Method for precisely controlling silicon steel clearance through one furnace and two tanks

Abstract

The invention relates to a method for accurately controlling silicon steel clearance through one furnace and two tanks. The method comprises the steps that (1) molten steel tanks are grouped; 2) determining the loading amount; (3) clearance is determined, and the loading amount of a main tank and the loading amount of an auxiliary tank are determined with the aim that the clearance of the main tank and the clearance of the auxiliary tank of the tank rinsing furnace are both controlled to range from 400 mm to 450 mm; when silicon steel is produced, the main tank controls tapping according to the clearance of 300-600mm, and the clearance of the auxiliary tank is finely adjusted according to the residual molten steel of the converter. By optimizing tapping operation, accurate control over the clearance of the molten steel tank can be guaranteed, production practice verifies that the effect is remarkable, the situation that refining cannot be conducted due to large clearance and steel is forcibly changed is avoided after self-implementation, economic losses caused by steel changing are reduced, and the economic benefits of enterprises are improved.

Description

Technical Field

[0001] The invention relates to the technical field of converter smelting, and in particular to a method for accurately controlling the clearance of silicon steel in one furnace and two tanks. Background Art

[0002] Some domestic steel production lines currently use a smelting mode of one converter with two tanks and refining LF-RH duplex. When using this mode to produce low-grade silicon steel, the following problems exist:

[0003] 1) Compared with LF furnace, RH furnace has stricter requirements on molten steel clearance. In addition, there is a requirement for the distance from the molten steel level to the edge of the tank (the molten steel tank cannot be filled too full, and the molten steel level is generally required to be more than 300mm away from the edge of the tank to prevent the molten steel from overflowing and burning the cladding, tank body and ear shaft). When producing silicon steel, the precision of steelmaking clearance control is required to be higher.

[0004] 2) When single tank steel is tapped, for different furnaces, when the turnover times of the molten steel tank are similar, due to the influence of tank turning quality and steel type, even if the steel tapping volume is the same, there will be differences in the clearance of the molten steel tank.

[0005] 3) When the one-furnace-two-tank method is used to tap steel, the two molten steel tanks are randomly matched and have different turnover times. For example, for two furnaces of steel with the same loading amount, the clearance of the four molten steel tanks after tapping under normal conditions is often quite different. It is usually difficult to achieve precise control of the clearance without affecting the lining and converter operation due to the remaining steel in the converter. Summary of the invention

[0006] The present invention provides a method for accurately controlling the clearance of silicon steel in one furnace and two tanks. By optimizing the steel tapping operation, the accurate control of the clearance of the molten steel tank can be ensured. The effect has been verified by production practice. Since its implementation, the situation in which the refining cannot be processed due to the large clearance and the steel is forced to be changed is avoided, the economic losses caused by the steel change are reduced, and the economic benefits of the enterprise are improved.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for accurately controlling the clearance of silicon steel in one furnace and two tanks, comprising the following steps:

[0009] 1) Grouping of molten steel tanks: Before silicon steel production, the converter and molten steel tanks are rinsed. When casting silicon steel, n molten steel tanks are used for one pouring, and m molten steel tanks are required for turnover. According to the order of the furnaces when rinsing the tanks, these m molten steel tanks are divided into groups of two each. Each group of molten steel tanks corresponds to one furnace of molten steel, that is, one furnace has two tanks.

[0010] 2) Determine the loading quantity: divide the two steel ladle tanks in each group into the main ladle tank and the auxiliary ladle tank, add up the tank ages of the main ladle tank and the auxiliary ladle tank in each group of steel ladle tanks, and then determine the total loading quantity M of the group of steel ladle tanks according to the sum of the tank ages N; N < 50 times, M = 202 ± 2 tons; 50 ≤ N < 100 times, M = 204 ± 2 tons; 100 ≤ N < 150 times, M = 206 ± 2 tons; N ≥ 150 times, M = 208 ± 2 tons;

[0011] 3) Determine the clearance: During RH treatment, the clearance of the main tank and the auxiliary tank are controlled within 300-600mm; first, the loading amount of the main tank and the auxiliary tank is determined with the goal of controlling the clearance of the main tank and the auxiliary tank of the rinsing furnace at 400-450mm; during silicon steel production, the main tank controls the steel tapping according to the clearance of 300-600mm, and the clearance of the auxiliary tank is fine-tuned according to the remaining molten steel in the converter, specifically adjusted at the rate of 100mm clearance for every additional 2-4 tons of molten steel; when the clearance of the auxiliary tank reaches 380-420mm during the steel tapping process, the furnace is lifted with the tank, and finally the clearance of the auxiliary tank is controlled to be above 300mm.

[0012] The mass content of sulfur in silicon steel products is ≤0.006%.

