A control method for reducing the amount of deoxidizing aluminum in RH refining deoxidation process

Abstract

The application discloses a control method for reducing the amount of deoxidizing aluminum in the RH refining deoxidizing process. The control method combines the accurate closed-loop control of the decarburization end oxygen value, the pre-deoxidization of carbon materials and the one-time hit model of aluminum deoxidization and alloying to form a complete RH low-carbon steel deoxidization optimization process. The method reduces the single consumption of RH deoxidizing aluminum of low-grade low-carbon steel to below 0.5 kg / ton of steel, significantly reduces the alloy production cost, improves the qualified rate of primary deoxidization of molten steel to above 93%, reduces the defect rate of steel plates after cold rolling to below 0.3%, improves the purity of molten steel and the comprehensive performance of products, and realizes the dual effects of reducing the amount of deoxidizing aluminum and improving the quality of molten steel.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and more particularly to a method for controlling the amount of deoxidized aluminum during the RH refining deoxidation process. Background Technology

[0002] RH vacuum degassing is a core process in low-carbon steel refining, and the rationality of the deoxidation process directly determines the purity of molten steel, the quality of cast billets, and production costs. With increasing market demand for low-carbon steel products such as cold-rolled sheets and appliance sheets, quality standards for surface quality and internal purity are continuously rising, thus placing higher demands on the precision of the RH refining deoxidation process.

[0003] Currently, domestic steel enterprises generally use the traditional single-aluminum deoxidation process for RH refining and deoxidation of low-grade, low-carbon steel. The oxygen value control at the decarburization endpoint relies on operator experience, and there is no standardized closed-loop oxygen control system. This is a common technical approach in the industry. The existing traditional process has the following technical shortcomings: 1. Excessive deoxidation aluminum consumption: In traditional processes, the RH aluminum consumption for low-grade low-carbon steel reaches 0.85~1.0 kg / ton of steel. Based on an aluminum price of 20 yuan / kg, the alloy cost per ton of steel is 17~20 yuan. For a company with an annual production capacity of 500,000 tons of low-carbon steel, the annual cost of deoxidation aluminum alone increases by 3.5 million to 5 million yuan, resulting in high aluminum consumption costs.

[0004] 2. Low precision in controlling oxygen value at the decarburization endpoint: Oxygen value fluctuates between 180 and 350 ppm. Operators blindly increase the amount of aluminum used for deoxidation in order to ensure the deoxidation effect, resulting in high randomness in operation and waste of resources.

[0005] 3. Insufficient purity of molten steel: The single aluminum deoxidation process produces a large number of aluminum oxide inclusions, resulting in problems such as subcutaneous inclusions and central porosity in the billet, with a defect rate of 1.2%. This increases the difficulty of quality control in subsequent continuous casting and rolling processes and reduces the qualified rate of finished products.

[0006] 4. Low deoxidation pass rate: Due to inaccurate oxygen value control, the pass rate of primary deoxidation for low-grade steel is only about 40%, requiring multiple additions of aluminum balls for secondary deoxidation, which increases the refining time per furnace by 5 to 8 minutes and reduces the efficiency of the production line. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for controlling the amount of deoxidized aluminum during RH refining deoxidation. This method constructs a three-in-one deoxidation process system integrating decarburization endpoint oxygen value control, carbonaceous material pre-deoxidation, and precise aluminum deoxidation control. It controls the endpoint oxygen value within the range of 200-270 ppm, with a control accuracy deviation of ≤±10 ppm. Utilizing the pre-deoxidation effect of the carbon-oxygen reaction, it effectively reduces aluminum oxide inclusions in the steel, lowering the defect rate of cold-rolled steel plates to below 0.3%, improving steel purity and overall product performance, and achieving multi-faceted optimization of the deoxidation process. Simultaneously, through narrow-range precise control of aluminum composition, the first-pass deoxidation qualification rate of low-grade steel is increased to over 93%, achieving standardized and intelligent operation of the deoxidation process, reducing reliance on operator experience, improving production line efficiency, significantly reducing alloy production costs, and filling the gap in the industry for multi-faceted deoxidation processes in low-carbon steel RH refining.

[0008] To achieve the above objectives, the present invention is accomplished through the following technical solutions.

