CN117467822A - Low-cost RH ultra-low carbon silicon steel smelting method - Google Patents

Low-cost RH ultra-low carbon silicon steel smelting method Download PDF

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CN117467822A
CN117467822A CN202311520297.XA CN202311520297A CN117467822A CN 117467822 A CN117467822 A CN 117467822A CN 202311520297 A CN202311520297 A CN 202311520297A CN 117467822 A CN117467822 A CN 117467822A
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low
ferrosilicon
equal
alloy
steel
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曾召鹏
赵家七
马建超
蔡小锋
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Jiangsu Shagang Group Co Ltd
Zhangjiagang Hongchang Steel Plate Co Ltd
Jiangsu Shagang Iron and Steel Research Institute Co Ltd
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Jiangsu Shagang Group Co Ltd
Zhangjiagang Hongchang Steel Plate Co Ltd
Jiangsu Shagang Iron and Steel Research Institute Co Ltd
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Priority to CN202311520297.XA priority Critical patent/CN117467822A/en
Publication of CN117467822A publication Critical patent/CN117467822A/en
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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
    • C21C7/10—Handling in a vacuum
    • 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
    • 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
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/006—Making ferrous alloys compositions used for making ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • 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)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Analytical Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

The invention discloses a low-cost RH ultra-low carbon silicon steel smelting method, which is used for solving the technical problem of high comprehensive cost of RH low carbon steel or ultra-low carbon steel alloy, and comprises the following process routes: molten iron desulfurization pretreatment, converter smelting, RH vacuum furnace smelting and continuous casting. In the RH vacuumizing treatment process, adding ferrosilicon alloy in batches according to the product components; when the Si content of the target steel grade is less than or equal to 1.0 percent by mass, using common ferrosilicon to replace ultralow-carbon low-sulfur ferrosilicon, and when the Si content of the target steel grade is more than 1.0 percent, using low-carbon low-sulfur ferrosilicon to replace ultralow-carbon low-sulfur ferrosilicon; when ferrosilicon is added in batches, the feeding time, feeding speed and lifting gas flow are controlled, C in the common alloy is removed, and meanwhile, the content of molten steel [ O ] is reduced. The invention greatly reduces the alloy cost, increases the cleanliness of molten steel and improves the comprehensive competitiveness of the product.

Description

Low-cost RH ultra-low carbon silicon steel smelting method
Technical Field
The invention relates to a low-cost RH ultra-low carbon silicon steel smelting method, and belongs to the technical field of steel smelting.
Background
In the modern metallurgical industry production, the external refining technology is one of the most important technological means, wherein the RH refining furnace is developed greatly with decarburization and degassing effects, and is technological equipment for producing high-quality steel products.
The RH refining furnace is composed of an exhaust system, a charging system, a blowing system, a vacuum tank, a dipping pipe, a steel ladle and a steel ladle lifting system, wherein the adding process of alloy raw materials in the furnace is accompanied with a series of physical and chemical phenomena such as oxygen lance blowing, vacuum chamber air suction, molten pool stirring, molten steel decarburization, element oxidation and the like, and the RH refining furnace is a relatively complex process. Therefore, the method has the advantages that the yield of RH alloy elements and the removal of impurity elements are difficult to control in a refined manner, so that when the RH refining furnace is used for smelting low-carbon steel and ultra-low-carbon steel (C is less than or equal to 0.0030 percent in percentage by mass), the steel products have severe requirements on C content, S, P and other impurity elements, in order to achieve the decarburization efficiency of molten steel, the yield of alloy elements and the control of impurity elements in production, high-quality alloys such as metal aluminum, metal manganese, ultra-low-carbon low-sulfur ferrosilicon and the like are often used for alloying the molten steel, the alloy cost is extremely high, the production cost is greatly increased, and a plurality of disadvantages are brought to the development of enterprises.
Patent application CN112553410A discloses a process for deoxidizing RH variety steel by silicon, which takes ordinary ferrosilicon as deoxidized material, utilizes the reaction of high oxygen content at the end point of a converter with ferrosilicon alloy to reduce RH initial oxygen content, thereby achieving the purpose of controlling cost, but the method adds ordinary ferrosilicon alloy in the tapping of the converter, on one hand, a large amount of nonmetallic inclusion can be generated, the pollution to molten steel is very large, and meanwhile, a large amount of alloy is added to cause huge temperature drop to molten steel, so that RH entering temperature is low; on the other hand, the C brought by the common ferrosilicon cannot be suitable for ultra-low carbon steel production, meanwhile, the risk of grid discharge exists in the control of impurity elements such as S, P, so that the RH (relative humidity) entering temperature is low, meanwhile, the problems of poor molten steel cleanliness, excessive C content, grid discharge of impurity elements and the like are caused, the method is not suitable for ultra-low carbon high-quality steel, and therefore, development of a low-cost smelting process method for high-quality low-carbon or ultra-low carbon steel with RH process is needed.
