CN114525392B - Preparation method of titanium-carbon bistable carbon structural steel cold-rolled sheet - Google Patents

Preparation method of titanium-carbon bistable carbon structural steel cold-rolled sheet Download PDF

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CN114525392B
CN114525392B CN202210162830.9A CN202210162830A CN114525392B CN 114525392 B CN114525392 B CN 114525392B CN 202210162830 A CN202210162830 A CN 202210162830A CN 114525392 B CN114525392 B CN 114525392B
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CN114525392A (en
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吾塔
向华
冯跃平
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Xinjiang Bayi Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • 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
    • C22C38/02—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C21D2211/003—Cementite
    • 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

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  • Heat Treatment Of Sheet Steel (AREA)

Abstract

The invention discloses a preparation method of a titanium-carbon bistable carbon structural steel cold-rolled sheet, which takes titanium carbon and nitride as nucleation points, reduces center segregation of a sheet blank through continuous casting with low superheat degree and constant pulling speed, eliminates the sheet blank through hot-charging rolling, reduces the grade of a hot-rolled steel strip (less than or equal to 0.5 grade), and thoroughly eliminates the center segregation of the cold-rolled sheet through cold-rolling annealing. The method uses trace titanium, carbon and nitrogen to form a small amount of titanium carbide precipitation strengthening, and titanium nitride particles are further precipitation strengthened after the cooling process and coiling process after hot rolling, so that the strength of the material is improved, and the cold-rolled sheet of high-strength and high-toughness high-quality carbon structural steel is produced through cold rolling and annealing to eliminate stress. The high-strength high-quality carbon structure cold-rolled sheet produced by the method has the tensile strength of 445 MPa-480 MPa; the elongation after break is 29-36%. The steel structure is spherical pearlite, the grain size is 9-9.5 grade, the metallographic structure of the finished cold-rolled sheet is detected in batches, and the banded structure is completely eliminated.

Description

Preparation method of titanium-carbon bistable carbon structural steel cold-rolled sheet
Technical Field
The invention relates to a preparation method of a titanium-carbon bistable carbon structural steel cold-rolled sheet, belonging to the fields of steel smelting and material processing.
Background
The high-toughness deep drawing cold-rolled sheet is generally rolled by adopting low-carbon and low-silicon components, such as automobile panels, household appliance panels and the like, wherein [ C ] is less than or equal to 0.002wt% and [ Si ] is less than or equal to 0.03wt%. The high-strength 25 # high-quality carbon structural steel cold-rolled sheet can be used as a high-quality bearing bush shell material, but the stamping forming performance is inferior to that of ultra-low carbon steel. The main problem of the material is that cracking occurs in the forming process, the application field of the material is limited, and the difficult problem is brought to the use of the material. Document retrieval: (1) The 2 nd period of 2019 of Xinjiang iron and steel discloses that the development of the high-quality carbon structural steel cold-rolled steel plate for the steel toe is made of the following components: c:0.25 to 28 weight percent, si:0.17 to 27wt%, mn:0.50 to 0.60 weight percent, P: less than or equal to 0.015wt percent, S: less than or equal to 0.0080wt percent, al:0.015 to 0.030wt%, ca:0.0008 to 0.0030wt%. The cold-rolled steel strip with the thickness of 1.8 mm to 2.5mm is produced, the tensile strength is 351 to 497MPa, the elongation after breaking is 24.5 to 31 percent, the steel structure is ferrite and spherical pearlite, and a 1.5-level strip-shaped structure exists. (2) In 2002, the "production of 25-steel cold-rolled spheroidized annealed steel strip" was published in 2 nd stage of steel rolling ", and spheroidized annealing test was performed by using a box-type electric furnace. The preheating treatment of the steel is added before austenitizing heating, and the flaky pearlite is cut off at the preheating temperature, so that more fine carbide particles are formed. The preheating temperature is close to the point A1 (720 ℃), and the temperature of the steel belt is uniformly reached to the preheating temperature through long preheating time. (3) The patent application number ZL 201810723750.X discloses a production method suitable for directly heating high-quality carbon structural steel slabs, the method adopts a dynamic soft reduction device to eliminate center segregation of 45 steel slabs, and the slabs realize direct hot-charging rolling.
Disclosure of Invention
The invention aims to provide a preparation method of a titanium-carbon bistable carbon structural steel cold-rolled sheet, which can eliminate the strip structure of materials caused by carbon and manganese reinforcement, further influence the cold stamping forming performance of steel, has simple production and strong applicability and operability, ensures the strength of the steel, and simultaneously has excellent cold deep stamping performance.