[0009] A method for controlling the amount of deoxidized aluminum during RH refining deoxidation includes the following steps: Step 1, Oxygen value control at the decarbonization endpoint: Before vacuuming is started, the molten steel is pretreated to determine the oxygen content, and the oxygen content of the molten steel is controlled to be <300ppm. The molten steel is then subjected to RH decarburization, and the oxygen content at the end of the decarburization is controlled to be 200~270ppm. In step 1, before vacuuming is started, if the oxygen value of the molten steel is ≥300ppm, weak stirring is performed to degas and reduce the oxygen value to below 300ppm.

[0010] In step 1, RH decarbonization is performed using either constant oxygen supply or supplemental oxygen supply.

[0011] In the above technical solution, RH decarburization adopts constant oxygen replenishment: after opening the valve and evacuating for 4-5 minutes, oxygen is replenished at 3-5 ppm / m³. 3 Forced oxygenation is performed according to the standard. After oxygenation, the molten steel is circulated for 3-5 minutes and the oxygen level is checked again. If the oxygen value is <200ppm, it is adjusted to 3-5ppm / m 3 The standard for mandatory oxygen supplementation will continue.

[0012] In the above technical solution, RH decarbonization adopts oxygen supplementation and oxygen determination: after opening the valve and evacuating the vacuum for 3-5 minutes, the oxygen value is detected. If the oxygen value is <250ppm, oxygen is supplemented at 3-5ppm / m 3 Forced oxygen supplementation is carried out according to the standard.

[0013] In the above technical solution, the oxygen probe determines the oxygen level, and the oxygen gun replenishes the oxygen supply.

[0014] In step 1, a portable oxygen analyzer and an online oxygen analyzer are set up at the decarbonization endpoint to ensure accurate oxygen value detection results and control the accuracy deviation ≤ ±10ppm.

[0015] Step 2, pre-deoxidation of carbonaceous materials: After RH decarburization is completed, carbonaceous materials are added within 3 to 5 minutes after the steel circulation begins to pre-deoxidize using the carbon-oxygen reaction. After adding the materials, the circulation and stirring are continued and the mixture is allowed to stand to allow CO gas to escape fully, avoid porosity defects in the steel, remove 30% to 40% of the oxygen content in the steel, and reduce the amount of aluminum used for subsequent deoxidation. In step 2, the carbonaceous deoxidizing material is one or more of pyrobutylene carburizer and high-carbon ferromanganese.

[0016] In step 2, oxygen is removed from molten steel at a rate of 100-120 ppm for every 20 kg of coke butadiene carburizing agent; oxygen is removed from molten steel at a rate of 100-120 ppm for every 330 kg of high-carbon ferromanganese.

[0017] In step 2, the molten steel circulation is carried out under stirring, with a stirring intensity ≥ 50 NL / (t). This ensures sufficient contact between carbonaceous materials and molten steel, resulting in high reaction efficiency.

[0018] In step 2, after feeding the material, continue to circulate and stir for 2-4 minutes, and then let it stand for 2-4 minutes.

[0019] Step 3: Precise Control of Aluminum Deoxidation A one-hit model for aluminum deoxidation alloying is adopted. The oxygen value at the decarburization endpoint and the target aluminum value are input, and the amount of aluminum balls to be added is automatically calculated. Aluminum balls are added to the pre-deoxidized molten steel according to the calculated amount of aluminum balls to carry out deoxidation. The target aluminum value is in the range of 0.02% to 0.05%. Under the premise of meeting the deoxidation requirements, the total amount of aluminum balls used is minimized. The calculation formula for the first hit model of aluminum deoxidation alloying is as follows: , where m Al The amount of aluminum balls added is expressed in kg; [O] represents the oxygen value at the decarburization endpoint, in ppm; m Al，O This represents the amount of aluminum balls required to deoxidize 100 ppm, in kg; [Al] 标 Expressed as target aluminum value, unit: %; m Al，Als This indicates the amount of aluminum balls required to adjust 0.01% [Als], in kg.

[0020] In step 3, when using high-level heats and / or low-level heats of type DQ1, an oxygen verification step is added before deoxidation in step 3. After ensuring that the oxygen value is within the qualified range of 200~270ppm, aluminum balls are added to the pre-deoxidized molten steel according to the calculated amount of aluminum balls to carry out deoxidation, ensuring that the deoxidation is successful on the first attempt.

[0021] In step 3, the aluminum deoxidation alloying one-hit model integrates core parameters such as the oxygen value at the decarburization endpoint, the weight of molten steel, the temperature of molten steel, and the composition of molten steel.

[0022] In the above technical solution, the pass rate of primary deoxidation of molten steel is controlled at over 80%.

