Method for producing non-oriented silicon steel by using high-sulfur molten iron

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a method for producing non-oriented silicon steel by using high-sulfur molten iron. Comprising the following steps of molten iron pretreatment, smelting, continuous casting, rolling and finished product obtaining. Wherein the pretreatment of the molten iron comprises the following steps: carrying out slagging-off treatment before the pretreatment of the high-sulfur molten iron, blowing magnesium powder to desulfurize after slagging-off, and slagging-off thoroughly after desulfurization; molten iron and waste steel are mixed into a converter, the adding amount of the waste steel, active lime and light-burned dolomite is controlled, the active lime is added into a tank in the tapping process, the content of S in a tapping argon station is 0.0045%-0.0075%, and if the content of S in the argon station is Slt; and if S is larger than or equal to 0.0045% and smaller than or equal to 0.0075% in an argon station, RH desulfurization treatment is conducted. According to the method, the method for producing the non-oriented silicon steel from the high-sulfur molten iron is achieved, and the non-oriented silicon steel can be produced smoothly under the abnormal molten iron condition.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and particularly to a method for producing non-oriented electrical steel using hot metal with high sulfur content. Background Art

[0002] In the actual production of steel mills, when producing non-oriented electrical steel, due to the relatively low sulfur requirement of the steel grade itself, the upper limit is generally controlled at about 0.005%. For hot metal, the sulfur content before desulfurization is usually required not to exceed 0.030%. If the sulfur content in the hot metal exceeds this range, it may not be suitable for producing non-oriented electrical steel. When the blast furnace hot metal does not meet the sulfur content requirement of non-oriented electrical steel, production cannot be carried out, which may lead to obstacles in the execution of enterprise contracts and serious economic losses. At the same time, the long-term inability to produce non-oriented electrical steel that meets the requirements will restrict the development of enterprises and affect enterprise efficiency.

[0003] Patent CN202110779711.3 discloses a method for desulfurizing hot metal with high sulfur content, including the steps of: removing sulfur from the hot metal with high sulfur content to obtain low-sulfur semi-steel with a sulfur content S < 0.005%. Patent CN201710068962.4 discloses a rapid desulfurization method for converter smelting. This method includes: during the tapping process of converter smelting, adding a desulfurizer into the ladle and blowing an inert gas into the ladle for desulfurization, and after tapping is completed, removing the desulfurized slag. The present invention effectively utilizes the impact force and heat source of molten steel during the tapping process for desulfurization, achieving efficient and low-cost desulfurization of hot metal.

[0004] It can be seen that in the currently publicly available materials in China, there is relatively little detailed introduction on producing non-oriented electrical steel under the condition of hot metal with high sulfur content, indicating that there are certain technical challenges in this field. Although there may be certain technical challenges in producing non-oriented electrical steel under the condition of hot metal with high sulfur content, considering production costs and economic benefits, enterprises may seek methods to reduce the desulfurization cost of hot metal and improve production efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for producing non-oriented electrical steel using hot metal with high sulfur content. Through the sulfur treatment process of hot metal pretreatment, the use of scrap steel, converter smelting, and RH desulfurization treatment, the production of non-oriented electrical steel using hot metal with high sulfur content is realized, enabling the sulfur component to meet the requirements of the steel grade, ensuring the normal production of non-oriented electrical steel under unfavorable hot metal conditions, guaranteeing the key varieties of enterprises, and at the same time improving enterprise efficiency and competitiveness.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] The present invention provides a method for producing non-oriented electrical steel using hot metal with high sulfur content, including the following process route: hot metal pretreatment - smelting - continuous casting - rolling - finished product; where:

[0008] Hot metal pretreatment: Before the pretreatment of high-sulfur hot metal, slag skimming is carried out. After slag skimming, magnesium powder is blown to desulfurize, and after desulfurization, the slag is skimmed clean.

[0009] Smelting: The hot metal and scrap steel are charged into the converter. The addition amounts of scrap steel, active lime and calcined dolomite are controlled. Active lime is added into the ladle during the tapping process. The S content at the tapping argon station is 0.0045% - 0.0075%. If the S content at the argon station is < 0.0045%, it is poured on the machine. If 0.0045% ≤ S ≤ 0.0075% at the argon station, RH desulfurization treatment is carried out.

[0010] In the above technical solution, further, the S content of the high-sulfur hot metal is 0.030% - 0.100%.

[0011] The relationship between the S content of the hot metal and the blowing amount of magnesium powder is as follows:

[0012] The blowing amount of magnesium powder = [0.72 + (S content of hot metal - 0.030%) * 1000] ± 0.01, unit: kg / t steel.

[0013] In the above technical solution, further, the S content of the hot metal after pretreatment ≤ 0.002%.

