CN109402326B - Refining process for LF furnace added molten iron - Google Patents

Refining process for LF furnace added molten iron Download PDF

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Publication number
CN109402326B
CN109402326B CN201910022535.1A CN201910022535A CN109402326B CN 109402326 B CN109402326 B CN 109402326B CN 201910022535 A CN201910022535 A CN 201910022535A CN 109402326 B CN109402326 B CN 109402326B
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steel
molten
iron
molten iron
refining
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CN109402326A (en
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战东平
王东伟
齐敏
王佳喜
屈乐欣
邱国兴
李长生
马竞翔
姜周华
张慧书
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Northeastern University China
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Northeastern University China
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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
    • 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
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • 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
    • 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)
  • Treatment Of Steel In Its Molten State (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)

Abstract

The invention discloses a refining process for adding molten iron into an LF (ladle furnace), and belongs to the field of ferrous metallurgy. The invention adds molten iron into an LF furnace to carry out external refining, and utilizes C in the molten iron and O in the molten steel to carry out oxidation reduction exothermic reaction to heat the molten steel, thereby reducing the consumption of graphite electrodes and the heating time, and removing the O in the molten steel, wherein the reaction formula is as follows: [C] and + [ O ] ═ co (g). Meanwhile, the generated gas can promote the floating of the inclusion. Therefore, the molten iron can partially replace the deoxidizer and the argon, so that the use of the deoxidizer and the argon is reduced, the consumption of a graphite electrode and the heating time are reduced, the electric energy is saved, the smelting period is shortened, and the production cost of steel products is reduced while the product quality is ensured; si and Mn in the molten iron can also be used as alloy elements, so that the alloy consumption is reduced, the price of the molten iron is reduced due to the price reduction of the iron ore in recent years, and the cost can be reduced and the benefit can be improved by making steel by using the molten iron more.

