Method for smelting low-sulfur steel in 210t converter

Abstract

The invention belongs to the technical field of steel production, relates to a method for smelting low-sulfur steel by a 210t converter, and aims at solving the problems of difficulty in sulfur content control, limited process path, lack of sulfur control means in the converter smelting process and the like in the existing converter low-sulfur steel smelting by the following technical scheme: firstly, strictly controlling the sulfur content of raw materials and auxiliary materials; controlling the sulfur content of the molten iron to be less than or equal to 0.001% by adopting a KR desulfurization process, and selecting low-sulfur waste steel, lime, magnesium balls and the like; secondly, optimizing an iron-steel ratio, and controlling the iron-steel ratio to be 840-900kg / t; thirdly, slag splashing operation is not carried out in a specific furnace time, replacement of furnace lining slag is achieved, and resulfurization in the converter smelting process is reduced; and finally, low-sulfur lime is added in the converter tapping process for slag washing desulfurization. By adopting the method disclosed by the invention, the converter smelting end point sulfur and the finished product sulfur can be stably controlled to be less than or equal to 0.004%, and subsequent processes such as LF refining are not needed, so that the production cost is reduced, and the production efficiency is improved. The method is particularly suitable for low-carbon steel series production which cannot be subjected to LF refining.

Description

Technical Field

[0001] The invention belongs to the technical field of steel production and relates to a method for smelting low-sulfur steel in a 210t converter. Background Art

[0002] In the field of steel production, converter steelmaking is a common steelmaking method. However, sulfur control is an important challenge in the converter steelmaking process. Sulfur is a harmful element that will reduce the quality and performance of steel, especially in special applications that require low-sulfur steel. Therefore, it is of great significance to develop effective low-sulfur steelmaking technology.

[0003] At present, there are some technologies to reduce the sulfur content in steel:

[0004] 1. Hot metal pretreatment: It is an economical way to desulfurize hot metal before adding it to the converter. The KR hot metal desulfurization process is a common stirring desulfurization process. The stirring head is inserted into the hot metal tank and rotated to form a vortex in the hot metal, and a desulfurizer is added for desulfurization.

[0005] 2. Converter low-slag smelting: By controlling the oxidizability of molten steel, avoiding overoxidation of steel slag, using manganese-rich mineralized slag, and realizing molten reduction of manganese ore through high-carbon steelmaking and reducing the amount of slag, the purpose of desulfurization is achieved.

[0006] 3. LF refining and RH refining: After the molten steel is smelted in a converter, the sulfur content can be further reduced by processes such as LF refining furnace or RH desulfurization powder injection. RH refining uses deep vacuum treatment to ensure the thermodynamic conditions for denitrification of the molten steel, protect the pouring during the continuous casting process, and prevent nitrogen increase.

[0007] Despite the above desulfurization technologies, there are still some problems in the smelting of low-sulfur steel in 210t converter:

[0008] 1. Difficulty in controlling sulfur content: In the existing technology, the sulfur content of the desulfurized hot metal entering the 210t converter is about 0.005%, the sulfur content of metallurgical lime used is 0.050%-0.080%, the sulfur content of dust removal ash briquette is 0.060%-0.080%, and the types of converter scrap steel used are mainly briquettes, heavy scrap, crushed materials, and recycled iron-containing resources. The final sulfur content of the converter after smelting with desulfurized hot metal is about 0.016%, which is difficult to meet the composition control requirements of low-sulfur steel.

[0009] 2. Limited process path: For some low-carbon steel series, LF refining is not possible due to the characteristics of the steel grade, so the low-sulfur requirements of steel production cannot be met under the existing process conditions.

[0010] 3. Lack of sulfur control methods in the converter smelting process: At present, the domestic process of reducing sulfur content generally adopts LF refining furnace, RH desulfurization powder injection and other processes, but the converter smelting process lacks effective means to control sulfur in molten steel.

[0011] 4. Converter resulfurization: During the converter smelting process, the sulfur content in the residual slag after splashing and the furnace lining slag is high, which is not conducive to the control of sulfur in the molten steel during the converter smelting process. Summary of the invention

[0012] In view of this, the purpose of the present invention is to solve the above-mentioned problems and provide a method for smelting 210t converter low-sulfur steel. By adjusting the converter production process, the sulfur content of molten steel at the end of converter smelting can meet the steel grade requirements and reduce dependence on refining furnaces.