[0014] The relationship between the S content of the hot metal after pretreatment and the addition amount of scrap steel is as follows:

[0015] The addition amount of scrap steel = [148 - (S content of hot metal after pretreatment - 0.0001%) * 100 * 10000] ± 2, unit: kg / t steel.

[0016] In the above technical solution, further, in the smelting process, the relationship between the S content of the hot metal and the addition amounts of converter active lime, calcined dolomite and active lime in the ladle during the tapping process is as follows:

[0017] Converter active lime = [31.5 + (S content of hot metal - 0.030%) * 20000] ± 0.5, unit: kg / t steel;

[0018] Calcined dolomite = [15 + (S content of hot metal - 0.030%) * 5000] ± 0.5, unit: kg / t steel;

[0019] Active lime in the ladle during the tapping process = [2.2 + (S content of hot metal - 0.030%) * 4000] ± 0.1, unit: kg / t steel.

[0020] In the above technical solution, further, the RH desulfurization treatment method is that during the RH vacuum refining process, a desulfurizer is added. The relationship between the S content at the argon station and the addition amount of the desulfurizer is as follows:

[0021] The addition amount of desulfurizer = [1.8 + (S content at argon station - 0.030%) * 80000] ± 0.1, unit: kg / t steel;

[0022] The chemical composition content of the desulfurizer is: CaF₂ 22% - 30%, CaO 62% - 72%, SiO₂ ≤ 8%, S ≤ 0.02%, TC ≤ 0.15%.

[0023] In the above technical solution, further, the tapping temperature in converter smelting is controlled at 1680 - 1710 °C.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The method of the present invention realizes the method for producing non-oriented electrical steel with high-sulfur hot metal, enables the smooth production of non-oriented electrical steel under abnormal hot metal conditions, improves the contract execution rate of non-oriented electrical steel, enhances the corporate credibility, guarantees the production capacity of the key steel grades of the enterprise, and at the same time improves the enterprise efficiency and competitiveness.

[0026] 2. Due to the high-sulfur hot metal, even if the S content after hot metal pretreatment is qualified, but due to the large amount of slag, the phenomenon of sulfur reversion will occur. Therefore, by the present invention, the amount of scrap steel is selected and matched to inhibit the sulfur reversion phenomenon. Specific embodiments

[0027] The following embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0028] Example 1

[0029] A method for producing non-oriented electrical steel using high-sulfur hot metal, the steel grade for smelting is AW600ZS, the ladle is of D grade, the turnover time is 100 min, the finished product requires S ≤ 0.005%, and the production method includes the following steps:

[0030] (1) Before hot metal desulfurization, S = 0.082%, the hot metal temperature is 1386 °C, the hot metal tapping amount for smelting this furnace of steel grade is 270 t, the slag skimming amount before desulfurization is 1.8 t, after slag skimming, blowing is carried out. Before desulfurization, S = 0.082%, the target setting for blowing is S = 0.001%. After slag skimming, magnesium powder is blown for desulfurization, the magnesium powder blowing amount is 335 kg. After blowing, slag skimming is carried out. After slag skimming is completed, the sampled S = 0.0013%, meeting the standard for entering the converter;

[0031] (2) Pour the hot metal and 36.5 t of scrap steel into the converter. Before desulfurization, the hot metal S = 0.082%. In the range of 0.08% < S ≤ 0.100%, 11.3 t of active lime and 4.75 t of lightly burned dolomite are used in this furnace smelting, and the oxygen accumulation reaches 11355 Nm 3At that time, the TSC test was carried out through the sublance. The TSC measurement data was blown to the end point, the lance was lifted, the end point temperature was 1685°C, the oxygen value was 466 ppm, the detection results of the rapid analyzer were C = 0.051%, P = 0.0153%, S = 0.0061%. During the tapping process, 1.15 t of active lime was added to the ladle. After tapping, a sample was taken at the argon station, and S = 0.0062%, which did not meet the requirements of the steel grade, and it was necessary to enter the next process of RH desulfurization;

[0032] (3) The addition amount of RH desulfurizer in this ladle is 810 kg, the particle size of the desulfurizer is 2 - 10 mm, and its chemical composition content is: CaF2 2% - 30%, CaO 62% - 72%, SiO2 ≤ 8%, S ≤ 0.02%, TC ≤ 0.15%. After RH desulfurization treatment, S = 0.0042%, which meets the requirements of the steel grade. It was cast on the machine, and the sulfur content of the billet was 0.0043%, meeting the requirements of the steel grade. Subsequently, continuous casting and rolling were carried out to obtain the finished product.

