CN108568503B - Method for accurately controlling carbon content of molten steel in 600MPa dual-phase steel tundish - Google Patents

Method for accurately controlling carbon content of molten steel in 600MPa dual-phase steel tundish Download PDF

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CN108568503B
CN108568503B CN201810392916.4A CN201810392916A CN108568503B CN 108568503 B CN108568503 B CN 108568503B CN 201810392916 A CN201810392916 A CN 201810392916A CN 108568503 B CN108568503 B CN 108568503B
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steel
equal
tundish
carbon
slag
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CN108568503A (en
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马德刚
李经哲
李阳
王耐
尹宽
王建兴
李波
武冠华
程入川
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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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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/111—Treating the molten metal by using protecting powders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0025—Adding carbon material
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

The invention discloses a method for accurately controlling the carbon content of molten steel in a 600MPa dual-phase steel tundish. The fluctuation of the carbon mass fraction of molten steel in a continuous casting tundish within the range of 0.010 percent is realized by controlling the endpoint of a decarburization converter, controlling steel tapping and feeding, controlling a deoxidation process, controlling LF narrow components, controlling the temperature in the whole steelmaking process and controlling the recarburization in a continuous casting process; the center segregation of the continuous casting billet can reach below B0.5 level, the oxygen mass fraction of the molten steel of the tundish is controlled within 30ppm, the nitrogen mass fraction is controlled within 50ppm, and the high-quality hot-rolled coil is produced by hot rolling and finally the high-quality continuous annealing product is produced by cold rolling.

Description

Method for accurately controlling carbon content of molten steel in 600MPa dual-phase steel tundish
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for accurately controlling the carbon content of molten steel in a 600MPa dual-phase steel tundish.
Background
In recent years, with the rapid development of the automobile industry in China, energy conservation and environmental protection become necessary trends of the development of modern automobiles, one important measure is the weight reduction of automobiles, high-strength dual-phase steel is used for replacing conventional steel and is researched and developed in various enterprises in China, ferrite-martensite dual-phase steel is just one of the dual-phase steel, the martensite content in a solid solution structure of the dual-phase steel reaches 35-50%, and the balance is ferrite. At present, the components of 600MPa ferrite martensite dual-phase steel mostly adopt a carbon manganese silicon system, and the component control range is shown in table 1.
TABLE 1600 MPa ferritic martensite dual-phase steel composition control range
Figure DEST_PATH_IMAGE002
The steel-making production process of 600MPa ferrite and martensite dual-phase steel mainly comprises the following steps: blast furnace, molten iron desulphurization, converter, LF and continuous casting. It is recognized in the art that: as the ferrite and martensite dual-phase steel with the pressure of 600MPa has greatly increased content of alloy elements such as Mn and Si elements in the component design, and in order to ensure low-cost control, the alloying materials used in the steelmaking production all adopt bulk materials such as medium-carbon ferromanganese, high-carbon ferromanganese and silicon-manganese alloy, the alloys all contain carbon elements, the refractory materials of a steel ladle and a tundish are both carbon materials, and the carburization of the refractory materials is also very unstable in the production process, so that the steel with higher alloy content has more difficulty in accurately controlling the carbon content within the range of 0.010 percent.
The main difficulty of the steel making of 600MPa ferrite and martensite dual-phase steel lies in the problem of narrow component control of the carbon mass fraction of molten steel in a tundish, a carburant and an alloy are used for carbon matching in the conventional process for adjusting the carbon content, a continuous casting tundish refractory material is built by using a dry material, the influence of the material and the refractory material on the mass fraction of the carbon in the molten steel is greatly influenced, and the process and the raw materials of the whole steel making process of converter and LF refining and continuous casting are required to be controlled when the carbon content of high alloy steel such as 600MPa dual-phase steel is adjusted to be within the range of 0.010%.
The production of 600MPa ferrite and martensite dual-phase steel by continuous casting of the medium slab matched with a 100-ton converter is more difficult because the nominal capacity of the converter is small, the tapping time of the converter is short, the alloy cannot be fully melted in the tapping process of the converter, the added alloy amount is large, the temperature drop of molten steel in the whole steelmaking process is not easy to control, the absorption rate of carbon in materials is very unstable, and the fluctuation of the mass fraction of molten steel in a continuous casting tundish is large due to the recarburization of continuous casting and ladle refractory materials, so that the production of high-quality 600MPa ferrite and martensite dual-phase steel by using the medium slab continuous casting machine matched with the 100-ton converter is challenging and innovative work when the carbon content in the continuous casting is controlled within the range of 0.010%.
Disclosure of Invention
The invention aims to provide a method for accurately controlling the carbon content of molten steel in a 600MPa dual-phase steel tundish. The carbon content of the molten steel of the 600MPa dual-phase steel continuous casting tundish is controlled within 0.010 percent by controlling the technological parameters of each procedure of steelmaking.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for accurately controlling the carbon content of molten steel in a 600MPa dual-phase steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting; in the middle slab continuous casting process, secondary cooling adopts a cooling mode combined with dynamic soft reduction, the withdrawal and straightening temperature is ensured to be more than or equal to 900 ℃, the withdrawal speed is controlled to be 1.3-1.5m/min, and the superheat degree is controlled to be 20-30 ℃.