[0013] In order to achieve the above object, the present invention adopts the following technical solutions:

[0014] A method for smelting low-sulfur steel in a 210t converter comprises the following steps:

[0015] S1. Preparation of raw and auxiliary materials: The sulfur content of molten iron is controlled to ≤0.001% through KR desulfurization process, and the desulfurization slag is cleaned at the same time, and the bright surface is ≥95%; low-sulfur scrap steel is used for the scrap steel entering the furnace, and each batch can be used only after passing the random inspection, and the sulfur content of the scrap steel is ≤0.003%; the sulfur content of lime and magnesium balls entering the furnace is ≤0.020%; the sulfur content of cold materials entering the furnace is ≤0.020%.

[0016] S2. Converter smelting control

[0017] During the converter smelting process, the sulfur content in the residual slag after splashing and the lining slag is high, and the sulfur in the molten steel during the converter smelting process is poorly controlled. Therefore, when producing low-sulfur steel grades (especially when the process path is limited), the high-sulfur slag on the original lining is replaced with low-sulfur slag. The specific operation is as follows:

[0018] Take the current furnace as furnace No. 0. After the smelting of the current furnace of the converter is completed, the slag is directly poured out after the molten steel is discharged, and no slag splashing operation is performed; starting from the 1st furnace, the low-sulfur raw materials prepared in S1 are used for the smelting of subsequent furnaces. The smelting end temperature of the 1st to 3rd furnaces is ≥1650℃, [O] ≥700ppm, and the slag is poured out after the converter is finished tapping, and no slag splashing operation is performed; observe whether the converter end sulfur meets the predetermined requirements. If so, the slag splashing operation is resumed in the subsequent furnaces to prevent the erosion of the converter refractory materials; 2 to 4 kg / t of low-sulfur lime is added during the converter tapping process for slag washing and desulfurization.

[0019] Furthermore, in S1, in order to reduce the impact of different iron-steel ratios on cold materials and scrap steel brought into the cold materials, especially the impact of the addition of cold materials on the resulfurization in the converter smelting process, the iron-steel ratio is controlled at 840-900 kg / t.

[0020] Furthermore, the sulfur content at the converter smelting end point and the sulfur content in the finished product are stably controlled to be ≤0.004%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention can stably control the sulfur at the end of converter smelting and the sulfur in the finished product to ≤0.004%, meeting the composition requirements of low-sulfur steel, and does not need to rely on subsequent processes such as LF refining, thereby reducing production costs and improving production efficiency. The present invention achieves more effective sulfur control through the following measures:

[0023] Strictly control the sulfur content of raw and auxiliary materials: The sulfur content of molten iron is controlled to ≤0.001% through the KR desulfurization process, and low-sulfur scrap steel, lime and magnesium balls and other raw and auxiliary materials are used to reduce the introduction of sulfur from the source.

[0024] Optimize the iron-steel ratio: control the iron-steel ratio at 840-900kg / t to reduce the impact of cold materials and scrap steel, especially the impact of cold materials on the resulfurization of the converter smelting process.

[0025] Lining slag replacement: By not performing slag splashing operations in specific furnaces, the high-sulfur slag on the original lining is replaced with low-sulfur slag, thereby reducing the resulfurization during the converter smelting process.

[0026] Slag washing and desulfurization: Low-sulfur lime is added during the converter steelmaking process for slag washing and desulfurization to further reduce the sulfur content in the molten steel.

[0027] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] Embodiment 1:

[0030] This embodiment is directed to a method for smelting low-sulfur steel in a 210t converter, and the specific implementation steps are as follows:

[0031] S1. Preparation of raw materials and auxiliary materials:

[0032] The KR desulfurization process is used to treat molten iron to control its sulfur content to ≤0.001%. At the same time, the desulfurization slag is cleaned and the bright surface is ≥95%.

[0033] Low-sulfur scrap steel is used as the scrap steel entering the furnace to ensure that each batch passes the random inspection and the sulfur content of the scrap steel is ≤0.002%.

[0034] The sulfur content of lime and magnesium balls entering the furnace is controlled at ≤0.015%.

[0035] The sulfur content of the cold material is controlled at ≤0.020%.

[0036] Iron-steel ratio requirements:

[0037] The iron-steel ratio is controlled at 880-910 kg / t to reduce the impact of cold materials and scrap steel brought into the cold materials on the resulfurization process of the converter smelting process.

[0038] S2. Converter smelting control:

[0039] After the smelting of the 0th furnace is completed, the slag is directly poured out after the molten steel is discharged, and no slag splashing operation is performed.

[0040] Starting from the first furnace, the low-sulfur raw materials prepared above were used for smelting. The smelting end point temperature of the first to third furnaces was controlled at ≥1660°C and [O] ≥750ppm.

