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CN-121975996-A - Method for preparing high-cleanliness ultra-low carbon steel by adopting semisteel

CN121975996ACN 121975996 ACN121975996 ACN 121975996ACN-121975996-A

Abstract

The invention relates to the technical field of steel smelting, in particular to a method for preparing high-cleanliness ultra-low carbon steel by adopting semisteel. The method comprises the working procedures of converter tapping, RH refining and slab continuous casting, wherein ladle slag modifier is added in the converter tapping process, and deoxidation alloying and composite desulfurization modifier balls are sequentially added in the RH refining working procedure to synchronously realize desulfurization and inclusion modification. The invention successfully solves the difficult problems of deep desulfurization and high cleanliness control faced by semisteel smelting of ultralow-carbon steel through the special ladle slag modifier, the unique double-layer composite desulfurization modifier ball and the matched refining process thereof, and has remarkable technical effect and is superior to the conventional process.

Inventors

  • ZHANG MIN
  • XIE FENG
  • BAI XUXU
  • WU CHENHUI
  • JIANG LIUDONG
  • YUAN BAOHUI

Assignees

  • 攀钢集团攀枝花钢铁研究院有限公司

Dates

Publication Date
20260505
Application Date
20260210

Claims (10)

  1. 1. A method for preparing high-cleanliness ultra-low carbon steel by adopting semisteel comprises the working procedures of converter tapping, RH refining and slab continuous casting, and is characterized in that, Adding ladle slag modifier in the tapping process of the converter; in the RH refining process, deoxidization alloying is sequentially carried out, and composite desulfurization modifier balls are added to synchronously realize desulfurization and inclusion modification, wherein the ladle slag modifier comprises ：CaO:3~9%,Al 2 O 3 :5~9%,SiO 2 ＜6%,CaCO 3 :26~34%,TiO 2 :7~12%,MAl:28~34%,MgCO 3 :5~10%, mass percent of unavoidable impurities in balance.
  2. 2. The method according to claim 1, wherein the ladle slag modifier is added to the ladle in an amount of 3-4.5 kg/t steel when tapping is performed to 4/5-5/6 in the tapping process of the converter.
  3. 3. The method of claim 1, wherein the composite desulfurization modifier balls comprise, by mass, 25-30% of CaO, 11-18% of CaCO 3 :50~59%,Na 3 AlF 6 and the balance of unavoidable impurities, and an inner inclusion modifier, by mass, 6.1-7.9% of Mg, 31-39% of Al, 2.1-2.8% of Te, 3.1-3.8% of Re, and the balance of iron and unavoidable impurities.
  4. 4. The method of claim 3, wherein the mass ratio of the outer layer desulfurizing agent to the inner layer inclusion modifying agent is 2-2.9:1.
  5. 5. The method according to claim 3, wherein the particle size of the outer layer desulfurizing agent is 700nm to 200 μm, and the particle size of the inner layer inclusion modifying agent is 0.5mm to 1.5mm.
  6. 6. The method of claim 3, wherein the outer layer and the inner layer of the composite desulfurization modifier ball are respectively wrapped by ultra-low carbon steel sheets with the thickness of 0.15-0.25 mm.
  7. 7. The method according to claim 1, wherein in the RH refining step, the composite desulfurization modifier balls are added within 1 to 3 minutes after the titanium alloying is completed, in an amount of 2.2 to 3.2kg/t of steel, and the steel is subjected to vacuum treatment for 4 to 7 minutes after the addition.
  8. 8. The method of claim 1, wherein the method is characterized by further comprising the steps of blowing argon into an empty ladle before tapping of the converter, wherein the argon blowing flow is 610-690 NL/min, the argon blowing time is 1-2 minutes, the clearance height of the ladle is 350-550 mm during tapping of the converter, and the tapping slag amount is less than 30mm.
  9. 9. The method according to claim 1, wherein the RH refining step further comprises judging whether oxygen decarburization is required or not according to oxygen activity in molten steel, and calculating oxygen blowing amount after judging that oxygen decarburization is required, controlling oxygen lance position to be 5.1-5.4 m when oxygen blowing amount is less than 30m 3 , oxygen blowing amount to be 1200-1400 m 3 /h, oxygen lance position to be 4.7-5.0 m when oxygen blowing amount is 30-70 m 3 , oxygen blowing amount to be 1500-1500 m 3 /h, oxygen lance position to be 4.4-4.7 m when oxygen blowing amount is more than 70m 3 , oxygen blowing amount to be 1900-480 m 3 /h, and oxygen blowing amount to be not more than 100m 3 .
  10. 10. The method according to claim 1, wherein in the RH refining step, the deoxidizing alloying step comprises adding aluminum particles or aluminum iron to deoxidize and alloy aluminum elements according to the steel type composition requirement, adding RH vacuum treatment to the aluminum particles or aluminum iron for 3-5min, and adding titanium sponge or ferrotitanium to alloy titanium.

