A method of smelting a medium-carbon aluminium-containing steel with reduced aluminium consumption

Abstract

The application discloses a smelting method for reducing aluminum consumption of medium-carbon aluminum-containing steel, which comprises the following steps: (1) before tapping, carbon powder and calcium carbide are added to the LF furnace, and the oxygen content of the molten steel is less than or equal to 40 ppm during the tapping process; (2) after the molten steel is poured into the LF furnace, lime is added first, then calcium carbide and carbon powder are added to perform slag surface deoxidization until the oxygen content of the molten steel is less than or equal to 8 ppm; (3) after deoxidization until the total content of FeO+MnO in the slag is less than or equal to 0.5% and the oxygen content of the molten steel is less than or equal to 8 ppm, calcium carbide is added into the LF furnace to continuously deoxidize for 7-10 min, and the total content of FeO+MnO in the slag is kept to be less than or equal to 0.5%; then, lime is added into the LF furnace to control the thickness of the top slag layer to be 70-150 mm; (4) after the alloying of other elements except C and Al elements of the molten steel is completed, the argon flow rate of bottom blowing is adjusted to be 250-350 L / min, calcium carbide and carbon powder are added to synchronously complete the deoxidization, desulfurization and recarburization of the molten steel; (5) after the oxygen content of the molten steel is less than or equal to 5 ppm, power is supplied to control the temperature of the molten steel to be 7-12 DEG C lower than the standard outlet temperature, then pure aluminum metal is added and short-arc power supply is performed, the argon flow rate of bottom blowing is 80-150 L / min, and power supply is performed for 1-2 min, thereby completing the aluminum alloying task; and the method can reduce the aluminum consumption of the medium-carbon aluminum-containing steel by 1.1-1.4 Kg / t of steel.

Description

Technical Field

[0001] This invention relates to the field of converter steelmaking technology, and in particular to a smelting method for reducing aluminum consumption in medium-carbon aluminum steel. Background Technology

[0002] Aluminum-containing steel requires the addition of metallic aluminum. Metallic aluminum is a strong oxidizing agent and typically participates in deoxidation first. Only after the oxygen content has been reduced to extremely low levels does the aluminum participate in alloying. Therefore, aluminum-containing steel generally consumes a high amount of metallic aluminum. This high aluminum consumption brings a series of drawbacks: firstly, aluminum is expensive, increasing steelmaking costs; secondly, after deoxidation, aluminum inclusions are in a flocculent form, making them difficult to remove. If they remain in the steel and exceed the standards in terms of total amount or size, they can easily cause defects such as poor fluidity during casting or cracks during subsequent processing and use by downstream users. Therefore, reducing aluminum consumption in medium-carbon aluminum-containing steel requires new technological support. Summary of the Invention

[0003] The purpose of this invention is to address the problems of high aluminum consumption in aluminum-containing steel, which leads to high steelmaking costs and high levels of aluminum inclusions that are difficult to remove and can cause poor fluidity during casting or cracks during subsequent steel processing. This invention provides a smelting method to reduce aluminum consumption in medium-carbon aluminum-containing steel.

[0004] A smelting method for reducing aluminum consumption in medium-carbon aluminum steel according to the present invention includes the following steps: (1) Before tapping the steel from the converter, add 1.5-2 kg / t of carbon powder and 1.6-2 kg / t of calcium carbide to the LF ladle furnace. During the tapping process, except for C and Al, the normal alloying process is followed. After tapping the steel to the LF ladle furnace, the O content of the molten steel is ≤40 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 6-7 kg / t of molten steel. Calcium carbide and carbon powder are then used to deoxidize the slag surface. 2-2.5 kg / t of molten steel and 1-1.5 kg / t of carbon powder are added to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface. After deoxidation of the slag surface, the oxygen content of the molten steel is ≤8 ppm. (3) After the molten steel slag surface is deoxidized to the point that the total FeO+MnO content in the slag is ≤0.5% and the oxygen content in the molten steel is ≤8ppm, continue to add 0.4-0.8Kg / t of calcium carbide to the ladle furnace and continue to deoxidize the slag surface for 7-10min to keep the FeO+MnO in the slag ≤0.5%; then add 2-3Kg / t of lime to the LF ladle furnace to control the thickness of the top slag layer at 70-150mm, so that the top slag fully covers the molten steel and avoids the molten steel surface being exposed; (4) Complete the alloying of the steel liquid with elements other than C and Al, so that the alloying elements are within the composition control range, and adjust the bottom blowing argon flow rate to 250-350 L / min, add 0.3-0.5 Kg / t of calcium carbide, and add carbon powder at the same time to make the C content reach the target range, and simultaneously complete the strong stirring deoxidation, desulfurization and carbonization process of the steel liquid. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is ≤5ppm. Power is supplied to control the temperature of the molten steel at 7-12℃ below the standard outlet temperature. Then, 1.1-1.5Kg / t of pure aluminum metal is added to the molten steel. After adding pure aluminum, short-arc power is supplied, and the arc voltage is controlled at 220-230V, the arc current at 39000-39500KA, the bottom blowing argon flow rate at 80-150L / min, and the power supply time is controlled at 1-2min. The aluminum alloying task is then completed.

