢，具体涉及一种具有优异的双面涂搪性能及搪后高强度性能的热轧钢板及其制造方法，该热轧钢板具有优异的双面搪瓷性能及搪后高强度性能，经780～920℃温度区间内两次高温搪烧后屈服强度仍可达400MPa以上，主要可应用于一些超大容积的污水处理罐、沼气发酵罐、淡水存储罐等搪瓷钢拼装型储罐的制造用材。
背景技术
众所周知，高强度双面搪瓷用热轧钢板主要用于拼装罐用搪瓷钢的基板，这种搪瓷拼装罐可应用于大型水处理设施、化工设施、环保设施等领域，如城市垃圾渗液和生活污水处理、工业污水处理、淡水存储等方面的拼装罐；也可作为厌氧发酵拼装罐、搪瓷钢板沼气池、组装式搪瓷钢板粮仓拼装罐等等。拼装罐体积范围较大，从几百立方米到数万立方米均有。
拼装罐用搪瓷钢板的加工工艺主要包括：首先将钢板进行一定弧度的弯折，再经酸洗或喷丸处理清除钢板表面氧化铁皮、锈斑等；然后采用湿法底釉和烧成，底釉的烧成温度一般为840～920℃，烧成温度及保温时间根据钢板厚度进行调整，对于6mm厚的钢板，烧成时间约为10～12min；再进行一次湿法面釉和烧成，面釉的烧成温度一般为780～850℃，面釉烧成温度及保温时间根据钢板厚度进行调整，对于6mm厚的钢板，烧成时间为9～11min。
作为这类用途的钢板首先必须具有良好涂搪适应性，主要是指钢板经双面搪瓷后不出现鳞爆缺陷；同时，需要钢板在经过两次高温(780～920℃)搪烧后仍具有较高的屈服强度，以保证作为大型结构件的使用安全性能。
钢板经搪瓷后产生鳞爆缺陷主要是由氢造成的,氢主要是在酸洗(金属溶解于酸中产生氢)和搪烧(粘土中含的结晶水与金属反应生成氢)过程中进入钢板的。钢板经双面搪瓷后较单面搪瓷更容易发生鳞爆，原因在于，双面搪瓷后钢板中贮存的氢更难逸出，当搪瓷制品在空气中冷却直到 瓷釉凝固时，氢来不及逸出而在钢板中达到过饱和状态，进而形成一定压力，当压力增大到会使瓷层脱落时，便形成鳞爆缺陷。所以，除了改进搪瓷工艺外，需要改善钢板本身的贮氢性能。如果钢板贮氢能力强，氢在钢板中的扩散就慢，在相同的搪瓷工艺下进入钢板中的氢就少，并且搪瓷结束后钢板容纳氢的能力也强，这将有利于防止搪瓷制品的鳞爆。钢中的晶界、位错、空穴、夹杂物和析出相等都是良好的贮氢陷阱，因此对于搪瓷钢，需要针对不同的搪瓷用途，调整钢的成分和生产工艺，以保证钢中有足够的贮氢陷阱，实现良好的抗鳞爆性能。
对于这种用途钢板经搪烧后屈服强度的要求，主要可参考拼装罐行业内对罐体结构安全的强度要求，即当静拉伸应力起控制作用的情况下，罐体壳体厚度由罐子的包含物所引起的应力计算，可由以下公式得出：
Figure PCTCN2019121964-appb-000001
公式中，t代表拼装罐壳体钢板的计算厚度(mm)；H代表液体从顶部最高液位到壳体某层钢板底部的设计高度(mm)；D代表罐体的直径(mm)；S代表螺栓的列到列之间的垂直距离(mm)；ρ代表储液密度(kg/m 3)；R el代表搪瓷钢板的屈服强度(kg/m 3)；d代表螺栓直径(mm)；γ代表分项系数。
根据这一计算公式可知，当拼装罐壳体钢板厚度固定的情况下，钢板屈服强度与罐体内溶液液位高度、罐体直径呈正比关系，即钢板屈服强度越高，可设计罐体直径越大、越高。而当其它条件一定的情况下，钢板的屈服强度与钢板厚度呈反比关系，即钢板屈服强度提高时，其厚度可以适当减薄，从而降低制造成本、节约资源。考虑到拼装罐在拼装施工时的便利性及拼装时的设计要求，在拼装罐行业内，钢板最大厚度一般控制在13mm及以下。
