WO2023274222A1 - 一种钢液的钙处理方法 - Google Patents

一种钢液的钙处理方法 Download PDF

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WO2023274222A1
WO2023274222A1 PCT/CN2022/101856 CN2022101856W WO2023274222A1 WO 2023274222 A1 WO2023274222 A1 WO 2023274222A1 CN 2022101856 W CN2022101856 W CN 2022101856W WO 2023274222 A1 WO2023274222 A1 WO 2023274222A1
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molten steel
calcium treatment
furnace
steel
ladle
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PCT/CN2022/101856
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English (en)
French (fr)
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胡汉涛
马志刚
吴雄
沈燕
王波
陈兆平
谢树元
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宝山钢铁股份有限公司
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Publication of WO2023274222A1 publication Critical patent/WO2023274222A1/zh

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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
    • C21C7/064—Dephosphorising; 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • 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
    • C21C7/10—Handling in a vacuum
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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

Definitions

  • the invention belongs to the field of metallurgical steelmaking technology, and in particular relates to a calcium treatment method for molten steel.
  • Iron and steel smelting experience is generally: carbonaceous reducing agent to reduce iron oxide - oxidizing agent to remove carbon in molten iron - metal reducing agent to remove oxygen in molten steel; as a common reducing agent, aluminum is often used as a final deoxidizer for molten steel , most of the reaction product Al2O3 with oxygen floats to the top slag of the ladle, and a small amount remains in the steel in the form of second-phase inclusions; in the subsequent rolling or processing, the much harder Al2O3 It interacts with the steel matrix, causing damage to the steel matrix, which becomes the cause of cracks in the steel and even directly produces cracks, reducing the mechanical properties of the steel.
  • Sulfur in steel as an element that is easy to segregate, can easily react with Mn to form manganese sulfide; after heating and pressure processing, manganese sulfide with good ductility forms a long strip-shaped second phase, the length of which can even reach more than 1m, which is greatly reduced.
  • the transverse impact performance of steel, and the pitting corrosion and hydrogen embrittlement of steel matrix are also closely related to the inclusion of manganese sulfide in steel.
  • Ca is usually added to the deoxidized molten steel to perform calcium treatment on the molten steel. After adding Ca, the following reaction occurs in molten steel
  • the Al 2 O 3 in the molten steel is transformed into calcium aluminate inclusions with lower hardness, and the sulfur in the steel reacts with Ca preferentially to inhibit the formation of manganese sulfide, thereby improving the mechanical properties and mechanical properties of the steel.
  • the common method of adding calcium to the molten steel is to add pure Ca wire, calcium-iron and silicon-calcium alloy wire to the molten steel at a high speed of 200-400m/min through the wire feeder at the special wire feeding position after the ladle is removed from the vacuum refining device.
  • the former is wrapped with a variety of special materials, and the latter two are filled in steel hollow tubes in the form of powder.
  • inert gas Ar or N 2
  • This method of adding calcium has at least several disadvantages: 1) It is necessary to set up a separate adding station, occupying the workshop space; 2) The ladle needs to be run in different processing positions, prolonging the entire refining time; 3) It is difficult to accurately control the flow rate of the stirring gas at the bottom of the ladle, This leads to uneven mixing of calcium in the molten steel (the stirring gas flow rate is too small) or the ladle top slag is blown away to expose the molten steel and is oxidized (the gas flow rate is too large); 4) When Ca wire is added to the ladle, the calcium reacts violently with the molten steel, It is easy to produce a lot of smoke and dust, polluting the environment.
  • the industry urgently needs to develop a new calcium treatment method for molten steel, which does not need to set up a separate calcium wire station, and can solve the disadvantages of adding calcium to the ladle in the form of calcium wire in the traditional way, so as to alleviate the crowded workshop, shorten the refining time, and improve The purity of molten steel and the effect of improving the environment.
  • the purpose of the present invention is to provide a calcium treatment method for molten steel.
  • By adding calcium to molten steel during vacuum refining of molten steel and canceling the calcium wire station it can solve the problem of traditional calcium wire processing.
  • the disadvantages of adding calcium to the ladle by adding calcium to the ladle can alleviate the crowding of the workshop, shorten the refining time, improve the purity of molten steel and improve the environment.
  • the present invention adopts the following technical solutions:
  • the invention provides a calcium treatment method for molten steel, which comprises the steps of adjusting the vacuum system pressure to 5-25kPa after the composition adjustment of the molten steel during vacuum refining, and then adding Ca to the molten steel for calcium treatment.
  • the present invention also provides a steelmaking method, including molten iron pretreatment, primary smelting, ladle refining furnace (LF furnace) refining, vacuum refining and casting, wherein, in the vacuum refining, after the liquid steel composition is adjusted, the vacuum System pressure to 5 ⁇ 25kPa, then add Ca to molten steel for calcium treatment.
