CN112795833A - Production method of 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet - Google Patents

Production method of 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet Download PDF

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CN112795833A
CN112795833A CN202011306147.5A CN202011306147A CN112795833A CN 112795833 A CN112795833 A CN 112795833A CN 202011306147 A CN202011306147 A CN 202011306147A CN 112795833 A CN112795833 A CN 112795833A
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continuous casting
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slag
steel
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CN112795833B (en
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毛文文
邝霜
李梦龙
路博勋
冯晓勇
石晓伟
孟庆勇
张仕骏
王朝
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Tangshan Iron and Steel Group Co Ltd
HBIS Co Ltd Tangshan Branch
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Tangshan Iron and Steel Group Co Ltd
HBIS Co Ltd Tangshan Branch
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/04Making ferrous alloys by melting
    • C22C33/06Making ferrous alloys by melting using master alloys
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10Supplying or treating molten metal
    • B22D11/11Treating the molten metal
    • B22D11/111Treating the molten metal by using protecting powders
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16Controlling or regulating processes or operations
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    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28Manufacture of steel in the converter
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    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006Adding metallic additives
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    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/06Deoxidising, e.g. killing
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    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/064Dephosphorising; Desulfurising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/068Decarburising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10Handling in a vacuum
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/08Ferrous alloys, e.g. steel alloys containing nickel
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/12Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/14Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C2007/0093Duplex process; Two stage processes
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

Abstract

A production method of a 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet, belonging to the technical field of metallurgy. The method comprises the working procedures of molten iron desulphurization, converter double-slag smelting, LF refining, RH refining and slab continuous casting; the converter double-slag smelting process comprises a dephosphorization stage and a decarburization stage, wherein high-nickel pig iron is added in the decarburization stage, and the molten steel at the smelting end point comprises 0.022-0.040% of [ C ], less than or equal to 0.008% of [ S ], less than or equal to 0.008% of [ P ], and 0.75-1.25% of [ Ni ]; the slab continuous casting process uses high alkalinity and high viscosity peritectic steel covering slag, the crystallizer adopts a slow cooling mode, the mass number of oxygen and nitrogen contents in the tundish molten steel is controlled to be less than or equal to 20ppm, less than or equal to 50ppm, and the superheat degree is 15-25 ℃. The invention can realize the production of the dual-phase steel continuous casting billet with high cleanliness, high performance uniformity and high surface quality by the fine control of the converter, the LF, the RH and the continuous casting procedures.

Description

Production method of 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a production method of a 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet.
Background
With the vigorous development of the automobile industry and the continuous deepening of energy-saving and environment-friendly concept, the light weight of automobiles becomes a necessary trend of automobile development, and the application of dual-phase steel is an important means for solving the problem. Domestic manufacturers continuously develop high-strength dual-phase steels of 590MPa, 780MPa, 980MPa, 1180MPa and other grades. Along with the improvement of the strength grade, the types and the contents of alloy elements in the dual-phase steel are more and more.
The Chinese patent application with the application number of 201510033944.3 discloses a 'high-nickel content ultra-low phosphorus steel smelting process method', the Ni content of high-nickel steel in the method is about 9.0%, Ni element is added into molten steel through a nickel plate, although the method solves the problem of great temperature drop caused by adding a large amount of nickel plates by adding coke into a converter, the addition of the coke can cause the reduction of the cleanliness of the molten steel, and the treatment cost of the subsequent refining process is increased. The Chinese patent application with the application number of 201210300692.2 discloses a method for smelting nickel-containing steel by adopting low-nickel pig iron in a converter, the method utilizes the low-nickel pig iron to replace a nickel plate to smelt nickel-containing steel, but the method is only suitable for the steel with the nickel content of 0.10-0.50 percent due to the low nickel content of the low-nickel pig iron. For medium nickel content steel, the low nickel pig iron is added in too much amount, which causes difficulty in melting in a converter, so that the method is not suitable for smelting medium nickel content dual-phase steel.