[0023] In the above technical solution, the defect rate of the cold-rolled steel sheet is below 0.3%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method of the present invention establishes a standardized closed-loop control system for oxygen fixation and oxygen replenishment, which improves the purity of molten steel by about 31%, reduces the content of aluminum oxide inclusions by more than 45%, solves problems such as subcutaneous inclusions and central porosity of billets, reduces the defect rate of cold-rolled steel plates from 1.2% to below 0.3%, and the composition fluctuation deviation is ≤ ±0.002%, providing a stable raw material base for subsequent continuous casting and rolling processes, improving the overall quality of finished materials, and increasing the qualified rate of finished materials by 0.9 percentage points.

[0025] (3) This invention reduces the consumption of deoxidized aluminum from the traditional 0.85~1.0 kg / ton of steel to 0.45~0.5 kg / ton of steel by precise control of oxygen value at the decarbonization endpoint and pre-deoxidation of carbonaceous materials, and reduces the total aluminum consumption per ton of steel by 0.35~0.5 kg; thus significantly reducing production costs and improving economic benefits.

[0026] (3) The present invention constructs an aluminum deoxidation alloying one-hit model, which realizes the accurate calculation of aluminum addition amount, increases the first deoxidation qualification rate of low-grade steel molten steel from 40% to more than 80%, solves the problem of secondary deoxidation. The model process operation is standardized and intelligent, reduces the dependence on the experience of operators, reduces the operation error rate to less than 0.5%, reduces the downtime of production line maintenance, and provides technical reference for the intelligent upgrading of RH refining process of steel enterprises.

[0027] (4) The process of the present invention is compatible with existing RH refining production lines. No new large-scale equipment is required. Only the operating parameters need to be optimized and an intelligent calculation model needs to be introduced. The transformation cost is low and the application is highly scalable. It can be widely used in domestic steel enterprises.

[0028] (5) The control method of this invention reduces the amount of aluminum used, thereby reducing energy consumption and carbon emissions in the aluminum smelting process, and reducing furnace heating energy consumption caused by secondary deoxidation. It can reduce gas consumption by approximately 50 m³ / s per furnace. 3 To achieve the green production goal of energy conservation and carbon reduction. Detailed Implementation

[0029] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0030] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0031] Examples 1-5 A method for controlling the amount of deoxidized aluminum during RH refining deoxidation includes the following steps: Step 1: Decarbonization endpoint oxygen value control Before vacuuming begins, 170 tons of molten steel (low-grade steel) undergo pretreatment with oxygen determination. The oxygen level of the molten steel before startup is measured to be 290 ppm. The molten steel then enters the RH decarburization process, where oxygen is determined using an oxygen probe. Oxygen is replenished using an oxygen lance (single slag furnace cycle). After the valve is opened for 4 minutes (vacuuming), oxygen is added at 4 ppm / m³. 3 Forced oxygen supplementation was performed according to the standard. After oxygen supplementation, the molten steel was circulated for 3 minutes and the oxygen was determined again. The oxygen value was measured to be 240 ppm, which is within the qualified range of 200~270 ppm. The oxygen value control at the decarburization endpoint was completed. At the decarburization endpoint, a portable oxygen analyzer and an online oxygen analyzer system were set up for dual detection. The dual detection verified that the oxygen value deviation was ±8 ppm, which meets the accuracy requirements.

[0032] Step 2: Pre-deoxidation of carbonaceous materials After RH decarburization is completed, based on the oxygen value of 240ppm at the decarburization endpoint, it is calculated that approximately 90ppm of oxygen needs to be removed. Coking coal recarburizer is selected as the carbonaceous deoxidizing material. Based on the calculation that 20kg of coking coal recarburizer removes 100ppm of oxygen, 18kg of coking coal recarburizer is added. The feeding timing is 4 minutes after the start of molten steel circulation (stirring intensity 55NL / (t)). After feeding, continue to circulate and stir for 2 minutes, then let stand for 2 minutes to allow CO gas to escape fully. After pre-deoxidation, the oxygen value of the molten steel is 150 ppm, which is within the qualified range of 150~250 ppm. The oxygen content removed is 90 ppm, and the removal rate is 37.5%.

[0033] Step 3: Precise Control of Aluminum Deoxidation Input the decarburization endpoint oxygen value and target aluminum value into the aluminum deoxidation alloying one-hit model, and the amount of aluminum balls to be added will be automatically calculated. After adding aluminum balls according to the calculated amount, the aluminum content of the finished product is detected to be 0.025%, which is within the control range of 0.02% to 0.05%, and meets the requirements.