目前现有的关于热轧双面搪瓷用钢的专利文献报道，其成分上普遍采用极低的S、N元素，并控制Ti与C元素比例，形成细小弥散的TiC析出相作为贮氢陷阱，实现双面搪瓷后钢板的抗鳞爆性能。但这类钢板经高温(780～920℃)搪烧后，位错密度显著下降，晶粒明显粗化，同时TiC析出相随着搪烧温度的升高及保温时间的延长会发生聚集长大及溶解、二次析 出再长大等一系列变化，也将导致搪烧后屈服强度大幅下降，通常仅能达到280MPa以上，无法满足大容积拼装罐的结构安全需要。如中国专利CN1966753A、CN100453678C、CN102312167A等。
发明内容
本发明的目的在于提供一种具有优异的双面涂搪性能及搪后高强度性能的热轧钢板及其制造方法，该钢板经双面搪瓷后不发生鳞爆缺陷且与瓷层密着结合良好；钢板经780～920℃温度区间内两次高温搪烧后，屈服强度仍可达400MPa以上；可满足一些超大型水处理设施、化工设施、环保设施等领域的工程结构件对搪瓷用钢的需求。
为达到上述目的，本发明的技术方案是：
本发明热轧钢板采用高C-Mn-Ti及低S-微Nb合金的成分体系，采用严格的热轧控轧工艺，获得细小的铁素体+珠光体组织结构，充分发挥细晶强化作用及珠光体组织强化作用。同时，在基体中形成的大量的5～25nm的TiC、NbC析出相，充分发挥析出强化作用。另一方面，利用基体中形成的TiC、NbC、Ti 4C 2S 2等第二相粒子作为贮氢陷阱，使钢板获得优异的抗鳞爆性能。
具体的，本发明的一种具有优异的双面涂搪性能及搪后高强度性能的热轧钢板，其成分重量百分比为：C：0.13～0.20％，Si：0.15～0.50％，Mn：1.0～2.3％，P≤0.03％，S：0.01～0.03％，Al：0.006～0.08％，N≤0.006％，Cr：0.03～0.10％，Ti：0.15～0.25％，Nb：0.02～0.12％，Cu：0.02～0.10％，其余为Fe和不可避免的杂质；且同时满足如下关系：
1.20≤3.125(％S)+6.25(％Ti)+5.65(％Nb)≤1.75；
(％C)*[(％Nb)*(％Ti)+(％Mn)]＞0.12。
另外需要说明的是，上述各公式中的％S、％Ti、％Nb、％C和％Mn分别表示钢板中相应元素的重量百分比，公式中％S、％Ti、％Nb、％C和％Mn代入的数值是百分号前的数值，例如实施例1中S的含量为0.016％，则代入的数值应当为0.016，而不是0.00016，其他元素的代入情况以此类推，不再赘述。
在本发明双面搪瓷用钢的成分设计中：
碳(C)：一方面，碳与钛生成化合物TiC，与铌生成化合物NbC，与钛和硫生成化合物Ti 4C 2S 2，这些第二相粒子弥散地分布在钢板微观组织中，可以作为不可逆的贮氢陷阱，避免搪瓷鳞爆缺陷的发生。另一方面，当第二相粒子充分析出后，钢中剩余的自由碳达到一定条件时形成珠光体组织，起到强化组织的作用。但当碳含量过高时，形成的珠光体比例过高，会导致搪瓷烧成过程中产生大量的CO气体，造成搪瓷层气泡结构不良，以及针孔等缺陷，严重影响涂搪质量，因此本发明中碳的含量限定为0.13～0.20％；
硅(Si)：硅元素在钢中起到固溶强化的作用，硅还可以提高抗高温变形能力，提高钢板在高温搪瓷烧成过程中的抗软化能力。但当硅含量过高时，钢的塑性变差，还可能影响钢板与瓷釉间的密着性能，因此本发明中硅含量限定为0.15～0.50％；
锰(Mn)：锰元素可以提高钢板强度，是保证钢板经两次高温搪烧后仍具有高强度的重要元素。锰在钢中还和铝、硅元素共同起到脱氧作用，锰的脱氧作用可促进钛元素的有效作用。锰元素具有扩大奥氏体相区，降低Ac3点温度的作用，这对钢板的搪瓷性能不利，因为奥氏体相相对于铁素体相溶氢能力更强，冷却后更易导致鳞爆缺陷发生；另外，锰元素过高会严重降低钢的塑性，所以不宜过量添加。本发明锰的含量控制在1.0～2.3％。