Disclosure of Invention
In order to solve the technical problem, the invention provides a production method of a 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet, wherein the nickel content of the steel is 0.75-1.25%, and the rest alloy elements comprise Mn, Si, Nb, Ti and the like. The invention adopts the following technical scheme:
a production method of a 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet comprises the following working procedures:
(1) molten iron desulphurization process: pre-skimming before desulfurization to ensure that the exposed surface of molten iron is more than or equal to 20 percent, skimming the slag on the surface of the molten iron after desulfurization to ensure that the exposed surface of the molten iron is more than or equal to 90 percent and the molten iron S fed into the converter is less than or equal to 0.010 percent;
(2) a converter double-slag smelting process: pouring slag twice in the smelting process, wherein the smelting process is divided into a dephosphorization stage and a decarburization stage, and adding high-nickel pig iron in the decarburization stage, wherein the molten steel at the smelting end point comprises 0.022-0.040% of [ C ], less than or equal to 0.008% of [ S ], less than or equal to 0.008% of [ P ] and 0.75-1.25% of [ Ni ]; the end point temperature is 1680-1700 ℃, the mass percentage of FeO in the converter final slag is less than or equal to 20%, and the tapping time is more than or equal to 3 min;
(3) an LF refining procedure: the composition and mass percentage of the molten steel when the steel is out of the station are 0.120-0.160% of [ C ], [ Mn ] 1.90-2.20%, 1.30-1.50% of [ Si ], [ Ni ] 0.75-1.25%, 0.020-0.040% of [ Nb ], [ Alt ] 0.032-0.050%, less than or equal to 0.003% of [ S ], [ P ] less than or equal to 0.009%, and less than or equal to 0.0050%;
(4) RH refining process: the molten steel comprises 0.120-0.160% of [ C ], 1.90-2.20% of [ Mn ], 1.30-1.50% of [ Si ], 0.75-1.25% of [ Ni ], 0.020-0.040% of [ Nb ], 0.032-0.050% of [ Alt ], 0.020-0.030% of [ Ti ], less than or equal to 0.003% of [ S ], less than or equal to 0.010% of [ P ] and less than or equal to 0.0050% of [ N ] in percentage by mass when the steel is taken out of the station;
(5) and a slab continuous casting process: the temperature of tundish molten steel is 1509-1519 ℃; the tundish uses a carbon-free low-silicon covering agent, and the casting powder uses peritectic steel casting powder with high alkalinity and high viscosity; the pulling speed is constant at 1.2 m/min, and the crystallizer is controlled in a slow cooling mode; the mass number of oxygen and nitrogen contents in the molten steel of the tundish is controlled to be less than or equal to 20ppm and less than or equal to 50ppm, and the superheat degree is controlled to be 15-25 ℃.
In the converter double-slag smelting process, oxygen supply in a dephosphorization stage is 30-35% of total oxygen supply, alkalinity is controlled to be 1.8-2.2, the weight content of FeO in slag is 19-26%, the weight content of MgO is 6-9%, the converter-reversing temperature is 1420-1460 ℃, and the converter-reversing amount is 30-65%; and adding high-nickel pig iron in the decarbonization stage, controlling the alkalinity to be 3.5-4.0, controlling the MgO content in the slag to be 8-10% and controlling the end-point oxygen level to be 450-700 ppm.
In the converter double-slag smelting process, double-slag blocking operation is adopted, the front block is a sliding plate, the rear block is a slag blocking cone which is matched with the sliding plate, and the thickness of slag is ensured to be less than or equal to 30 mm; preparing manganese from medium-carbon ferromanganese and high-carbon ferromanganese and preparing silicon from silicon iron after the converter is fired; the adding amount of lime is 3.5-4.0 kg/t steel; when tapping 1/5, starting feeding, adopting a feeding sequence of strong first and weak second: lime → steel grit aluminum → medium and high carbon ferromanganese → ferrosilicon, alloy and slag making material are added before tapping 4/5.