Disclosure of Invention
In order to solve the problems, the invention discloses a simple, effective, reasonable in design and high in operability low-cost RH ultra-low carbon silicon steel smelting method, which comprises the following specific technical scheme:
a low-cost RH ultra-low carbon silicon steel smelting method comprises the following process routes: the method comprises the steps of molten iron desulfurization pretreatment, converter smelting, RH vacuum furnace smelting and continuous casting, and comprises the following steps:
step 1: and (3) desulfurizing and preprocessing molten iron: carrying out desulfurization pretreatment on molten iron by using a desulfurization station;
step 2: smelting in a converter: oxygen blowing and slag making smelting are carried out on the pretreated molten iron by using a top-bottom combined blown converter;
step 3: smelting in an RH vacuum furnace: hoisting molten steel after the converter treatment to an RH treatment station, and then carrying out vacuum decarburization and alloying treatment;
step 4: continuous casting: and carrying out whole-process protection casting on the molten steel after RH vacuum treatment.
Further, the step 1 molten iron desulfurization pretreatment comprises the following steps:
(1) Carrying out desulfurization pretreatment on molten iron by using a KR desulfurization station: after the treatment is finished, the molten iron should satisfy: s is less than or equal to 0.0015 percent, and the temperature is more than or equal to 1300 ℃.
(2) Slagging off after desulfurization is finished: after slag skimming, the [ scum area ]/[ molten iron surface area ] < 2.0%.
Further, the step 2 converter smelting comprises the following steps:
(1) Smelting the desulphurized molten iron by using a top-bottom combined blown converter: blowing molten iron by using a supersonic oxygen lance to achieve the purposes of decarburization, heating and oxidizing impurity elements; lime, dolomite and iron ore are used for slagging so as to achieve the purposes of desulfurizing, dephosphorizing and adsorbing impurities. The end temperature of the converter is controlled to be 1645-1690 ℃, the content of C is 0.03-0.08% and the content of O is 0.03-0.08% according to mass percent;
(2) Tapping by a converter: slag is strictly forbidden in the tapping process of the converter, lime is added when the tapping amount is 20% -30%, and the lime addition amount is 1.5kg/t-3.5kg/t; adding a low-aluminum slag surface deoxidizer to carry out modification treatment on slag after tapping of the converter, wherein the addition amount of the low-aluminum slag surface deoxidizer is 1.0kg/t-2.0kg/t; the ladle bottom blowing stirring is started in the whole tapping process, the bottom blowing flow is 1.5 NL/(t.min) -4.0 NL/(t.min), and the ladle bottom blowing stirring can be transported to an RH processing station after the stirring time is more than 3min.
Further, the vacuum furnace smelting in the step 3 RH comprises the following steps:
(1) RH molten steel inlet station oxygen determination and temperature measurement, and inlet station molten steel: the temperature is more than or equal to 1610 ℃, wherein the temperature of a casting furnace is more than or equal to 1615 ℃; c content is 0.025% -0.075%, O content is 0.025% -0.075%, and T.Fe in slag is less than or equal to 15%;
(2) RH vacuum pumping treatment, adding ferrosilicon alloy in batches according to product components when the RH vacuum chamber pressure is less than or equal to 100mbar and the molten steel O content is less than or equal to 0.045 percent according to mass percent, wherein the ferrosilicon alloy is common ferrosilicon or low-carbon low-sulfur ferrosilicon, when the target steel grade Si is less than or equal to 1.0 percent, using common ferrosilicon to replace ultra-low-carbon low-sulfur ferrosilicon, and when the target steel grade Si is more than 1.0 percent, using low-carbon low-sulfur ferrosilicon to replace ultra-low-carbon low-sulfur ferrosilicon. The ferrosilicon alloy is added in batches: the first batch of alloy, the clean circulation, the second batch of alloy, the clean circulation, the third batch of alloy and the clean circulation until decarburization is finished, 60% of alloy is added into the first two batches, the adding speed is 100-300kg/min, the lifting gas flow is 0.3-0.6/NL (t.min), the lifting gas flow is 1.0-1.3/NL (t.min) during the clean circulation, the rest alloy is added into the third batch, the clean circulation time is ensured to be longer than 5min until decarburization is finished, and specific control parameters of alloy addition are shown in Table 1:
TABLE 1 ferrosilicon addition control parameters
Wherein the common ferrosilicon comprises the following components in percentage by mass: c:0.10% -0.20%, si:70% -80%, P is less than or equal to 0.025%, S is less than or equal to 0.030%, al:1.80% -2.2%, and the balance is iron and unavoidable impurity components; the low-carbon low-sulfur ferrosilicon comprises the following components in percentage by mass: c:0.01% -0.03%, si:75% -85%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, al:0.10% -0.30%, and the balance of iron and unavoidable impurity components;
(3) After molten steel decarburization is finished, sequentially adding metal aluminum and metal manganese for alloying, adding a special slag surface deoxidizer for low-carbon steel into the slag surface during alloying, wherein the adding amount is 1.5kg/t-2.5kg/t, then carrying out clean circulation treatment, the clean circulation time is more than or equal to 6min, finally breaking the blank steel, and the T.Fe content in the steel slag is less than or equal to 5%. Wherein the metallic aluminum component used in the alloying includes: al is more than or equal to 99 percent, and the balance is iron and unavoidable impurity components; the ultra-low carbon low sulfur ferrosilicon comprises the following components in percentage by mass: c:0.007% -0.014%, si:80% -90%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, al:0.05% -0.10%, and the balance of iron and unavoidable impurity components; the manganese metal comprises the following components in percentage by mass: mn is more than or equal to 96 percent, C:0.02% -0.08%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, al is less than or equal to 0.005%, and the balance is iron and unavoidable impurity components.