磷(P)：磷是严重损害钢的韧性和塑性的元素，但也是不可避免的杂质元素，本发明中磷控制在≤0.03％
硫(S)：在不加钛的钢中，硫通常与锰化合形成MnS，这是一种塑性优良的夹杂物，它会随着钢坯的变形而延展，最终严重损害钢板的横向塑性和韧性，因此在不加钛的钢中硫含量应尽量低。但是在加钛钢中，硫优先与钛元素形成化合物Ti 4C 2S 2，可以起到一定的贮氢作用，提高钢板抗鳞爆性能。因此本发明中硫元素限定为0.01～0.03％；
钛(Ti)和氮(N)：钛是形成强碳氮化物的元素，有利于固定钢中的氮，形成的氮化钛能使钢坯加热时奥氏体晶粒不过分长大，细化原始奥氏体晶粒。
钛在钢板中可以与碳化合生成纳米级的TiC及微米级的TiN第二相粒 子，二者均可作为贮氢陷阱，提高钢板的抗鳞爆性能。同时，纳米级的TiC粒子是析出强化的主要贡献者，而微米级的TiN粒子起不到析出强化作用。因为钛优先与氮生成TiN，所以过高的N含量会降低TiC的析出量，进而会降低钢板的强度性能，因此本发明中氮元素含量限定为≤0.006％，更优选为≤0.005％。
此外，钛在钢中还可以与碳、硫化合生成Ti 4C 2S 2析出相，也可以作为贮氢陷阱提高搪瓷抗鳞爆性能。但钛含量过高一方面会增加成本，另一方面对钢板的力学性能不利，因此本发明中钛元素含量限定为0.15～0.25％；
铌(Nb)：铌是最有效的细化晶粒的微合金化元素。铌在钢中以置换固溶原子的形式存在时，因其原子比铁原子尺寸大，易在位错上偏聚，对位错攀移产生强烈的拖拽作用，使再结晶形核受到抑制，因而对再结晶具有强烈的阻止作用。在控轧过程中，对延缓奥氏体再结晶和细化晶粒的作用极其显著，适量的添加铌元素，在轧制过程中不会发生再结晶，这样得到的伸长的奥氏体晶粒由于形核的晶界及亚晶界面积增加，就能相变成细小的晶粒，达到细晶强化的作用。另外，铌可以形成NbC，对位错的钉扎及对亚晶界的迁移具有阻止作用，从而大大提高钢的强度；同时其还可作为不可逆的贮氢陷阱，起到抗鳞爆的作用。铌是贵重合金元素，过量添加会增加钢种成本，本发明中铌元素含量限定为0.02～0.12％。
铝(Al)：铝为强脱氧元素，为了保证钢中的氧含量尽量的低，本发明中铝含量控制在0.006～0.08％；
铜(Cu)和铬(Cr)：适量的铜和铬元素添加有利于表面沉积，进而提高其与瓷釉间的密着性能，改善抗鳞爆性能。钢中的Cr一部分置换铁形成合金渗碳体(Fe、Cr)3C，提高其稳定性，一部分溶入铁素体，产生固溶强化，提高铁素体的强度和硬度；但过高的铜、铬元素含量不但会增加成本，而且会使钢板耐蚀性能增强，反而会不利于钢板在搪瓷过程中涂搪密着性能，因此，本发明中铜、铬元素含量分别限定为Cu：0.02～0.10％，Cr：0.03～0.10％。
钒(V)：是强碳、氮化物形成元素，可以单独析出VC第二相粒子，还可以与Ti复合析出(Ti、V)C，作为不可逆贮氢陷阱起到抗鳞爆的作 用；同时，也能起到一定的析出强化作用。钒也是较贵重的合金元素，过量添加会增加钢种成本。本发明中元素含量限定为V：0.02～0.10％。
且上述添加元素还需同时满足如下关系：
1.20≤3.125(％S)+6.25(％Ti)+5.65(％Nb)≤1.75，满足该关系式，可以保证钢板组织中形成的TiC、NbC、Ti 4C 2S 2等析出相具有足够高的重量份数(或体积份数)，同时，在本发明提出的控制轧制及冷却工艺下，可以在单位体积内形成足够的析出相数量(Nv)。它们作为不可逆的贮氢陷阱，在钢板搪烧后冷却过程中，阻碍氢向搪瓷层界面扩散集聚，从而避免鳞爆缺陷的发生。所以，满足该关系式是保证钢板具有双面搪瓷抗鳞爆性能的重要条件。此外，TiC、NbC析出相还起到析出强化作用，是保证钢板具有高强度的重要条件。其为本发明成分设计的关键创新之一；