A method for preparing a titanium-carbon bistable carbon structural steel cold-rolled sheet,
1) The cold-rolled sheet steel comprises the following components in percentage by mass: [C] the method comprises the following steps 0.27 to 0.29 percent wt percent, ti: 0.010-0.020 wt%, [ Mn ]:0.55 to 0.65 weight percent; si:0.18 to 0.25 weight percent, P: less than or equal to 0.015wt percent, S: less than or equal to 0.004wt percent, al:0.020 to 0.040 weight percent, N:0.0030 to 0.0045wt%, cu: less than or equal to 0.02wt percent, cr: less than or equal to 0.02 weight percent, ni: less than or equal to 0.015wt percent, and the balance of iron and unavoidable impurities;
2) The production process is as follows: molten iron desulfurization pretreatment, top-bottom combined blown converter smelting, LF refining, slab continuous casting, strip steel hot continuous rolling, strip steel pickling, strip steel cold continuous rolling, strip steel heat treatment, and the thickness of the produced cold rolled steel strip is 0.80-2.5 mm;
(1) Carrying out deep desulfurization treatment on molten iron, adopting a KR method to carry out desulfurization treatment, adding 5kg/t of a desulfurizing agent, wherein the main composition of the desulfurizing agent is 80% of active lime and 20% of fluorite, adding the desulfurizing agent, stirring for 15min, and then carrying out slag tapping on molten iron with [ S ] less than or equal to 0.002% after the desulfurization treatment;
(2) Smelting in a converter, wherein [ S ] in scrap steel is less than or equal to 0.015wt%, [ Cu ] is less than or equal to 0.05wt%, [ Cr ] is less than or equal to 0.05wt%, the [ Ni ] is less than or equal to 0.05wt%, the content of [ C ] in the converter is 0.08-0.10 wt%, the content of [ P ] is not more than 0.010wt%, the temperature of molten steel tapped from the converter is controlled to 1630-1650 ℃, the tapping process adopts deoxidization alloying of silicon-manganese alloy and aluminum-iron, aluminum is added into ton steel to semi-deoxidize the molten steel, the [ S ] in the steel ladle is less than or equal to 0.008wt%, the [ N ] is less than or equal to 0.0025wt%, slag is tapped from the converter, and the amount of oxidized slag in the steel ladle is not more than 80kg;
(3) The LF refining uses ferrosilicon and calcium carbide deoxidization to carry out diffusion deoxidization, the calcium carbide addition amount is 1.5 kg/t, the ferrosilicon addition amount is 0.8-1.0 kg/t, the initial temperature of LF refining is more than 1530 ℃, the power transmission time of LF refining of each furnace steel is not more than 20min, the total use time of LF refining treatment is controlled between 40 and 42min, the nitrogen addition amount of molten steel in the LF refining process is less than 0.0010wt%, the molten steel is stirred by argon bottom blowing, and the flow is 15-20 NL/min; molten steel after LF treatment is fed into a silicon-calcium wire for treatment, and molten steel nitrogen content [ N ] after LF refining treatment is finished]≤0.0035wt%、[S]≤0.0040wt%，[Ca]The content is controlled to be 0.0015 to 0.0035 weight percent, other elements meet the control requirement of molten steel of a smelting finished product, and the LF refining final slag comprises the following components: caO content is 50-53 wt%, siO 2 The content of FeO is about 12 to 15 weight percent, the content of Al is less than or equal to 1.0 weight percent 2 O 3 28 to 32 weight percent of MgO, 8 weight percent of CaF 2 The content is not more than 5wt%, and the later stage of LF treatment prohibits precipitation deoxidation by aluminum, and aluminum is usedCarrying out submerged arc refining on a diffusion deoxidizer or a top slag modifier, an accelerator and a foaming agent, adding ferrotitanium for alloying at the end of LF refining, wherein the recovery rate of titanium is required to be more than 70%, and preventing the generation of oxide inclusions and nitride inclusions of titanium;
(4) Continuously casting a slab, wherein the thickness of the slab is 250mm, the width of the slab is 1250mm mm or 1500mm, and the length is 9.8m; the steel feeding temperature at the LF refining end point is controlled according to the continuous casting superheat degree of 20 ℃, the baking temperature of an empty ladle is more than 1200 ℃, the baking time is more than 2.5h, the temperature of the baked ladle is more than 800 ℃, the number of turnover ladles is not more than 4, a high-alkalinity covering agent is added into a tundish to heat the molten steel, and the superheat degree of the continuous casting molten steel is 15+/-5 ℃. For example, the width of the slab is 1250mm, the continuous casting slab drawing speed is 1.1m/min, and the specification of the width of the slab is set. The continuous casting process is put into a slab pressing device, the rolling reduction of the slab is 5-6 mm, the center segregation level of the low power of the slab is less than or equal to level 1 (Mannesmann standard), and the slab is hot-fed and hot-packed for rolling after being cut;