In the molten iron desulphurization process, after magnesium powder and lime are injected into a ladle for desulphurization, slag is removed completely, and [ S ] in molten iron subjected to molten iron pretreatment desulphurization is less than or equal to 0.030%.
In the smelting process of the decarburization converter, the bottom blowing of nitrogen and argon is switched to be less than or equal to 40%, the front blocking of the sliding plate, the slag blocking cone and the rear blocking of the sliding plate are adopted, and the thickness of the slag is less than or equal to 30 mm; adding silicon-manganese alloy for manganese and silicon, silicon-iron for silicon, aluminum-iron, aluminum wire, petroleum coke or forged coal for recarburization in the tapping process, wherein the granularity of the recarburization agent is required to be 2-5mm, the sum of the granularity of less than 2mm and the granularity of more than 5mm is not more than 5%, sequentially adding lime, the recarburization agent for pre-deoxidation, the silicon-manganese alloy, the silicon-iron and the aluminum-iron in the feeding sequence, starting feeding when tapping 1/3, adding 3.5-4.0kg of lime per ton of steel, adding slag-making materials and alloys before tapping 3/4, adding aluminum-iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping.
According to the smelting process of the decarburization converter, the ladle bottom blowing flow is not less than 800NL/min and the gas pressure is not less than 1.1MPa in the process of adding lime to a recarburizing agent for pre-deoxidation at the beginning of tapping, the ladle bottom blowing flow is not less than 600NL/min and the gas pressure is 0.8MPa from the beginning of adding alloy to the end of adding aluminum iron, the ladle gas flow is not less than 50NL/min after adding aluminum iron, the gas pressure is not less than 0.1MPa, the ladle bottom blowing flow is not less than 600NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in after tapping, and the ladle bottom blowing is closed after the aluminum wire is driven in.
In the smelting process of the decarburization converter, the alkalinity of final slag is 3.0-4.5; controlling the mass percent of molten steel components [ C ]: 0.020-0.045%, less than or equal to 0.015% of S, and less than or equal to 0.015% of P; the end point temperature is 1660-1700 ℃, the mass percent of FeO in the final slag is less than or equal to 21 percent, and the tapping time is more than or equal to 3 min.
In the LF refining process, in the aspect of carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, bottom blowing argon is more than or equal to 800NL/min, the gas pressure is more than or equal to 1.1MPa, the bottom blowing flow is controlled to be more than or equal to 600NL/min when slag is added for slagging in LF (ladle furnace) refining, the gas pressure is more than or equal to 0.8MPa, the steel ladle gas flow is more than or equal to 500NL/min when an alloy material is added, and the gas pressure is more than or equal; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is more than or equal to 400NL/min, the gas pressure is more than or equal to 0.5MPa, when the calcium wire is fed, the gas flow of the steel ladle is more than or equal to 50NL/min, the gas pressure is more than or equal to 0.1MPa, and the carbon content at the LF outlet is controlled to be 0.070-0.080%.
According to the LF refining process, the mass percent of molten steel components [ C ] is controlled: 0.070-0.080%, [ Mn ]: 1.60-1.90%, [ Si ]: 0.40-0.60%, [ S ] is less than or equal to 0.003%, [ P ] is less than or equal to 0.018%, [ Als ]: 0.030-0.060%, N is less than or equal to 0.0050%; the LF outlet molten steel temperature is determined according to the casting blank section and the continuous casting furnace number, and is specifically shown in Table 2.
TABLE 2 corresponding relationship between LF furnace outlet temperature and casting blank section and casting heat
Figure DEST_PATH_IMAGE004
In the slab casting process, the molten steel is sealed and protected by adding argon into a long nozzle from a ladle to a tundish, and the temperature of the molten steel in the continuous casting tundish is 1539-.
In the process of the continuous casting of the medium plate blank, a tundish adopts a slag wall and a slag weir, the baking temperature of the tundish is more than or equal to 1100 ℃, the baking time is more than or equal to 3 hours, the tundish adopts a magnesium refractory, an aluminum carbon water feeding port, an aluminum carbon stopper rod and an immersion type water gap, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, a crystallizer adopts medium carbon steel protective slag with high alkalinity and low viscosity, the content of C is controlled to be 0-10 percent, and SiO is controlled to be 0-10 percent224-35% of CaO, 25-40% of Al2O3Controlling the melting point at 1100 + -50 deg.C and the viscosity at 0.5-2.5 poise at 0-6%.
In the middle slab continuous casting process, the production process is stably controlled, the fluctuation range of the carbon content of molten steel in a continuous casting tundish is stably controlled to be within 0.010 percent, the quality of the molten steel is better, the oxygen mass fraction of the molten steel in the tundish is controlled to be less than or equal to 30ppm, and the nitrogen mass fraction is controlled to be less than or equal to 50 ppm.
TABLE 3.1 corresponding relationship between continuous casting pulling rate and casting blank section
Figure DEST_PATH_IMAGE006
Table 3.2600 MPa dual phase steel product chemical composition control range:
Figure DEST_PATH_IMAGE008
the balance in table 4 is iron and unavoidable impurities.