[0034] The calculation formula for the first hit model of aluminum deoxidation alloying is as follows: ; Where, m Al The amount of aluminum balls added is expressed in kg, [O] represents the oxygen value at the decarburization endpoint (ppm), and mAl，O The amount of aluminum balls (kg) required to remove 100 ppm of oxygen is expressed as [Al]. 标 Expressed as target aluminum value (%), m Al，Als This represents the amount of aluminum balls (kg) required to adjust 0.01% [Als].

[0035] Taking the control of a production line consisting of 5 RH furnaces as an example, in actual operation, the oxygen value at the decarburization endpoint and the target aluminum value are input into the system terminal. The system completes the calculation according to the preset calculation formula and automatically calculates the amount of aluminum balls to be added, as shown in Table 1.

[0036] Table 1

[0037] After RH refining, the molten steel underwent a full range of tests, and the results are shown in Table 2. Table 2

[0038] The content of aluminum oxide inclusions is all below 0.002%, and the purity of molten steel is improved by about 31%, which is better than the traditional process indicators. The composition fluctuation deviation is all within ±0.002%. The first deoxidation qualification rate of molten steel obtained by the control method of this invention is 94%, achieving the dual effect of reducing deoxidized aluminum and improving the quality of molten steel.

[0039] For the continuous casting of RH-refined molten steel, the billets obtained after continuous casting in Examples 1-5 were subjected to non-destructive testing and found to be free of defects such as subcutaneous inclusions and central porosity. The billets were then hot-rolled and then cold-rolled to obtain cold-rolled steel plates. The defect rate of the cold-rolled steel plate obtained in Example 1 was 0.20%, the defect rate of the cold-rolled steel plate obtained in Example 2 was 0.21%, the defect rate of the cold-rolled steel plate obtained in Example 3 was 0.20%, the defect rate of the cold-rolled steel plate obtained in Example 4 was 0.20%, and the defect rate of the cold-rolled steel plate obtained in Example 5 was 0.19%.

[0040] Compared with existing traditional processes, the method of the present invention achieves significant economic, quality, production efficiency, and technical benefits, as detailed below: 1. Significantly improves steel quality and reduces product defect rate. (1) This invention reduces the total oxygen content in molten steel from the traditional 250-350 ppm to 150-250 ppm by precisely controlling the oxygen value at the decarburization endpoint and pre-deoxidizing with carbonaceous materials, thereby increasing the purity of molten steel by about 31%. (2) The content of aluminum oxide inclusions is reduced by more than 45%, the billet is free of defects such as subcutaneous inclusions and central porosity, and the defect rate of cold-rolled steel plate is reduced from 1.2% to below 0.3%, which is better than the traditional process indicators, and the qualified rate of finished products is increased by 0.9 percentage points; (3) Improved uniformity of steel composition. The billet of Example 1 was tested without subcutaneous inclusions and central porosity. The composition fluctuation deviation was ≤ ±0.002%, which provides a stable raw material base for subsequent continuous casting and rolling processes and improves the overall quality of finished products.

[0041] 2. Significantly reduce production costs and improve economic efficiency. (1) The deoxidation aluminum consumption per unit is reduced from the traditional 0.85~1.0 kg / ton of steel to 0.45~0.5 kg / ton of steel, and the total aluminum consumption per ton of steel is reduced by 0.35~0.5 kg. Based on the aluminum price of 20 yuan / kg, the alloy cost per ton of steel is reduced by 7~10 yuan. Taking Example 1 as an example, the deoxidation aluminum consumption per furnace is 0.45 kg / ton of steel, which is 0.4 kg / ton of steel lower than the traditional process. The deoxidation aluminum cost per furnace is reduced by 1320 yuan (165 tons × 0.4 kg × 20 yuan).

[0042] (2) For enterprises with an annual production capacity of 500,000 tons of low-carbon steel, simply adding the total aluminum content can reduce costs by 3.5 million to 5 million yuan per year; (3) The cost of carbon deoxidation materials is much lower than that of aluminum. The combined deoxidation cost of coking agent and high carbon manganese iron is only 1 / 5 of that of aluminum deoxidation, which further reduces the overall cost of the process.