(％C)*[(％Nb)*(％Ti)+(％Mn)]＞0.12，该关系式是保证钢板经两次高温搪烧后仍具有400MPa以上屈服强度水平的重要条件。通常，高温搪烧过程会导致钢板中析出相长大、晶粒粗化，析出强化及细晶强化作用减弱，进而导致钢板屈服强度降低。控制C、Nb、Ti、Mn元素满足此关系式，一方面，可以使钢板经高温搪烧后仍具有细小弥散分布的第二相颗粒，充分发挥析出强化作用，同时，利用这些析出相对晶界的钉扎作用避免铁素体晶粒粗化，充分发挥细晶强化的作用。另一方面，可以在Nb、Ti合金元素的碳化物充分析出后，仍剩余适量的C元素来形成足够比例的珠光体组织，均匀分布于铁素体基体中起到进一步的强化作用。该关系式是基于充分研究钢板的化学成分与搪后强度性能的关系获得的图1的试验结果确定的。其为本发明成分设计的关键创新之一。
在金相显微镜下，热轧钢板的微观基体组织为铁素体+珠光体，铁素体晶粒直径为8～20μm，单位面积珠光体比例为3～20％，且在透射电镜下测量得到热轧钢板基体中弥散分布着5～25nm的TiC、NbC析出相。
热轧钢板在其厚度为5～13mm的情况下，热轧态屈服强度为556～654MPa，经780～920℃温度区间内两次高温搪烧后，屈服强度为435～476MPa。
本发明所述的搪后400MPa级热轧双面搪瓷用钢的制造方法，包括如下步骤：
1)冶炼、铸造
按上述成分，铁水预处理、转炉冶炼、RH真空脱气处理及连铸/模铸；
2)加热、轧制
铸坯于1150～1260℃温度加热后，粗轧成中间坯，粗轧温度大于1000℃；然后在800～1050℃温度区间精轧，精轧终轧温度为800～900℃；
3)冷却，采用层流冷却，冷却速度控制在4～30℃/s；
4)卷取，卷取温度为550～680℃。
优选的，所述终轧温度为830～880℃。
优选的，所述层流冷却的冷却速度控制在6～15℃/s。
优选的，所述卷取温度为580～640℃。
在本发明双面搪瓷用钢的制造方法中：
1)冶炼和真空脱气：确保钢液的具体成分要求，除去钢中氢气等有害气体，并加入锰、钛、铌等必要的合金元素，通过锰元素来提高钢板的强度，通过钛、铌元素来细化原始奥氏体晶粒度，同时进行合金元素的调整。
2)铸造：铸造可以采用连铸或模铸的方式，保证铸坯内部成分均匀和表面质量良好，如采用模铸的方式，模铸的钢锭还需经初轧机轧制成钢坯。
3)热轧和冷却：将铸坯于1150～1260℃加热后，粗轧成中间坯，粗轧温度大于1000℃，然后在800～1050℃温度区间精轧，终轧温度为800～900℃。连铸坯或钢坯在1200～1260℃温度下加热，一方面可以获得均匀的奥氏体组织，另一方面可以使钛的化合物尽可能充分溶解，有利于在接下来的工序中重新析出并形成细小弥散的含钛析出相。热轧后采用层流冷却控制技术，以4～30℃/s的冷却速度进行水冷。冷却过程采用水冷，钛、铌会以化合物的形式析出，呈细小弥散状态均匀分部在钢基体中。同时，通过控制冷却，钢中的铁素体组织得到细化，而冷速过高不利于钛的析出物充分析出。另外，冷速过高还会导致相变发生，不利于获得铁素体与珠光体混合组织。因此，通过4～30℃/s的冷却速度水冷至卷取温度，然后 空冷至室温，一方面可以提高钢板的强度，另一方面可以提高钢板的抗鳞爆性能。
4)卷取：卷取温度控制在550～680℃，在这一温度区间作为卷取温度，有利于获得适当尺寸的析出相并均匀分布于钢基体中，对于提高钢板强度，提高钢板贮氢性能都非常重要。
与现有技术相比，本发明具有下列有益效果：