The design idea of the invention is as follows: in the production of 600MPa ferrite and martensite dual-phase steel by a medium plate blank continuous casting machine, the fluctuation of the carbon mass fraction in the molten steel component of a continuous casting tundish is within the range of 0.010 percent, and higher requirements on the end point control of a decarburization converter, the steel tapping feeding control, the deoxidation process control, the LF narrow component control, the temperature control in the whole steelmaking process and the recarburization control in the continuous casting process are met, so that the fluctuation of the carbon mass fraction in the molten steel of the continuous casting tundish is within the range of 0.010 percent.
In the method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel tundish, the standard of the detection method refers to GBT 4336-2016 (conventional method) for measuring the contents of multiple elements in carbon steel and medium and low alloy steel), and the low-grade tissue rating of the casting blank refers to YB/T153-2015 (high-quality structural steel continuous casting blank low-grade tissue defect rating chart).
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: 1. the invention realizes that the fluctuation of the carbon mass fraction of molten steel in a continuous casting tundish is within the range of 0.010 percent by controlling the end point of a decarburization converter, controlling steel tapping and feeding, controlling a deoxidation process, controlling LF narrow components, controlling the temperature in the whole steelmaking process and controlling the recarburization in a continuous casting process. 2. The center segregation of the continuous casting billet can reach below B0.5 level, the mass fraction of molten steel in the tundish is controlled within 30ppm, the mass fraction of nitrogen is controlled within 50ppm, and high-quality hot-rolled coils are produced by hot rolling and finally high-quality continuous annealing products are produced by cold rolling.
Drawings
FIG. 1 is a macroscopic effect chart of a continuous casting slab produced in example 1;
FIG. 2 is a macroscopic examination effect diagram of the continuous casting slab produced in example 2;
FIG. 3 is a macroscopic examination effect diagram of the continuous casting slab produced in example 3;
FIG. 4 is a macroscopic examination effect diagram of the continuous casting slab produced in example 4;
FIG. 5 is a macroscopic examination effect diagram of the continuous casting slab produced in example 5;
FIG. 6 is a macroscopic examination effect diagram of the continuous casting slab produced in example 6;
FIG. 7 is a low power test result chart of the continuous casting slab produced in example 7.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The decarburization converter in the following examples is a 100 ton medium-sized and small-sized converter.
Example 1
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1050mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.030%;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 40 percent, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 30 mm; adding a silicon-manganese alloy for manganese and silicon, silicon for silicon iron, aluminum iron, an aluminum wire and a petroleum coke recarburizer for deoxidation in the tapping process, sequentially adding lime, the recarburizer for pre-deoxidation, the silicon-manganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 3.5 kg/ton of steel, adding a slag-making material and an alloy before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that the ladle bottom blowing flow rate is 800NL/min and the gas pressure is 1.1MPa in the process of adding lime to the recarburizing agent pre-deoxidation at the beginning of tapping, when the alloy is added to the aluminum iron is added, the ladle bottom blowing flow rate is 600NL/min and the gas pressure is 0.8MPa, the ladle gas flow rate is 50NL/min and the gas pressure is 0.1MPa after the aluminum iron is added, the ladle bottom blowing flow rate is 600NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in after tapping is finished, and the ladle bottom blowing is closed after the aluminum wire is driven in;
the alkalinity of the final slag is 3.0, and the mass percent of the components of the molten steel is controlled as follows: 0.020%, [ S ]: 0.015%, [ P ]: 0.015 percent; the final temperature is 1660 ℃, the mass percent of FeO in the final slag is 21%, and the tapping time is 3 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, bottom blowing argon gas is 800NL/min, the gas pressure is 1.1MPa, the bottom blowing flow is controlled at 600NL/min and the gas pressure is 0.8MPa when slag is added for slagging in LF (ladle furnace) refining, and the steel ladle gas flow is 500NL/min and the gas pressure is 0.7MPa when an alloy material is added; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is 400NL/min, the gas pressure is 0.5MPa, when the calcium wire is fed, the gas flow of the steel ladle is 50NL/min, the gas pressure is 0.1MPa, and the carbon content at the LF outlet is controlled to be 0.071%;
controlling the mass percent of molten steel components [ C ]: 0.071%, [ Mn ]: 1.635%, [ Si ]: 0.46%, [ S ]: 0.001%, [ P ]: 0.018%, [ Als ]: 0.043%, [ N ]: 0.0035%; the temperature of the LF outlet molten steel is 1599-1609 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a ladle to a tundish by adding argon into a long nozzle, and keeping the temperature of molten steel in the continuous casting tundish at 1539 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft reduction, the withdrawal and straightening temperature is 900 ℃, and the withdrawal speed is controlled to be 1.4-1.5 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag blocking wall and a slag blocking weir, the baking temperature of the tundish is 1100 ℃, the baking time is 3 hours, the tundish adopts a magnesium refractory, an aluminum carbon feeding port, an aluminum carbon stopper rod and an immersion type water port, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 15ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 25 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 1 is a low power test result diagram of a continuous casting slab produced in example 1, and it can be seen from FIG. 1 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