Description

Refining process for LF furnace added molten iron
Technical Field
The invention relates to the field of ferrous metallurgy, in particular to a refining process for adding molten iron into an LF (ladle furnace).
Background
An LF Furnace (Ladle Furnace), i.e. a Ladle refining Furnace, was developed and used by japan university and iron and steel companies in 1971, and the main metallurgical functions of the LF Furnace include: (1) the temperature is raised by electric arc generated between the graphite electrode and the molten steel, and the temperature in the furnace can be accurately controlled; (2) forming reducing atmosphere deoxidation in the furnace by using a graphite electrode; (3) bottom blowing argon gas for stirring to promote the floating of impurities; (4) white slag refining and the like. The method is rapidly developed into an indispensable external refining process for iron and steel enterprises due to simple equipment, flexible operation, low investment cost and good refining effect. But for iron and steel smelting, the existing process and technology are improved, so that the production cost is reduced, and the production of high-quality products is more and more paid more attention by enterprises.
In the refining process of the LF furnace, a graphite electrode is adopted for heating and raising the temperature and creating a reducing atmosphere, and bottom blowing argon is adopted for stirring molten steel to promote impurities to float. But the process inevitably consumes a great deal of graphite electrodes, electric energy, Ar gas, slag, refractory materials and the like in the refining process.
In the actual production process of the steel enterprises, in order to reduce the burden of the converter and enable the whole production flow of steel to be more compact and efficient, the molten iron pretreatment desulphurization, desiliconization and dephosphorization technology is rapidly developed, and the technology is now an indispensable link in the production flow of the steel enterprises. With the improvement of the hot metal pretreatment process, the quality of the blast furnace hot metal pretreated by the hot metal is continuously improved, and the mass fraction of harmful elements such as S, P in the hot metal can meet the requirements of final products through the hot metal pretreatment technology. And beneficial elements such as Mn and the like are also contained in the blast furnace molten iron after the molten iron pretreatment, and if the blast furnace molten iron is directly used for LF refining, the elements such as Mn, Si and the like in the molten iron can be recovered, so that the alloy consumption in the LF refining process is reduced. According to the found literature, domestic LF refining and related research are mainly focused on optimizing LF production process and production equipment at present, and the application of LF furnace and molten iron refining process is not reported in literature.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a refining process of an LF furnace by adding molten iron, which improves and optimizes the refining process of the LF furnace and solves the problems of high cost, large energy and resource consumption and low production efficiency of the traditional refining process of the LF furnace at present.
An LF furnace molten iron adding refining process comprises the following steps:
step 1: during the tapping process of the converter, adding a slagging agent into a ladle, blowing argon, lowering an electrode when the ladle enters a refining position of an LF furnace, and electrifying and heating to start slagging and refining;
step 2: obtaining molten steel A after 8-12 min of slagging refining, measuring the temperature of the molten steel A, sampling, measuring the mass fraction of oxygen in the molten steel A, calculating the addition amount of molten iron according to the mass fraction of oxygen in the molten steel A when the mass fraction of oxygen in the molten steel A is 0.06 +/-0.03%, and adding the required molten iron into an LF furnace;
and step 3: after molten iron is added, refining is continued for 4-6min to obtain molten steel B, temperature measurement and sampling are carried out on the molten steel B, a slag former is added, and alloying operation is carried out to obtain refined molten steel C;
and 4, step 4: and feeding a Ca-Si wire into the molten steel C, carrying out soft argon blowing, finishing final refining, and entering the next working procedure.
In the step 2, the temperature of molten steel in the LF refining furnace before the molten iron is added is 1500-1550 ℃. In the step 2, the adding amount of the molten iron is determined according to formulas (I) and (II);
msteel×xSteel-4％×mIron＝(mSteel+mIron)×xTarget(I)
mPractice of＝α×mIron(II)
In the formulae (I), (II):
msteel-mass of molten steel in the LF furnace, t;
xsteel-mass fraction of O in the molten steel,%;
miron-theoretically calculating the amount of iron water added, t;
xtargetTaking x as mass fraction of O in refined molten steelTarget＝0.001％；
mPractice of-the actual amount of molten iron added, t;
the coefficient α is 1-3.
In the step 2, the added molten iron is one or more of pretreated molten iron.
Compared with the prior art, the invention has the beneficial effects that:
the invention adds molten iron into an LF furnace to carry out external refining, and utilizes C in the molten iron and O in the molten steel to carry out oxidation reduction exothermic reaction to heat the molten steel, thereby reducing the consumption of graphite electrodes and the heating time, and removing the O in the molten steel, wherein the reaction formula is as follows: [C] and + [ O ] ═ co (g). Meanwhile, the generated gas can promote the floating of the inclusion. Therefore, the molten iron can partially replace the deoxidizer and the argon, so that the use of the deoxidizer and the argon is reduced, the consumption of a graphite electrode and the heating time are reduced, the electric energy is saved, the smelting period is shortened, and the production cost of steel products is reduced while the product quality is ensured; si and Mn in the molten iron can also be used as alloy elements, so that the alloy consumption is reduced, the price of the molten iron is reduced due to the price reduction of the iron ore in recent years, and the cost can be reduced and the benefit can be improved by making steel by using the molten iron more.
Detailed Description
The specific embodiment of the refining process for adding molten iron into the LF furnace is as follows:
example 1
The refining process of adding molten iron into a 120t LF furnace comprises the following specific steps:
step 1, after converter tapping, adding a slag former into a 120t LF furnace, starting to connect argon blowing, descending an electrode after entering a refining position of the LF furnace, and electrifying and heating to raise the temperature of molten steel to 1500-1550 ℃; starting refining operation;
step 2, obtaining molten steel A after slagging and refining for 10min, measuring the temperature of the molten steel A, sampling and detecting, wherein the measured temperature of the molten steel A is 1530 ℃; detecting that the mass fraction of oxygen in the molten steel is 0.065% by adopting a chemical element full analysis method, and calculating the addition of the molten iron according to the formulas (I) and (II) to obtain:
msteel×xSteel-4％×mIron＝(mSteel+mIron)×xTarget(I)
mPractice of＝α×mIron(II)
Figure BDA0001941288720000031
mIron1.92t, so the amount of iron water m actually addedPractice ofα × 1.92t, where α is 2.5, mPractice of＝2.5×1.92t＝4.8t。
And step 3: adding 4.8t of molten iron, continuously refining, obtaining molten steel B after 5min, measuring the temperature of the molten steel B, sampling, measuring the temperature of the molten steel B to be 1570 ℃, adding a slagging constituent, and carrying out alloying operation to obtain refined molten steel C;
and 4, step 4: and (3) feeding a Ca-Si wire into the refined molten steel C, carrying out soft argon blowing to finish the final refining, and entering the next procedure, wherein the smelting time is about 45 min.
Compared with the traditional process (namely, the full molten steel LF refining process is adopted), when the process disclosed by the invention is adopted for production, the heating time of the graphite electrode of the LF furnace is shortened by 5-15 min, and the soft argon blowing time is shortened by 8-12 min.
Example 2
The refining process of adding molten iron into a 120t LF furnace comprises the following specific steps:
step 1, after converter tapping, starting to connect argon blowing for a 120t LF furnace, adding a slagging agent, entering an LF furnace refining position, descending an electrode, and electrifying and heating to raise the temperature of molten steel to 1500-1550 ℃; starting slagging and refining operation;
step 2: obtaining molten steel A after 10min of slagging and refining, and sampling and detecting the molten steel A to obtain the molten steel A with the temperature of 1536 ℃; detecting that the mass fraction of oxygen in the molten steel A is 0.054% by adopting a chemical element total analysis method, and calculating the adding amount of the molten iron according to the formulas (I) and (II) to obtain:
msteel×xSteel-4％×mIron＝(mSteel+mIron)×xTarget(I)
mPractice of＝α×mIron(II)
Figure BDA0001941288720000032
mIron1.59t, so the amount of iron water m actually addedPractice ofα × 1.59t, where α is 2.5, mPractice of＝2.5×1.59t＝4.77t。
And step 3: adding 4.77t molten iron, continuously refining for 10min to obtain molten steel B, measuring the temperature of the molten steel B, sampling and detecting, measuring the temperature of the molten steel B to be 1577 ℃, adding a slagging constituent, and carrying out alloying operation to obtain refined molten steel C;
and 4, step 4: and (3) feeding a Ca-Si wire into the refined molten steel C, carrying out soft argon blowing to finish the final refining, and entering the next procedure, wherein the smelting time is 43 min.
Compared with the traditional process (namely, the full molten steel LF refining process is adopted), when the process disclosed by the invention is adopted for production, the heating time of the graphite electrode of the LF furnace is shortened by 5-15 min, and the soft argon blowing time is shortened by 8-12 min.