Description

Method for preparing high-cleanliness ultra-low carbon steel by adopting semisteel Technical Field The invention relates to the technical field of steel smelting, in particular to a method for preparing high-cleanliness ultra-low carbon steel by adopting semisteel. Background For ultra-low carbon steel (carbon content is generally less than or equal to 0.003%) such as automobile panels, household steel and electrical steel, the production process faces an inherent technical contradiction that the RH vacuum refining process needs to rely on dissolved oxygen in the steel to finish deep decarburization, so that the molten steel cannot be deoxidized in advance in the tapping stage of a converter. This process feature means that the molten steel remains in a high oxygen state when it enters the refining process, thereby eliminating the possibility of deep desulfurization by reducing slag in the LF furnace. Therefore, the sulfur content control of such steel grades is entirely dependent on the desulfurization effect of the molten iron pretreatment stage. However, for steel grades with a large addition amount of alloy (such as high grade electrical steel) or ultra-low carbon steel with an extremely high requirement for cleanliness, it is difficult to achieve stable ultra-low sulfur control (usually [ S ]. Ltoreq.0.0010%) by means of molten iron pretreatment alone. This is mainly due to the inevitable "reversion" that occurs during the subsequent converter smelting and alloying process-sulfur elements contained in the final slag, alloy and auxiliary materials from the converter re-enter the molten steel. In order to solve the difficult problem, three technical paths are generally adopted in the industry, namely, a high-alkalinity and large-slag-amount operation method adopted by the steel, wherein the slag alkalinity (R=3.5-4.0) is controlled, the slag amount is increased to inhibit sulfur recovery, the steel tapping sulfur content can be controlled below 0.0075% but is difficult to be further reduced to an ultralow level of 0.0010%, an electric furnace process adopted by the Ansai Le Mida is adopted, the steel scraps are taken as main raw materials to fundamentally avoid converter sulfur recovery, the equipment investment of the path is large, the energy consumption is high, and the ultralow-sulfur alloy and auxiliary materials are comprehensively selected, so that the production cost is sharply promoted, and the large-scale and economic production is not facilitated. Therefore, under the framework of the existing main flow process flow of converter-RH-continuous casting, a smelting method capable of synchronously realizing deep desulfurization and inclusion fine control in an RH process without depending on an LF furnace and obviously increasing cost is developed, and becomes a key for breaking through the bottleneck of high-quality ultra-low carbon steel production. Disclosure of Invention In view of this, the method for preparing ultra-low carbon steel with high cleanliness by using semisteel according to the present invention is at least proposed against the technical blank in the background art. The invention provides a method for preparing high-cleanliness ultra-low carbon steel by adopting semisteel, which comprises the steps of converter tapping, RH refining and slab continuous casting, wherein a ladle slag modifier is added in the converter tapping process, deoxidation alloying is sequentially carried out in the RH refining process, and composite desulfurization modifier balls are added to synchronously realize desulfurization and inclusion modification, wherein the ladle slag modifier comprises ：CaO:3~9%,Al2O3:5~9%,SiO2＜6%,CaCO3:26~34%,TiO2:7~12%,MAl:28~34%,MgCO3:5~10%, parts of unavoidable impurities by mass percent. In some embodiments, when tapping is performed to 4/5-5/6 in the converter tapping process, ladle slag modifier is added into the ladle, wherein the addition amount of ladle slag modifier is 3-4.5 kg/t of steel. In some embodiments, the composite desulfurization modifier sphere comprises, by mass, 25-30% of CaO, 11-18% of CaCO 3:50~59%,Na3AlF6 and the balance of unavoidable impurities, 31-39% of Al, 2.1-2.8% of Te, 3.1-3.8% of Re, and the balance of iron and unavoidable impurities. In some embodiments, the mass ratio of the outer layer desulfurizing agent to the inner layer inclusion modifying agent is 2-2.9:1. In some embodiments, the particle size of the outer layer of desulfurizing agent is 700nm to 200 μm and the particle size of the inner layer of inclusion modifying agent is 0.5mm to 1.5mm. In some embodiments, the outer layer and the inner layer of the composite desulfurization modifier sphere are respectively wrapped by an ultra-low carbon steel sheet with the thickness of 0.15-0.25 mm. In some embodiments, in the RH refining process, the composite desulfurization modifier balls are added within 1-3 minutes after titanium alloying is completed, the addition amount is 2.2-3.2 kg/t st