Example 2
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1051mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.025 percent;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 35 percent, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 27 mm; adding a silicomanganese alloy for manganese and silicon, silicon for silicon and silicon for silicon, aluminum iron, an aluminum wire and a forged coal recarburizer for deoxidation in the tapping process, sequentially adding lime, the recarburizer for pre-deoxidation, the silicomanganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 4.0 kg/ton of steel, adding slag-making materials and alloys before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that the ladle bottom blowing flow rate is 850NL/min and the gas pressure is 1.5MPa in the process of adding lime to the recarburizing agent pre-deoxidation at the beginning of tapping, when the alloy is added to the aluminum iron is added, the ladle bottom blowing flow rate is 630NL/min and the gas pressure is 0.8MPa, the ladle gas flow rate is 60NL/min and the gas pressure is 0.3MPa after the aluminum iron is added, the ladle bottom blowing flow rate is 620NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in after tapping is finished, and the ladle bottom blowing is closed after the aluminum wire is driven in;
the alkalinity of the final slag is 4.5, and the mass percent of the components of the molten steel is controlled as follows: 0.045%, [ S ]: 0.010%, [ P ]: 0.012%; the end point temperature is 1700 ℃, the mass percent of FeO in the final slag is 20%, and the tapping time is 3.2 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, argon gas is blown at the bottom at 820NL/min and the gas pressure is 1.2MPa, the bottom blowing flow is controlled at 650NL/min and the gas pressure is 1.0MPa when slag is added in LF (ladle furnace) refining for slagging, and the steel ladle gas flow is 520NL/min and the gas pressure is 0.8MPa when an alloy material is added; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is 450NL/min, the gas pressure is 0.6MPa, when the calcium wire is fed, the gas flow of the steel ladle is 60NL/min, the gas pressure is 0.3MPa, and the carbon content at the LF outlet is controlled to be 0.074%;
controlling the mass percent of molten steel components [ C ]: 0.074%, [ Mn ]: 1.647%, [ Si ]: 0.43%, [ S ]: 0.001%, [ P ]: 0.014%, [ Als ]: 0.042%, [ N ]: 0.0036%; the temperature of the LF outlet molten steel is 1575-1590 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a ladle to a tundish by adding argon into a long nozzle, and controlling the temperature of molten steel in a continuous casting tundish to be 1560 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft reduction, the withdrawal and straightening temperature is 950 ℃, and the withdrawal speed is controlled to be 1.4-1.5 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag wall and a slag weir, the baking temperature of the tundish is 1150 ℃, the baking time is 3.5 hours, the tundish adopts a magnesium refractory, an aluminum carbon feeding port, an aluminum carbon stopper rod and an immersion type water port, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 12ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 33 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 2 is a low power test result diagram of a continuous casting slab produced in example 2, and it can be seen from FIG. 2 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
Example 3
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the following steps of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1150mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.027%;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 37%, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 25 mm; adding a silicon-manganese alloy for manganese and silicon, silicon for silicon iron, aluminum iron, an aluminum wire and a petroleum coke recarburizer for deoxidation in the tapping process, sequentially adding lime, the recarburizer for pre-deoxidation, the silicon-manganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 3.6 kg/ton of steel, adding a slag-making material and an alloy before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that the ladle bottom blowing flow is 830NL/min and the gas pressure is 1.2MPa in the process of adding lime to the recarburizing agent pre-deoxidation at the beginning of tapping, when the alloy is added to the aluminum iron is added completely, the ladle bottom blowing flow is 700NL/min, the gas pressure is 0.8MPa, the ladle gas flow is 60NL/min and the gas pressure is 0.4MPa after the aluminum iron is added, the ladle bottom blowing flow is 650NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in after tapping, and the ladle bottom blowing is closed after the aluminum wire is driven in;
the alkalinity of the final slag is 3.2, and the mass percent of the components of the molten steel is controlled as follows: 0.025%, [ S ]: 0.013%, [ P ]: 0.010%; the end point temperature is 1670 ℃, the mass percent of FeO in the final slag is 18 percent, and the tapping time is 3.5 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after the steel ladle enters an LF (ladle furnace) workstation, the steel ladle bottom blowing is started, a slag shell is broken, argon is blown at the bottom at 840NL/min, the gas pressure is 1.3MPa, the bottom blowing flow is controlled at 670NL/min and the gas pressure is 0.9MPa when slag is added in LF (ladle furnace) refining for slagging, the steel ladle gas flow is 530NL/min and the gas pressure is 0.8 MPa; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow rate of the steel ladle is 430NL/min, the gas pressure is 0.7MPa, when the calcium wire is fed, the gas flow rate of the steel ladle is 54NL/min, the gas pressure is 0.2MPa, and the carbon content at the LF outlet is controlled at 0.072%;