In the converter double-slag smelting process, the components and the weight ratio of the high-nickel pig iron are 12-15% of Ni, 2.5-3.0% of C, less than or equal to 0.040% of P, more than or equal to 3.2% of Si, and the balance of iron and inevitable impurities.
In the LF refining process, niobium is added by using ferrocolumbium at the temperature of the molten steel of not less than 1590 ℃, the micro-positive pressure operation in the furnace is ensured by adjusting the opening of a dust removal valve in the refining process, the molten steel and the molten slag are respectively deoxidized by an aluminum wire and an aluminum wire section, and the end point slag sample TFe + MnO is ensured to be not more than 1.0%.
In the RH refining process, the RH lifting gas flow is 80-100 Nm3H; after vacuum circulation for 5 min, the components of the molten steel are subjected to titanium preparation and final alloy component adjustment, and then the pure degassing time is kept to be more than or equal to 8 min.
In the slab continuous casting process, the crystallizer water distribution adopts a slow cooling mode, the water quantity of a wide surface is 3500-3600L/min, the flow of a narrow surface is 490-500L/min, and the fluctuation of the liquid level of the crystallizer is controlled to be less than or equal to +/-3 mm; and after the continuous casting billet is off-line, surface cleaning is carried out by using a flame cleaning machine or a slab sharpening machine, and the depth is 2-3 mm.
In the slab continuous casting process, argon is adopted for protection in the whole casting process; the carbon-free tundish magnesium refractory, the carbon-free aluminum argon blowing water feeding port and the argon blowing stopper rod are used, the tundish baking temperature is more than or equal to 1100 ℃, and the baking time is more than or equal to 3 hours.
In the slab continuous casting process, the alkalinity of the peritectic steel casting powder with high alkalinity and high viscosity is 1.20-1.30, and the viscosity is 1.10-1.15 poise.
The continuous casting billet produced by the method finally produces high-strength dual-phase steel products with uniform performance and high surface quality after hot rolling and cold rolling processes.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the invention obviously improves the cleanliness of molten steel by reasonable component design and fine control of the whole process of each working procedure of converter, LF, RH and continuous casting, combines flame cleaning or casting blank grinding, realizes the production of high-cleanliness, uniform structure and high-surface quality and high-strength dual-phase steel, and produces the continuous casting blank meeting the use requirement of subsequent processing. Through the fine control of each process, the total oxygen content of the tundish is stably controlled to be less than 20ppm, and the average is 11.9 ppm. The casting blank has no obvious segregation phenomenon inside, nickel element does not generate enrichment phenomenon, and the surface of the casting blank has no defects of cracks, depressions and the like. The high nickel pig iron is adopted to replace nickel plates and low nickel pig iron, so that the alloying cost can be obviously reduced, and the problem ofThe problem of insufficient heat of the converter. By adopting the converter double-slag operation, the P content in the finished product can be stably controlled below 0.010 percent, and the requirement of the product on the P element is met. The converter adopts an alloy feeding mode of firstly strong and then weak, which is beneficial to the absorption of precious alloy elements. By adopting the configuration of LF and RH double refining, the tapping temperature of the converter is reduced, the service life of the converter lining is prolonged, the number and the size of inclusions in steel are greatly reduced, and the average density of the inclusions is 6.5/mm2The size of the inclusions is mainly concentrated below 10 mu m, and the maximum size of the inclusions is 30 mu m; the configuration of molten iron pretreatment and LF refining is adopted to ensure that the S element of the steel grade is controlled below 0.003 percent. The casting blank crack sensitivity caused by high nickel content can be well reduced by adopting the low-pulling-speed, slow-cooling of the crystallizer and high-viscosity covering slag, and the occurrence of surface defects is avoided.