  • the molten steel is circulated for 2 to 8 minutes, and then the pressure of the vacuum system is adjusted; and/or
  • the amount of Ca added is 0.1-0.25kg/t steel, and the Ca addition method is vacuum addition; and/or
  • the molten steel is circulated for 1-8 minutes, and the vacuum refining is completed;
  • the contents of chemical components S, Mn, Al and Ca in the molten steel satisfy: S ⁇ 0.0020wt%, Mn: 0.1-2.2wt%, for example 0.1-2.0wt%, Al: 0.015-0.1wt% %, Ca: 0.0005 ⁇ 0.0025wt%; and/or
  • the vacuum refining device used in the vacuum refining is RH vacuum circulation degassing refining furnace (RH furnace), vacuum decarburization furnace (VD furnace) or vacuum oxygen blowing decarburization furnace (VOD furnace).
  • the Ca is added to the molten steel from an elevated bin of a vacuum refining device.
  • the vacuum refining device adopts an RH furnace
  • Ar blowing and stirring is carried out at the bottom of the ladle throughout, and the flow rate of Ar is controlled to be 10-50 NL/(h ⁇ t steel).
  • the molten iron is desulfurized to an S content of ⁇ 20ppm.
  • tapping amount When the tapping amount reaches 1/6-1/4, preferably 1/5, add lime 1.5-3.5kg/t steel to the ladle, and add aluminum slag 0.3-1.5kg/t steel to the ladle before the end of tapping; and / or
  • the molten steel S content in the ladle is ⁇ 80ppm;
  • the device used for the primary refining is a converter or an argon oxygen decarburization furnace (AOD furnace) or an electric furnace.
  • the ladle slag thickness is less than 80 mm, and the molten steel S content in the ladle is ⁇ 80 ppm;
  • the thickness of the ladle slag is less than 300mm, and the S content of the molten steel in the ladle is ⁇ 20ppm.
  • the ratio of the mass percentage of CaO to the mass percentage of Al 2 O 3 in the inclusions of the slab obtained by casting is 0.7-1.1.
  • the density of the inclusions in the slab obtained from the casting is 7.0-8.0/mm2.
  • the calcium treatment method or steelmaking method targets steel with the following chemical composition: C: 0.01-0.1wt%, Si ⁇ 0.03wt%, Mn: 0.8-2.2wt% , Al: 0.02-0.08wt%, Ti: 0.02-0.08wt%, P ⁇ 0.015wt%, S ⁇ 0.0020wt%, N ⁇ 0.004wt%, the balance is Fe and unavoidable impurities.
  • the calcium treatment method or the steelmaking method further includes a hot rolling step after the casting.
  • the flaw detection defect rate of the hot-rolled sheet obtained after the hot rolling is 0, and/or the impact energy KV2 at -20°C is 430-475J.
  • no soot is released into the atmosphere during the calcium treatment.
  • the vacuum refining device used in the vacuum refining is a RH furnace.
  • the time from RH exhaust to ladle lifting is 30-35 minutes.
  • no Ca addition station is set up separately during the calcium treatment process.
  • Fig. 1 is the schematic flow sheet of the steelmaking method of some embodiments of the present invention.
  • Fig. 2 is a graph showing the relationship between the saturation concentration of Ca in molten steel at different temperatures and the pressure of the vacuum system according to the present invention.
  • the steelmaking method provided by the present invention includes molten iron pretreatment, primary smelting, LF furnace refining, vacuum refining and casting.
  • vacuum refining after the liquid steel composition is adjusted, adjust the vacuum system pressure to 5-25kPa, Then add Ca in molten steel and carry out calcium treatment;
  • the above-mentioned calcium treatment method and steelmaking method of molten steel are applicable to calcium treatment class steel products, and its technological process is as follows:
  • Hot metal pretreatment-primary smelting furnace (converter, AOD furnace, electric furnace, etc.)-LF furnace-vacuum refining furnace-casting (die casting, continuous casting).
  • the primary smelting furnace can be a converter, an AOD furnace, or an electric furnace.
  • ladle top slag modification is carried out, and then LF furnace refining is carried out.
  • the ladle slag thickness is less than 80mm, and the S content of molten steel in the ladle is ⁇ 80ppm; after LF refining, the ladle slag thickness is less than 300mm, and the S content of molten steel in the ladle is ⁇ 20ppm.
  • the molten steel obtained in the LF furnace refining process is transferred to the vacuum refining device.
  • the molten steel continues to circulate for 2 to 8 minutes, and then adjust the vacuum system pressure to 5 to 25kPa, and then to the steel Ca is added to the molten steel for calcium treatment.
  • the amount of Ca added is 0.1-0.25kg/t steel.
  • the Ca addition method is vacuum addition. Ca can be added to the molten steel from the high-level silo of the vacuum refining device.