(1)本发明相比于以往的搪瓷用钢创造性地采用了高C-Mn-Ti，及低S-微Nb合金成分体系，并控制各元素间满足关系式：
1.20≤3.125(％S)+6.25(％Ti)+5.65(％Nb)≤1.75；
(％C)*[(％Nb)*(％Ti)+(％Mn)]＞0.12；
结合适当的控轧及层流冷却控制工艺，最终获得细小的铁素体+珠光体基体组织，及弥散分布于基体组织中的TiC、NbC、Ti 4C 2S 2等析出相，从而使钢板具备了优异的双面搪瓷抗鳞爆性能；
(2)本发明采用较高的C元素含量，利用Ti、Nb合金元素与C元素化合并在基体中形成大量的5～25nm的TiC、NbC析出相。同时，过剩的C元素在控轧控冷过程中形成适当比例的珠光体组织，起到强化基体作用。在经过780～920℃高温搪烧后，一方面，因细小弥散的TiC、NbC析出相钉扎晶界的作用，使搪烧后钢板的铁素体晶粒组织仍十分细小。在细晶强化、珠光体组织强化及析出强化的共同作用下，使得高温搪烧后钢板的屈服强度仍可达400MPa以上。可广泛应用作一些大型水处理设施、化工设施、环保设施等领域的拼装罐等具有高强度要求、高涂搪性能要求的结构件的基板。
附图说明
图1是试验研究获得的钢板的化学成分与搪后屈服强度性能的关系。
图2是本发明实施例A1热轧钢板的金相组织，由铁素体和12.5％的珠光体组成，铁素体平均晶粒直径为10μm。
图3是在透射电子显微镜下观察到本发明实施例A1热轧钢板基体组织中析出相的形貌，主要为直径5～25nm的TiC、NbC析出相。
图4是本发明实施例A1热轧钢板经两次高温搪烧后的金相显微组织， 由细小的铁素体和珠光体组成，铁素体晶粒平均直径约8μm。
具体实施方式
以下通过实施例和附图对本发明作进一步说明。
实施例A1
双面搪瓷用钢的化学成分重量百分比为：C：0.14％、Si：0.23％、Mn：1.68％，S：0.016％，Al：0.036％，N：0.005％，Cr：0.055％，Ti：0.19％，Nb：0.046％，Cu：0.045％，其余为Fe和不可避免杂质元素。
具有上述化学成分比重的冶炼完成的钢水经真空脱气处理后进行连铸，连铸坯厚度为250mm，所得连铸坯于1230℃加热，保温2小时后经8道次轧制成厚度为10mm的钢板，粗轧出口温度1060℃，精轧开轧温度1040℃，终轧温度850℃，之后层流水冷，冷却速度10℃/s，卷取温度600℃。
采用上述成分和工艺参数进行冶金加工，热轧态钢板的屈服强度为580MPa，抗拉强度为640MPa，延伸率30％。180°冷弯试验(d＝1.5a)，钢板完好无裂纹。
将实施例A1钢板进行双面湿法搪瓷处理，搪瓷工艺：搪底釉—烧结(890℃×11min)—空冷—搪面釉—烧结(800℃×10min)—空冷。搪瓷后钢板静置48小时后观察双面均没有发生鳞爆现象，且经液压压头装置顶压变形实验验证钢板与瓷釉间密着性能优良。高温搪烧后钢板屈服强451MPa，抗拉强度565MPa，延伸率35％。
图2为实施例A1钢板的金相组织，由铁素体+12.5％珠光体组成。
图3为实施例A1钢板微观组织中的析出相形貌，弥散分布着大量的TiC、NbC析出相。
图4为两次高温搪烧后实施例A1钢板的显微组织，可见，高温搪烧后铁素体晶粒十分细小，平均直径约8μm。
其它实施例A2～A7及对比例B1～B4的具体化学成分(wt％)参见表1，主要轧制工艺参数参见表2，搪瓷前后力学性能及涂搪性能结果参见表3，屈服强度根据国标GB/T 228.1-2010测定。