controlling the mass percent of molten steel components [ C ]: 0.072%, [ Mn ]: 1.65%, [ Si ]: 0.45%, [ S ]: 0.001%, [ P ]: 0.013%, [ Als ]: 0.038%, [ N ]: 0.0033%; the temperature of the LF outlet molten steel is 1575-1590 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a steel ladle to a tundish by adopting a long nozzle and adding argon, and controlling the temperature of molten steel in a continuous casting tundish to be 1542 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft reduction, the withdrawal and straightening temperature is 920 ℃, and the withdrawal speed is controlled to be 1.4-1.5 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag blocking wall and a slag blocking weir, the baking temperature of the tundish is 1120 ℃, the baking time is 3.3 hours, the tundish adopts a magnesium refractory, an aluminum carbon feeding port, an aluminum carbon stopper rod and an immersion type water port, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 10ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 25 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 3 is a low power test result diagram of a continuous casting slab produced in example 3, and it can be seen from FIG. 3 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
Example 4
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1151mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.023%;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 30%, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 22 mm; adding a silicon-manganese alloy for manganese and silicon, silicon for silicon and silicon for silicon, aluminum iron, an aluminum wire and a forged coal recarburizer for deoxidation in the tapping process, sequentially adding lime, a recarburizer for pre-deoxidation, the silicon-manganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 3.7 kg/ton of steel, adding slag-making materials and alloys before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that lime is added to a ladle bottom blowing flow 825NL/min and gas pressure is 1.1MPa in the pre-deoxidation process of a recarburizing agent when tapping is started, when alloy is added to the aluminum iron is added completely, the ladle bottom blowing flow 660NL/min and the gas pressure are 0.8MPa, the ladle gas flow 52NL/min and the gas pressure are 0.1MPa after the aluminum iron is added, after tapping is finished, the ladle bottom blowing flow 635NL/min and the gas pressure are 0.8MPa when an aluminum wire is driven in, and after the aluminum wire is driven in, ladle bottom blowing is closed;
the alkalinity of the final slag is 3.6, and the mass percent of the components of the molten steel is controlled as follows: 0.030%, [ S ]: 0.010%, [ P ]: 0.007%; the final temperature is 1680 ℃, the mass percent of FeO in the final slag is 17 percent, and the tapping time is 4 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, bottom blowing argon gas is 800NL/min, the gas pressure is 1.1MPa, the bottom blowing flow is controlled at 600NL/min and the gas pressure is 0.8MPa when slag is added for slagging in LF (ladle furnace) refining, and the steel ladle gas flow is 500NL/min and the gas pressure is 0.7MPa when an alloy material is added; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is 400NL/min, the gas pressure is 0.5MPa, when the calcium wire is fed, the gas flow of the steel ladle is 50NL/min, the gas pressure is 0.1MPa, and the carbon content at the LF outlet is controlled to be 0.075%;
controlling the mass percent of molten steel components [ C ]: 0.075%, [ Mn ]: 1.61%, [ Si ]: 0.44%, [ S ]: 0.001%, [ P ]: 0.016%, [ Als ]: 0.040%, [ N ]: 0.0030%; the temperature of the LF outlet molten steel is 1570-1585 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a steel ladle to a tundish by adopting a long nozzle and adding argon, and controlling the temperature of molten steel in a continuous casting tundish to be 1550 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft pressure, the withdrawal and straightening temperature is 970 ℃, and the withdrawal speed is controlled to be 1.4-1.5 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag blocking wall and a slag blocking weir, the baking temperature of the tundish is 1200 ℃, the baking time is 4 hours, the tundish adopts a magnesium refractory, an aluminum carbon feeding port, an aluminum carbon stopper rod and an immersion type water port, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 15ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 35 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 4 is a low power test result diagram of a continuous casting slab produced in example 4, and it can be seen from FIG. 4 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
Example 5
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1300mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.020%;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 40%, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 29 mm; adding a silicon-manganese alloy for manganese and silicon, silicon for silicon iron, aluminum iron, an aluminum wire and a petroleum coke recarburizer for deoxidation in the tapping process, sequentially adding lime, the recarburizer for pre-deoxidation, the silicon-manganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 3.8 kg/ton of steel, adding a slag-making material and an alloy before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that the ladle bottom blowing flow rate is 900NL/min and the gas pressure is 1.5MPa in the process of adding lime to the recarburizing agent pre-deoxidation at the beginning of tapping, when the alloy is added to the aluminum iron is added, the ladle bottom blowing flow rate is 700NL/min, the gas pressure is 0.8MPa, the ladle gas flow rate is 60NL/min after the aluminum iron is added, the gas pressure is 0.5MPa, after tapping, the ladle bottom blowing flow rate is 700NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in, and after the aluminum wire is driven in, the ladle bottom blowing is closed;