  • the molten steel continues to circulate for 1-8 minutes, and the vacuum refining ends; after the final vacuum refining, the contents of S, Mn, Al and Ca in the molten steel meet: S ⁇ 0.002wt%, Mn: 0.1-2.2wt%, For example, 0.1 ⁇ 2.0wt%, Al: 0.015 ⁇ 0.1wt%, Ca: 0.0005 ⁇ 0.0025wt%; the vacuum refining device used in the above vacuum refining adopts RH furnace or VD furnace or VOD furnace, and RH furnace is the preferred vacuum refining device; wherein when the vacuum refining device adopts the RH furnace, in order to ensure that Ca is fully mixed, in the above-mentioned calcium treatment, during the entire Ca addition, Ar blowing and stirring is carried out at the bottom of the ladle, and the Ar flow rate is controlled to be 10-50NL/( h ⁇ t steel). At the same time, it is preferable to control the ladle slag thickness to be less than 300mm during the whole
  • the molten steel is cast to obtain a slab, wherein the ratio of the mass percentage of CaO to the mass percentage of Al 2 O 3 in the inclusions of the slab is 0.7-1.1.
  • the density of inclusions in the slab is 7.0-8.0/mm 2 .
  • the treatment object of the liquid steel calcium treatment method of the present invention is steel with the following main chemical composition, such as hot-rolled steel: C: 0.01-0.1wt%, Si ⁇ 0.03wt%, Mn: 0.8-2.2wt% %, Al: 0.02-0.08wt%, Ti: 0.02-0.08wt%, P ⁇ 0.015wt%, S ⁇ 0.0020wt%, N ⁇ 0.004wt%, and the balance is Fe.
  • main chemical composition such as hot-rolled steel: C: 0.01-0.1wt%, Si ⁇ 0.03wt%, Mn: 0.8-2.2wt% %, Al: 0.02-0.08wt%, Ti: 0.02-0.08wt%, P ⁇ 0.015wt%, S ⁇ 0.0020wt%, N ⁇ 0.004wt%, and the balance is Fe.
  • the amount of calcium added it is necessary to make the formed oxide inclusions in the liquid phase, and no single solid phase Al 2 O 3 inclusions can exist. If the amount of Ca added is too large, CaO will be formed, which will easily lead to an increase in the unqualified rate of hot-rolled sheet flaw detection, which will lead to an increase in the risk of corrosion of cold-rolled sheets in subsequent production, and an increase in raw material costs; if the amount of Ca added is too low, the molten steel will The reaction of Al 2 O 3 inclusions is not sufficient, there is a single solid-phase Al 2 O 3 inclusions, and even MnS is formed in hot-rolled products; according to theoretical calculations and actual verification, the upper limit of Ca addition is 0.25kg/ t steel, the lower limit is 0.1kg/t steel.
  • the molten steel calcium treatment method of the present invention will be further introduced in conjunction with specific examples below.
  • the following examples and comparative examples belong to hot-rolled products, and the main components are: C: 0.01-0.1wt%, Si ⁇ 0.03wt%, Mn: 0.8-2.2wt%, Al: 0.02-0.08wt%, Ti : 0.02 ⁇ 0.08wt%, P ⁇ 0.015wt%, S ⁇ 0.0020wt%, N ⁇ 0.004wt%, and Fe.
  • the process route adopted in this embodiment is: molten iron pretreatment (desulfurization, dephosphorization) ⁇ primary smelting (converter top-bottom combined blowing smelting, tapping) ⁇ ladle top slag modification ⁇ LF furnace refining (heating, deoxidation, desulfurization, Alloying) ⁇ RH furnace vacuum refining (vacuum degassing, adjusting composition, adding Ca for Ca treatment) ⁇ casting ⁇ hot rolling.
  • This example is a typical furnace for smelting in the present invention: the converter blowing is completed, the slag is blocked and the steel is tapped, when the tapping amount reaches 1/5, lime is added at 2.5kg/t of steel, and at the end of tapping, aluminum slag is added at 1.2kg/t of steel .
  • the thickness of ladle slag is 65mm, and the sulfur content of molten steel in the ladle is 75ppm; after LF furnace refining, the sulfur content of molten steel in the ladle is 20ppm, and the thickness of ladle slag is 220mm.
  • Vacuum refining of molten steel to remove gas adjust the composition of molten steel to the specified value, circulate the molten steel for 5 minutes, adjust the vacuum pressure above the molten steel to 7kPa, add pure Ca 0.15kg/t steel, and add Ca at the bottom of the ladle throughout the process Perform Ar blowing and stirring, and control the Ar flow rate to 20NL/(h ⁇ t steel), then continue to circulate the molten steel for 5 minutes, and end the vacuum treatment.
  • the thickness of the ladle slag is less than 300mm; casting, followed by hot rolling;
  • the performance parameters of the obtained slab and the hot-rolled plate obtained after hot rolling are shown in Table 2.