(5) Hot charging of the slab at 680-740 ℃, extracting of the slab heating furnace at 1200 ℃ +/-15 ℃, water spraying and descaling of the upper surface and the lower surface of the discharged slab by adopting a high-pressure water column with the pressure of 20MPa, and 7-pass rough rolling under the conditions that the included angle between the sprayed water column and the surface of the slab is 15 degrees, the rough rolling start temperature is 1160-1190 ℃ and the rolling speed is 3.0-4.5 m/s, wherein the thickness of a rough rolling intermediate steel plate is 40-43 mm; the final rolling temperature is 880+/-10 ℃, the hot rolled steel strip after finish rolling is subjected to structure transformation through weak cooling of the laminar flow front section, the finish rolled steel strip after laminar cooling is coiled in a coiling machine, the coiling temperature is 675+/-10 ℃, the steel coil is naturally cooled to room temperature, the metallographic structure of the steel plate is ferrite and pearlite, the grain size is 8.5, and the maximum band structure of the steel is 0.5;
(6) The method comprises the steps of pickling, cold continuous rolling and heat treatment, wherein the hot rolled coil of the incoming material is pickled, then cold continuous rolling is carried out, the cold rolling compression ratio is 50-55wt%, ferrite of the hot rolled coil of the incoming material is elongated and plastically deformed along the rolling direction through the cold continuous rolling, high-density dislocation is accumulated in the ferrite, bending and crushing of partial cementite sheets occur, the spacing between the pearlite sheets is reduced, the cementite sheets are increased through deformation instability in the cold rolling process, conditions are provided for the evolution of cementite in the annealing process, the thickness of the incoming material is 3.5mm, the cold rolled coil is rolled into a cold rolled plate with the thickness of 1.6mm, then the cold rolled coil is subjected to bright annealing, the annealing temperature is 645+/-5 ℃, the heating time is 9.5 hours, the heat preservation time is 15 hours, and the cover waiting time is 55 minutes.
The solution of the strip structure of the finished cold-rolled sheet steel adopts a carbon and titanium bistable component design method, titanium carbon and titanium nitride are used as nucleation points, the central segregation of a plate blank is reduced through continuous casting with low superheat degree and constant drawing speed, the plate blank is eliminated through hot-charging rolling, the grade of a hot-rolled steel strip is reduced (less than or equal to 0.5 grade), and the central segregation of the cold-rolled sheet is thoroughly eliminated through cold-rolling annealing. The method uses trace titanium, carbon and nitrogen to form a small amount of titanium carbide precipitation strengthening, and titanium nitride particles are further precipitation strengthened after the cooling process and coiling process after hot rolling, so that the strength of the material is improved, and the cold-rolled sheet of high-strength and high-toughness high-quality carbon structural steel is produced through cold rolling and annealing to eliminate stress. The high-strength high-quality carbon structure cold-rolled sheet produced by the method has the tensile strength of 445 MPa-480 MPa; the elongation after break is 29-36%. The steel structure is spherical pearlite, the grain size is 9-9.5 grade, the metallographic structure of the finished cold-rolled sheet is detected in batches, and the banded structure is completely eliminated. The composition and the corresponding properties of the steel are shown in Table 1.
Remarks: the tensile properties test specimen gauge length was 50mm.
The high-strength high-quality carbon structural steel cold-rolled steel produced by the method meets the requirements of users for various performance users, the thickness of the steel plate is 0.8-2.0 mm, the thickness is mainly 1.6mm, the difficult problem of poor stamping forming performance caused by the strip-shaped structure of the steel plate material is completely solved, and batch supply is realized.