Drawings
FIG. 1 is a graph showing the segregation at the center of a low power sample after erosion in a continuous casting slab in example 1 of the present invention;
FIG. 2 is a graph showing the segregation at the center of the low power sample after the erosion of the continuous casting slab in example 2 of the present invention;
FIG. 3 is a graph showing the segregation at the center of the low power sample after erosion in the slab of example 3 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples.
Examples 1 to 12
The production process flow of the 1300 MPa-level medium nickel dual-phase steel continuous casting billet comprises the following steps: KR desulfurization of molten iron → double slag smelting of a converter → LF refining → RH refining → continuous slab casting. The invention has no special limitation on the processing capacity of each process and the specification of the continuous casting billet, and the specific operation steps are as follows:
(1) molten iron desulfurization step
Pre-slagging is carried out after the ladle enters the station to ensure that the exposed surface of the molten iron is more than or equal to 20 percent, and after desulfurization, slag on the surface of the molten iron is completely removed, the exposed surface of the molten iron is more than or equal to 90 percent, the outbound molten iron S is ensured to be less than or equal to 0.010 percent, and the outbound molten iron temperature is more than or equal to 1300 ℃. The process parameter control of each example is shown in table 1.
(2) Converter double-slag smelting process
A. And (3) a converter smelting dephosphorization stage: the average temperature of molten iron entering the furnace is 1300-1360 ℃, S is less than or equal to 0.008 percent, and P: 0.090-0.140%; the oxygen supply amount is 30-35% of the total oxygen supply amount, the alkalinity is controlled to be 1.8-2.2, the weight content of FeO in the slag is 19-26%, the weight content of MgO is 6-9%, the furnace reversing temperature is 1420-1460 ℃, and the slag reversing amount is 30-65%; the process parameter control of each example is shown in table 1.
TABLE 1 molten iron desulfurization and dephosphorization in converter smelting stage parameters of each example
Figure DEST_PATH_IMAGE002
B. And (3) a converter smelting decarburization stage: adding slag-forming materials for about 2min, and then adding high-nickel pig iron, wherein the components and the weight ratio of the high-nickel pig iron are 12-15% of Ni, 2.5-3.0% of C, less than or equal to 0.040% of P, more than or equal to 3.2% of Si, and the balance of iron and inevitable impurities. Controlling the alkalinity to be 3.5-4.0, wherein the mass percent of FeO in the converter final slag is less than or equal to 20%, the weight content of MgO is 8-10%, the end point temperature is 1680-1700 ℃, the end point oxygen position is 450-700 ppm, the components and the mass percent of the end point molten steel are [ C ] 0.022-0.040%, [ S ] is less than or equal to 0.008%, [ P ] is less than or equal to 0.008%, [ Ni ] 0.75-1.25%;
C. the converter tapping adopts a front baffle and rear baffle process, the front baffle adopts a slag blocking plug, the rear baffle adopts a sliding plate and a slag blocking cone to jointly block slag, the slag is controlled through infrared slag tapping detection, and the slag tapping thickness is less than or equal to 30 mm. When tapping 1/5, starting feeding, adopting a feeding sequence of strong first and weak second: lime → steel sand aluminum → medium carbon ferromanganese → high carbon ferromanganese → ferrosilicon, alloy and slagging material are added before the steel is tapped 4/5, the lime is added by 3.5-4.0 kg/t steel, the tapping time is more than or equal to 3min, and the carbon drawing time is less than or equal to 1 time. The process parameter control of each example is shown in tables 2 and 3.