  • Table 1 is a comparison of other situations in which the solution of the present invention is applied in actual production, and comparative examples 1 to 6, which adopt a conventional wire feeding process to add Ca cored wire for Ca treatment.
  • the process route adopted in Examples 1-6 is: molten iron pretreatment (desulfurization, dephosphorization) ⁇ primary smelting (converter top-bottom combined blowing smelting, tapping) ⁇ ladle top slag modification ⁇ LF furnace refining (heating, deoxidation , desulfurization, alloying) ⁇ RH furnace vacuum refining (vacuum degassing, adjusting composition, adding Ca for Ca treatment) ⁇ casting ⁇ hot rolling.
  • the process route adopted in comparative examples 1-6 is: molten iron pretreatment (desulfurization, dephosphorization) ⁇ primary smelting (converter top-bottom combined blowing smelting, tapping) ⁇ ladle top slag modification ⁇ LF furnace refining (heating, deoxidation, Desulfurization, alloying) ⁇ RH furnace vacuum refining (vacuum degassing, adjusting composition) ⁇ adding Ca-containing cored wire at the wire feeding station for Ca treatment ⁇ casting ⁇ hot rolling. See Table 1 and Table 2 for the specific control parameters of the examples and comparative examples and the properties of the slab and the hot-rolled plate.
  • the density of inclusions in the slab is 7.0-8.0 pieces/mm 2 , and the ratio of the mass percentage of inclusion CaO to the mass percentage of Al 2 O 3 is 0.7-1.1 , the defect detection rate of the hot-rolled plate is all 0, the impact energy KV2 at -20°C is 430-475J, the time from RH exhaust to ladle lifting is 30-35min, and no smoke is released into the atmosphere during the Ca treatment process; implementation Example Compared with the comparative example, the technology of the present invention is used to carry out Ca treatment on molten steel, and the density of inclusions in the slab is 10-20% lower than that of the conventional wire-feeding process; The conventional wire feeding process has a small number of flaw detection defects; the impact energy KV2 of the hot-rolled plate at -20°C is about 450J, which is equivalent to the conventional wire feeding process; the average time from RH exhaust to ladle lifting is 34 minutes, which is about 10 minutes shorter than the conventional wire feeding process