Further, the step 4 of performing the whole process protection casting on the molten steel after the RH vacuum treatment comprises the following steps: the ladle long nozzle, the argon seal, the tundish covering agent, the immersed nozzle and the crystallizer casting powder are adopted for casting, so that the oxidation of molten steel and alloy components is prevented.
Further, according to the smelting method of the low-cost RH ultra-low carbon silicon steel, the content of Si in the smelted steel grade is 0.80-3.10% by mass percent, the comprehensive yield of Si element in the silicon alloy is more than 90% during RH tapping, and the yield of Mn element in the manganese alloy is more than 97%.
The principle of the invention is as follows:
firstly, through controlling molten iron and converter tapping conditions, the influence of impurity elements such as S, P is reduced to the greatest extent, and S, P exceeding standard caused by adding a large amount of alloy is prevented. The steel tapping temperature of the converter is too low, so that the oxygen content of molten steel is increased due to RH oxygen blowing and heating, and meanwhile, the oxygen content of molten steel is directly increased due to steel tapping peroxidation, so that the problems of low yield of alloy elements, high alloy loss and poor cleanliness of molten steel are finally caused. Therefore, the converter end point must be controlled, combined with slag modification, to stabilize the RH incoming molten steel temperature and C, O conditions, and to ensure that the RH vacuum treatment conditions are appropriate.
And secondly, during RH treatment, the alloy with low price is used for replacing expensive high-quality alloy, and meanwhile, the O content of molten steel is reduced, the alloying loss is reduced, and the aim of greatly reducing the smelting cost is fulfilled.
The adding time of the ferrosilicon alloy is determined by researching the balance and reaction mechanism of C, si and O under high vacuum. According to the change rule of the pressure and the content of C in the vacuum chamber, the vacuum degree is less than 100mbar when ferrosilicon is added, the mass percent of molten steel [ O ] is less than 0.045%, at the moment, the residual [ O ] of molten steel can be utilized to remove C in ferrosilicon, and on one hand, the influence of C brought by common alloy on low-carbon steel or ultra-low-carbon steel can be directly reduced; on the other hand, the method can reduce the residual O of the molten steel, comprehensively reduce the loss in the subsequent alloying, and improve the cleanliness of the molten steel, thereby achieving multiple purposes.
Meanwhile, in order to ensure complete removal of C carried in ferrosilicon, when ferrosilicon is added, the ferrosilicon is added in batches for multiple times, and meanwhile, the adding speed and the lifting gas flow are required to be controlled. The purpose of the method is to reduce the circulation of molten steel, prolong the stay time of ferrosilicon alloy in a vacuum chamber and ensure that C carried by the alloy fully reacts with molten steel residue O in the vacuum chamber. The purpose of increasing the flow rate of lifting gas during the clean circulation is to timely push the replacement of molten steel in the vacuum chamber, ensure the subsequent alloy decarburization effect, and because the residual oxygen in the molten steel in the vacuum chamber is reduced due to the C reaction carried by the molten steel and the alloy in the vacuum chamber, the flow rate of lifting gas is increased immediately after the addition of each batch of alloy is finished, and ensure the decarburization effect of the alloy in the next batch, therefore, the addition time and the addition speed of ferrosilicon alloy are required to be controlled.
Next, determining an alloying sequence of metal aluminum and metal manganese by researching an alloy oxidation sequence, and when the Si content of the target steel grade is less than or equal to 1.0%, using common ferrosilicon to replace ultralow-carbon low-sulfur ferrosilicon; when the Si content of the target steel grade is more than 1.0%, the alloy addition amount is large, and in order to prevent incomplete C removal and excessive S, P impurity elements, low-carbon low-sulfur ferrosilicon is used for replacing ultralow-carbon low-sulfur ferrosilicon. After molten steel alloying, in order to prevent slag from transferring oxygen, a special slag surface deoxidizer for low-carbon steel is added to ensure that the net circulation time is more than or equal to 8min to remove Al 2 O 3 And (5) carrying out inclusion, and finally breaking the blank and tapping. And finally, protecting casting through the whole continuous casting process, so as to achieve the aim of preventing molten steel and alloy elements from oxidizing and ensure the qualified product quality.
