CN111944940A - Method for controlling inclusions in IF steel - Google Patents

Method for controlling inclusions in IF steel Download PDF

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Publication number
CN111944940A
CN111944940A CN201910396244.9A CN201910396244A CN111944940A CN 111944940 A CN111944940 A CN 111944940A CN 201910396244 A CN201910396244 A CN 201910396244A CN 111944940 A CN111944940 A CN 111944940A
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steel
slag
converter
oxygen
equal
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Inventor
董廷亮
刘丽香
陈明毅
耿豪
赵军普
张学辉
李牧明
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Jiangsu Jicui Metallurgy Technology Institute Co ltd
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Jiangsu Jicui Metallurgy Technology Institute Co ltd
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    • 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
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/02—Dephosphorising or desulfurising
    • 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
    • C21C5/30—Regulating or controlling the blowing
    • C21C5/35—Blowing from above and through the bath
    • 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
    • C21C5/36—Processes yielding slags of special composition
    • 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
    • C21C7/04—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
    • C21C7/068—Decarburising
    • 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
    • C21C7/072—Treatment with gases
    • 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
    • C21C7/076—Use of slags or fluxes as treating agents
    • 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
    • C21C7/10—Handling in a vacuum
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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

Abstract

The invention belongs to the technical field of steel smelting, and discloses a method for controlling inclusions in IF steel. The adopted process route is as follows: molten iron pretreatment → converter smelting → RH vacuum treatment → slab continuous casting. The [ S ] in the molten iron after the pretreatment and desulfurization of the molten iron is less than or equal to 0.0030 percent, and slag skimming is carried out; the sulfur in the waste steel and the lime is controlled by smelting in the converter, and the carbon content, the oxygen activity and the molten steel temperature at the end point of the converter are controlled; tapping, controlling slag discharging and modifying top slag; RH vacuum treatment is firstly carried out natural decarburization, oxygen is supplemented and blown according to the oxygen determination condition, and then deoxidation, alloying and sedation treatment are carried out; the continuous casting adopts full-protection casting, adopts carbon-free double-layer covering agent and carbon-free covering slag, and adopts residual steel operation. The invention effectively controls the inclusions in the IF steel and improves the purity of the IF steel.