  • the liquid steel calcium treatment method of the present invention does not need to set up a separate Ca addition station, which saves workshop space; saves the process of ladle running at different processing positions, shortens the refining time; the molten steel has no risk of bare leakage, and the steel
  • the purity of the liquid is stable and controllable; no large amounts of smoke and dust are directly released into the factory building, reducing environmental pollution.

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Abstract

本发明公开了一种钢液的钙处理方法，其中钢液的钙处理方法包括铁水预处理、初炼、真空精炼和浇铸，真空精炼中，钢液成分调整结束后，调整真空系统压力至5～25kPa，然后向钢液中添加Ca进行钙处理。该钢液的钙处理方法，通过在钢液真空精炼中，向钢液中添加钙，取消钙线工位，能够解决传统以钙线形式向钢包中加钙的弊端，达到缓解厂房拥挤，缩短精炼时间，提高钢液纯净度和改善环境的效果。

Description

一种钢液的钙处理方法 技术领域
本发明属于冶金炼钢工艺领域，尤其涉及一种钢液的钙处理方法。
背景技术
钢铁冶炼经历一般为：碳质还原剂还原铁氧化物-氧化剂脱除铁液中的碳-金属还原剂脱除钢液中的氧；作为常用的还原剂铝，常常用作钢液终脱氧剂，与氧的反应产物三氧化二铝绝大部分上浮至钢包顶渣中，少量以第二相夹杂物形式残留钢中；在随后轧制或加工过程中，硬度大得多的三氧化二铝与钢基体相互作用，造成钢基体损伤，成为钢中裂纹的诱因甚至直接产生裂纹，降低钢的力学性能。
钢中硫作为一种易偏析元素，极易与Mn反应，生成硫化锰；随后加热和压力加工时，延展性良好的硫化锰形成长带状第二相，长度甚至达1m以上，大幅度降低钢的横向冲击性能，且钢基体点腐蚀和氢脆与钢中硫化锰夹杂也有密切联系。
鉴于此，为消除或抑制钢中Al 2O 3和MnS危害，通常会向脱氧后的钢液中加入Ca，对钢液进行钙处理。加入Ca后，钢液中发生下述反应
2[Ca]+[S]＝(CaS)(s)                       (1)
x[Ca]+y(Al 2O 3)＝(xCaO·zAl 2O 3)+2(y-z)[Al]    (2)
使得钢液中Al 2O 3转化为硬度较低的铝酸钙类夹杂，钢中的硫优先与Ca反应抑制硫化锰的生成，进而提高钢的力学性能和机械性能。
向钢液加入钙的常见方法是钢包移出真空精炼装置后，通过喂丝机在专用喂丝位，以200-400m/min高速向钢液中加入纯Ca线、钙铁和硅钙合金线，前者以多种特殊材料包裹，后二者以粉末形式填充于钢制空心管内，同时辅以钢包底部吹入惰性气体(Ar或N 2)搅拌钢液，使得加入钢液中的钙充分混合均匀。这种钙 加入方式至少存在几个弊端：1)需单独设立加入工位，占据厂房空间；2)钢包需要运行于不同处理位置，延长整个精炼时间；3)钢包底部搅拌气体流量难以精确控制，导致钢液中钙混合不均匀(搅拌气体流量过小)或钢包顶渣吹开钢液裸露而被氧化(气体流量偏大)；4)向钢包加入Ca线时，钙与钢液反应激烈，易产生大量烟尘，污染环境。
鉴于上述情况，业界亟待研发一种新的钢液钙处理方法，无需单独设立钙线工位，能够解决传统以钙线形式向钢包中加钙的弊端，达到缓解厂房拥挤，缩短精炼时间，提高钢液纯净度和改善环境的效果。
发明内容
针对现有技术存在的上述缺陷，本发明目的是提供一种钢液的钙处理方法，通过在钢液真空精炼中，向钢液中添加钙，取消钙线工位，能够解决传统以钙线形式向钢包中加钙的弊端，达到缓解厂房拥挤，缩短精炼时间，提高钢液纯净度和改善环境的效果。
为实现上述目的，本发明采用如下技术方案：
本发明提供了一种钢液的钙处理方法，包括真空精炼中，钢液成分调整结束后，调整真空系统压力至5～25kPa，然后向钢液中添加Ca进行钙处理。本发明还提供了一种炼钢方法，包括铁水预处理、初炼、钢包精炼炉(LF炉)精炼、真空精炼和浇铸，其中，所述真空精炼中，钢液成分调整结束后，调整真空系统压力至5～25kPa，然后向钢液中添加Ca进行钙处理。
优选地，所述真空精炼中：
所述钢液成分调整结束后，钢液循环2～8min，再调整真空系统压力；和/或
所述钙处理过程中，Ca的添加量为0.1～0.25kg/t钢，Ca的添加方式为真空加入；和/或
所述钙处理结束后，钢液循环1～8min，真空精炼结束；和/或
整个真空精炼过程中钢包渣厚度小于300mm；和/或