the alkalinity of the final slag is 4.2, and the mass percent of the components of the molten steel is controlled as follows: 0.040%, [ S ]: 0.008%, [ P ]: 0.010%; the final temperature is 1690 ℃, the mass percent of FeO in the final slag is 16 percent, and the tapping time is 3.8 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after the steel ladle enters an LF (ladle furnace) workstation, the steel ladle bottom blowing is started, a slag shell is broken, bottom blowing argon gas is 870NL/min, the gas pressure is 1.3MPa, the bottom blowing flow is controlled at 680NL/min and 0.9MPa when slag is added in LF (ladle furnace) refining for slagging, the steel ladle gas flow is 530NL/min when an alloy material is added, and the gas pressure is 0.9 MPa; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is 450NL/min, the gas pressure is 0.7MPa, when the calcium wire is fed, the gas flow of the steel ladle is 52NL/min, the gas pressure is 0.2MPa, and the carbon content at the LF outlet is controlled to be 0.075%;
controlling the mass percent of molten steel components [ C ]: 0.075%, [ Mn ]: 1.605%, [ Si ]: 0.44%, [ S ]: 0.001%, [ P ]: 0.014%, [ Als ]: 0.042%, [ N ]: 0.0035%; the temperature of the LF outlet molten steel is 1570-1585 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a steel ladle to a tundish by adopting a long nozzle and adding argon, and continuously casting the molten steel in the tundish at the molten steel temperature of 1556 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft reduction, the withdrawal and straightening temperature is 930 ℃, and the withdrawal speed is controlled to be 1.4-1.5 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag blocking wall and a slag blocking weir, the baking temperature of the tundish is 1140 ℃, the baking time is 3.5 hours, the tundish adopts a magnesium refractory, an aluminum carbon water feeding port, an aluminum carbon stopper rod and an immersion type water inlet, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 14ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 34 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 5 is a low power test result diagram of a continuous casting slab produced in example 5, and it can be seen from FIG. 5 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
Example 6
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1301mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.030%;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 40 percent, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 30 mm; adding a silicon-manganese alloy for manganese and silicon, silicon for silicon iron, aluminum iron, an aluminum wire and a petroleum coke recarburizer for deoxidation in the tapping process, sequentially adding lime, the recarburizer for pre-deoxidation, the silicon-manganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 3.5 kg/ton of steel, adding a slag-making material and an alloy before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that the ladle bottom blowing flow rate is 800NL/min and the gas pressure is 1.1MPa in the process of adding lime to the recarburizing agent pre-deoxidation at the beginning of tapping, when the alloy is added to the aluminum iron is added, the ladle bottom blowing flow rate is 600NL/min and the gas pressure is 0.8MPa, the ladle gas flow rate is 50NL/min and the gas pressure is 0.1MPa after the aluminum iron is added, the ladle bottom blowing flow rate is 600NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in after tapping is finished, and the ladle bottom blowing is closed after the aluminum wire is driven in;
the alkalinity of the final slag is 3.0, and the mass percent of the components of the molten steel is controlled as follows: 0.020%, [ S ]: 0.015%, [ P ]: 0.015 percent; the final temperature is 1660 ℃, the mass percent of FeO in the final slag is 21%, and the tapping time is 3 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, bottom blowing argon gas is 800NL/min, the gas pressure is 1.1MPa, the bottom blowing flow is controlled at 600NL/min and the gas pressure is 0.8MPa when slag is added for slagging in LF (ladle furnace) refining, and the steel ladle gas flow is 500NL/min and the gas pressure is 0.7MPa when an alloy material is added; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is 400NL/min, the gas pressure is 0.5MPa, when the calcium wire is fed, the gas flow of the steel ladle is 50NL/min, the gas pressure is 0.1MPa, and the carbon content at the LF outlet is controlled to be 0.070%;
controlling the mass percent of molten steel components [ C ]: 0.070%, [ Mn ]: 1.60%, [ Si ]: 0.40%, [ S ]: 0.003%, [ P ]: 0.018%, [ Als ]: 0.030%, [ N ]: 0.0050%; the temperature of the LF outlet molten steel is 1570-1585 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a ladle to a tundish by adding argon into a long nozzle, and keeping the temperature of molten steel in the continuous casting tundish at 1539 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft reduction, the withdrawal and straightening temperature is 925 ℃, and the withdrawal speed is controlled to be 1.3-1.4 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag blocking wall and a slag blocking weir, the baking temperature of the tundish is 1100 ℃, the baking time is 3 hours, the tundish adopts a magnesium refractory, an aluminum carbon feeding port, an aluminum carbon stopper rod and an immersion type water port, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 30ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 50 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 6 is a low power test result diagram of a continuous casting slab produced in example 6, and it can be seen from FIG. 6 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
Example 7
