Arsenic removal method for arsenic-containing molten iron

Abstract

The invention discloses an arsenic removal method for arsenic-containing molten iron, and belongs to the technical field of steel smelting processes. The process comprises the following steps: adding a silicon-calcium-barium alloy and a small amount of desulfurizing agent into arsenic-containing molten iron subjected to KR desulfurization, promoting the arsenic removal reaction by stirring, and finally removing arsenic-containing slag, thereby obtaining the low-arsenic molten iron. By means of the method, the arsenic content in the molten iron can be reduced to 0.0050% or below from 0.0080%-0.0200%, and the production requirement of the low-arsenic variety steel is met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and relates to a dearsenicization technology for arsenic-containing molten iron and related process parameters. Background Art

[0002] Arsenic, a harmful element in steel, tends to segregate at steel interfaces. Studies have shown that arsenic levels of 0.006% to 0.011% in steel can cause significant temper brittleness. With socioeconomic development, market demands for increasingly stringent steel performance are increasing. For example, steels for cryogenic containers, acid-resistant pipelines, and fine-filament cords require arsenic content below 0.0070%.

[0003] Since arsenic is less oxidizing than iron, it is difficult to remove it through converter blowing and oxidation. Therefore, there are currently few patents disclosed in this regard and there are many deficiencies. Chinese patent CN202310821810.2 discloses a method for dearsenicizing molten steel with a high arsenic content. Dearsenicization is carried out by adding rare earths to the molten steel, and the dearsenicization rate is relatively high; however, the cost of the alloys required for dearsenicization and deoxidation is very high, and the applicability of the steel type is insufficient. For example, fine wire cord steel requires acidic slag to be produced during the LF furnace production process, and desulfurization is impossible. However, research has shown that both oxygen and sulfur content will affect the dearsenicization effect. The lower the oxygen and sulfur content, the better the dearsenicization effect. Therefore, due to the influence of sulfur content, this type of steel is difficult to remove arsenic to below the requirement of 0.0070% using the existing method for dearsenicizing molten steel after the arsenic content in the molten steel exceeds the requirement. Summary of the Invention

[0004] The present invention aims to provide a method for removing arsenic from arsenic-containing molten iron, which can reduce the arsenic content in the molten iron from 0.0080% to 0.0200% to below 0.0050%.

[0005] A method for removing arsenic from arsenic-containing molten iron comprises the following steps: 1) Add 15-20kg / t of desulfurizer to molten iron with an arsenic content of 0.0080% to 0.0200% for KR deep desulfurization treatment. After desulfurization, the molten iron S is ≤ 0.0015%. After desulfurization, more than 80% of the sulfur-containing slag on the surface of the molten iron is scraped off; 2) Add 4-6 kg / t silicon-calcium-barium alloy and 2-4 kg / t desulfurizer to the desulfurized molten iron and stir for more than 5 minutes. After stirring, remove the slag again to obtain low-arsenic molten iron with an arsenic content of As < 0.005%.

[0006] Furthermore, the standard requirements for the desulfurizer in step 1) are CaO ≥ 75%, CaF2 6% to 12%, S < 0.03%, SiO < 5.0%, moisture < 0.5%, activity ≥ 280 ml, and the addition amount is 2 to 4 kg / t.

[0007] Furthermore, the standard requirements for the silicon-calcium-barium alloy in step 2) are Si ≥ 52%, Ca > 12.5%, Ba > 13.5%, Ca + Ba ≥ 28 MJ / kg, P ≤ 0.10%, S ≤ 0.15%, and the particle size is 10-50 mm, with no more than 5% of the particles < 10 mm and no more than 5% of the particles > 50 mm.

[0008] Furthermore, the standard requirements for the silicon-calcium-barium alloy in step 2) are Si ≥ 52%, Ca > 12.5%, Ba > 13.5%, Ca + Ba ≥ 28 MJ / kg, P ≤ 0.10%, S ≤ 0.15%, and the particle size is 10-50 mm, with no more than 5% of the particles < 10 mm and no more than 5% of the particles > 50 mm.

[0009] The present invention has the beneficial effect of adding a silicon-calcium-barium alloy and a small amount of desulfurizer to arsenic-containing molten iron after KR desulfurization, promoting the dearsenicization reaction through stirring, and finally scraping off the arsenic-containing slag to obtain low-arsenic molten iron. By adopting this invention, the arsenic content in the molten iron can be reduced from 0.0080% to 0.0200% to below 0.0050%, meeting the production needs of various low-arsenic steel varieties. DETAILED DESCRIPTION

[0010] The technical solution of the present invention is further described below in conjunction with specific implementation methods. Example 1

[0011] A method for removing arsenic from arsenic-containing molten iron comprises the following steps: 1000 kg of desulfurizer was added to the molten iron and desulfurization was carried out by stirring. After desulfurization, more than 80% of the sulfur-containing slag on the surface of the molten iron was scraped off and sampled. The test results showed that S=0.0012% and As=0.0110%.

[0012] 74 tons of molten iron. According to calculation, 300kg of silicon-calcium-barium alloy and 200kg of desulfurizer were added to the molten iron after desulfurization, and stirred for 5 minutes. After dearsenicization, the arsenic-containing slag on the surface was scraped off and sampled to obtain low-arsenic molten iron. The test results showed that S=0.0006% and As=0.0044%. Example 2

[0013] A method for removing arsenic from arsenic-containing molten iron comprises the following steps: (1) Add 1200 kg of desulfurizer to the molten iron and desulfurize by stirring. After desulfurization, scrape off more than 80% of the sulfur-containing slag on the surface of the molten iron and take samples. The test results show that S = 0.0008% and As = 0.0200%.

[0014] (2) 74 tons of molten iron. According to calculation, 450 kg of silicon-calcium-barium alloy and 200 kg of desulfurizer were added to the molten iron after desulfurization. The mixture was stirred for 5 minutes. After dearsenicization, the arsenic slag on the surface was scraped off and sampled to obtain low-arsenic molten iron. The test results showed that S = 0.0006% and As = 0.0049%.

Claims

1. A method for removing arsenic from arsenic-containing molten iron, characterized in that The process steps include: 1) Add 15-20kg / t of desulfurizer to molten iron with an arsenic content of 0.0080% to 0.0200% for KR deep desulfurization treatment. After desulfurization, the S content in the molten iron is ≤ 0.0015%. After desulfurization, remove more than 80% of the sulfur-containing slag on the surface of the molten iron; 2) Add 4-6 kg / t silicon-calcium-barium alloy and 2-4 kg / t desulfurizer to the desulfurized molten iron and stir for more than 5 minutes. After stirring, remove the slag again to obtain low-arsenic molten iron with an arsenic content of As < 0.005%.

2. The method for removing arsenic from arsenic-containing molten iron according to claim 1, wherein: The standard requirements for the desulfurizer in step 1) are CaO ≥ 75%, CaF2 6% to 12%, S < 0.03%, SiO < 5.0%, moisture < 0.5%, activity ≥ 280 ml, and the addition amount is 2 to 4 kg / t.

3. The method for removing arsenic from arsenic-containing molten iron according to claim 1, wherein: Step 2) The standard requirements for the silicon-calcium-barium alloy are Si ≥ 52%, Ca > 12.5%, Ba > 13.5%, Ca + Ba ≥ 28 MJ / kg, P ≤ 0.10%, S ≤ 0.15%, and a particle size of 10 to 50 mm, with no more than 5% of the particles < 10 mm and no more than 5% of the particles > 50 mm.