TABLE 2 converter smelting Process parameters-1 of the examples
Figure DEST_PATH_IMAGE004
TABLE 3. converter smelting Process parameters of the examples-2
Figure DEST_PATH_IMAGE006
(3) LF refining Process
A. Measuring temperature, sampling and analyzing components after the steel ladle enters the station, and supplementing aluminum by using an aluminum wire according to the oxidability of molten steel and the content of Alt of the molten steel, wherein the Alt is required to be 0.32-0.50%;
B. the adjustment mode of the manganese element needs to be selected according to the content of C in the molten steel entering the station, if the content of C is less than or equal to 0.160 percent, high-carbon ferromanganese is added for manganese, and if the content of C is more than 0.160 percent, medium-carbon ferromanganese is added for manganese; the silicon element is added by ferrosilicon; adding ferrocolumbium to adjust the niobium content when the temperature of the molten steel is higher than 1590 ℃;
C. the micro-positive pressure operation in the furnace is ensured by adjusting the opening degree of a dust removal valve in the refining process, in order to ensure the desulfurization effect, molten steel and molten slag are respectively deoxidized through an aluminum wire and an aluminum wire section, and the final-point slag sample TFe + MnO is less than or equal to 1.0 percent;
D. the composition and mass percentage of the molten steel when the steel is out of the station are 0.120-0.160% of [ C ], [ Mn ] 1.90-2.20%, 1.30-1.50% of [ Si ], [ Ni ] 0.75-1.25%, 0.020-0.040% of [ Nb ], [ Alt ] 0.032-0.050%, less than or equal to 0.003% of [ S ], [ P ] less than or equal to 0.009%, and less than or equal to 0.0050%;
the control of the LF refining process parameters of each example is shown in Table 4.
TABLE 4 LF refining Process parameters for the examples
Figure DEST_PATH_IMAGE008
(4) RH refining step
A. The mechanical vacuum pump device is in the processing mode, the lowest vacuum degree is pumped when the processing is started, and the RH lifting gas flow is controlled to be 80-100 Nm3H is used as the reference value. After vacuum circulation for 5 min, temperature measurement, sampling and component analysis are carried out;
B. according to the sampling analysis result, the Ti element is added and the other elements are micro-adjusted to the molten steel components, and then the pure degassing time is kept to be more than or equal to 8 min;
C. the composition and mass percentage of the molten steel during the station leaving are 0.120-0.160% of [ C ], [ Mn ], [ 1.90-2.20%, [ Si ], [ 1.30-1.50%, [ Ni ], [ 0.75-1.25%, [ Nb ], [ 0.020-0.040%, [ Alt ], [ 0.032-0.050%, [ Ti ], [ 0.020-0.030%, [ S ] less than or equal to 0.003%, [ P ] less than or equal to 0.010% and [ N ] less than or equal to 0.0050%, and the station leaving temperature is determined according to the section of the casting blank and the continuous casting furnace number;
the RH refining procedure parameters of each example are controlled as shown in Table 5.
TABLE 5 RH refining procedure parameters of the examples
Figure DEST_PATH_IMAGE010
(5) Slab continuous casting process
A. Controlling the temperature of the molten steel of the tundish to be 1509-1519 ℃, if the temperature is the casting heat, controlling the temperature to be 1509-1529 ℃, adopting argon protection in the whole casting process, and controlling the argon blowing of the ladle long nozzle, the stopper rod and the tundish upper nozzle as shown in table 6;
TABLE 6 argon blowing control flow and pressure in slab continuous casting process
Figure DEST_PATH_IMAGE012
B. The method comprises the following steps of (1) using a carbon-free tundish magnesium refractory, a carbon-free aluminum argon blowing water feeding port, an argon blowing stopper and a carbon-free low-silicon covering agent, wherein the baking temperature of the tundish is more than or equal to 1100 ℃, and the baking time is more than or equal to 3 hours;
C. the casting powder is peritectic steel casting powder with high alkalinity and high viscosity, the alkalinity is 1.20-1.30, and the viscosity is 1.10-1.15 poise;
D. the mass numbers of oxygen and nitrogen contents of the tundish molten steel are controlled to be less than or equal to 20ppm and less than or equal to 50ppm, and the superheat degree is controlled to be 15-25 ℃; the crystallizer water distribution adopts a slow cooling mode, the water quantity of the wide surface is 3500-3600L/min, and the flow of the narrow surface is 490-500L/min; controlling the fluctuation of the liquid level of the crystallizer to be less than or equal to +/-3 mm in the pouring process, keeping the pulling speed constant at 1.2 m/min, and controlling the crystallizer by adopting a slow cooling mode;
E. and after the continuous casting billet is off-line, the surface of the continuous casting billet is cleaned by using a flame cleaning machine or a slab sharpening machine, the depth is 2-3mm, and the surface quality is ensured.