The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel FL590X steel tundish comprises the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting, wherein the section of a casting blank is 1050mm, and the specific process steps are as follows:
(1) molten iron desulphurization: desulfurizing molten iron after blast furnace smelting, blowing magnesium powder and lime into a ladle for desulfurization, then completely raking out slag, and feeding the molten iron into a furnace [ S ]: 0.025 percent;
(2) smelting in a decarburization converter: the bottom blowing of nitrogen and argon is switched to 35 percent, a sliding plate is adopted for front blocking, a slag blocking cone and a sliding plate are adopted for rear slag blocking, and the slag discharging thickness is 27 mm; adding a silicon-manganese alloy for manganese and silicon, silicon for silicon iron, aluminum iron, an aluminum wire and a petroleum coke recarburizer for deoxidation in the tapping process, sequentially adding lime, a recarburizer for pre-deoxidation, the silicon-manganese alloy, the silicon iron and the aluminum iron, starting to add materials when tapping 1/3, wherein the adding amount of the lime is 4.0 kg/ton of steel, adding a slag-making material and an alloy before tapping 3/4, adding the aluminum iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping;
the method comprises the steps that the ladle bottom blowing flow rate is 850NL/min and the gas pressure is 1.5MPa in the process of adding lime to the recarburizing agent pre-deoxidation at the beginning of tapping, when the alloy is added to the aluminum iron is added, the ladle bottom blowing flow rate is 630NL/min and the gas pressure is 0.8MPa, the ladle gas flow rate is 60NL/min and the gas pressure is 0.3MPa after the aluminum iron is added, the ladle bottom blowing flow rate is 620NL/min and the gas pressure is 0.8MPa when an aluminum wire is driven in after tapping is finished, and the ladle bottom blowing is closed after the aluminum wire is driven in;
the alkalinity of the final slag is 4.5, and the mass percent of the components of the molten steel is controlled as follows: 0.045%, [ S ]: 0.010%, [ P ]: 0.012%; the end point temperature is 1700 ℃, the mass percent of FeO in the final slag is 20%, and the tapping time is 3.2 min;
(3) LF refining: in carbon alloying, the alloy is preferentially used for carbon matching, and when Mn and Si elements meet the requirements, a carbon wire is used for carbon adjustment; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, argon gas is blown at the bottom at 820NL/min and the gas pressure is 1.2MPa, the bottom blowing flow is controlled at 650NL/min and the gas pressure is 1.0MPa when slag is added in LF (ladle furnace) refining for slagging, and the steel ladle gas flow is 520NL/min and the gas pressure is 0.8MPa when an alloy material is added; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the steel ladle is 450NL/min, the gas pressure is 0.6MPa, when the calcium wire is fed, the gas flow of the steel ladle is 60NL/min, the gas pressure is 0.3MPa, and the carbon content at the LF outlet is controlled to be 0.080%;
controlling the mass percent of molten steel components [ C ]: 0.080%, [ Mn ]: 1.90%, [ Si ]: 0.60%, [ S ]: 0.001%, [ P ]: 0.014%, [ Als ]: 0.060%, [ N ]: 0.0050%; the temperature of the LF outlet molten steel is 1599-1609 ℃;
(4) and (3) continuous casting of the medium plate blank: sealing and protecting molten steel from a ladle to a tundish by adding argon into a long nozzle, and controlling the temperature of molten steel in a continuous casting tundish to be 1560 ℃; the secondary cooling adopts a cooling mode combined with dynamic soft pressure, the withdrawal and straightening temperature is 970 ℃, and the withdrawal speed is controlled to be 1.3-1.4 m/min; the tundish temperature and superheat degree are controlled as shown in a table 4;
the tundish adopts a slag wall and a slag weir, the baking temperature of the tundish is 1150 ℃, the baking time is 3.5 hours, the tundish adopts a magnesium refractory, an aluminum carbon feeding port, an aluminum carbon stopper rod and an immersion type water port, the refractory of the tundish is built by coating materials, a carbon-free low-silicon covering agent is used, and the crystallizer adopts high-alkalinity and low-viscosity medium carbon steel covering slag.
The production process of the embodiment is stably controlled, the fluctuation range of the carbon content of the molten steel of the continuous casting tundish is stably controlled to be 0.070-0.080%, the quality of the molten steel is good, the oxygen mass fraction of the molten steel of the tundish is controlled to be 12ppm, and the nitrogen mass fraction of the molten steel of the tundish is controlled to be 33 ppm.
The continuous casting billet produced by the embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the subcutaneous part of the casting billet have no slag inclusion defects; the high-quality hot-rolled coil produced by hot rolling has excellent surface quality, and the high-quality continuous annealing product is finally produced by cold rolling.
FIG. 7 is a low power test result of the continuous casting slab produced in example 7, and it can be seen from FIG. 7 that the continuous casting slab has no central crack and central porosity.
The chemical composition and the mass percentage of the FL590X steel product of the embodiment are shown in Table 5.
TABLE 4 tundish temperature and degree of superheat (. degree. C.) in FL590X steel in examples 1 to 7
Figure DEST_PATH_IMAGE010
TABLE 5 chemical composition and content (%)
Figure DEST_PATH_IMAGE012
The balance in table 5 is iron and unavoidable impurities.
According to the invention, the continuous casting billet produced by each embodiment has no central crack and central porosity in low-power inspection, the central segregation reaches below B0.5 level, and the surface and the skin of the casting billet have no slag inclusion defect; the hot rolled coil has excellent surface quality.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and it is intended to cover in the claims the invention as defined in the appended claims.