[0013] LF-RH double refining is adopted, and the interval time from the end of steel tapping to the start of casting is controlled at 140-145 minutes.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] By producing silicon steel in the one-furnace-two-tank mode and optimizing the steel-tapping operation, the clearance of the molten steel tank can be precisely controlled. The effect has been verified by production practice. Since its implementation, it has avoided the situation where the refining cannot be handled due to large clearance and the steel is forced to be converted, reducing the economic losses caused by steel conversion and improving the economic benefits of the enterprise. DETAILED DESCRIPTION

[0016] The method for accurately controlling the clearance of silicon steel in one furnace and two tanks of the present invention comprises the following steps:

[0017] 1) Grouping of molten steel tanks: Before silicon steel production, the converter and molten steel tanks are rinsed. When casting silicon steel, n molten steel tanks are used for one pouring, and m molten steel tanks are required for turnover. According to the order of the furnaces when rinsing the tanks, these m molten steel tanks are divided into groups of two each. Each group of molten steel tanks corresponds to one furnace of molten steel, that is, one furnace has two tanks.

[0018] 2) Determine the loading quantity: divide the two steel ladle tanks in each group into the main ladle tank and the auxiliary ladle tank, add up the tank ages of the main ladle tank and the auxiliary ladle tank in each group of steel ladle tanks, and then determine the total loading quantity M of the group of steel ladle tanks according to the sum of the tank ages N; N < 50 times, M = 202 ± 2 tons; 50 ≤ N < 100 times, M = 204 ± 2 tons; 100 ≤ N < 150 times, M = 206 ± 2 tons; N ≥ 150 times, M = 208 ± 2 tons;

[0019] 3) Determine the clearance: During RH treatment, the clearance of the main tank and the auxiliary tank are controlled within 300-600mm; first, the loading amount of the main tank and the auxiliary tank is determined with the goal of controlling the clearance of the main tank and the auxiliary tank of the rinsing furnace at 400-450mm; during silicon steel production, the main tank controls the steel tapping according to the clearance of 300-600mm, and the clearance of the auxiliary tank is fine-tuned according to the remaining molten steel in the converter, specifically adjusted at the rate of 100mm clearance for every additional 2-4 tons of molten steel; when the clearance of the auxiliary tank reaches 380-420mm during the steel tapping process, the furnace is lifted with the tank, and finally the clearance of the auxiliary tank is controlled to be above 300mm.

[0020] The mass content of sulfur in silicon steel products is ≤0.006%.

[0021] LF-RH double refining is adopted, and the interval time from the end of steel tapping to the start of casting is controlled at 140-145 minutes.

[0022] The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0023] [Example]

[0024] In this embodiment, the steel types produced by the 180t converter of a certain steelmaking production line are mainly aluminum steel and QB steel with low sulfur requirements. The mass percentage of sulfur in the incoming iron is usually around 0.040%. Therefore, the molten iron entering the converter does not need to be desulfurized, and only desulfurization treatment is performed in the refining LF furnace.

[0025] Silicon steel requires low sulfur content (S mass content in the finished product ≤ 0.006%), so when producing silicon steel on this production line, low-sulfur hot metal is needed, and the converter and steel ladle are rinsed in advance to reduce the sulfur content in the system. When the steel is discharged from the steel ladle, the clearance of the steel ladle is controlled at 400-450mm.

[0026] This embodiment adopts a one-furnace-two-tank mode in the production line. When casting silicon steel, 12 tanks of molten steel are required for one pour. LF-RH double refining is adopted. The interval time from the end of steel tapping to the start of casting is controlled at 140-145 minutes. Eight molten steel tanks are configured for turnover to meet production requirements. The loading amount and clearance when rinsing the tanks are controlled according to the silicon steel grade. When producing silicon steel, the loading amount is checked according to the steel tapping clearance of the auxiliary tank.

[0027] The specific operations are as follows:

[0028] 1) Grouping of molten steel tanks: According to the order of the furnaces when the tanks are rinsed, 12 tanks of molten steel are needed for one pouring of silicon steel. Arranging 8 molten steel tanks for turnover can meet the requirements. These 8 molten steel tanks are divided into 4 groups, each group corresponds to one furnace of steel (i.e. one furnace and two tanks).

[0029] 2) Determine the loading volume: Each group of steel ladle is divided into main ladle and auxiliary ladle. The age of main ladle and auxiliary ladle in each group of steel ladle is added together, and then the total loading volume M of the group of steel ladle is determined according to the sum of ladle ages (turnover times) N; the sum of ladle ages is proportional to the loading volume, that is, the greater the sum of ladle ages, the greater the loading volume. According to practical experience, N < 50 times, M = 202 ± 2 tons; 50 ≤ N < 100 times, M = 204 ± 2 tons; 100 ≤ N < 150 times, M = 206 ± 2 tons; N ≥ 150 times, M = 208 ± 2 tons.

[0030] 3) Determine the clearance: The principle of RH treatment is that the clearance of the main tank and the auxiliary tank are controlled within 300-600mm; first, the loading amount of the main tank and the auxiliary tank is determined with the goal of controlling the clearance of the main tank and the auxiliary tank of the rinsing furnace within 400-450mm; during silicon steel production, the main tank controls the steel output according to the clearance of 300-600mm, and the clearance of the auxiliary tank is fine-tuned according to the remaining molten steel in the converter, specifically adjusted according to the clearance of 100mm for every additional 3 tons of molten steel. The adjusted loading amount and clearance are shown in Table 2; when the clearance of the auxiliary tank is close to 400mm during the steel tapping process, the furnace is lifted with the tank, and finally the clearance of the auxiliary tank is controlled above 300mm.