Description of the embodiments
A method for preparing a titanium-carbon bistable carbon structural steel cold-rolled sheet,
1) The cold-rolled sheet steel comprises the following components in percentage by mass: [C] the method comprises the following steps 0.27 to 0.29 percent wt percent, ti: 0.010-0.020 wt%, [ Mn ]:0.55 to 0.65 weight percent; si:0.18 to 0.25 weight percent, P: less than or equal to 0.015wt percent, S: less than or equal to 0.004wt percent, al:0.020 to 0.040 weight percent, N:0.0030 to 0.0045wt%, cu: less than or equal to 0.02wt percent, cr: less than or equal to 0.02 weight percent, ni: less than or equal to 0.015wt percent, and the balance of iron and unavoidable impurities;
2) The production process is as follows: molten iron desulfurization pretreatment, top-bottom combined blown converter smelting, LF refining, slab continuous casting, strip steel hot continuous rolling, strip steel pickling, strip steel cold continuous rolling, strip steel heat treatment, and the thickness of the produced cold-rolled steel strip is 0.80-2.5 mm of cold-rolled steel coil transverse cutting plate;
(1) Carrying out deep desulfurization treatment on molten iron, adopting a KR method to carry out desulfurization treatment, adding 5kg/t of a desulfurizing agent, wherein the main composition of the desulfurizing agent is 80wt% of active lime and 20wt% of fluorite, adding the desulfurizing agent, stirring for 15min, and then removing slag from the top of a molten iron tank after the desulfurizing treatment;
(2) Smelting in a converter, wherein [ S ] in scrap steel is less than or equal to 0.015wt%, [ Cu ] is less than or equal to 0.05wt%, [ Cr ] is less than or equal to 0.05wt%, the [ Ni ] is less than or equal to 0.05wt%, the content of [ C ] in the converter is 0.08-0.10 wt%, the content of [ P ] is not more than 0.010wt%, the temperature of molten steel tapped from the converter is controlled to 1630-1650 ℃, the tapping process adopts deoxidization alloying of silicon-manganese alloy and aluminum-iron, aluminum is added into ton steel to semi-deoxidize the molten steel, the [ S ] in the steel ladle is less than or equal to 0.008wt%, the [ N ] is less than or equal to 0.0025wt%, slag is tapped from the converter, and the amount of oxidized slag in the steel ladle is not more than 80kg;
(3) The LF refining uses ferrosilicon and calcium carbide deoxidization to carry out diffusion deoxidization, the calcium carbide addition amount is 1.5 kg/t, the ferrosilicon addition amount is 0.8-1.0 kg/t, the initial temperature of LF refining is more than 1530 ℃, the power transmission time of LF refining of each furnace steel is not more than 20min, the total use time of LF refining treatment is controlled between 40 and 42min, the nitrogen addition amount of molten steel in the LF refining process is less than 0.0010%, and the flow rate of argon bottom blowing stirring molten steel is 15-20 NL/min; molten steel after LF treatment is fed into a silicon-calcium wire for treatment, and molten steel nitrogen content [ N ] after LF refining treatment is finished]≤0.0035wt%、[S]≤0.0040wt%，[Ca]The content is controlled to be 0.0015 to 0.0035 weight percent, other elements meet the control requirement of molten steel of a smelting finished product, and the LF refining final slag comprises the following components: caO content is 50-53 wt%, siO 2 The content of FeO is about 12 to 15 weight percent, the content of Al is less than or equal to 1.0 weight percent 2 O 3 28 to 32 weight percent of MgO, 8 weight percent of CaF 2 The content is not more than 5wt%, and the later stage of LF treatment is forbiddenAluminum is used for precipitation deoxidation, aluminum-containing diffusion deoxidizer or top slag modifier, promoter and foaming agent are used for submerged arc refining, ferrotitanium is added for alloying at the end of LF refining, the recovery rate of titanium is required to be more than 70%, and the generation of oxide inclusion and nitride inclusion of titanium is prevented;
(4) Continuously casting a slab, wherein the thickness of the slab is 250mm, the width of the slab is 1250mm mm or 1500mm, and the length is 9.8m; the steel feeding temperature at the LF refining end point is controlled according to the continuous casting superheat degree of 20 ℃, the baking temperature of an empty ladle is more than 1200 ℃, the baking time is more than 2.5h, the temperature of the baked ladle is more than 800 ℃, the number of turnover ladles is not more than 4, a high-alkalinity covering agent is added into a tundish to heat the molten steel, and the superheat degree of the continuous casting molten steel is 15+/-5 ℃. For example, the width of the slab is 1250mm, the continuous casting slab drawing speed is 1.1m/min, and the specification of the width of the slab is set. The continuous casting process is put into a slab pressing device, the rolling reduction of the slab is 5-6 mm, the center segregation level of the low power of the slab is less than or equal to level 1 (Mannesmann standard), and the slab is hot-fed and hot-packed for rolling after being cut;
