CN-121992172-A - Method for modifying ultra-low carbon steel slag

Abstract

The invention discloses a method for modifying ultra-low carbon steel slag. Aiming at the technical problem that the ultra-low carbon steel slag has strong oxidizing property and is easy to cause secondary oxidation of clean molten steel after smelting in an RH refining furnace, the invention provides a modification method of the ultra-low carbon steel slag. Firstly, after molten steel enters a treatment position of an RH refining furnace, before an immersion pipe of the RH refining furnace is inserted into the molten steel, adding an aluminum slag surface deoxidizer into ladle slag in a range of one side of a down pipe of the immersion pipe to carry out primary slag modification, secondly, adding the aluminum slag surface deoxidizer into a ladle slag area which is not subjected to primary modification after decarburization of the RH refining furnace is finished to carry out secondary slag modification, and thirdly, adding the aluminum slag surface deoxidizer into a vortex core area formed by inserting the immersion pipe to carry out tertiary slag modification after vacuum treatment and emptying of the RH refining furnace.

Inventors

• LI NING
• YAN XINHUA
• FENG KONGFANG
• Guo tianyang
• ZHANG XIANGZE
• FENG QINGXIAO
• LIU XINYUAN
• LIU YUJUN

Assignees

• 张家港中美超薄带科技有限公司
• 江苏省沙钢钢铁研究院有限公司
• 江苏沙钢集团有限公司
• 江苏沙钢钢铁有限公司

Dates

Publication Date

20260508

Application Date

20260120

Claims (11)

1. 1. A method for upgrading ultra-low carbon steel slag, the method comprising the steps of: S1, preliminary slag modification, namely adding an aluminum slag surface deoxidizer into the preliminary slag modification area to carry out preliminary slag modification in the preliminary slag modification stage; S2, secondary slag modification, namely adding the aluminum slag surface deoxidizer into the secondary slag modification area to carry out secondary slag modification in the secondary slag modification stage; And S3, three times of slag modification, namely adding the aluminum slag surface deoxidizer into the three times of slag modification areas to carry out the three times of slag modification in the three times of slag modification stage.
2. 2. The method according to claim 1, wherein the aluminum slag surface deoxidizer comprises, by mass, 10-55% of metallic aluminum, 10-30% of CaO, 2-7% of CaF 2 ：5-20%、Al 2 O 3 ：5-25%、SiO 2 and other unavoidable impurities.
3. 3. The method according to claim 1, wherein in step S1, the preliminary slag modification stage is after the molten steel enters the RH refining furnace treatment site before the dip tube of the RH refining furnace is inserted into the molten steel.
4. 4. The method according to claim 1, wherein in step S1, the preliminary slag-modified region is ladle slag in a dip tube downcomer side region.
5. 5. The method according to claim 1, characterized in that in step S1 the primary slag-modified aluminium slag surface deoxidizer is used in an amount of 0.2-1.0 kg/ton steel.
6. 6. The method according to claim 1, wherein in step S2, the secondary slag modification stage is performed after decarburization in the RH refining furnace is completed.
7. 7. The method according to claim 1, wherein in step S2, the secondary slag-modified region is a ladle slag other region not primarily modified.
8. 8. The method according to claim 1, characterized in that in step S2 the secondary slag-modified aluminium slag surface deoxidizer is used in an amount of 0.2-1.0 kg/ton steel.
9. 9. The method according to claim 1, wherein in step S3, the three slag modification stages are after the vacuum treatment of the RH refining furnace is completed and the furnace is broken.
10. 10. The method according to claim 1, wherein in step S3, the tertiary slag-modified region is a vortex core region formed by dip tube insertion.
11. 11. The method according to claim 1, characterized in that in step S3 the tertiary slag-modified aluminium slag surface deoxidizer is used in an amount of 0.1-1.0 kg/ton steel.