从上述实施例可以看出，采用上述成分和工艺参数进行加工的成品钢 板，热轧成品的厚度范围在5～13mm之间，屈服强度为556～654MPa，经780～920℃温度区间内两次高温搪烧后，屈服强度为435～476MPa。最终获得的搪瓷钢板经48小时以后观察表面，双面均无鳞爆现象发生；经液压压头装置顶压变形实验，钢板与瓷层之间密着性能优良，完全满足用户使用要求。而从对比例B1～B4来看，当M*<1.20时，钢板经双面搪瓷后出现了鳞爆问题，当N*<0.12时，经高温搪烧后钢板屈服强度达不到400MPa以上水平。
表1.实施例A2～A7及对比例B1～B4的化学成分
(wt.％，余量为Fe及其他不可避免的杂质)
Figure PCTCN2019121964-appb-000002
注：M*＝3.125(％S)+6.25(％Ti)+5.65(％Nb)；N*＝(％C)*[(％Nb)*(％Ti)+(％Mn)]
Figure PCTCN2019121964-appb-000003
Figure PCTCN2019121964-appb-000004
Figure PCTCN2019121964-appb-000005

Claims (9)

  1. 一种热轧钢板，其特征在于，其成分重量百分比为：C：0.13～0.20％，Si：0.15～0.50％，Mn：1.0～2.3％，P≤0.03％，S：0.01～0.03％，Al：0.006～0.08％，N≤0.006％，Cr：0.03～0.10％，Ti：0.15～0.25％，Nb：0.02～0.12％，Cu：0.02～0.10％，其余为Fe和不可避免的杂质；且同时满足如下关系：
    1.20≤3.125(％S)+6.25(％Ti)+5.65(％Nb)≤1.75；
    (％C)*[(％Nb)*(％Ti)+(％Mn)]＞0.12。
  2. 如权利要求1所述的热轧钢板，其特征在于，还包含V：0.01～0.10％，以重量百分比计。
  3. 如权利要求1或2所述的热轧钢板，其特征在于，所述热轧钢板的微观基体组织为铁素体+珠光体，铁素体晶粒直径为8～20μm，单位面积珠光体比例为3～20％，且基体中弥散分布着5～25nm的TiC、NbC析出相。
  4. 如权利要求1或2或3所述的热轧钢板，其特征在于，所述热轧钢板，在其厚度为5～13mm的情况下，热轧态屈服强度为556～654MPa，经780～920℃温度区间内两次高温搪烧后，屈服强度为435～476MPa。
  5. 如权利要求1～4中任何一项所述的热轧钢板的制造方法，其特征在于，其包括如下步骤：
    1)冶炼、铸造
    按权利要求1或2所述成分，铁水预处理、转炉冶炼、RH真空脱气处理及连铸/模铸；
    2)加热、轧制
    铸坯于1150～1260℃加热后，粗轧成中间坯，粗轧温度大于1000℃；
    在800～1050℃温度区间精轧，终轧温度为800～900℃；
    3)冷却，采用层流冷却，冷却速度控制在4～30℃/s；
    4)卷取，卷取温度为550～680℃。
  6. 如权利要求5所述的热轧钢板的制造方法，其特征在于，步骤2)精轧终轧温度为830～880℃。
  7. 如权利要求5所述的热轧钢板的制造方法，其特征在于，所述层流冷 却的冷却速度控制在6～15℃/s。
  8. 如权利要求5所述的热轧钢板的制造方法，其特征在于，所述卷取温度为580～640℃。
  9. 如权利要求5～8中任何一项所述的热轧钢板的制造方法，其特征在于，所制得的热轧钢板，在其厚度为5～13mm的情况下，热轧态屈服强度为556～654MPa，经780～920℃温度区间内两次高温搪烧后，屈服强度为435～476MPa。
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