[0031] After steel tapping is completed, the steel tapping volume, clearance, remaining steel volume and whether slag is leaking from the main and auxiliary tanks are recorded.

[0032] The loading volume and clearance of the main and auxiliary tanks for the tank washing furnace are shown in Table 1. The loading volume and clearance of the main and auxiliary tanks for the production of silicon steel are shown in Table 2.

[0033] Table 1 Loading quantity and clearance of main and auxiliary tanks in the tank washing furnace

[0034]

[0035] Table 2: Loading volume and clearance of main and auxiliary tanks during silicon steel production

[0036]

[0037] In this embodiment, a total of 238 silicon steel cans were produced from August to October 2023, of which 17 cans were forced to be converted to steel due to large headroom that made refining impossible. After applying the method of the present invention, no accidents of converting to steel due to large headroom have occurred since November 2023.

[0038] Compared with the previous situation where the refining process could not be processed due to large headroom and the steel was forced to be changed (silicon steel to aluminum steel), the benefits obtained after the improvement measures in this embodiment are calculated as follows:

[0039] 1) Temperature loss when silicon steel is changed to aluminum steel;

[0040] The tapping temperature of silicon steel is 1700℃, and that of aluminum steel is 1640℃. The temperature of 1 ton of scrap steel is calculated at 8℃, the quantity of good billets is calculated at 183 tons, the unit price of molten iron is calculated at 2786 yuan, and the unit price of scrap steel is calculated at 2605 yuan. The unit cost of steel materials in the implementing month is calculated, i.e.: (1700-1640) / 8×(2786-2605) / 183=7.42 yuan / ton.

[0041] 2) Loss of steel material when silicon steel is converted to aluminum steel;

[0042] The average FeO value at the converter end point of silicon steel is 23%, and the average FeO value at the converter end point of aluminum steel is 19%. The converter slag amount of this production line is calculated as 73.5kg / t, that is: (23%-19%)×73.5×56 / 72 / 100=2.28kg / t.

[0043] Calculated based on the monthly steel unit price of 2,995 yuan / ton, that is: 2.28×2,995 / 1,000=6.83 yuan / ton.

[0044] 3) The total loss of converting silicon steel to aluminum steel is 7.42+6.83=14.25 yuan / ton.

[0045] 4) Before the implementation, from August to October 2023, a total of 238 cans of silicon steel were produced, of which 17 cans were converted to steel due to large-scale clearance, and the conversion rate was 7.1%. The production line produces 1.5 million tons of silicon steel annually. The contribution rate after implementation is calculated at 70%, and the annual benefit is: 150×7.1%×14.25×70%=1.0623 million yuan.

[0046] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for accurately controlling the clearance of silicon steel in one furnace and two tanks, characterized in that: The steps include: 1) Grouping of molten steel tanks: Before silicon steel production, the converter and molten steel tanks are rinsed. When casting silicon steel, n molten steel tanks are used for one pouring, and m molten steel tanks are required for turnover. According to the order of the furnaces when rinsing the tanks, these m molten steel tanks are divided into groups of two each. Each group of molten steel tanks corresponds to one furnace of molten steel, that is, one furnace has two tanks. 2) Determine the loading quantity: divide the two steel ladle tanks in each group into the main ladle tank and the auxiliary ladle tank, add up the tank ages of the main ladle tank and the auxiliary ladle tank in each group of steel ladle tanks, and then determine the total loading quantity M of the group of steel ladle tanks according to the sum of the tank ages N; N < 50 times, M = 202 ± 2 tons; 50 ≤ N < 100 times, M = 204 ± 2 tons; 100 ≤ N < 150 times, M = 206 ± 2 tons; N ≥ 150 times, M = 208 ± 2 tons; 3) Determine the clearance: During RH treatment, the clearance of the main tank and the auxiliary tank are controlled within 300-600mm; first, the loading amount of the main tank and the auxiliary tank is determined with the goal of controlling the clearance of the main tank and the auxiliary tank of the rinsing furnace at 400-450mm; during silicon steel production, the main tank controls the steel tapping according to the clearance of 300-600mm, and the clearance of the auxiliary tank is fine-tuned according to the remaining molten steel in the converter, specifically adjusted at the rate of 100mm clearance for every additional 2-4 tons of molten steel; when the clearance of the auxiliary tank reaches 380-420mm during the steel tapping process, the furnace is lifted with the tank, and finally the clearance of the auxiliary tank is controlled above 300mm.

2. The method for accurately controlling the clearance of silicon steel in one furnace and two tanks according to claim 1 is characterized in that: The mass content of sulfur in silicon steel products is ≤0.006%.

3. The method for accurately controlling the clearance of silicon steel in one furnace and two tanks according to claim 1 is characterized in that: LF-RH double refining is adopted, and the interval time from the end of steel tapping to the start of casting is controlled at 140-145 minutes.

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