The invention has the beneficial effects of greatly reducing the alloy cost and increasing the cleanliness of molten steel. The expensive high-grade alloy is replaced by the common alloy, so that the consumption of low-carbon steel or ultra-low carbon steel high-grade alloy is reduced, and the smelting cost is greatly reduced; the ferrosilicon alloy is added in batches, and the charging time, the charging speed and the lifting gas flow are effectively controlled, so that C in the common alloy is removed, the oxygen element content of molten steel is reduced, the alloy consumption is further reduced, and the cleanliness of the molten steel is improved.
Drawings
FIG. 1 is a process flow diagram of the present invention.
FIG. 2 is a graph showing the balance of carbon, silicon and oxygen at different vacuum degrees in the implementation process of the technical scheme of the invention.
Fig. 3 is a schematic diagram of local Si element enrichment in steel during implementation of the technical scheme of the invention.
Fig. 4 is a schematic diagram showing reduction of silicon element by aluminum in the implementation process of the technical scheme of the invention.
FIG. 5 is a diagram showing SiO in inclusions during the implementation of the present invention 2 Schematic diagram of the percentage of the components.
Detailed Description
The invention is further elucidated below in connection with the drawings of the invention. It should be understood that the following detailed description is merely illustrative of the invention and is not intended to limit the scope of the invention.
Examples
Example 1
An ultra-low carbon silicon steel is smelted, and the process route is as follows: KR desulfurization pretreatment, 180t top-bottom combined blown converter, RH vacuum furnace and slab continuous casting, wherein the RH alloying sequence of the invention is ordinary ferrosilicon, metallic aluminum and metallic manganese. The chemical components of the finished product are as follows by mass percent: c is less than or equal to 0.0030 percent, si:0.87% -1.02%, al:0.23% -0.38%, mn:0.15 to 0.25 percent, P is less than or equal to 0.025 percent, S is less than or equal to 0.0030 percent, and the specific process parameters of smelting in a certain furnace according to the process route of the invention are as follows:
(1) Pretreatment of KR desulfurization station: the condition of the incoming molten iron is S: not more than 0.0400%, molten iron temperature not less than 1350 ℃, molten iron S after desulfurization pretreatment is finished: 0.0015% and the temperature is 1307 ℃.
(2) Smelting in a converter: 180t of converter top and bottom combined blowing decarburization and dephosphorization, wherein the converter end temperature is 1687 ℃, the C content is 0.033 percent and the O content is 0.080 percent according to mass percent; when the tapping amount of the converter is 40 t, adding 420kg of high-quality lime, wherein the ladle bottom blowing flow rate in the tapping process is 330 NL.min -1 Adding 300kg of low-aluminum slag surface deoxidizer after tapping, stirring for 4min, and then conveying to RH treatment;
(3) RH vacuum treatment: the temperature measurement of RH incoming molten steel is 1625 ℃, the C content is 0.031%, the O content is 0.073%, and the T.Fe content in slag is 15%. Because the adding amount of the steel type ferrosilicon alloy is smaller (the target Si is less than or equal to 1.0%), common ferrosilicon is selected to replace ultralow-carbon low-sulfur ferrosilicon, vacuum pumping is started after a ladle is lifted to a processing station, when the pressure of a vacuum chamber is reduced to 100mbar, the content of molten steel O is measured to be 0.045%, and 2452kg of common ferrosilicon is started to be added. The first batch amount was 750kg, and the lift gas flow rate was 60 NL.min -1 The feeding speed was 150kg/min, and the lifting gas flow rate at the end of feeding was set to 180 NL.min -1 After a clean cycle of 2min a second batch was added; the adding amount of the second batch of common ferrosilicon is 750kg, and the lifting gas flow rate is 70 NL.min -1 The feeding speed was 200kg/min, and the lifting gas flow rate at the end of feeding was set to 200 NL.min -1 After a clean cycle of 1.5min a third batch was added; the addition amount of the third batch of common ferrosilicon is 952kg, and the flow rate of the lifting gas is 80 NL.min -1 The feeding speed is 300kg/min, and the materials are fedThe end lift gas flow is set to 290 NL.min -1 After the clean circulation is carried out for 3min, 795kg of metallic aluminum and 232kg of metallic manganese are sequentially added for alloying, 350kg of special slag surface deoxidizer for low carbon steel is added to the slag surface during RH alloying, the clean circulation is finished for 6min, the steel is broken, and the content of T.Fe in RH steel slag is 5%.
(4) Continuous casting: and adopting a large ladle long nozzle, an argon seal, a tundish covering agent, a submerged nozzle and crystallizer casting powder to perform whole-process protection casting.
The main components of the common ferrosilicon used in the RH vacuum furnace are as follows by mass percent: c:0.12%, si:77%, P:0.024%, S:0.003%, al:1.94% of iron and the balance of unavoidable impurity components, and the price of the common ferrosilicon alloy is 8.7 yuan/kg. The steel grade is smelted according to the process method of the invention, and the main chemical components during RH tapping are as follows by mass percent: c:0.0023%, si:0.96%, al:0.34%, mn:0.19%, P:0.019%, S:0.0027 percent, and Fe and other trace elements, the comprehensive yield of Si element is 91.6 percent, the yield of Al element is 77.7 percent, and the yield of Mn element is 98.2 percent. The cost of common ferrosilicon is about 118.4 yuan/t, the cost of metallic aluminum is about 91.9 yuan/t, the cost of metallic manganese is about 27.7 yuan/t, and the total ton of steel alloy cost is about 238.0 yuan/t.