[0005] The medium-carbon aluminum-containing steel mentioned in this invention refers to a steel grade in which the mass percentage of carbon is 0.25-0.45% and the mass percentage of al is 0.020-0.060%.

[0006] The converter mentioned in this invention is a 130t top-and-bottom combined blowing converter, and the LF ladle furnace is a 130t ladle furnace that is matched with the converter.

[0007] The carbon powder of the present invention has a C mass percentage of ≥92% and the calcium carbide has a CaC2 mass percentage of ≥95%.

[0008] The pure aluminum metal described in this invention has an Al content of ≥99.9% by mass.

[0009] The smelting method of this invention can reduce aluminum consumption in medium-carbon aluminum steel by 1.1-1.4 kg / t of steel, resulting in significant economic benefits.

[0010] This invention is based on in-depth theoretical and practical research on the smelting process of medium-carbon aluminum steel. Due to the high carbon content of medium-carbon steel, this characteristic can be utilized to redistribute the aluminum deoxidation and alloying task, weakening its deoxidation capacity. Inexpensive carbonaceous materials are used to first complete deoxidation and desulfurization (the core of reducing Al consumption is to use carbonaceous materials for deoxidation instead of Al deoxidation: including converter deoxidation, LF deoxidation, and adding C powder to assist deoxidation and desulfurization during strong desulfurization). Aluminum is added only after the oxygen content in the steel is extremely low and the sulfur content meets the composition control requirements. At this point, aluminum mainly participates in alloying, thereby reducing aluminum consumption. It is important to note that the stirring intensity of the molten steel should be controlled during carbon addition and desulfurization to avoid air intake causing aluminum loss. Based on the above theoretical research, the process principle of this invention is as follows: (1) Before tapping the steel from the converter, add 1.5-2 kg / t of carbon powder and 1.6-2 kg / t of calcium carbide to the LF ladle furnace. Adding carbon powder and calcium carbide to the ladle furnace in advance can utilize the strong impact mode of the tapping process to quickly reduce the oxygen content of the molten steel from the converter to ≤40 ppm after it enters the ladle furnace. During the tapping process, except for C and Al (the reason for not adding C is to reserve carbon space to retain the deoxidation capacity of carbon), other alloys such as silicon and manganese are operated according to the normal alloying process. After the steel is tapped to the LF ladle furnace, the oxygen content of the molten steel can be quickly reduced to ≤40 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 6-7 kg / t of molten steel. Continue to use calcium carbide and carbon powder for slag surface deoxidation. Add 2-2.5 kg / t of calcium carbide and 1-1.5 kg / t of carbon powder to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface (adding to the vent hole will increase carbon, so carbon space should be reserved to retain carbon deoxidation capacity). Through the above slag surface deoxidation operation, the oxygen content of the molten steel can be rapidly reduced to ≤8 ppm. (3) After the molten steel slag surface is deoxidized to the total FeO+MnO content in the slag ≤0.5% and the oxygen content in the molten steel ≤8ppm, continue to add 0.4-0.8Kg / t of calcium carbide to the ladle furnace to continuously deoxidize the slag surface for 7-8min, keeping the FeO+MnO in the slag ≤0.5%; then add 2-3Kg / t of lime to the LF ladle furnace, control the thickness of the top slag layer to 70-150mm, and ensure that the top slag fully covers the molten steel to avoid the molten steel surface being exposed; (4) Complete the alloying of the steel liquid with elements other than C and Al, so that the alloying elements are within the composition control range, and adjust the low blowing argon flow rate to 250-350 L / min, add calcium carbide (CaC2) 0.3-0.5 Kg / t steel liquid, and add carbon powder at the same time to make the C content reach the target range (add carbon powder while desulfurizing to complete carbon increase, and carbon powder can also complete the deoxidation of steel liquid and assist in desulfurization during the carbon increase process). Taking advantage of the high carbon content of medium carbon steel, complete the desulfurization and carbon increase of steel liquid simultaneously, and carry out strong stirring desulfurization of steel liquid, and complete the deoxidation, desulfurization and carbon increase process of steel liquid simultaneously. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is ≤5ppm. The temperature of the molten steel is controlled at 7-12℃ below the standard outlet temperature by power supply. Then, 1.1-1.5Kg / t of pure aluminum metal is added to the molten steel. After adding pure aluminum, short-arc power supply is used, controlling the arc voltage at 220-230V, the arc current at 39000-39500KA, the bottom blowing argon flow rate at 80-150L / min, and the power supply time at 1-2min. This completes the aluminum alloying task. This operation allows Al to participate in the alloying almost entirely, thereby significantly reducing the Al consumption per ton of steel.