所述真空精炼结束后，钢液中的化学成分S、Mn、Al和Ca含量满足：S≤0.0020wt％，Mn：0.1～2.2wt％、例如0.1～2.0wt％，Al：0.015～0.1wt％，Ca：0.0005～0.0025wt％；和/或
所述真空精炼中所用的真空精炼装置为RH真空循环脱气精炼炉(RH炉)或真空脱碳炉(VD炉)或真空吹氧脱碳炉(VOD炉)。
优选地，从真空精炼装置的高位料仓向钢液中加入所述Ca。
优选地，所述真空精炼装置采用RH炉时，所述添加Ca的过程中，在钢包底部全程进行吹Ar搅拌，控制Ar流量为10～50NL/(h·t钢)。
优选地，所述铁水预处理过程中，铁水脱硫至S含量≤20ppm。
优选地，所述初炼过程中：
出钢量达到1/6～1/4、优选1/5时，向钢包中加入石灰1.5～3.5kg/t钢，出钢结束前，向钢包中加入铝渣0.3～1.5kg/t钢；和/或
出钢结束后，钢包中钢液S含量≤80ppm；和/或
所述初炼所用的装置为转炉或氩氧脱碳炉(AOD炉)或电炉。
优选地，所述LF炉精炼过程中：
所述LF炉精炼前，钢包渣厚度小于80mm，钢包中钢液S含量≤80ppm；和/或
所述LF炉精炼后，钢包渣厚度小于300mm，钢包中钢液S含量≤20ppm。
优选地，所述浇铸得到的铸坯的夹杂物中，CaO的质量百分比与Al 2O 3的质量百分比的比值为0.7～1.1。
优选地，所述浇铸得到的铸坯中夹杂物的密度为7.0～8.0个/mm2。
在一个或多个实施方案中，所述钙处理方法或炼钢方法的处理对象为具有以下化学成分的钢：C：0.01～0.1wt％，Si≤0.03wt％，Mn：0.8～2.2wt％，Al：0.02～0.08wt％，Ti：0.02～0.08wt％，P≤0.015wt％，S≤0.0020wt％，N≤0.004wt％，余量为Fe和不可避免的杂质。
在一个或多个实施方案中，所述钙处理方法或炼钢方法在所述浇铸后还包括热轧步骤。
优选地，所述热轧后得到的热轧板的探伤缺陷率为0，和/或-20℃冲击功KV2为430～475J。
优选地，所述钙处理过程中无烟尘释放至大气中。
优选地，所述真空精炼中所用的真空精炼装置为RH炉。
优选地，所述真空精炼过程中，从RH排气开始至钢包起吊时间为30～35min。
优选地，所述钙处理过程中不单独设立Ca加入工位。
本发明所提供的钢液的钙处理方法和炼钢方法还具有以下几点有益效果：
1、无需单独设立Ca加入工位，节省厂房空间；
2、省掉钢包运行于不同处理位置的过程，缩短了精炼时间；
3、钢液无裸漏风险，钢液纯净度稳定可控；
4、无大量烟尘直接释放到厂房内，降低了环境污染。
附图说明
通过阅读参照以下附图对非限制性实施例所作的详细描述，本发明的其它特征、目的和优点将会变得更明显：
图1为本发明的一些实施方式的炼钢方法的流程示意图；
图2为本发明在不同温度下的钢液中Ca的饱和浓度与真空系统压强的关系图。
具体实施方式
为了能更好地理解本发明的上述技术方案，下面结合实施例进一步说明本发明的技术方案。
结合图1所示，本发明所提供炼钢方法包括铁水预处理、初炼、LF炉精炼、真空精炼和浇铸，真空精炼中，钢液成分调整结束后，调整真空系统压力至5～25kPa，然后向钢液中添加Ca进行钙处理；其中上述的钢液的钙处理方法和炼钢方法适用对象为钙处理类钢产品，其工艺流程如下：
铁水预处理-初炼炉(转炉、AOD炉、电炉等)-LF炉-真空精炼炉-浇铸(模铸、连铸)。
上述钢液的钙处理方法和炼钢方法中：
铁水预处理过程中，对铁水深脱硫至S含量≤20ppm；然后送入初炼炉进行初炼，当出钢量达到1/6～1/4、优选1/5时，向钢包中加入石灰1.5～3.5kg/t钢、例如2.0kg/t钢、2.5kg/t钢、3.0kg/t钢，出钢结束前，向钢包加入铝渣0.3～1.5kg/t钢、例如0.5kg/t钢、0.8kg/t钢、1.0kg/t钢、1.2kg/t钢，需要特别注意的是，要严格控制进入钢包中的炉渣量，出钢结束后，钢包中顶渣厚度应小于80mm；其中初炼炉可以是转炉、AOD炉、电炉。
为满足超低碳钢成品对硫的要求以及减轻后续真空精炼中的脱硫负荷，需严格控制钢液中的硫含量：钢液中硫的控制，在铁水预处理中，对铁水深脱硫至S含量≤20ppm；初炼完成后，严格控制初炼炉(例如转炉)炉料的硫含量，出钢后钢包中S≤80ppm(即LF冶炼前钢液中硫含量S≤80ppm)，减轻后续精炼炉的脱硫负荷，进而控制整个真空精炼过程中钢包渣厚度小于300mm。
在一些实施方案中，初炼出钢后，进行钢包顶渣改质，然后进行LF炉精炼。
LF炉精炼过程中：在LF炉精炼前，钢包渣厚度小于80mm，钢包中钢液S含量≤80ppm；经LF炉精炼后，钢包渣厚度小于300mm，钢包中钢液S含量≤20ppm。
真空精炼过程中，将LF炉精炼过程得到的钢液转入真空精炼装置中，在钢液成分调整结束后，钢液继续循环2～8min，再调整真空系统压力至5～25kPa，然后向钢液中加入Ca进行钙处理，其中在钙处理过程中Ca的添加量为0.1～0.25kg/t钢，Ca的添加方式为真空加入，可以从真空精炼装置的高位料仓向钢液中加入Ca；添加Ca之后，钢液继续循环1～8min，真空精炼结束；最终真空精炼结束后，钢液中S、Mn、Al和Ca含量满足：S≤0.002wt％，Mn：0.1～2.2wt％、例如0.1～2.0wt％，Al：0.015～0.1wt％，Ca：0.0005～0.0025wt％；上述真空精炼中所使用的真空精炼装置采用RH炉或VD炉或VOD炉，RH炉为优选的真空精炼装置；其中当真空精炼装置采用RH炉时，为保证Ca充分混匀，在上述钙处理中，整个Ca的添加中，在 钢包底部全程进行吹Ar搅拌，并控制Ar流量为10～50NL/(h·t钢)。同时优选控制整个真空精炼过程中钢包渣厚度小于300mm。
