Smelting method of low-carbon aluminum killed molten steel

Abstract

The invention discloses a smelting method of low-carbon aluminum killed molten steel, and mainly solves the technical problems of large molten steel quality fluctuation and low steel ladle top slag component control precision when the existing low-carbon aluminum killed molten steel is subjected to argon blowing refining treatment by adopting an argon blowing station. According to the technical scheme, the smelting method of the low-carbon aluminum killed molten steel comprises the steps that (1) the molten steel smelting process is controlled, a top-bottom combined blowing converter is adopted for smelting, and at the converter blowing end point, the product value of the mass percent content of carbon in the molten steel and the mass percent content of dissolved oxygen in the molten steel is smaller than or equal to 0.0025; (2) molten steel sedation control; (3) converter tapping control is conducted, and automatic tapping, sliding plate slag stopping and infrared automatic slag judging control are adopted; and 4) molten steel argon blowing refining control. According to the method, the calcium-aluminum ratio and the total iron mass percent content in the steel ladle top slag are accurately controlled to be 0.75%-1.25% and 1.0%-4.0% respectively.

Description

Technical Field

[0001] The invention relates to a method for smelting molten steel, in particular to a method for smelting low-carbon aluminum-killed molten steel, and belongs to the technical field of steel smelting and continuous casting. Background Art

[0002] Low-carbon aluminum-killed steel has a wide range of uses and requires high cleanliness of molten steel. There are three main steelmaking processes, namely "converter-argon blowing station-continuous casting", "converter-LF furnace-continuous casting" and "converter-RH furnace-continuous casting". The "converter-argon blowing station-continuous casting" process is short and efficient, and its smelting cost has significant advantages over the other two processes, but it is also the most difficult to handle molten steel. This is because the refining treatment cycle of this process is short, and the ladle top slag cannot be adjusted during the refining process. The ladle top slag modification materials are all added during the converter steelmaking process.

[0003] The existing ladle top slag control process is to add a fixed amount of ladle top slag modification materials during the converter tapping process to adjust the ladle top slag composition. However, due to the influence of factors such as the fluctuation of converter smelting end point control and different tapping conditions, the ladle top slag composition control accuracy is low. The calcium-aluminum ratio of the ladle top slag is controlled to be 0.50-2.12, and the total iron content is controlled to be

[0004] 1.07%~9.91%; the ability of ladle top slag to adsorb inclusions in molten steel is uncontrollable, and the oxygen content of molten steel is controlled to be 0.0014%~0.0032%, with an average of 0.0023%.

[0005] Chinese patent CN107201422A discloses a method for producing low-carbon steel, which improves the cleanliness level of molten steel by tapping and deoxidizing at low temperature in a converter, treating molten steel in an argon blowing station, and refining molten steel in a refining furnace. The process requires slagging in a refining furnace, controlling the calcium-aluminum ratio of the ladle slag to 1.0-1.5, and improving the ability of the ladle top slag to absorb inclusions in molten steel.

[0006] Chinese patent CN115612786A discloses a method for accurately controlling the CaO / Al2O3 value of SPHC steel. LF refining is carried out after the steel is tapped from the converter. Lime and composite refining slag are added in batches during the LF refining heating process, which is conducive to accurately controlling the CaO / Al2O3 value of the ladle top slag and improving the desulfurization efficiency and the stability of product quality.

[0007] In the existing smelting process of low-carbon aluminum killed molten steel, precise control of the composition of the ladle top slag requires refining treatment in the LF furnace, which cannot solve the technical problems of large fluctuations in molten steel quality and low precision in controlling the composition of the ladle top slag when the low-carbon aluminum killed molten steel is refined by argon blowing in an argon blowing station. Summary of the invention

[0008] The purpose of the present invention is to provide a smelting method for low-carbon aluminum killed molten steel, which mainly solves the technical problems of large fluctuations in molten steel quality and low control accuracy of ladle top slag composition when the existing low-carbon aluminum killed molten steel is treated by argon blowing refining in an argon blowing station.

[0009] The technical solution adopted by the present invention is a smelting method of low-carbon aluminum killed molten steel, comprising the following steps:

[0010] 1) Control of converter smelting process, adopting top and bottom combined blowing converter smelting, the product value of the mass percentage content of carbon in molten steel and the mass percentage content of dissolved oxygen in molten steel is ≤0.0025; when the oxygen blowing amount is 80% to 90% of the total oxygen amount, the oxygen lance position is controlled to be a low lance position, and the low lance position is: H0+H0*(0.10 to 0.15), H0 is the height of the molten steel surface in the converter; the slag basicity at the end of converter blowing is controlled to be 3.0 to 6.0, and the basicity is w(CaO) / w(SiO2), w(CaO) and w(SiO2) are the mass percentage contents of CaO and SiO2 in the slag at the end of converter blowing, respectively, in %; the auxiliary lance is used to detect the molten steel temperature and the oxygen content in the molten steel, and the w[O] in the molten steel at the end of converter blowing is 0.03% to 0.07%, and the converter blowing is completed when the molten steel temperature at the end of converter blowing is 1610 to 1650°C;