[0033] Example 2

[0034] A method for producing non-oriented electrical steel using high-sulfur hot metal, the steel grade for smelting is AW800ZS, the ladle is grade D, the turnover time is 100 min, and the finished product requirement is S ≤ 0.005%. The production method includes the following steps:

[0035] (1) Before hot metal desulfurization, S = 0.052%, the hot metal temperature is 1379°C, the hot metal output of this furnace of steel grade is 270 t, 1.3 t of slag is removed before desulfurization, and after slag removal, blowing is carried out. Before desulfurization, S = 0.052%, the blowing target is set at S = 0.001%. After slag removal, magnesium powder is blown for desulfurization, the blowing amount of magnesium powder is 254 kg, and after blowing, slag is removed. After slag removal is completed, the sample is taken and S = 0.0008%, meeting the standard for entering the converter;

[0036] (2) The hot metal and 38.1 t of scrap steel are charged into the converter. Before desulfurization, the hot metal S = 0.052%. In this furnace of smelting, 9.7 t of active lime and 4.35 t of lightly burned dolomite are used. When the oxygen accumulation reaches 11511 Nm 3 At that time, the TSC test was carried out through the sublance. The TSC measurement data was blown to the end point, the lance was lifted, the end point temperature was 1688°C, the oxygen value was 426 ppm, the detection results of the rapid analyzer were C = 0.053%, P = 0.0163%, S = 0.0041%. During the tapping process, 0.83 t of active lime was added to the covered ladle. After tapping, a sample was taken at the argon station, and S = 0.0042%, meeting the requirements of the steel grade. It was cast on the machine, and the sulfur content of the billet was 0.0041%, meeting the requirements of the steel grade. Subsequently, continuous casting and rolling were carried out to obtain the finished product.

[0037] The above embodiments are only the preferred embodiments of the present invention and do not limit the implementation manners. The protection scope of the present invention shall be subject to the scope defined by the claims. Based on the above description, other different forms of changes or modifications can also be made. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for producing non-oriented silicon steel using high-sulfur molten iron, characterized in that: The process includes the following: molten iron pretreatment - smelting - continuous casting - rolling - finished product; among which: Hot metal pretreatment: Before pretreatment of high-sulfur hot metal, slag is removed, and magnesium powder is sprayed for desulfurization after slag removal. After desulfurization, the slag is removed cleanly; Smelting: Add molten iron and scrap steel into the converter, control the amount of scrap steel, active lime and light-burned dolomite added, add active lime into the tank during the steel-making process, and the S content of the steel-making argon station is 0.0045% to 0.0075%. If the S content of the argon station is <0.0045%, pour it on the machine. If the argon station is 0.0045%≤S≤0.0075%, carry out RH desulfurization treatment.

2. The method for producing non-oriented silicon steel using high-sulfur molten iron according to claim 1, characterized in that: The sulfur content of the high-sulfur molten iron is 0.030% to 0.100%; The S content of molten iron and the injection amount of magnesium powder satisfy the following relationship: The injection amount of magnesium powder = [0.72 + (molten iron S content - 0.030%) * 1000] ± 0.01, unit: kg / t steel.

3. The method for producing non-oriented silicon steel using high-sulfur molten iron according to claim 1, characterized in that: After pretreatment, the S content of molten iron is ≤0.002%; The S content of molten iron after pretreatment and the amount of scrap steel added satisfy the following relationship: The amount of scrap steel added = [148-(S content of molten iron after pretreatment-0.0001%)*100*10000]±2, unit: kg / t steel.

4. The method for producing non-oriented silicon steel using high-sulfur molten iron according to claim 1, characterized in that: In the smelting process, the S content of molten iron and the amount of active lime added to the converter, light-burned dolomite, and active lime in the steelmaking process tank meet the following relationship: Converter active lime = [31.5 + (S content of molten iron - 0.030%) * 20000] ± 0.5, unit: kg / t steel; Light-burned dolomite = [15 + (S content of molten iron - 0.030%) * 5000] ± 0.5, unit: kg / t steel; Active lime in the tank during steel tapping process = [2.2 + (S content in molten iron - 0.030%) * 4000] ± 0.1, unit: kg / t steel.

5. The method for producing non-oriented silicon steel using high-sulfur molten iron according to claim 1, characterized in that: The RH desulfurization treatment method is to add a desulfurizer during the RH vacuum refining process, and the S content in the argon station and the amount of the desulfurizer added satisfy the following relationship: The amount of desulfurizer added = [1.8 + (argon station S content - 0.030%) * 80000] ± 0.1, unit: kg / t steel.

6. The method for producing non-oriented silicon steel using high-sulfur molten iron according to claim 1, characterized in that: The steel tapping temperature of converter smelting is controlled at 1680~1710℃.