Description

Method for controlling inclusions in IF steel
Technical Field
The invention belongs to the technical field of steel smelting, and particularly relates to a method for controlling inclusions in IF steel.
Background
IF Steel (Interstitial-Free Steel), which is Interstitial Free Steel, is sometimes called ultra low carbon Steel, has excellent deep drawing properties and is widely used in the automotive industry. In the IF steel, because the content of C, N is low, a certain amount of strong carbon-nitrogen compound forming elements such as titanium (Ti), niobium (Nb) and the like are added, and interstitial atoms such as carbon, nitrogen and the like in the steel are completely fixed into the carbon-nitrogen compound, so that the obtained clean ferritic steel without interstitial atoms, namely the ultra-low carbon interstitial-free steel.
High quality IF steel requires extremely high control of elements such as C, S, N in the steel in order to obtain good deep drawability, and also requires that the steel should not contain large-sized live cluster inclusions, particularly inclusions of not less than 50 μm, in order to obtain good surface quality, because such inclusions are extremely likely to form cold rolling surface defects during cold rolling, resulting in defective steel sheets. On the other hand, Al generated in deoxidation2O3The impurities are difficult to completely remove, and are easy to gather and grow in the casting process, so that the nozzle is nodulated, the nozzle is blocked, the smooth production is influenced, and the quality of steel is damaged.
The invention aims to reduce the generation of deoxidation product alumina and promote the removal of alumina while ensuring the control of the IF steel composition, avoid the occurrence of nozzle blockage and reduce the number of inclusions in steel.
Disclosure of Invention
The invention aims to provide a method for controlling inclusions in IF steel, which solves the technical problem of removing alumina inclusions in the IF steel.
In order to achieve the purpose, the technical scheme of the invention is as follows: a method for controlling inclusions in IF steel adopts the following process route: molten iron pretreatment → converter smelting → RH vacuum treatment → slab continuous casting, and the specific process parameters are as follows:
(1) pretreating molten iron: pre-desulfurizing molten iron, wherein S in the molten iron after desulfurization is less than or equal to 0.0030 percent, and slagging-off treatment is carried out after desulfurization;
(2) smelting in a converter: the scrap steel ratio is less than or equal to 20 percent, high-sulfur scrap steel is not used, and the weight percentage of sulfur in the scrap steel is less than or equal to 0.0060 percent; controlling the quality of lime, wherein the sulfur content in the lime is less than or equal to 0.05 percent; smelting by using a converter with good combined blowing; the end point carbon content [ C ] of the converter is 0.035-0.050%, the end point temperature T is 1700-1720 ℃, and the end point oxygen activity a [ O ] is 600-800 ppm; controlling FeO in the final slag of the converter to be below 25 percent;
(3) tapping by a converter: smelting by using a converter with good combined blowing; the scrap steel ratio is less than or equal to 20 percent, high-sulfur scrap steel is not used, and the weight percentage of sulfur in the scrap steel is less than or equal to 0.0060 percent; controlling the quality of lime, wherein the sulfur content in the lime is less than or equal to 0.05 percent; the end point carbon content [ C ] of the converter is 0.035-0.050%, the end point temperature T is 1700-1720 ℃, and the end point oxygen activity a [ O ] is 600-800 ppm; controlling FeO in the final slag of the converter to be below 25 percent;
(4) RH vacuum treatment: in the vacuum treatment process, firstly, the carbon content in the steel is controlled in a natural decarburization mode, and the natural decarburization time is 8 min; then oxygen determination is carried out, if the oxygen determination is not less than 250ppm, oxygen supplement blowing is not carried out; if the fixed oxygen value is less than 250ppm, the blowing is performed with the amount of oxygen being equal to the weight of the molten steel x (250-fixed oxygen value) x 7 x 10-4(m3) After the supplementary blowing, carrying out vacuum treatment for 3-5 min; after the decarburization is finished, oxygen is determined, aluminum is added for deoxidation, and the adding amount of the aluminum is 0.0014 multiplied by the oxygen determination value multiplied by the weight (kg) of the molten steel; adding a modifier into the vacuum chamber for treatment for 5-8 min after 1min after adding aluminum; alloying, and breaking the blank after vacuum circulation treatment for 5-8 min; and (5) after the vacuum is finished, carrying out sedation treatment on the molten steel, wherein the sedation time is more than or equal to 20 min.
(5) Slab casting: in order to prevent secondary oxidation, nitrogen increase and carbon increase in the casting process, full-protection casting is adopted in the continuous casting process; in order to prevent carburetion and adsorption inclusion, the tundish adopts a carbon-free double-layer covering agent and carbon-free covering slag; in order to prevent ladle slag from flowing into the tundish, residual steel operation is adopted.
Further, in the method for controlling the inclusions in the IF steel, the modifier used in converter tapping and RH vacuum treatment is a high-aluminum high-calcium modifier.
Further, the above method for controlling inclusions in IF steel, wherein the amount of molten steel remaining per ladle is more than 3% by weight of the ladle during slab casting.
Further, the method for controlling the inclusion in the IF steel, wherein a tundish covering agent adopted in the slab casting process is a double-layer covering agent, and an upper layer is an alkaline covering agent and adsorbs the inclusion; the lower layer is an acidic covering agent to reduce temperature drop.
The invention has the beneficial effects that: the invention provides a method for cooperatively controlling inclusions in IF steel through the whole process of molten iron pretreatment → converter smelting → RH vacuum treatment → slab continuous casting production from the aspects of smooth process, realization of production of high-cleanliness IF steel, low production cost, small harm to environment and equipment, easy operation and large-scale production, and provides an important technical support for stable production of high-quality IF steel.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
In the examples shown in tables 1 to 4, taking a steel plate with a top-bottom combined blown converter smelting mark of DC06 as an example, the smelting process flow is molten iron pretreatment → converter smelting → RH vacuum treatment → slab continuous casting, and the specific operations are as follows:
TABLE 1 smelting raw material parameters of the converter of the present invention
Figure BDA0002058228990000031
TABLE 2 converter smelting end point and post-tapping index of the examples of the present invention
Figure BDA0002058228990000032
Table 3 RH treatment parameters of the examples of the invention
Figure BDA0002058228990000033
The results of the grain size analysis of inclusions on the test heats using the ASPEX inclusion scanner are shown in table 4.
TABLE 4 inclusions in finished steels according to examples of the invention
Figure BDA0002058228990000034
As can be seen from table 4: after the process is used, the IF steel has no inclusion with the grain diameter of more than or equal to 50 mu m, and the inclusion with the grain diameter of 20-50 mu m is less than 1.2 inclusions/mm2。

Claims (4)