Comparative example 1
An ultra-low carbon silicon steel is smelted, and the process route is as follows: KR desulfurization pretreatment, 180t top-bottom combined blown converter, RH vacuum furnace, slab continuous casting, and RH alloying sequence of metal aluminum, ultralow carbon low sulfur ferrosilicon and metal manganese. The chemical components of the finished product are as follows by mass percent: c is less than or equal to 0.0030 percent, si:0.87% -1.02%, al:0.23% -0.38%, mn:0.15% -0.25%, P is less than or equal to 0.025%, S is less than or equal to 0.0030%, and specific process parameters of smelting in a certain furnace are as follows:
(1) Pretreatment of KR desulfurization station: the condition of the incoming molten iron is S: not more than 0.0400%, molten iron temperature not less than 1350 ℃, molten iron S after desulfurization pretreatment is finished: 0.0014% at 1305 ℃.
(2) Smelting in a converter: 180t converter top and bottom combined blowing decarburization and dephosphorization, wherein the end temperature of the converter is 1669 ℃, the C content is 0.042 percent, the O content is 0.059 percent according to mass percent, and the ladle bottom blowing flow in the tapping process is 350 NL.min -1 Stirring for 5min, and then conveying to RH treatment;
(3) RH vacuum treatment: the temperature measurement of RH incoming molten steel is 1612 ℃, the C content is 0.040%, the O content is 0.056%, and the T.Fe content in slag is 18%. And (3) after the steel ladle is lifted to a treatment station, vacuumizing is started, when the vacuum degree of a vacuum chamber is less than 1.0mbar, a deep decarburization mode is started until decarburization is finished, the oxygen content in molten steel is measured to be 0.035% after decarburization is finished, then 897kg of metallic aluminum, 2366kg of ultralow-carbon low-sulfur ferrosilicon and 246kg of metallic manganese are sequentially added, alloying is carried out, finally, steel is broken out after 5 minutes of clean cycle treatment, and the T.Fe content in RH steel slag is 7.0%.
(4) Continuous casting: and adopting a large ladle long nozzle, an argon seal, a tundish covering agent, a submerged nozzle and crystallizer casting powder to perform whole-process protection casting.
The RH vacuum furnace comprises the following ultra-low carbon and low sulfur ferrosilicon components in percentage by mass: c:0.009%, si:81%, P:0.018%, S:0.0014%, al:0.06 percent of iron and unavoidable impurity components, and the price of the ultralow-carbon low-sulfur ferrosilicon alloy is 19.5 yuan/kg. The main chemical components during final RH tapping are as follows by mass percent: c:0.0019%, si:1.03%, al:0.32%, mn:0.20%, P:0.017%, S:0.0019%, and Fe and other trace elements, the comprehensive yield of Si element is 96.7%, the yield of Al element is 64.8%, and the yield of Mn element is 98.6%. The cost of the ultralow-carbon low-sulfur ferrosilicon is about 256.3 yuan/t, the cost of the metallic aluminum is about 103.7 yuan/t, the cost of the metallic manganese is about 29.4 yuan/t, and the total ton steel alloy cost is about 389.4 yuan/t.
In the embodiment 1, the cost for smelting the steel alloy is only 238.0 yuan/t, 151.4 yuan can be saved for ton steel, and the alloy cost is greatly reduced by 38.9%.
Example 2
A high-grade ultra-low carbon silicon steel is smelted, and the process route is as follows: KR desulfurization pretreatment, 180t top-bottom combined blown converter, RH vacuum furnace, slab continuous casting, and the RH alloying sequence of the invention is low carbon and low sulfur ferrosilicon, metallic aluminum and metallic manganese. The chemical components of the finished product are as follows by mass percent: c is less than or equal to 0.0025 percent, si:1.85% -2.05%, al:0.25% -0.40%, mn:0.25% -0.40%, P is less than or equal to 0.020%, S is less than or equal to 0.0030%, and specific process parameters of smelting in a certain furnace according to the process route of the invention are as follows:
(1) Pretreatment of KR desulfurization station: the condition of the incoming molten iron is S: not more than 0.0400%, molten iron temperature not less than 1350 ℃, molten iron S after desulfurization pretreatment is finished: 0.0014% at 1311 ℃.