[0011] The beneficial effects of this invention are as follows: (1) This invention reduces aluminum consumption in aluminum-containing steel, reducing Al consumption per ton of steel by 1.1-1.4 kg, which significantly reduces the cost of steelmaking alloys; (2) This invention utilizes the high carbon content of medium carbon steel to first complete deep deoxidation of molten steel, and simultaneously complete desulfurization and further deep deoxidation during carbon addition, and finally complete aluminum alloying, which is in line with the green and low-consumption steelmaking concept. (3) The process flow of the present invention is simple and clear, highly operable, and easy to control. Detailed Implementation

[0012] To better explain the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments. The following embodiments are merely illustrative of the technical solution of the present invention and do not limit the present invention in any way. The sequence numbers of the following embodiments are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0013] Example 1 This embodiment uses the smelting of 20CrMo steel as an example to explain the present invention. In this embodiment, the target content of C is 0.20-0.25%, the target content of S is ≤0.005%, and the target content of Alt is 0.020-0.045%.

[0014] This embodiment of a smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel includes the following steps: (1) Before tapping the steel from the converter, 1.5 kg / t of carbon powder and 1.6 kg / t of calcium carbide are added to the LF ladle furnace. During the tapping process, except for C and Al, Si, Mn and other alloys are operated according to the normal alloying process. After the steel is tapped to the LF ladle furnace, the oxygen content of the molten steel is reduced to 40 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 6 kg / t of molten steel. Calcium carbide and carbon powder are then used to deoxidize the slag surface. 2 kg / t of calcium carbide and 1 kg / t of carbon powder are added to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface. After slag surface deoxidation, the oxygen content of the molten steel is reduced to 8 ppm. At this time, the C content in the molten steel is 0.10%, the S content is 0.015%, the Alt content is 0.002%, and the aluminum consumption is 0 kg / t. (3) After the molten steel slag surface is deoxidized to the point that the total FeO+MnO content in the slag is ≤0.5% and the oxygen content in the molten steel is ≤8ppm, continue to add 0.4Kg / t of calcium carbide to the ladle furnace and continue to deoxidize the slag surface for 7min to keep the FeO+MnO in the slag ≤0.5%; then add 2Kg / t of lime to the LF ladle furnace to control the thickness of the top slag layer at 70mm, so that the top slag fully covers the molten steel and avoids the molten steel surface being exposed; at this time, the C content in the molten steel is 0.11%, the S content is 0.014%, the Alt content is 0.002%, and the aluminum consumption is 0Kg / t; (4) Complete the alloying of the steel liquid with elements other than C and Al, so that the alloying elements are within the composition control range, and adjust the bottom blowing argon flow rate to 250 L / min. Add 0.3 Kg / t of calcium carbide to the steel liquid, and add carbon powder at the same time to make the C content reach the target range. Simultaneously complete the strong stirring deoxidation, desulfurization and carbonization process of the steel liquid. At this time, the C content in the steel liquid is 0.20%, the S content is 0.005%, the Alt content is 0.002%, and the aluminum consumption is 0 Kg / t. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is 5 ppm. Power is supplied to control the temperature of the molten steel at 7°C below the standard outlet temperature. Then, 1.1 kg / t of pure aluminum metal is added to the molten steel. After adding the pure aluminum, short-arc power is supplied, controlling the arc voltage at 220V, the arc current at 39000KA, the bottom-blowing argon flow rate at 80 L / min, and the power supply time at 1 min, thus completing the aluminum alloying task. At this time, the C content in the molten steel is 0.20%, the S content is 0.005%, the Alt content is 0.020%, and the aluminum consumption is 1.1 kg / t.