The control of the slab continuous casting process parameters for each example are shown in Table 7.
The chemical components and the mass percentage of the medium-nickel dual-phase steel continuous casting billet produced by the process are shown in the table 8.
TABLE 7 slab continuous casting Process parameters for the examples
Figure DEST_PATH_IMAGE014
TABLE 8 chemical composition and mass% of Ni dual-phase steel continuous casting blank/% in each example
Figure DEST_PATH_IMAGE016
The continuous casting billet produced by the process has no defects of center cracks, center looseness, center segregation and the like through low-power inspection, has no slag inclusion defects on the surface and the subcutaneous part of the casting billet, and can well meet the requirements of the subsequent cold rolling process.
TABLE 9 quality index table of Ni dual-phase steel continuous casting slab in each example
Figure DEST_PATH_IMAGE018

Claims (9)

1. A production method of a 1300 MPa-level medium-nickel dual-phase steel continuous casting blank is characterized by comprising the following working procedures:
(1) molten iron desulphurization process: pre-skimming before desulfurization to ensure that the exposed surface of molten iron is more than or equal to 20 percent, skimming the slag on the surface of the molten iron after desulfurization to ensure that the exposed surface of the molten iron is more than or equal to 90 percent and the molten iron S fed into the converter is less than or equal to 0.010 percent;
(2) a converter double-slag smelting process: pouring slag twice in the smelting process, wherein the smelting process is divided into a dephosphorization stage and a decarburization stage, and adding high-nickel pig iron in the decarburization stage, wherein the molten steel at the smelting end point comprises 0.022-0.040% of [ C ], less than or equal to 0.008% of [ S ], less than or equal to 0.008% of [ P ] and 0.75-1.25% of [ Ni ]; the end point temperature is 1680-1700 ℃, the mass percentage of FeO in the converter final slag is less than or equal to 20%, and the tapping time is more than or equal to 3 min;
(3) an LF refining procedure: the composition and mass percentage of the molten steel when the steel is out of the station are 0.120-0.160% of [ C ], [ Mn ] 1.90-2.20%, 1.30-1.50% of [ Si ], [ Ni ] 0.75-1.25%, 0.020-0.040% of [ Nb ], [ Alt ] 0.032-0.050%, less than or equal to 0.003% of [ S ], [ P ] less than or equal to 0.009%, and less than or equal to 0.0050%;
(4) RH refining process: the molten steel comprises 0.120-0.160% of [ C ], 1.90-2.20% of [ Mn ], 1.30-1.50% of [ Si ], 0.75-1.25% of [ Ni ], 0.020-0.040% of [ Nb ], 0.032-0.050% of [ Alt ], 0.020-0.030% of [ Ti ], less than or equal to 0.003% of [ S ], less than or equal to 0.010% of [ P ] and less than or equal to 0.0050% of [ N ] in percentage by mass when the steel is taken out of the station;
(5) and a slab continuous casting process: the temperature of tundish molten steel is 1509-1519 ℃; the tundish uses a carbon-free low-silicon covering agent, and the casting powder uses peritectic steel casting powder with high alkalinity and high viscosity; the pulling speed is constant at 1.2 m/min, and the crystallizer is controlled in a slow cooling mode; the mass number of oxygen and nitrogen contents in the molten steel of the tundish is controlled to be less than or equal to 20ppm and less than or equal to 50ppm, and the superheat degree is controlled to be 15-25 ℃.