真空精炼后钢液进行浇铸，得到铸坯，其中铸坯的夹杂物中，CaO的质量百分比与Al 2O 3的质量百分比的比值为0.7～1.1。铸坯中夹杂物的密度为7.0～8.0个/mm 2。
在一些实施方案中，本发明钢液钙处理方法的处理对象为具有以下主要化学成分的钢、例如热轧钢：C：0.01～0.1wt％，Si≤0.03wt％，Mn：0.8～2.2wt％，Al：0.02～0.08wt％，Ti：0.02～0.08wt％，P≤0.015wt％，S≤0.0020wt％，N≤0.004wt％，余量为Fe。
上述整个钢液的钙处理方法中，由于Ca的蒸汽压较高(983℃时1.33kPa)，因此其易挥发。系统真空度越高，Ca挥发速率越大。结合图2所示，一定温度下，Ca在钢液中的饱和浓度随真空系统压力的增加而增加，基于本发明要求在Ca加入前，真空系统的真空度需调整至5～25kPa，并保持稳定，以此来降低Ca的挥发速率，提高Ca在钢液中的饱和浓度，并使之保持稳定；通过真空加Ca后，为确保加入钢液中的Ca混合均匀且与已有的夹杂物反应充分，加Ca后钢液至少循环1min，考虑到连铸浇铸周期、钢液温降和能源消耗等因素，加Ca后钢液循环时间不超过8min。
关于钙的加入量，需使得生成的氧化物夹杂物呈液相形式，且不能存在单独的固相Al 2O 3夹杂。加入的Ca量过大，导致CaO生成，易造成热轧板探伤不合格率上升，进而导致后续生产的冷轧板锈蚀风险加大，以及原料成本上升；Ca的加入量过低，则钢液中Al 2O 3类夹杂物反应不充分，有单独的固相Al 2O 3夹杂存在，热轧产品中甚至有MnS生成；根据理论计算和实际情况验证，Ca的加入量上限为0.25kg/t钢，下限为0.1kg/t钢。
下面结合具体的例子对本发明的钢液钙处理方法进一步介绍。下述实施例以及对比例属热轧类产品，以主要组成成分为：C：0.01～0.1wt％、Si≤0.03wt％、Mn： 0.8～2.2wt％、Al：0.02～0.08wt％、Ti：0.02～0.08wt％、P≤0.015wt％、S≤0.0020wt％、N≤0.004wt％以及Fe。
实施例1
本实施例所采用的工艺路线为：铁水预处理(脱硫、脱磷)→初炼(转炉顶底复吹冶炼、出钢)→钢包顶渣改质→LF炉精炼(升温、脱氧、脱硫、合金化)→RH炉真空精炼(真空脱气、调整成分、添加Ca进行Ca处理)→浇铸→热轧。
本实施例为本发明冶炼的典型炉次：转炉吹炼结束，挡渣出钢，出钢量达到1/5时，加入石灰2.5kg/t钢，出钢末期加入铝渣1.2kg/t钢。LF处理前，钢包渣厚度为65mm，钢包中钢液硫含量75ppm；LF炉精炼结束，钢包中钢液硫含量20ppm，钢包渣厚度220mm。钢液真空精炼处理脱除气体，调整钢液成分至规格值，钢液循环5min，调整钢液上方真空压力至7kPa，添加纯Ca 0.15kg/t钢，整个Ca的添加中，在钢包底部全程进行吹Ar搅拌，并控制Ar流量为20NL/(h·t钢)，然后钢液继续循环5min，结束真空处理，整个真空精炼过程中钢包渣厚度小于300mm；浇铸，随后热轧；其中浇铸后得到的铸坯以及热轧后得到的热轧板的性能参数详见表2。
表1为实际生产中应用本发明方案例的其他情况、对比例1～6采用常规喂线工艺添加Ca包芯线进行Ca处理的工艺的情况对比。其中实施例1～6所采用的工艺路线为：铁水预处理(脱硫、脱磷)→初炼(转炉顶底复吹冶炼、出钢)→钢包顶渣改质→LF炉精炼(升温、脱氧、脱硫、合金化)→RH炉真空精炼(真空脱气、调整成分、添加Ca进行Ca处理)→浇铸→热轧。对比例1-6所采用的工艺路线为：铁水预处理(脱硫、脱磷)→初炼(转炉顶底复吹冶炼、出钢)→钢包顶渣改质→LF炉精炼(升温、脱氧、脱硫、合金化)→RH炉真空精炼(真空脱气、调整成分)→喂线工位添加含Ca包芯线进行Ca处理→浇铸→热轧。实施例和对比例具体控制参数以及铸坯、热轧板的性能情况详见表1和表2。实施例1-6中，真空精炼结束后，钢液中S、Mn、Al和Ca含量满足：S≤0.002wt％，Mn：0.1～2.0wt％，Al：0.015～0.1wt％，Ca：0.0005～0.0025wt％。
表1
Figure PCTCN2022101856-appb-000001
表2
Figure PCTCN2022101856-appb-000002
结合表1、表2可知，实施例1～6中，铸坯中夹杂物的密度为7.0～8.0个/mm 2，夹杂物CaO的质量百分比与Al 2O 3的质量百分比的比值0.7～1.1，热轧板的探伤缺陷率全部为0，-20℃冲击功KV2为430～475J，从RH排气开始至钢包起吊时间为30～35min，且Ca处理过程中无烟尘释放至大气中；实施例与对比例相比，采用本发明的技术对钢液进行Ca处理，铸坯中夹杂物的密度较常规喂线工艺低10～20％；本发明的热轧板探伤缺陷率全部为0，常规喂线工艺则存在少量探伤缺陷；热轧板-20℃冲击功KV2约450J，与常规喂线工艺相当；从RH排气开始至钢包起吊时间平均值34min，较常规喂线工艺缩短10min左右；且本发明的Ca处理中无烟尘释放至大气中。由此可见，与常规喂线工艺相比，本发明的钢液钙处理方法生产的产品性能相当，而稳定性更好，能大幅度提高生产效率，且对环境无污染。