[0015] In this embodiment, the converter is a 130t top-and-bottom combined blowing converter, and the LF ladle furnace is a 130t ladle furnace that is matched with the converter, the same below.

[0016] In this embodiment, the carbon powder contains ≥92% C by mass and the calcium carbide contains ≥95% CaC2 by mass, and the same applies below.

[0017] In this embodiment, the mass percentage of Al in the pure aluminum metal is ≥99.9%, and the same applies below.

[0018] After refining using the smelting method of this embodiment, the C content in the molten steel is 0.20%, the S content is 0.005%, the Alt content is 0.020%, and the aluminum consumption is 1.1 kg / t; compared with the conventional method, the aluminum consumption is reduced by 1.1 kg / t of steel.

[0019] Example 2 This embodiment uses the smelting of 20CrMo steel as an example to explain the present invention. In this embodiment, the target content of C is 0.20-0.25%, the target content of S is ≤0.005%, and the target content of Alt is 0.020-0.045%.

[0020] This embodiment of a smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel includes the following steps: (1) Before tapping the steel from the converter, 1.7 kg / t of carbon powder and 1.8 kg / t of calcium carbide are added to the LF ladle furnace. During the tapping process, except for C and Al, Si, Mn and other alloys are operated according to the normal alloying process. After the steel is tapped to the LF ladle furnace, the oxygen content of the molten steel is reduced to 35 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 6.5 kg / t of molten steel. Calcium carbide and carbon powder are used to continue deoxidizing the slag surface. 2.3 kg / t of molten steel and 1.2 kg / t of molten steel are added to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface. After the slag surface is deoxidized, the oxygen content of the molten steel drops to 7 ppm. At this time, the C content in the molten steel is 0.11%, the S content is 0.014%, the Alt content is 0.002%, and the aluminum consumption is 0 kg / t. (3) After the molten steel slag surface is deoxidized to the total FeO+MnO content in the slag ≤0.5% and the oxygen content in the molten steel 7ppm, continue to add 0.6Kg / t of calcium carbide to the ladle furnace and continue deoxidizing the slag surface for 8.5min to maintain the FeO+MnO content in the slag at 0.4%; then add 2.5Kg / t of lime to the LF ladle furnace to control the thickness of the top slag layer at 90mm, so that the top slag fully covers the molten steel and avoids the molten steel surface being exposed; at this time, the C content in the molten steel is 0.12%, the S content is 0.013%, the Alt content is 0.002%, and the aluminum consumption is 0Kg / t; (4) Alloying of the steel liquid with elements other than C and Al is completed, so that the alloying elements are within the composition control range. The flow rate of bottom blowing argon is adjusted to 300 L / min. 0.3 Kg / t of calcium carbide is added to the steel liquid, and carbon powder is added at the same time to make the C content reach the target range. The strong stirring deoxidation, desulfurization and carbonization process of the steel liquid is completed simultaneously. At this time, the C content in the steel liquid is 0.22%, the S content is 0.004%, the Alt content is 0.002%, and the aluminum consumption is 0 Kg / t. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is 4 ppm. Power is supplied to control the temperature of the molten steel to 10°C below the standard outlet temperature. Then, 1.3 kg / t of pure aluminum metal is added to the molten steel. After adding the pure aluminum, short-arc power supply is used, controlling the arc voltage at 225V, the arc current at 39200KA, the bottom-blowing argon flow rate at 100 L / min, and the power supply time at 1.5 min, thus completing the aluminum alloying task. At this time, the C content in the molten steel is 0.22%, the S content is 0.004%, the Alt content is 0.030%, and the aluminum consumption is 1.3 kg / t.

[0021] After refining using the smelting method of this embodiment, the C content in the molten steel is 0.22%, the S content is 0.004%, the Alt content is 0.030%, and the aluminum consumption is 1.3 kg / t; compared with the conventional method, the aluminum consumption is reduced by 1.2 kg / t of steel.