(2) Smelting in a converter: 180t of converter top and bottom combined blowing decarburization and dephosphorization, wherein the end temperature of the converter is 1669 ℃, the content of C is 0.039% and the content of O is 0.063% by mass percent; when the tapping amount of the converter is 45 t, 400kg of high-quality lime is added, and the ladle bottom blowing flow rate in the tapping process is 350 NL.min -1 280kg of low-aluminum slag surface deoxidizer is added after tapping, and the mixture is stirred for 3min and then conveyed to RH treatment;
(3) RH vacuum treatment: the temperature measurement of RH incoming molten steel is 1612 ℃, the C content is 0.037%, the O content is 0.061%, and the T.Fe content in slag is 15%. Because the adding amount of the steel type ferrosilicon alloy is large (the target Si is more than 1.0%), the low-carbon low-sulfur ferrosilicon is selected to replace the ultralow-carbon low-sulfur ferrosilicon, the steel ladle is lifted to a treatment station and then vacuumized, when the pressure of a vacuum chamber is reduced to 100mbar, the content of molten steel O is measured to be 0.043%, and 4923kg of low-carbon low-sulfur ferrosilicon is added. The first batch amount was 1480kg and the lift gas flow rate was 90 NL.min -1 The feeding speed was 200kg/min, and the lifting gas flow rate at the end of feeding was set to 200 NL.min -1 After a clean cycle of 3min a second batch was added; the addition amount of the second batch of common ferrosilicon is 1480kg, and the flow rate of the lifting gas is 100 NL.min -1 The feeding speed was 300kg/min, and the lifting gas flow rate at the end of feeding was set to be 230 NL.min -1 After a clean cycle of 3min a third batch was added; the adding amount of the third batch of common ferrosilicon is 1963kg, and the lifting gas flow rate is 110 NL.min -1 The feeding speed was 300kg/min, and the lifting gas flow rate at the end of feeding was set at 320 NL.min -1 After the clean circulation is carried out for 4min, 867kg of metal aluminum and 415kg of metal manganese are sequentially added for alloying, 300kg of special slag surface deoxidizer for low carbon steel is added to the slag surface during RH alloying, the clean circulation is carried out for 7min after the alloying is finished, the steel is broken, and the content of T.Fe in RH steel slag is 5%.
(4) Continuous casting: and adopting a large ladle long nozzle, an argon seal, a tundish covering agent, a submerged nozzle and crystallizer casting powder to perform whole-process protection casting.
The main components of the low-carbon low-sulfur ferrosilicon used in the RH vacuum furnace are as follows by mass percent: c:0.014%, si:77%, P:0.017%, S:0.002%, al:0.09 percent of iron and unavoidable impurity components, and the price of the low-carbon low-sulfur ferrosilicon alloy is 13.5 yuan/kg. The steel grade is smelted according to the process method of the invention, and the main chemical components during RH tapping are as follows by mass percent: c:0.0015%, si:1.95%, al:0.32%, mn:0.29%, P:0.016%, S:0.0019%, and Fe and other trace elements, the comprehensive yield of Si element is 92.6%, the yield of Al element is 67.1%, and the yield of Mn element is 97.8%. The cost of the low-carbon low-sulfur ferrosilicon is about 369.2 yuan/t, the cost of the metallic aluminum is about 100.2 yuan/t, the cost of the metallic manganese is about 49.8 yuan/t, and the total ton steel alloy cost is about 519.2 yuan/t.
Comparative example 2
A high-grade ultra-low carbon silicon steel is smelted, and the process route is as follows: KR desulfurization pretreatment, 180t top-bottom combined blown converter, RH vacuum furnace, slab continuous casting, and RH alloying sequence of metal aluminum, ultralow carbon low sulfur ferrosilicon and metal manganese. The chemical components of the finished product are as follows by mass percent: c is less than or equal to 0.0025 percent, si:1.85% -2.05%, al:0.25% -0.40%, mn:0.25% -0.40%, P is less than or equal to 0.020%, S is less than or equal to 0.0030%, and specific process parameters of smelting in a certain furnace are as follows:
(1) Pretreatment of KR desulfurization station: the condition of the incoming molten iron is S: not more than 0.0400%, molten iron temperature not less than 1350 ℃, molten iron S after desulfurization pretreatment is finished: 0.0015% at 1308 ℃.
(2) Smelting in a converter: 180t converter top and bottom combined blowing decarburization and dephosphorization, wherein the end temperature of the converter is 1675 ℃, the C content is 0.037 percent, the O content is 0.066 percent according to mass percent, and the ladle bottom blowing flow in the tapping process is 260 NL.min -1 Stirring for 4min, and then conveying to RH treatment;
(3) RH vacuum treatment: the temperature measurement of RH incoming molten steel is 1618 ℃, the C content is 0.035%, the O content is 0.065%, and the T.Fe content in slag is 17% by mass percent. And (3) after the steel ladle is lifted to a treatment station, vacuumizing is started, when the vacuum degree of a vacuum chamber is less than 1.0mbar, a deep decarburization mode is started until decarburization is finished, the O content in molten steel is measured to be 0.034% after decarburization is finished, then 956kg of metallic aluminum, 4598kg of ultralow-carbon low-sulfur ferrosilicon and 398kg of metallic manganese are sequentially added, alloying is carried out, finally, steel is broken out after 8 minutes of clean cycle treatment, and the T.Fe content in RH steel slag is 8.0%.