[0011] 2) Steel quenching control: at the end of converter blowing, the bottom blowing gas supply intensity is controlled to 0.10~0.14Nm 3 / (min·t), stir for 1 to 4 minutes, and then tap the steel immediately;

[0012] 3) Control of steel tapping from the converter, using automatic steel tapping, slide plate slag blocking and infrared automatic slag judgment control, controlling the slag amount of the converter to 3-7 kg per ton of steel; when the amount of molten steel tapped from the converter reaches 15%-25% of the total amount of molten steel, add desulfurized lime; when the amount of molten steel tapped from the converter reaches 35%-45% of the total amount of molten steel, add aluminum-iron alloy, manganese-iron alloy and carbon powder, and the amount of manganese-iron alloy and carbon powder added is determined according to the target composition of the molten steel; when slag is detected at the end of steel tapping, immediately close the slide plate mechanism and add aluminum particles to the ladle top slag; control the calcium-aluminum ratio (w(CaO) / w(Al2O3)) in the ladle top slag to 0.75-1.25, and the total iron content in the ladle top slag to 1.0%-4.0% by mass;

[0013] 4) content and temperature of molten steel; regulating the temperature of molten steel to 1585-1600°C, feeding aluminum wire into the molten steel for argon blowing refining control, transporting the molten steel in the ladle to the argon blowing station for regulating the temperature of molten steel and aluminum content, after the molten steel in the ladle is transported to the argon blowing station, firstly, introducing argon into the molten steel in the ladle to stir the molten steel for 2.0-3.0 minutes, and controlling the argon flow rate to 30-50 liters / hour; then detecting the free oxygen in the molten steel in the ladle to deoxidize the molten steel with aluminum, regulating the aluminum and oxygen elements in the molten steel to the target composition, and controlling the argon flow rate to 20-30 liters / hour; weakly stirring the molten steel after feeding the aluminum wire, controlling the argon flow rate to 10-20 liters / hour, and weakly stirring the molten steel for 5-8 minutes to obtain qualified molten steel.

[0014] In step 3) of the present invention, the weight percentage of the chemical composition of the desulfurized lime is CaO ≥ 90%, SiO2 ≤ 2.5% and the burnout is not more than 5%; the weight percentage of the chemical composition of the aluminum-iron alloy is Al 48-54%, Fe 42-48% and others ≤ 4%; the weight percentage of the chemical composition of the aluminum particles is Al ≥ 97%, others ≤ 3%.

[0015] The amount of desulfurized lime added is: m 脱硫石灰 =66.6×w[O]×m 钢水 +m 渣 ×(0.78×w[O] 0.54 +0.014×w(Al2O3)-1.18×w(CaO)), in kilograms;

[0016] The amount of aluminum-iron alloy added is: m 铝铁 =50×w[O], unit is kg / ton steel;

[0017] The amount of aluminum particles added is: m 铝粒 =0.3×m 渣 ×w[O] 0.54 , in kilograms;

[0018] Wherein, w[O] is the mass percentage of dissolved oxygen in the molten steel at the end of converter blowing, in %; m 钢水 is the amount of molten steel, in tons; m 渣 is the amount of slag in the converter, in kilograms; w(CaO) and w(Al2O3) are the mass percentages of CaO and Al2O3 in the slag at the end of converter blowing, in %.

[0019] The technical solution of the present invention is based on the following research and experiments of the applicant:

[0020] 1. In terms of the control of the amount of slag per ton of steel in the converter, firstly, the present invention promotes the slag-gold reaction in the converter to tend to equilibrium, combines the temperature of the molten steel at the end of the converter blowing, the oxygen content of the molten steel at the end of the converter blowing and the basicity of the slag at the end of the converter blowing, and obtains the influence relationship between the physical properties of the slag at the end of the converter blowing and the amount of slag per ton of steel in the converter; secondly, the present invention uses the steel-tapping process of automatic steel-tapping, slide plate slag blocking and infrared automatic slag judgment to control the human factors affecting the slag at the steel-tapping. Statistical analysis of data shows that when the temperature of the molten steel at the end of the converter blowing is 1610-1650℃, the oxygen content of the molten steel at the end of the converter blowing is 0.03%-0.07%, and the basicity of the slag at the end of the converter blowing is 3.0-6.0, the steel-tapping process of automatic steel-tapping, slide plate slag blocking and infrared automatic slag judgment can control the amount of slag per ton of steel in the converter to 3-7 kg.