(5) Hot charging of the slab at 680-740 ℃, extracting of the slab heating furnace at 1200 ℃ +/-15 ℃, water spraying and descaling of the upper surface and the lower surface of the discharged slab by adopting a high-pressure water column with the pressure of 20MPa, and 7-pass rough rolling under the conditions that the included angle between the sprayed water column and the surface of the slab is 15 degrees, the rough rolling start temperature is 1160-1190 ℃ and the rolling speed is 3.0-4.5 m/s, wherein the thickness of a rough rolling intermediate steel plate is 40-43 mm; the final rolling temperature is 880+/-10 ℃, the hot rolled steel strip after finish rolling is subjected to structure transformation through weak cooling of the laminar flow front section, the finish rolled steel strip after laminar cooling is coiled in a coiling machine, the coiling temperature is 675+/-10 ℃, the steel coil is naturally cooled to room temperature, the metallographic structure of the steel plate is ferrite and pearlite, the grain size is 8.5, and the maximum band structure of the steel is 0.5;
(6) The method comprises the steps of pickling, cold continuous rolling and heat treatment, wherein the hot rolled coil of the incoming material is pickled, then cold continuous rolling is carried out, the cold rolling compression ratio is 50-55%, ferrite of the hot rolled coil of the incoming material is elongated and plastically deformed in the rolling direction through the cold continuous rolling, high-density dislocation is accumulated in the ferrite, bending and crushing occur on partial cementite sheets, the interlayer spacing of pearlite sheets is reduced, the deformation instability of the cementite sheets in the cold rolling process is increased, conditions are provided for the evolution of cementite in the annealing process, the thickness of the incoming material is 3.5mm, the cold rolled sheet with the thickness of 1.6mm is rolled, then the cold rolled coil is subjected to bright annealing, the annealing temperature is 645+/-5 ℃, the heating time is 9.5 hours, the heat preservation time is 15 hours, and the cover waiting time is 55 minutes.

Claims (1)

1. A preparation method of a titanium-carbon bistable carbon structural steel cold-rolled sheet is characterized by comprising the following steps of:
1) The cold-rolled sheet steel comprises the following components in percentage by mass: [C] the method comprises the following steps 0.27 to 0.29 percent wt percent, ti: 0.010-0.020 wt%, [ Mn ]:0.55 to 0.65 weight percent; si:0.18 to 0.25 weight percent, P: less than or equal to 0.015wt percent, S: less than or equal to 0.004wt percent, al:0.020 to 0.040 weight percent, N:0.0030 to 0.0045wt%, cu: less than or equal to 0.02wt percent, cr: less than or equal to 0.02 weight percent, ni: less than or equal to 0.015wt percent, and the balance of iron and unavoidable impurities;
2) The production process is as follows: molten iron desulfurization pretreatment, top-bottom combined blown converter smelting, LF refining, slab continuous casting, strip steel hot continuous rolling, strip steel pickling, strip steel cold continuous rolling and strip steel heat treatment, wherein the thickness of a produced cold rolled steel coil or a cold rolled steel coil transverse cutting plate is 0.80-2.5 mm;
(1) Carrying out deep desulfurization treatment on molten iron, adopting a KR method to carry out desulfurization treatment, adding 5kg/t of a desulfurizing agent, wherein the main composition of the desulfurizing agent is 80% of active lime and 20% of fluorite, adding the desulfurizing agent, stirring for 15min, and then carrying out slag tapping on molten iron with [ S ] less than or equal to 0.002% after the desulfurization treatment;
(2) Smelting in a converter, wherein [ S ] in scrap steel is less than or equal to 0.015wt%, [ Cu ] is less than or equal to 0.05wt%, [ Cr ] is less than or equal to 0.05wt%, the [ Ni ] is less than or equal to 0.05wt%, the content of [ C ] in the converter is 0.08-0.10 wt%, the content of [ P ] is not more than 0.010wt%, the temperature of molten steel tapped from the converter is controlled to 1630-1650 ℃, the tapping process adopts deoxidization alloying of silicon-manganese alloy and aluminum-iron, aluminum is added into ton steel to semi-deoxidize the molten steel, the [ S ] in the steel ladle is less than or equal to 0.008wt%, the [ N ] is less than or equal to 0.0025wt%, slag is tapped from the converter, and the amount of oxidized slag in the steel ladle is not more than 80kg;