(4) Continuous casting: and adopting a large ladle long nozzle, an argon seal, a tundish covering agent, a submerged nozzle and crystallizer casting powder to perform whole-process protection casting.
The RH vacuum furnace comprises the following ultra-low carbon low sulfur ferrosilicon components in percentage by mass: c:0.009%, si:81%, P:0.018%, S:0.002%, al:0.06 percent of iron and unavoidable impurity components, and the price of the ultralow-carbon low-sulfur ferrosilicon alloy is 19.5 yuan/kg. The main chemical components during final RH tapping are as follows by mass percent: c:0.0014%, si:1.99%, al:0.32%, mn:0.21%, P:0.015%, S:0.0017 percent, and Fe and other trace elements, the comprehensive yield of Si element is 96.2 percent, the yield of Al element is 60.9 percent, and the yield of Mn element is 98.8 percent. The cost of the ultra-low carbon low sulfur ferrosilicon is about 498.1 yuan/t, the cost of the metallic aluminum is about 110.5 yuan/t, the cost of the metallic manganese is about 47.5 yuan/t, and the total ton steel alloy cost is about 656.1 yuan/t.
In the embodiment 2, the cost for smelting the steel alloy is only 519.2 yuan/t, 136.9 yuan can be saved for ton of steel, and the alloy cost is greatly reduced by 20.9%.
FIG. 2 shows the carbon-silicon-oxygen balance at various vacuum levels, and it can be seen that Si is more strongly bonded to [ O ] than C when the vacuum level is < 500mbar and C < 0.070%; when the vacuum degree is less than 200mbar and C is more than 0.020%, the binding capacity of C and [ O ] is stronger than that of Si; when the vacuum degree is less than 100mbar and C is more than 0.003%, the binding capacity of C and O is stronger than that of Si. If the ferrosilicon is added too early, the RH vacuum chamber pressure is higher (more than 500 mbar), the oxidizing property of molten steel is strong (O is more than 0.050%), the bonding capability of Si element and molten steel residual O is stronger than C, so that a large amount of Si element is oxidized, and the element yield is reduced; if the adding time is too late, the pressure of a vacuum chamber is low (less than 1.0 mbar), but the high-speed decarburization period of molten steel is over, the oxygen content in the steel is low (less than 0.030%), the carbon-oxygen reaction is weakened, and a large amount of ferrosilicon alloy is added to cause carburetion of the molten steel, so that decarburization is incomplete, and finally the C content exceeds the standard. So when the vacuum degree is less than 100mbar, the residual O in the molten steel can react with C in the common ferrosilicon alloy preferentially along with the continuous reduction of the vacuum degree, thereby achieving the aim of decarburizing and preserving silicon.
Fig. 3 is a schematic diagram of enrichment of local Si element in steel, and the addition speed and the lifting gas flow are controlled to prevent enrichment of Si element caused by massive accumulation of alloy, increase of local Si element concentration, and finally oxidation loss of Si element.
FIG. 4 is a schematic diagram showing reduction of Si element by aluminum, and FIG. 5 is a schematic diagram showing an example of reduction of Si element by aluminum, although the adding method of ferrosilicon alloy has been determined by controlling vacuum degree and molten steel residual O, si element is inevitably oxidized during adding because of the structural characteristics of RH vacuum chamber, so metallic aluminum is added during alloying, on one hand, molten steel can be further deoxidized, and molten steel is purified; on the other hand, the Si element oxidized in the earlier stage can be reduced, and the yield of the Si element is comprehensively improved as shown in fig. 4 and 5.
The technical means disclosed by the scheme of the invention is not limited to the technical means disclosed by the technical means, and also comprises the technical scheme formed by any combination of the technical features.
With the above-described preferred embodiments according to the present invention as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the description, but must be determined according to the scope of claims.

Claims (11)

1. A low-cost RH ultra-low carbon silicon steel smelting method is characterized by comprising the following steps: the method comprises the steps of molten iron desulfurization pretreatment, converter smelting, RH vacuum furnace smelting and continuous casting, and comprises the following steps:
step 1: and (3) desulfurizing and preprocessing molten iron: carrying out desulfurization pretreatment on molten iron by using a desulfurization station;
step 2: smelting in a converter: oxygen blowing and slag making smelting are carried out on the pretreated molten iron by using a top-bottom combined blown converter;
step 3: smelting in an RH vacuum furnace: the molten steel after the converter treatment is lifted to an RH processing station, then vacuum decarburization and alloying treatment are carried out, and ferrosilicon is added in batches according to the product components in the RH vacuumizing treatment process;
when the Si content of the target steel grade is less than or equal to 1.0%, using common ferrosilicon to replace ultralow-carbon low-sulfur ferrosilicon, and when the Si content of the target steel grade is more than 1.0% in terms of mass percent, using low-carbon low-sulfur ferrosilicon to replace ultralow-carbon low-sulfur ferrosilicon;
when ferrosilicon is added in batches, the feeding time, feeding speed and lifting gas flow are controlled, C in the common alloy is removed, and meanwhile, the content of molten steel [ O ] is reduced;
step 4: continuous casting: and carrying out whole-process protection casting on the molten steel after RH vacuum treatment.
2. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 1, wherein after the pretreatment of molten iron desulfurization in step 1 is completed, the molten iron should satisfy: s is less than or equal to 0.0015 percent, and the temperature is more than or equal to 1300 ℃.
3. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 2, wherein the slag is removed after the molten iron desulfurization pretreatment process is finished, and the [ slag area ]/[ molten iron surface area ]. Ltoreq.2.0% after the slag removal.
4. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 1, wherein in step 2, the top-bottom combined blown converter is used to smelt the desulphurized molten iron; blowing molten iron by using a supersonic oxygen lance; lime, dolomite and iron ore are used for slagging, the end temperature of the converter is controlled at 1645-1690 ℃, the content of C is 0.03-0.08% by mass percent, and the content of O is 0.03-0.08%.
5. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 1, wherein in the step 2, slag is strictly forbidden in the tapping process of the converter, lime is added when the tapping amount is 20% -30%, and the lime addition amount is 1.5kg/t-3.5kg/t; adding a low-aluminum slag surface deoxidizer to carry out modification treatment on slag after tapping of the converter, wherein the addition amount of the low-aluminum slag surface deoxidizer is 1.0kg/t-2.0kg/t; the ladle bottom blowing stirring is started in the whole tapping process, the bottom blowing flow is 1.5 NL/(t.min) -4.0 NL/(t.min), and the stirring time is more than 3min.
6. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 1, wherein the molten steel lifted to the RH processing station in step 3 satisfies: the temperature is more than or equal to 1610 ℃, wherein the temperature of a casting furnace is more than or equal to 1615 ℃; the content of C is 0.025-0.075% by mass, the content of O is 0.025-0.075% by mass, and the content of T.Fe in the slag is less than or equal to 15%.
7. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 1, wherein in the step 3, RH vacuum pumping treatment is performed, and when the pressure of an RH vacuum chamber is less than or equal to 100mbar and the O content of molten steel is less than or equal to 0.045% in percentage by mass, ferrosilicon is added in batches: the method comprises the steps of alloy preparation in the first batch, clean circulation, alloy preparation in the second batch, clean circulation, alloy preparation in the third batch, clean circulation until decarburization is finished, 60% of alloy is added in the first two batches, the adding speed is 100-300kg/min, and the rest alloy is added in the third batch, so that the clean circulation time is ensured to be longer than 5min until decarburization is finished.
8. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 7, wherein the flow rate of the lifting gas is reduced at the time of alloy addition, and the flow rate of the lifting gas is 0.3-0.6 NL/(t·min); increasing the lift gas flow rate in the net circulation, wherein the lift gas flow rate in the net circulation is 1.0-1.3 NL/(t.min), and the lift gas flow rate is increased immediately after the addition of each batch of alloy is finished.
9. The method according to claim 1, wherein in the step 3, aluminum and manganese are added in sequence for alloying after decarburization of molten steel, a slag surface deoxidizer special for low carbon steel is added to the slag surface during alloying, the addition amount is 1.5kg/t-2.5kg/t, the net circulation treatment is performed, the net circulation time is more than or equal to 6min, finally, the steel is broken, and the T.Fe content in the steel slag is less than or equal to 5%.
10. The low-cost RH ultra-low carbon silicon steel according to claim 9, wherein the alloy components used for the alloying treatment are:
the metal aluminum comprises the following components in percentage by mass: al is more than or equal to 99 percent, and the balance is iron and unavoidable impurity components; the ultra-low carbon low sulfur ferrosilicon comprises the following components in percentage by mass: c:0.007% -0.014%, si:80% -90%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, al:0.05% -0.10%, and the balance of iron and unavoidable impurity components; the manganese metal comprises the following components in percentage by mass: mn is more than or equal to 96 percent, C:0.02% -0.08%, P is less than or equal to 0.015%, S is less than or equal to 0.015%, al is less than or equal to 0.005%, and the balance is iron and unavoidable impurity components;
the ferrosilicon alloy is common ferrosilicon or low-carbon low-sulfur ferrosilicon, wherein the common ferrosilicon comprises the following components in percentage by mass: c:0.10% -0.20%, si:70% -80%, P is less than or equal to 0.025%, S is less than or equal to 0.030%, al:1.80% -2.2%, and the balance is iron and unavoidable impurity components; the low-carbon low-sulfur ferrosilicon comprises the following components in percentage by mass: c:0.01% -0.03%, si:75% -85%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, al:0.10% -0.30%, and the balance of iron and unavoidable impurity components.
11. The method for smelting low-cost RH ultra-low carbon silicon steel according to claim 1, wherein the step 4 of performing full process protection casting on the molten steel after RH vacuum treatment comprises: and casting by using a large ladle long nozzle, an argon seal, a tundish covering agent, a submerged nozzle and mold flux.
CN202311520297.XA 2023-11-15 2023-11-15 Low-cost RH ultra-low carbon silicon steel smelting method Pending CN117467822A (en)

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