[0043] 3. Improve production efficiency and optimize production line operation rhythm. (1) The application of the aluminum deoxidation alloying first hit model has increased the first deoxidation qualification rate of low-grade steel from 40% to more than 80%, solved the problem of secondary deoxidation, and shortened the refining time of a single furnace by 3 to 5 minutes. (2) The overall operating rate of the production line will increase by 2%. Based on the annual operating time of 8,000 hours for the three RH production lines, an additional 15,000 tons of low carbon steel can be produced annually, with an additional output value of about RMB 3 million (based on the market price of RMB 4,000 per ton of low carbon steel). (3) The process operation is standardized and intelligent, reducing the reliance on the experience of operators, reducing the error rate to below 0.5%, and reducing the downtime of production line maintenance.

[0044] 4. It aligns with the trend of green development and achieves energy conservation and carbon reduction. (1) Reducing the use of aluminum reduces energy consumption and carbon emissions in the aluminum smelting process. Based on a reduction of 250 tons of aluminum used per year (500,000 tons of production capacity), carbon emissions can be reduced by about 1,500 tons per year (based on carbon emissions of 6 tons / ton of aluminum smelting).

[0045] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for controlling the amount of deoxidized aluminum during RH refining deoxidation, characterized in that, Includes the following steps: Step 1: Before starting the vacuum process, control the oxygen value of the molten steel to <300ppm, and perform RH decarburization on the molten steel, controlling the oxygen value at the end of the decarburization process to be 200~270ppm. Step 2: After RH decarburization is completed, add carbonaceous deoxidizing material for pre-deoxidation within 3 to 5 minutes after the steel circulation starts. After adding the material, continue to circulate, stir, and let stand to remove 30% to 40% of the oxygen content in the steel. Step 3: Using the aluminum deoxidation alloying one-hit model, input the oxygen value at the decarburization endpoint and the target aluminum value, and automatically calculate the amount of aluminum balls to be added; add aluminum balls to the pre-deoxidized molten steel according to the calculated amount of aluminum balls to carry out deoxidation, wherein the target aluminum value is in the range of 0.02%~0.05%; The calculation formula for the first hit model of aluminum deoxidation alloying is as follows: , where m Al The amount of aluminum balls added is expressed in kg; [O] represents the oxygen value at the decarburization endpoint, in ppm; m Al，O This represents the amount of aluminum balls required to deoxidize 100 ppm, in kg; [Al] 标 Expressed as target aluminum value, unit: %; m Al，Als This indicates the amount of aluminum balls required to adjust 0.01% [Als], in kg.

2. The control method according to claim 1, characterized in that, Before starting the vacuum process, if the oxygen value of the molten steel is ≥300ppm, perform weak stirring to degas and reduce the oxygen level to below 300ppm.

3. The control method according to claim 1, characterized in that, RH decarbonization employs either constant oxygen supply or supplemental oxygen supply.

4. The control method according to claim 3, characterized in that, RH decarbonization uses constant oxygen supplementation: after opening the valve for 4-5 minutes, apply oxygen at 3-5 ppm / m³. 3 Forced oxygenation is performed according to the standard. After oxygenation, the molten steel is circulated for 3-5 minutes and the oxygen level is checked again. If the oxygen value is <200ppm, it is adjusted to 3-5ppm / m³. 3 The standard for mandatory oxygen supplementation will continue.

5. The control method according to claim 3, characterized in that, RH decarbonization uses oxygen supplementation and oxygen control: After opening the valve for 3-5 minutes, check the oxygen level. If the oxygen level is <250ppm, adjust the oxygen level to 3-5ppm / m³. 3 Forced oxygen supplementation is carried out according to the standard.

6. The control method according to claim 1, characterized in that, The molten steel circulation is carried out under stirring, with a stirring intensity ≥50NL / (t). (min); after feeding, continue to circulate and stir for 2-4 minutes, then let stand for 2-4 minutes.

7. The control method according to claim 1, characterized in that, The carbonaceous deoxidizing material is one or more of pyrobutylene recarburizer and high-carbon ferromanganese.

8. The control method according to claim 7, characterized in that, For every 20 kg of the coking agent, oxygen is removed from molten steel at 100-120 ppm; for every 330 kg of the high-carbon ferromanganese, oxygen is removed from molten steel at 100-120 ppm.

9. The control method according to claim 1, characterized in that, When using high-level heats and / or low-level heats of type DQ1, an oxygen verification step is added before deoxidation in step 3. After ensuring that the oxygen value is within the qualified range of 200~270ppm, aluminum balls are added to the pre-deoxidized molten steel according to the calculated amount of aluminum balls to carry out deoxidation, ensuring a successful deoxidation in one go.

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