Description

Method for modifying ultra-low carbon steel slag Technical Field The invention belongs to the technical field of ferrous metallurgy refining, and relates to a method for modifying ultra-low carbon steel slag. More particularly, the invention relates to a control method for improving the cleanliness of ultra-low carbon steel by modifying slag in different areas in stages in an RH vacuum refining process, which is particularly suitable for producing high-end ultra-low carbon steel such as automobile plates, electrical steel, ultra-thin strip deep drawing steel and the like. Background In the production process of ultra-low carbon steel (C is less than or equal to 0.0030 percent), deep decarburization treatment is generally carried out through an RH process. The RH refining furnace realizes the decarburization task by the principle of carbon-oxygen reaction in a vacuum environment, so that molten steel before entering the RH refining furnace needs to be subjected to high oxygen conditions (the oxygen content of the molten steel is generally more than or equal to 400 ppm), and ladle top slag usually has higher oxygen potential (FeO+MnO is generally more than or equal to 10%). Although the cleanliness of molten steel is very high (the number of inclusions above 1 micron is about 10/mm < 2 >) after RH vacuum smelting, after RH emptying process, the molten steel with high cleanliness inevitably contacts slag with high oxidability and air, and serious secondary oxidation reaction is initiated, so that the number of inclusions in the steel is increased by more than 20% (up to 12/mm < 2 >). The secondary oxidation not only worsens the quality of casting blank and affects the performance of products, but also can cause the blocking of a continuous casting tundish nozzle to cause casting stopping accidents under serious conditions, thereby bringing great economic loss to iron and steel enterprises. In the prior art, the traditional slag surface modification method either advances slag modification at RH, which can interfere with decarburization reaction kinetics at the initial stage of RH, or carries out slag modification after RH is over, and at this time, secondary oxidation already occurs, so that the loss of cleanliness cannot be recovered. Publication No. CN120818731A develops a top slag modification of an ultralow-carbon single-connection process, namely, ladle top slag modification of a converter process and ladle top slag modification of an RH process, which reduces the oxidizing property of slag and can reduce a certain secondary oxidation degree, but the modification has a certain negative influence on an oxygen decarburization process of molten steel and cannot improve the secondary oxidation contacted with air in the process of breaking the air. Therefore, there is an urgent need in the art to develop a new method of staged, zoned, precise slag modification to improve the technical barrier to secondary oxidation of clean molten steel during the refining process. Disclosure of Invention Based on the background technology, the invention aims to provide a staged and regional RH refining slag surface modification method. According to the method, the special aluminum slag surface deoxidizer is put into different areas of the ladle slag surface at three special time points in the treatment stage of the RH refining furnace, so that the RH decarburization reaction is ensured to be smoothly carried out, the problem of secondary oxidization of clean molten steel is solved, and finally the cleanliness of the ultra-low carbon steel water is improved. More specifically, the invention adopts the following technical scheme. According to one aspect of the invention, a method for modifying ultra-low carbon steel slag is provided, which is characterized in that the method comprises the following steps: S1, preliminary slag modification, namely adding an aluminum slag surface deoxidizer into the preliminary slag modification area to carry out preliminary slag modification in the preliminary slag modification stage; S2, secondary slag modification, namely adding the aluminum slag surface deoxidizer into the secondary slag modification area to carry out secondary slag modification in the secondary slag modification stage; And S3, three times of slag modification, namely adding the aluminum slag surface deoxidizer into the three times of slag modification areas to carry out the three times of slag modification in the three times of slag modification stage. According to the method of the invention, preferably, the chemical components of the aluminum slag surface deoxidizer comprise, by mass, 10-55% of metallic aluminum, 10-30% of CaO, 2-7% of CaF 2：5-20%、Al2O3：5-25%、SiO2 and other unavoidable impurities. According to the method of the present invention, preferably, in step S1, the preliminary slag modification stage is that after molten steel enters the RH refining furnace treatment site, the dip tube of the RH refining furnace i