[0022] Example 3 This embodiment uses the smelting of 20CrMo steel as an example to explain the present invention. In this embodiment, the target content of C is 0.20-0.25%, the target content of S is ≤0.005%, and the target content of Alt is 0.020-0.045%.

[0023] This embodiment of a smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel includes the following steps: (1) Before tapping the steel from the converter, 2 kg / t of carbon powder and 2 kg / t of calcium carbide are added to the LF ladle furnace. During the tapping process, except for C and Al, Si, Mn and other alloys are operated according to the normal alloying process. After the steel is tapped to the LF ladle furnace, the oxygen content of the molten steel is reduced to 40 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 7 kg / t of molten steel. Calcium carbide and carbon powder are used to continue deoxidizing the slag surface. 2.5 kg / t of molten steel and 1.5 kg / t of molten steel are added to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface. After the slag surface is deoxidized, the oxygen content of the molten steel drops to 6 ppm. At this time, the C content in the molten steel is 0.12%, the S content is 0.013%, the Alt content is 0.002%, and the aluminum consumption is 0 kg / t. (3) After the molten steel slag surface is deoxidized to the total FeO+MnO content in the slag of 0.3% and the oxygen content of the molten steel of 6ppm, continue to add 0.8Kg / t of calcium carbide to the ladle furnace and continue to deoxidize the slag surface for 9.5min to keep FeO+MnO in the slag ≤0.5%; then add 3Kg / t of lime to the LF ladle furnace to control the thickness of the top slag layer at 150mm, so that the top slag fully covers the molten steel and avoids the molten steel surface being exposed; at this time, the C content in the molten steel is 0.13%, the S content is 0.012%, the Alt content is 0.002%, and the aluminum consumption is 0Kg / t; (4) Complete the alloying of the steel liquid with elements other than C and Al, so that the alloying elements are within the composition control range, and adjust the bottom blowing argon flow rate to 300 L / min, add 0.5 Kg / t of calcium carbide to the steel liquid, and add carbon powder at the same time to make the C content reach the target range. Simultaneously complete the strong stirring deoxidation, desulfurization and carbonization process of the steel liquid; at this time, the C content in the steel liquid is 0.25%, the S content is 0.003%, the Alt content is 0.002%, and the aluminum consumption is 0 Kg / t. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is 3 ppm. Power is supplied to control the temperature of the molten steel at 12°C below the standard outlet temperature. Then, 1.5 kg / t of pure aluminum metal is added to the molten steel. After adding the pure aluminum, short-arc power supply is used, controlling the arc voltage at 230V, the arc current at 39500KA, the bottom-blowing argon flow rate at 150 L / min, and the power supply time at 2 min, thus completing the aluminum alloying task. At this time, the C content in the molten steel is 0.25%, the S content is 0.003%, the Alt content is 0.045%, and the aluminum consumption is 1.5 kg / t.

[0024] After refining using the smelting method of this embodiment, the C content in the molten steel is 0.25%, the S content is 0.003%, the Alt content is 0.045%, and the aluminum consumption is 1.5 kg / t; compared with the conventional method, the aluminum consumption is reduced by 1.4 kg / t of steel.

[0025] Example 4 This embodiment uses the smelting of 40Mn2 steel as an example to explain the present invention. In this embodiment, the target content of C in the steel is 0.37-0.44%, the target content of S is ≤0.005%, and the target content of Alt is 0.030-0.050%.