2. The production method of the 1300 MPa-grade medium nickel dual-phase steel continuous casting billet is characterized in that in the converter dual-slag smelting process, the oxygen supply amount in the dephosphorization stage is 30-35% of the total oxygen supply amount, the alkalinity is controlled to be 1.8-2.2, the weight content of FeO in the slag is 19-26%, the weight content of MgO is 6-9%, the converter-reversing temperature is 1420-1460 ℃, and the slag-reversing amount is 30-65%; and adding high-nickel pig iron in the decarbonization stage, controlling the alkalinity to be 3.5-4.0, controlling the MgO content in the slag to be 8-10% and controlling the end-point oxygen level to be 450-700 ppm.
3. The production method of the 1300 MPa-level medium nickel dual-phase steel continuous casting billet according to claim 2, characterized in that the converter dual-slag smelting process adopts a dual-slag-blocking operation, wherein a front block is a sliding plate, a rear block is a slag-blocking cone matched with the sliding plate, and the slag thickness is ensured to be less than or equal to 30 mm; preparing manganese from medium-carbon ferromanganese and high-carbon ferromanganese and preparing silicon from silicon iron after the converter is fired; the adding amount of lime is 3.5-4.0 kg/t steel; when tapping 1/5, starting feeding, adopting a feeding sequence of strong first and weak second: lime → steel grit aluminum → medium and high carbon ferromanganese → ferrosilicon, alloy and slag making material are added before tapping 4/5.
4. The production method of 1300 MPa-grade medium nickel dual-phase steel continuous casting billets according to claim 3, characterized in that in the converter dual-slag smelting process, the high nickel pig iron comprises 12-15 wt% of Ni, 2.5-3.0 wt% of C, less than or equal to 0.040 wt% of P, more than or equal to 3.2 wt% of Si, and the balance of iron and inevitable impurities.
5. The production method of the 1300 MPa-grade medium nickel dual-phase steel continuous casting billet according to the claim 4, characterized in that in the LF refining process, niobium is added by ferroniobium, the niobium is added when the temperature of molten steel is not less than 1590 ℃, the micro-positive pressure operation in a furnace is ensured by adjusting the opening of a dust removal valve in the refining process, and the molten steel and the molten slag are respectively deoxidized by an aluminum wire and an aluminum wire section, so that the end-point slag sample TFe + MnO is not more than 1.0%.
6. The production method of 1300 MPa-grade medium nickel dual-phase steel continuous casting billet according to claim 5, characterized in that in the RH refining process, the RH lifting gas flow is 80-100 Nm3H; after vacuum circulation for 5 min, the components of the molten steel are subjected to titanium preparation and final alloy component adjustment, and then the pure degassing time is kept to be more than or equal to 8 min.
7. The production method of the 1300 MPa-grade medium nickel dual-phase steel continuous casting billet according to claim 6, characterized in that in the slab continuous casting process, the crystallizer water distribution adopts a slow cooling mode, the water amount of a wide surface is 3500-3600L/min, the flow of a narrow surface is 490-500L/min, and the fluctuation of the liquid level of the crystallizer is controlled to be less than or equal to +/-3 mm; and after the continuous casting billet is off-line, surface cleaning is carried out by using a flame cleaning machine or a slab sharpening machine, and the depth is 2-3 mm.
8. The production method of the 1300 MPa-grade medium nickel dual-phase steel continuous casting billet according to any one of claims 1 to 7, characterized in that in the slab continuous casting process, argon protection is adopted in the whole casting process; the carbon-free tundish magnesium refractory, the carbon-free aluminum argon blowing water feeding port and the argon blowing stopper rod are used, the tundish baking temperature is more than or equal to 1100 ℃, and the baking time is more than or equal to 3 hours.
9. The production method of the 1300 MPa-grade medium-nickel dual-phase steel continuous casting billet according to claim 8, wherein in the slab continuous casting process, the alkalinity of the high-alkalinity and high-viscosity peritectic steel casting powder is 1.20-1.30, and the viscosity is 1.10-1.15 poise.
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