(3) The LF refining uses ferrosilicon and calcium carbide deoxidization to carry out diffusion deoxidization, the calcium carbide addition amount is 1.5 kg/t, the ferrosilicon addition amount is 0.8-1.0 kg/t, the initial temperature of the LF refining is more than 1530 ℃, the LF refining power transmission time of each furnace steel is not more than 20min,the total use time of LF refining treatment is controlled to be 40-42 min, the nitrogen increment of molten steel in the LF refining process is less than 0.0010%, and the flow of argon bottom blowing stirring molten steel is 15-20 NL/min; molten steel after LF treatment is fed into a silicon-calcium wire for treatment, and molten steel nitrogen content [ N ] after LF refining treatment is finished]≤0.0035wt%、[S]≤0.0040wt%，[Ca]The content is controlled to be 0.0015 to 0.0035 weight percent, other elements meet the control requirement of molten steel of a smelting finished product, and the LF refining final slag comprises the following components: caO content is 50-53 wt%, siO 2 The content of FeO is 12-15 wt%, feO is less than or equal to 1.0wt%, al 2 O 3 28 to 32 weight percent of MgO, 8 weight percent of CaF 2 The content is not more than 5wt%, aluminum is forbidden to be used for precipitation deoxidation in the later stage of LF treatment, aluminum-containing diffusion deoxidizer or top slag modifier, promoter and foaming agent are used for submerged arc refining, ferrotitanium is added for alloying in the final stage of LF refining, and the recovery rate of titanium is required to be more than 70wt%, so that the generation of oxide inclusion and nitride inclusion of titanium is prevented;
(4) Continuously casting a slab, wherein the thickness of the slab is 250mm, the width of the slab is 1250mm or 1500mm, and the length is 9.8m; the steel temperature at the LF refining end point is controlled according to the continuous casting superheat degree of 20 ℃, the baking temperature of an empty ladle is more than 1200 ℃, the baking time is more than 2.5 hours, the temperature of the baked ladle is more than 800 ℃, the number of turnover ladles is not more than 4, a high-alkalinity covering agent is added into a tundish to heat the molten steel, and the superheat degree of the continuous casting molten steel is 15+/-5 ℃;
(5) Hot charging of the slab at 680-740 ℃, extracting of the slab heating furnace at 1200 ℃ +/-15 ℃, water spraying and descaling of the upper surface and the lower surface of the discharged slab by adopting a high-pressure water column with the pressure of 20MPa, and 7-pass rough rolling under the conditions that the included angle between the sprayed water column and the surface of the slab is 15 degrees, the rough rolling start temperature is 1160-1190 ℃ and the rolling speed is 3.0-4.5 m/s, wherein the thickness of a rough rolling intermediate steel plate is 40-43 mm; the final rolling temperature is 880+/-10 ℃, the hot rolled steel strip after finish rolling is subjected to structure transformation through weak cooling of the laminar flow front section, the finish rolled steel strip after laminar cooling is coiled in a coiling machine, the coiling temperature is 675+/-10 ℃, the steel coil is naturally cooled to room temperature, the metallographic structure of the steel plate is ferrite and pearlite, the grain size is 8.5, and the maximum band structure of the steel is 0.5;
(6) The method comprises the steps of pickling, cold continuous rolling and heat treatment, wherein the hot rolled coil of the incoming material is pickled, then cold continuous rolling is carried out, the cold rolling compression ratio is 50-55%, ferrite of the hot rolled coil of the incoming material is elongated and plastically deformed in the rolling direction through the cold continuous rolling, high-density dislocation is accumulated in the ferrite, bending and crushing occur on partial cementite sheets, the interlayer spacing of pearlite sheets is reduced, the deformation instability of the cementite sheets in the cold rolling process is increased, conditions are provided for the evolution of cementite in the annealing process, the thickness of the incoming material is 3.5mm, the cold rolled sheet with the thickness of 1.6mm is rolled, then the cold rolled coil is subjected to bright annealing, the annealing temperature is 645+/-5 ℃, the heating time is 9.5 hours, the heat preservation time is 15 hours, and the cover waiting time is 55 minutes.
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