Claims (3)

1. A refining process for adding molten iron into an LF furnace is characterized by comprising the following steps:
step 1: during the tapping process of the converter, adding a slagging agent into a ladle, blowing argon, lowering an electrode when the ladle enters a refining position of an LF furnace, and electrifying and heating to start slagging and refining;
step 2: obtaining molten steel A after 8-12 min of slagging refining, measuring the temperature of the molten steel A, sampling, measuring the mass fraction of oxygen in the molten steel A, calculating the adding amount of molten iron according to the formulas (I) and (II) when the mass fraction of the oxygen in the molten steel A is 0.06% +/-0.03%, and adding the required molten iron into an LF furnace:
m steel×x Steel-4%×m Iron=(m Steel+m Iron)×x Target(I)
m Practice of=α×m Iron(II)
In the formulae (I), (II):
m steelThe mass of the liquid steel in the LF furnace, t,
x steel-the mass fraction of O in the molten steel,%,
m ironTheoretical calculation of the amount of iron water added, t,
x targetTaking x target =0.001% of the mass fraction of O in the refined molten steel,
m practice of-the actual amount of molten iron added, t,
coefficient of performanceαTaking 1-3;
and step 3: after molten iron is added, refining is continued for 4-6min to obtain molten steel B, temperature measurement and sampling are carried out on the molten steel B, a slag former is added, and alloying operation is carried out to obtain refined molten steel C;
and 4, step 4: and (4) absorbing Ca-Si wires into the molten steel C, carrying out soft argon blowing, finishing final refining, and entering the next working procedure.
2. The refining process of LF added molten iron as claimed in claim 1, wherein in step 2, the temperature of molten iron in the LF refining furnace before adding molten iron is 1500-1550 ℃.
3. The refining process of the LF furnace with the added molten iron as claimed in claim 1, wherein in the step 2, the molten iron is one or more of pretreated molten iron.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960547A (en) * 1972-12-18 1976-06-01 Youngstown Sheet And Tube Company Steelmaking process
JPH0617497B2 (en) * 1987-10-16 1994-03-09 株式会社神戸製鋼所 Method for producing pig iron for casting for melting cupola
CN102839255A (en) * 2012-09-07 2012-12-26 南京钢铁股份有限公司 Method for rapidly deoxidizing and remaining carbon by secondarily adding melted iron to electric furnace

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960547A (en) * 1972-12-18 1976-06-01 Youngstown Sheet And Tube Company Steelmaking process
JPH0617497B2 (en) * 1987-10-16 1994-03-09 株式会社神戸製鋼所 Method for producing pig iron for casting for melting cupola
CN102839255A (en) * 2012-09-07 2012-12-26 南京钢铁股份有限公司 Method for rapidly deoxidizing and remaining carbon by secondarily adding melted iron to electric furnace

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