[0041] After the converter is finished tapping, the slag is drained cleanly without slag splashing. Observe whether the converter end sulfur meets the predetermined requirements. If so, the subsequent heats will resume slag splashing.

[0042] During the steel-making process, 3-5 kg / t of low-sulfur lime is added for slag washing and desulfurization.

[0043] result:

[0044] Through the above implementation steps, the final sulfur content of converter smelting and the finished sulfur content are stably controlled at ≤0.003%, meeting the composition requirements of low-sulfur steel.

[0045] Embodiment 2:

[0046] This embodiment further optimizes the method for smelting low-sulfur steel in a 210t converter, and the specific implementation steps are as follows:

[0047] S1. Preparation of raw materials and auxiliary materials:

[0048] The KR desulfurization process is used to treat molten iron to control its sulfur content to ≤0.001%. At the same time, the desulfurization slag is cleaned and the bright surface is ≥95%.

[0049] The scrap steel entering the furnace is low-sulfur scrap steel, and each batch can only be used after passing the random inspection. The sulfur content of the scrap steel is ≤0.003%.

[0050] The sulfur content of lime and magnesium balls entering the furnace is controlled at ≤0.020%.

[0051] The sulfur content of the cold material is controlled at ≤0.018%.

[0052] Iron-steel ratio requirements:

[0053] The iron-steel ratio is controlled at 850-910 kg / t to reduce the impact of cold materials and scrap steel brought into the cold materials on the resulfurization process of the converter smelting process.

[0054] S2. Converter smelting control:

[0055] After the smelting of furnace No. 0 is completed, the slag is directly poured out without any slag splashing operation.

[0056] Starting from the first furnace, the above-mentioned low-sulfur raw materials are used for smelting. The smelting end temperature of the first to third furnaces is ≥1675°C, and [O] is ≥700ppm.

[0057] After the converter is finished tapping, the slag is drained cleanly without slag splashing. Observe whether the converter end sulfur meets the predetermined requirements. If so, resume slag splashing.

[0058] During the steel-making process, 2-4 kg / t of low-sulfur lime is added for slag washing and desulfurization.

[0059] result:

[0060] This embodiment optimizes the iron-steel ratio and strictly controls the raw and auxiliary materials, so that the sulfur at the converter smelting end point and the finished product sulfur are stably controlled at ≤0.004%, effectively improving the production efficiency and quality of low-sulfur steel.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for smelting 210t converter low-sulfur steel, characterized in that: The steps include: S1. Preparation of raw and auxiliary materials: The sulfur content of molten iron is controlled to ≤0.001% through KR desulfurization process, and the desulfurization slag is cleaned at the same time, and the bright surface is ≥95%; low-sulfur scrap steel is used for the scrap steel entering the furnace, and each batch can be used only after passing the random inspection, and the sulfur content of the scrap steel is ≤0.003%; the sulfur content of lime and magnesium balls entering the furnace is ≤0.020%; the sulfur content of cold materials entering the furnace is ≤0.020%. S2. Converter smelting control During the converter smelting process, the sulfur content in the residual slag after splashing and the lining slag is high, and the sulfur in the molten steel during the converter smelting process is poorly controlled. Therefore, when producing low-sulfur steel grades, the high-sulfur slag on the original lining is replaced with low-sulfur slag. The specific operation is as follows: Take the current furnace as furnace No.

0. After the smelting of the current furnace of the converter is completed, the slag is directly poured out after the molten steel is discharged, and no slag splashing operation is performed; starting from the 1st furnace, the low-sulfur raw materials prepared in S1 are used for the smelting of subsequent furnaces. The smelting end temperature of the 1st to 3rd furnaces is ≥1650℃, [O] ≥700ppm. After the steelmaking of the converter is completed, the slag is poured out, and no slag splashing operation is performed; observe whether the sulfur at the end of the converter meets the predetermined requirements. If so, the slag splashing operation is resumed in the subsequent furnaces to prevent the erosion of the converter refractory materials; 2 to 4 kg / t of low-sulfur lime is added during the converter steelmaking process for slag washing and desulfurization.

2. The method for smelting 210t converter low-sulfur steel according to claim 1, characterized in that: In S1, in order to reduce the impact of different iron-steel ratios on cold materials and scrap steel brought into the cold materials, especially the impact of the addition of cold materials on the resulfurization in the converter smelting process, the iron-steel ratio is controlled at 840-900 kg / t.

3. The method for smelting 210t converter low-sulfur steel according to claim 2, characterized in that: The sulfur content at the converter smelting end point and in the finished product are both stably controlled to be ≤0.004%.