[0021] 2. Regarding the control of the composition of the ladle top slag, firstly, the present invention predicts the aluminum-iron alloy required for the deoxidation of the molten steel and the amount of Al2O3 produced according to the characteristics of the deoxidation of the molten steel during the converter steel-tapping process of low-carbon aluminum-killed steel; secondly, the present invention predicts the amount of aluminum particles required for the deoxidation of the ladle top slag and the amount of Al2O3 produced according to the amount of slag under the converter steel-tapping process and the mass percentage content of the total iron in the converter blowing terminal slag; finally, the present invention calculates the amount of desulfurized lime according to the amount of slag under the converter, the composition of the converter blowing terminal slag, the amount of Al2O3 produced by the deoxidation of the molten steel and the amount of Al2O3 produced by the deoxidation of the ladle top slag, with the goal of controlling the calcium-aluminum ratio in the ladle top slag to be 0.75-1.25 and the mass percentage content of the total iron to be 1.0%-4.0%. The ladle top slag of the present invention has the characteristics of low liquidus temperature, high viscosity and high surface tension, which can well adsorb inclusions in the molten steel and promote better separation of steel and slag.

[0022] Compared with the prior art, the present invention has the following positive effects: 1. The amount of converter slag in the method of the present invention is controlled by the converter blowing endpoint parameters and the steel-making process, and the amount of converter slag per ton of steel is controlled to 3-7 kg, which significantly reduces the amount of converter slag, and can reduce the use of ladle top slag materials, on the one hand reducing the smelting cost; on the other hand, it is conducive to the rapid melting and slag formation of materials, and provides conditions for the realization of the target composition of ladle top slag. 2. The method of the present invention accurately controls the calcium-aluminum ratio and the total iron mass percentage content in the ladle top slag to 0.75-1.25 and 1.0%-4.0%, respectively. The ladle top slag has the characteristics of low liquidus temperature, high viscosity, and high surface tension, which can well absorb inclusions in molten steel, and at the same time can promote better separation of steel and slag, so that the product quality is stable. DETAILED DESCRIPTION

[0023] The present invention is further illustrated below with reference to specific embodiments 1 to 5.

[0024] In embodiments 1 to 5 of the present invention, a 250-ton top and bottom combined blowing converter is used to smelt low-carbon aluminum killed steel, wherein embodiments 1 to 3 are SPHC steels; embodiments 4 to 5 are SPHD steels; the production method includes: converter smelting, argon blowing treatment of molten steel in an argon blowing station, and continuous casting process production. The control parameters of molten steel production in the embodiments of the present invention are shown in Tables 1 to 4.

[0025] Table 1 Converter smelting control parameters of the embodiment of the present invention

[0026]

[0027]

[0028] Table 2 Prediction of molten steel calming parameters and converter slag amount in the embodiment of the present invention

[0029]

[0030] Table 3. Control of steel-making charging and ladle top slag composition in the embodiment of the present invention

[0031]

[0032] Note that in Table 3, the calcium-aluminum ratio is w(CaO) / w(Al2O3), w(CaO) and w(Al2O3) are the mass percentages of CaO and Al2O3 in the slag at the end of converter blowing, respectively, in %.

[0033] Table 4 Composition and temperature of molten steel at the outlet of argon blowing station in the embodiment of the present invention

[0034]

[0035] When SPHC and SPHD steels are produced by the converter smelting-argon blowing refining-continuous casting process, the present invention realizes accurate prediction of the amount of slag in the converter tapping process through the molten steel smelting process, molten steel calming, converter tapping and molten steel argon blowing refining process control, realizes dynamic adjustment of the amount of desulfurized lime and aluminum particles added in the converter tapping process, improves the control accuracy of the calcium-aluminum ratio and the mass percentage content of the total iron in the ladle top slag, effectively reduces the total oxygen content of the molten steel, and improves the cleanliness of the molten steel.

[0036] As shown in Examples 1 to 5 of the present invention, compared with the existing conventional process, the amount of desulfurized lime and aluminum particles added in the method of the present invention is dynamically adjusted, while the desulfurized lime and aluminum slag in the original process are added in fixed amounts. The method of the present invention greatly improves the control stability of the calcium-aluminum ratio and the total iron content of the ladle top slag, and the calcium-aluminum ratio is improved from 0.72-1.32 to 1.15-1.23, and the total iron content is improved from 1.47-5.91% to 1.17-1.82%. The total oxygen content of the molten steel is further improved from 0.0014-0.0032% to 0.0014-0.0019%, and the average value is reduced from 0.0023% to 0.0016%, a decrease of 0.0007%.