[0026] This embodiment of a smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel includes the following steps: (1) Before tapping the steel from the converter, 2 kg / t of carbon powder and 2 kg / t of calcium carbide are added to the LF ladle furnace. During the tapping process, except for C and Al, Si, Mn and other alloys are operated according to the normal alloying process. After the steel is tapped to the LF ladle furnace, the oxygen content of the molten steel is reduced to 35 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 7 kg / t of molten steel. Calcium carbide and carbon powder are used to deoxidize the slag surface. 2.5 kg / t of molten steel and 1.2 kg / t of molten steel are added to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface. After the slag surface is deoxidized, the oxygen content of the molten steel drops to 6 ppm. At this time, the C content in the molten steel is 0.20%, the S content is 0.015%, the Alt content is 0.002%, and the aluminum consumption is 0 kg / t. (3) After the molten steel slag surface is deoxidized to the total FeO+MnO content in the slag ≤0.5% and the oxygen content in the molten steel 6ppm, continue to add 0.8Kg / t of calcium carbide to the ladle furnace and continue deoxidizing the slag surface for 10min to keep the FeO+MnO in the slag at 0.35%; then add 2-3Kg / t of lime to the LF ladle furnace to control the thickness of the top slag layer at 150mm, so that the top slag fully covers the molten steel and avoids the molten steel surface being exposed; at this time, the C content in the molten steel is 0.21%, the S content is 0.013%, the Alt content is 0.002%, and the aluminum consumption is 0Kg / t; (4) Complete the alloying of the steel liquid with elements other than C and Al, so that the alloying elements are within the composition control range, and adjust the bottom blowing argon flow rate to 300 L / min, add 0.5 Kg / t of calcium carbide to the steel liquid, and add carbon powder at the same time to make the C content reach the target range. Simultaneously complete the strong stirring deoxidation, desulfurization and carbonization process of the steel liquid; at this time, the C content in the steel liquid is 0.44%, the S content is 0.004%, the Alt content is 0.002%, and the aluminum consumption is 0 Kg / t. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is 4 ppm. Power is supplied to control the temperature of the molten steel to 10°C below the standard outlet temperature. Then, 1.6 kg / t of pure aluminum metal is added to the molten steel. After adding the pure aluminum, short-arc power supply is used, controlling the arc voltage at 225V, the arc current at 39200KA, the bottom-blowing argon flow rate at 100 L / min, and the power supply time at 2 min, thus completing the aluminum alloying task. At this time, the C content in the molten steel is 0.44%, the S content is 0.004%, the Alt content is 0.050%, and the aluminum consumption is 1.6 kg / t.

[0027] After refining using the smelting method of this embodiment, the C content in the molten steel is 0.44%, the S content is 0.004%, the Alt content is 0.050%, and the aluminum consumption is 1.6 kg / t; compared with the conventional method, the aluminum consumption is reduced by 1.3 kg / t of steel.

[0028] Comparative Example 1 This comparative example also uses 40Mn2 steel as an example for comparison. In this comparative example steel, the target content of C is 0.37-0.44%, the target content of S is ≤0.005%, and the target content of Alt is 0.030-0.050%.

[0029] (1) Before tapping from the converter, carbon powder, calcium carbide and other pre-deoxidation are not added. During the tapping process, C, Al, Si, Mn and other alloys are operated according to the normal alloying process. The consumption of aluminum for deoxidation is relatively high. The aluminum consumption during the converter alloying process is 1.4Kg / t. After tapping to the LF ladle furnace, the oxygen content of the molten steel is reduced to 45-80ppm. (2) There is no restriction on the timing of adding aluminum after the molten steel enters the LF ladle furnace. Aluminum is added at the same time as lime when entering the station. The amount of aluminum added is 0.7-1Kg / t of molten steel. Aluminum deoxidation is mainly used for slag surface deoxidation. The amount of calcium carbide added is small, only 0.7Kg / t of molten steel. No carbon powder is added for slag surface deoxidation. The S content is 0.014%, the Alt content is 0.042%, and the cumulative aluminum consumption is 2.1Kg / t. (3) After the molten steel slag surface is deoxidized to the total FeO+MnO content in the slag ≤0.5% and the oxygen content of the molten steel is 8ppm, 0.2Kg / t of aluminum is added to the ladle furnace and the slag surface is continuously deoxidized for 6min to maintain the FeO+MnO content in the slag at 0.4%; no more lime is added to the LF ladle furnace and the thickness of the top slag layer is controlled at 60mm. In order to control the requirement that the top slag fully covers the molten steel, the molten steel surface will occasionally be exposed; at this time, the C content in the molten steel is 0.38%, the S content is 0.013%, the Alt content is 0.036%, and the aluminum consumption is 2.3Kg / t; (4) Alloying of the steel liquid with elements other than sulfur was completed, so that the alloying elements were within the composition control range. The bottom blowing argon flow rate was adjusted to 500 L / min (the steel liquid surface was exposed). 0.5 kg / t of aluminum was added to the steel liquid for desulfurization and to compensate for the aluminum loss caused by the exposure of the steel liquid during the strong blowing of argon. No carbon powder was added to assist in desulfurization. At this time, the C content in the steel liquid was 0.39%, the S content was 0.004%, the Alt content was 0.035%, and the aluminum consumption was 2.8 kg / t. (5) After the desulfurization task is completed, the oxygen content of the molten steel is 4 ppm. Power is supplied to control the temperature of the molten steel at the standard outlet temperature. There is no limit on the power supply time. When power is supplied, 0.1 kg / t of aluminum is added to compensate for the aluminum loss during power supply. At this time, the C content in the molten steel is 0.39%, the S content is 0.004%, the Alt content is 0.030%, and the aluminum consumption is 2.9 kg / t.