Claims (7)

1. The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel tundish is characterized by comprising the working procedures of blast furnace smelting, molten iron desulphurization, decarburization converter smelting, LF refining and medium slab continuous casting; in the smelting process of the decarburization converter, in the process of adding lime into the recarburizing agent for pre-deoxidation at the beginning of tapping, the bottom blowing flow of the steel ladle is more than or equal to 800NL/min, and the gas pressure is more than or equal to 1.1 MPa; when the alloy is added to the aluminum iron, the bottom blowing flow of the steel ladle is more than or equal to 600NL/min, and the gas pressure is 0.8 MPa; after the aluminum iron is added, the gas flow of the steel ladle is more than or equal to 50NL/min, the gas pressure is more than or equal to 0.1MPa, after the steel tapping is finished, the bottom blowing flow of the steel ladle is more than or equal to 600NL/min when an aluminum wire is driven in, and the gas pressure is 0.8 MPa; closing the bottom blowing of the steel ladle after the aluminum wire is driven into the steel ladle; in the LF refining process, carbon is preferably matched by using an alloy in carbon alloying, and when Mn and Si elements meet requirements, carbon is adjusted by using a carbon wire; in the control of the steel ladle bottom blowing process, after a steel ladle enters an LF (ladle furnace) workstation, steel ladle bottom blowing is started, a slag shell is broken, bottom blowing argon is more than or equal to 800NL/min, the gas pressure is more than or equal to 1.1MPa, the bottom blowing flow is controlled to be more than or equal to 600NL/min when slag is added for slagging in LF (ladle furnace) refining, the gas pressure is more than or equal to 0.8MPa, the steel ladle gas flow is more than or equal to 500NL/min when an alloy material is added, and the gas pressure is more than or equal; when the carbon wire is used for adjusting carbon in the later stage of refining, the gas flow of the ladle is more than or equal to 400NL/min, the gas pressure is more than or equal to 0.5 MPa; when calcium wires are fed, the gas flow of a steel ladle is more than or equal to 50NL/min, the gas pressure is more than or equal to 0.1MPa, and the mass percent [ C ] of the components of the molten steel is controlled in the LF refining process]：0.070-0.076%，[Mn]：1.60-1.66%，[Si]：0.40-0.48%，[S]≤0.003%，[P]≤0.018%，[Als]：0.030-0.039%，[N]Less than or equal to 0.0050 percent; the LF outlet molten steel temperature is determined according to the casting blank section and the continuous casting heat; in the middle slab continuous casting process, a cooling mode combined with dynamic soft reduction is adopted for secondary cooling, the withdrawal and straightening temperature is guaranteed to be more than or equal to 900 ℃, the withdrawal speed is controlled to be 1.3-1.5m/min, and the superheat degree is controlled to be 20-30 ℃; the crystallizer uses high-alkalinity and low-viscosity medium carbon steel covering slag, wherein the content of C is controlled to be 0-10 percent, and SiO is controlled224-35% of CaO, 25-40% of Al2O3Controlling the melting point at 1100 + -50 deg.C and the viscosity at 0.5-2.5 poise at 0-6%.
2. The method as claimed in claim 1, wherein in the molten iron desulfurization step, after the molten iron is desulfurized by injecting magnesium powder and lime, the slag is removed, and [ S ] in the molten iron after the molten iron pretreatment desulfurization is less than or equal to 0.030%.
3. The method for accurately controlling the carbon content of the molten steel of the 600MPa dual-phase steel tundish according to claim 1, wherein in the decarburization converter smelting process, the bottom blowing of nitrogen and argon is switched to be less than or equal to 40%, a sliding plate front stop, a slag blocking cone and a sliding plate rear slag blocking are adopted, and the slag thickness is less than or equal to 30 mm; adding silicon-manganese alloy for manganese and silicon, silicon-iron for silicon, aluminum-iron, aluminum wire, petroleum coke or forged coal for recarburization in the tapping process, wherein the granularity of the recarburization agent is required to be 2-5mm, the sum of the granularity of less than 2mm and the granularity of more than 5mm is not more than 5%, sequentially adding lime, the recarburization agent for pre-deoxidation, the silicon-manganese alloy, the silicon-iron and the aluminum-iron in the feeding sequence, starting feeding when tapping 1/3, adding 3.5-4.0kg of lime per ton of steel, adding slag-making materials and alloys before tapping 3/4, adding aluminum-iron for deoxidation in the tapping process, and driving the aluminum wire for deep deoxidation after tapping.
4. The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel tundish according to claim 1, wherein in the decarburization converter smelting process, the final slag alkalinity is 3.0-4.5; controlling the mass percent of molten steel components [ C ]: 0.020-0.045%, less than or equal to 0.015% of S, and less than or equal to 0.015% of P; the end point temperature is 1660-1700 ℃, the mass percent of FeO in the final slag is less than or equal to 21 percent, and the tapping time is more than or equal to 3 min.
5. The method as claimed in any one of claims 1 to 4, wherein the method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel tundish is characterized in that in the middle slab continuous casting process, the molten steel is protected by sealing the steel from the ladle to the tundish by a long nozzle and adding argon, and the molten steel temperature in the continuous casting tundish is 1539-1560 ℃.
6. The method for accurately controlling the carbon content of the molten steel of the 600MPa dual-phase steel tundish according to any one of claims 1 to 4, wherein in the middle slab continuous casting process, the tundish adopts a slag wall and a slag weir, the baking temperature of the tundish is more than or equal to 1100 ℃, the baking time is more than or equal to 3 hours, the tundish adopts a magnesium refractory, an aluminum carbon upper nozzle, an aluminum carbon stopper rod and a submerged nozzle, the tundish refractory adopts coating masonry, and a carbon-free low-silicon covering agent is used.
7. The method for accurately controlling the carbon content of the molten steel in the 600MPa dual-phase steel tundish according to any one of claims 1 to 4, wherein in the middle slab continuous casting process, the fluctuation range of the carbon content of the molten steel in the continuous casting tundish is stably controlled within 0.010 percent, the oxygen mass fraction of the molten steel in the tundish is controlled to be less than or equal to 30ppm, and the nitrogen mass fraction is controlled to be less than or equal to 50 ppm.
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