综上所述，本发明的钢液钙处理方法，无需单独设立Ca加入工位，节省厂房空间；省掉钢包运行于不同处理位置的过程，缩短了精炼时间；钢液无裸漏风险，钢液纯净度稳定可控；无大量烟尘直接释放到厂房内，降低了环境污染。
本技术领域中的普通技术人员应当认识到，以上的实施例仅是用来说明本发明，而并非用作为对本发明的限定，只要在本发明的实质精神范围内，对以上所述实施例的变化、变型都将落在本发明的权利要求书范围内。

Claims (15)

  1. 一种钢液的钙处理方法或炼钢方法，其特征在于，
    所述钙处理方法包括真空精炼中，钢液成分调整结束后，调整真空系统压力至5～25kPa，然后向钢液中添加Ca进行钙处理；
    所述炼钢方法包括铁水预处理、初炼、LF炉精炼、真空精炼和浇铸，其中，所述真空精炼中，钢液成分调整结束后，调整真空系统压力至5～25kPa，然后向钢液中添加Ca进行钙处理。
  2. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述真空精炼中：
    所述钢液成分调整结束后，钢液循环2～8min，再调整真空系统压力；和/或
    所述钙处理过程中，Ca的添加量为0.1～0.25kg/t钢，Ca的添加方式为真空加入；和/或
    所述钙处理结束后，钢液循环1～8min，真空精炼结束；和/或
    整个真空精炼过程中钢包渣厚度小于300mm；和/或
    所述真空精炼结束后，钢液中的化学成分S、Mn、Al和Ca含量满足：S≤0.0020wt％，Mn：0.1～2.2wt％，Al：0.015～0.1wt％，Ca：0.0005～0.0025wt％；和/或
    所述真空精炼中所用的真空精炼装置为RH炉或VD炉或VOD炉。
  3. 根据权利要求2所述的钢液的钙处理方法或炼钢方法，其特征在于，所述真空精炼装置采用RH炉，所述添加Ca的过程中，在钢包底部全程进行吹Ar搅拌，控制Ar流量为10～50NL/(h·t钢)。
  4. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述铁水预处理过程中，铁水深脱硫至S含量≤20ppm。
  5. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述初炼过程中：
    出钢量达到1/6～1/4、优选1/5时，向钢包中加入石灰1.5～3.5kg/t钢，出钢结束前，向钢包中加入铝渣0.3～1.5kg/t钢；和/或
    出钢结束后，钢包中钢液S含量≤80ppm；和/或
    所述初炼所用的装置为转炉或AOD炉或电炉。
  6. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述LF炉精炼过程中：
    所述LF炉精炼前，钢包渣厚度小于80mm，钢包中钢液S含量≤80ppm；和/或
    所述LF炉精炼后，钢包渣厚度小于300mm，钢包中钢液S含量≤20ppm。
  7. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述浇铸处理后得到铸坯，所述铸坯的夹杂物中，CaO的质量百分比与Al 2O 3的质量百分比的比值为0.7～1.1。
  8. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述钙处理方法或炼钢方法的处理对象为具有以下化学成分的钢：C：0.01～0.1wt％，Si≤0.03wt％，Mn：0.8～2.2wt％，Al：0.02～0.08wt％，Ti：0.02～0.08wt％，P≤0.015wt％，S≤0.0020wt％，N≤0.004wt％，余量为Fe和不可避免的杂质。
  9. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述钙处理方法或炼钢方法在所述浇铸后还包括热轧步骤。
  10. 根据权利要求9所述的钢液的钙处理方法或炼钢方法，其特征在于，所述热轧后得到的热轧板的探伤缺陷率为0，和/或-20℃冲击功KV2为430～475J。
  11. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述钙处理过程中无烟尘释放至大气中。
  12. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述真空精炼中所用的真空精炼装置为RH炉。
  13. 根据权利要求12所述的钢液的钙处理方法或炼钢方法，其特征在于，所述真空精炼过程中，从RH排气开始至钢包起吊时间为30～35min。
  14. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，所述钙处理过程中不单独设立Ca加入工位。
  15. 根据权利要求1所述的钢液的钙处理方法或炼钢方法，其特征在于，从真空精炼装置的高位料仓向钢液中加入所述Ca。
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