[0030] The smelting results of Examples 1-5 using the method of the present invention and the smelting results of Comparative Example 1 using the conventional method show that the aluminum consumption of Comparative Example 1 is 2.9 kg / t, while the aluminum consumption of Examples 1-5 is only 1.1-1.4 kg / t. This demonstrates that the method of the present invention is feasible and has extremely high economic benefits.

Claims

1. A smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel, characterized in that... Includes the following steps: (1) Before tapping the steel from the converter, add 1.5-2 kg / t of carbon powder and 1.6-2 kg / t of calcium carbide to the LF ladle furnace. During the tapping process, except for C and Al, the normal alloying process is followed. After tapping the steel to the LF ladle furnace, the O content of the molten steel is ≤40 ppm. (2) After the molten steel enters the LF ladle furnace, lime is first added to cover the slag surface. The amount of lime added is 6-7 kg / t of molten steel. Calcium carbide and carbon powder are then used to deoxidize the slag surface. 2-2.5 kg / t of molten steel and 1-1.5 kg / t of carbon powder are added to the LF ladle furnace. When adding carbon powder, avoid the bottom blowing argon vent hole on the molten steel surface. After deoxidation of the slag surface, the oxygen content of the molten steel is ≤8 ppm. (3) After the molten steel slag surface is deoxidized to the point that the total FeO+MnO content in the slag is ≤0.5% and the oxygen content in the molten steel is ≤8ppm, continue to add 0.4-0.8Kg / t of calcium carbide to the ladle furnace and continue to deoxidize the slag surface for 7-10min to keep the FeO+MnO in the slag ≤0.5%; then add 2-3Kg / t of lime to the LF ladle furnace to control the thickness of the top slag layer at 70-150mm, so that the top slag fully covers the molten steel and avoids the molten steel surface being exposed; (4) Complete the alloying of the steel liquid with elements other than C and Al, so that the alloying elements are within the composition control range, and adjust the bottom blowing argon flow rate to 250-350 L / min, add 0.3-0.5 Kg / t of calcium carbide, and add carbon powder at the same time to make the C content reach the target range, and simultaneously complete the strong stirring deoxidation, desulfurization and carbonization process of the steel liquid. (5) After completing the desulfurization and carbonization tasks, the oxygen content of the molten steel is ≤5ppm. Power is supplied to control the temperature of the molten steel at 7-12℃ below the standard outlet temperature. Then, 1.1-1.5Kg / t of pure aluminum metal is added to the molten steel. After adding pure aluminum, short-arc power is supplied, and the arc voltage is controlled at 220-230V, the arc current at 39000-39500KA, the bottom blowing argon flow rate at 80-150L / min, and the power supply time is controlled at 1-2min. The aluminum alloying task is then completed.

2. The smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel according to claim 1, characterized in that: The medium-carbon aluminum-containing steel refers to a steel grade in which the mass percentage of carbon is 0.25-0.45% and the mass percentage of al is 0.020-0.060%.

3. The smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel according to claim 1, characterized in that: The converter is a 130t top-and-bottom combined blowing converter, and the LF ladle furnace is a 130t ladle furnace that is matched with the converter.

4. The smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel according to claim 1, characterized in that: The carbon powder contains ≥92% C by mass, and the calcium carbide contains ≥95% CaC2 by mass.

5. The smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel according to claim 1, characterized in that: The pure aluminum metal contains ≥99.9% Al by mass.

6. The smelting method for reducing aluminum consumption in medium-carbon aluminum-containing steel according to claim 1, characterized in that: Using the method described in claim 1, the aluminum consumption of medium-carbon aluminum steel is reduced by 1.1-1.4 kg / t of steel.