[0037] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for smelting low-carbon aluminum-killed molten steel, characterized in that: The method comprises the following steps: 1) Control of converter smelting process, adopting top and bottom combined blowing converter smelting, the product value of the mass percentage content of carbon in molten steel and the mass percentage content of dissolved oxygen in molten steel is ≤0.0025; when the oxygen blowing amount is 80% to 90% of the total oxygen amount, the oxygen lance position is controlled to be a low lance position, and the low lance position is: H0+H0*(0.10 to 0.15), H0 is the height of the molten steel surface in the converter; the slag basicity at the end of converter blowing is controlled to be 3.0 to 6.0, and the basicity is w(CaO) / w(SiO2), w(CaO) and w(SiO2) are the mass percentage contents of CaO and SiO2 in the slag at the end of converter blowing, respectively, in %; the auxiliary lance is used to detect the molten steel temperature and the oxygen content in the molten steel, and the w[O] in the molten steel at the end of converter blowing is 0.03% to 0.07%, and the converter blowing is completed when the molten steel temperature at the end of converter blowing is 1610 to 1650°C; 2) Steel quenching control: at the end of converter blowing, the bottom blowing gas supply intensity is controlled to 0.10~0.14Nm 3 / (min·t), stir for 1 to 4 minutes, and then tap the steel immediately; 3) Control of steel tapping from the converter, using automatic steel tapping, slide plate slag blocking and infrared automatic slag judgment control, controlling the slag amount of the converter to 3-7 kg per ton of steel; when the amount of molten steel tapped from the converter reaches 15%-25% of the total amount of molten steel, add desulfurized lime; when the amount of molten steel tapped from the converter reaches 35%-45% of the total amount of molten steel, add aluminum-iron alloy, manganese-iron alloy and carbon powder, and the amount of manganese-iron alloy and carbon powder added is determined according to the target composition of the molten steel; when slag is detected at the end of steel tapping, immediately close the slide plate mechanism and add aluminum particles to the ladle top slag; control the calcium-aluminum ratio (w(CaO) / w(Al2O3)) in the ladle top slag to 0.75-1.25, and the total iron content in the ladle top slag to 1.0%-4.0% by mass; 4) content and temperature of molten steel; regulating the temperature of molten steel to 1585-1600°C, feeding aluminum wire into the molten steel for argon blowing refining control, transporting the molten steel in the ladle to the argon blowing station for regulating the temperature of molten steel and aluminum content, after the molten steel in the ladle is transported to the argon blowing station, firstly, introducing argon into the molten steel in the ladle to stir the molten steel for 2.0-3.0 minutes, and controlling the argon flow rate to 30-50 liters / hour; then detecting the free oxygen in the molten steel in the ladle to deoxidize the molten steel with aluminum, regulating the aluminum and oxygen elements in the molten steel to the target composition, and controlling the argon flow rate to 20-30 liters / hour; weakly stirring the molten steel after feeding the aluminum wire, controlling the argon flow rate to 10-20 liters / hour, and weakly stirring the molten steel for 5-8 minutes to obtain qualified molten steel.

2. The smelting method of low-carbon aluminum killed molten steel as claimed in claim 1, characterized in that: In step 3), the amount of desulfurized lime added is: m 脱硫石灰 =66.6×w[O]×m 钢水 +m 渣 ×(0.78×w[O] 0.54 +0.014×w(Al2O3)-1.18×w(CaO)), in kilograms; the amount of aluminum-iron alloy added is: m 铝铁 =50×w[O], unit is kg / ton steel; the amount of aluminum particles added is: m 铝粒 =0.3×m 渣 ×w[O] 0.54 , in kilograms; Wherein, w[O] is the mass percentage of dissolved oxygen in the molten steel at the end of converter blowing, in %; m 钢水 is the amount of molten steel, in tons; m 渣 is the amount of slag in the converter, in kilograms; w(CaO) and w(Al2O3) are the mass percentages of CaO and Al2O3 in the slag at the end of converter blowing, in %.

3. The smelting method of low-carbon aluminum killed molten steel as claimed in claim 1, characterized in that: In step 3), the weight percentages of the chemical components of the desulfurized lime are CaO ≥ 90%, SiO2 ≤ 2.5% and the burning loss is not more than 5%.

4. The method for smelting low-carbon aluminum killed molten steel as claimed in claim 1, characterized in that: In step 3), the weight percentages of the chemical components of the aluminum-iron alloy are Al 48-54%, Fe 42-48% and others ≤ 4%.

5. The smelting method of low-carbon aluminum killed molten steel as claimed in claim 1, characterized in that: In step 3), the weight percentage of the chemical components of the aluminum particles is Al ≥ 97%, and the others ≤ 3%.

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