1. A method for controlling inclusions in IF steel adopts the following process route: molten iron pretreatment → converter smelting → RH vacuum treatment → slab continuous casting, and the specific process parameters are as follows:
(1) pretreating molten iron: pre-desulfurizing molten iron, wherein S in the molten iron after desulfurization is less than or equal to 0.0030 percent, and slagging-off treatment is carried out after desulfurization;
(2) smelting in a converter: smelting by using a converter with good combined blowing; the scrap steel ratio is less than or equal to 20 percent, high-sulfur scrap steel is not used, and the weight percentage of sulfur in the scrap steel is less than or equal to 0.0060 percent; controlling the quality of lime, wherein the sulfur content in the lime is less than or equal to 0.05 percent; the end point carbon content [ C ] of the converter is 0.035-0.050%, the end point temperature T is 1700-1720 ℃, and the end point oxygen activity a [ O ] is 600-800 ppm; controlling FeO in the final slag of the converter to be below 25 percent;
(3) tapping by a converter: the tapping is not deoxidized; controlling the slag discharging amount during tapping, ensuring successful slag stopping, and ensuring that the target slag thickness is less than or equal to 50 mm; top slag, a slag melting agent and a modifier are added in the tapping process to modify the top slag of the steel ladle, so that the content of FeO and MnO in the steel slag is less than or equal to 5 percent; argon is blown in the whole process of ladle bottom blowing in the tapping process;
(4) RH vacuum treatment: in the vacuum treatment process, firstly, the carbon content in the steel is controlled in a natural decarburization mode, and the natural decarburization time is 8 min; then oxygen determination is carried out, if the oxygen determination is not less than 250ppm, oxygen supplement blowing is not carried out; if the fixed oxygen value is less than 250ppm, the blowing is performed with the amount of oxygen being equal to the weight of the molten steel x (250-fixed oxygen value) x 7 x 10-4(m3) After the supplementary blowing, carrying out vacuum treatment for 3-5 min; after the decarburization is finished, oxygen is determined, aluminum is added for deoxidation, and the adding amount of the aluminum is 0.0014 multiplied by the oxygen determination value multiplied by the weight (kg) of the molten steel; adding a modifier into the vacuum chamber for treatment for 5-8 min after 1min after adding aluminum; alloying, and breaking the blank after vacuum circulation treatment for 5-8 min; and (5) after the vacuum is finished, carrying out sedation treatment on the molten steel, wherein the sedation time is more than or equal to 20 min.
(5) Slab casting: in order to prevent secondary oxidation, nitrogen increase and carbon increase in the casting process, full-protection casting is adopted in the continuous casting process; in order to prevent carburetion and adsorption inclusion, the tundish adopts a carbon-free double-layer covering agent and carbon-free covering slag; in order to prevent ladle slag from flowing into the tundish, residual steel operation is adopted.
2. The method of controlling inclusions in IF steel according to claim 1 wherein the modifier used in the converter tapping and RH vacuum treatment is a high alumina high calcium modifier.
3. The method of controlling inclusions in IF steel according to claim 1 wherein the amount of molten steel remaining per ladle during slab casting is greater than 3% by weight of the ladle.
4. The method of controlling inclusions in IF steel as claimed in claim 1, wherein the tundish covering agent used in the slab casting process is a double-layer covering agent, and the upper layer is an alkaline covering agent to adsorb inclusions; the lower layer is an acidic covering agent to reduce temperature drop.
CN201910396244.9A 2019-05-14 2019-05-14 Method for controlling inclusions in IF steel Pending CN111944940A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115323115A (en) * 2022-09-15 2022-11-11 湖南华菱涟源钢铁有限公司 Method for improving cleanliness of filter steel
CN115418431A (en) * 2022-08-03 2022-12-02 新疆八一钢铁股份有限公司 Operation method for external pretreatment of high-sulfur steel scrap
CN115558736A (en) * 2022-10-17 2023-01-03 湖南华菱涟源钢铁有限公司 Method for improving molten steel cleanliness of IF steel

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CN102719600A (en) * 2012-03-29 2012-10-10 鞍钢股份有限公司 Production method of ultra-low carbon steel
CN102816898A (en) * 2012-09-25 2012-12-12 鞍钢股份有限公司 Method for modifying interstitial-free steel top slag
US20130056167A1 (en) * 2010-06-23 2013-03-07 Feng Zhang Method for controlling extremely low ti in extra low carbon alsi-killed steel
CN107012282A (en) * 2016-01-27 2017-08-04 鞍钢股份有限公司 Method for improving purity of high-quality ultra-low carbon steel
CN107354269A (en) * 2017-05-26 2017-11-17 内蒙古包钢钢联股份有限公司 The method that RH complex deoxidizations produce ultra-low-carbon steel

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Publication number Priority date Publication date Assignee Title
CN101550475A (en) * 2009-05-15 2009-10-07 首钢总公司 Method for producing ultra-low-carbon steel
US20130056167A1 (en) * 2010-06-23 2013-03-07 Feng Zhang Method for controlling extremely low ti in extra low carbon alsi-killed steel
CN102719600A (en) * 2012-03-29 2012-10-10 鞍钢股份有限公司 Production method of ultra-low carbon steel
CN102816898A (en) * 2012-09-25 2012-12-12 鞍钢股份有限公司 Method for modifying interstitial-free steel top slag
CN107012282A (en) * 2016-01-27 2017-08-04 鞍钢股份有限公司 Method for improving purity of high-quality ultra-low carbon steel
CN107354269A (en) * 2017-05-26 2017-11-17 内蒙古包钢钢联股份有限公司 The method that RH complex deoxidizations produce ultra-low-carbon steel

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115418431A (en) * 2022-08-03 2022-12-02 新疆八一钢铁股份有限公司 Operation method for external pretreatment of high-sulfur steel scrap
CN115323115A (en) * 2022-09-15 2022-11-11 湖南华菱涟源钢铁有限公司 Method for improving cleanliness of filter steel
CN115323115B (en) * 2022-09-15 2024-01-30 湖南华菱涟源钢铁有限公司 Method for improving cleanliness of filter steel
CN115558736A (en) * 2022-10-17 2023-01-03 湖南华菱涟源钢铁有限公司 Method for improving molten steel cleanliness of IF steel

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Application publication date: 20201117