Method for controlling tapping slag amount of converter for argon blowing refining of low-carbon aluminum killed steel

Abstract

The invention discloses a method for controlling the tapping slag amount of a converter for argon blowing refining of low-carbon aluminum killed steel. The method mainly solves the technical problems that an existing method for measuring the tapping slag amount of the converter has potential safety hazards and is high in cost, poor in accuracy and hysteretic. According to the technical scheme, the control method for the tapping slag amount of the argon blowing refining low-carbon aluminum killed steel converter comprises the steps that (1) the molten steel smelting process is controlled, specifically, the temperature of molten steel and the oxygen content in the molten steel are detected through a sublance, and converter blowing is finished when w [O] in the molten steel at the converter blowing end point is 0.03%-0.08% and the temperature of the molten steel at the converter blowing end point is 1620-1660 DEG C; (2) molten steel sedation control; and (3) converter tapping control is conducted, automatic tapping, sliding plate slag stopping and infrared automatic slag judging control are adopted, and when slag discharging is detected at the last stage of tapping, a sliding plate mechanism is closed immediately. The method is high in calculation precision, free of extra cost, high in applicability, free of hysteresis and free of high-temperature operation risks.

Description

Technical Field

[0001] The invention relates to a converter steelmaking and tapping process, in particular to a method for controlling the amount of slag in a converter for tapping low-carbon aluminum killed steel refined by argon blowing, and belongs to the technical field of steel smelting and continuous casting. Background Art

[0002] Steel is an indispensable basic material for industrial society. In 2020, China's crude steel output was 1.0648 billion tons, breaking through 1 billion tons for the first time, accounting for 57.1% of the world's crude steel output. The converter smelting process is the main process, contributing about 90% of the crude steel output. Due to the differences in smelting steel grades, fluctuations in converter smelting endpoint control, and different slag blocking processes for steel tapping, the fluctuation range of converter slag volume is large, resulting in low precision in controlling the composition of the ladle top slag, which is not conducive to the control of molten steel cleanliness.

[0003] Low-carbon aluminum killed steel is mostly refined by argon blowing. The typical smelting process is converter smelting - argon blowing station argon blowing molten steel - continuous casting. Due to the short treatment cycle of argon blowing station argon blowing molten steel, it is impossible to adjust the ladle top slag during the refining process. The ladle top slag modification materials are added during the converter tapping process. Due to the lack of prediction of the amount of slag under the converter, the composition of the ladle top slag fluctuates greatly, and the product quality fluctuates violently.

[0004] The existing method for measuring the amount of slag in the converter is mostly a volume measurement method. The implementation method is to first measure the thickness of the top slag, calculate the volume of the slag layer in combination with the inner diameter of the ladle, and multiply the obtained slag layer volume by the slag layer density to obtain the slag layer mass. However, the main problem with this method is that the slag layer thickness is difficult to measure accurately and the density of the slag cannot be accurately determined, resulting in poor accuracy of the measurement results.

[0005] Chinese patent CN114136833A discloses a method for measuring the amount of slag in a converter. During the converter steel-tapping process, after deoxidation and alloying are completed, barium carbonate is added to the ladle. After the steel-tapping is completed, a slag sample is taken from the ladle, and the amount of slag in the converter is calculated by detecting the content of barium oxide in the ladle slag sample. This method requires operators to take slag samples under high temperature conditions, which has certain safety hazards. At the same time, barium carbonate needs to be added, which increases production costs.

[0006] Chinese patent CN113420446A discloses a method for calculating the amount of slag in the steel strip of a converter. After the converter is tapped, molten steel and slag enter the ladle, the slag on the top of the ladle is modified, and a set of equations is listed using the conservation of the total mass of the slag and the conservation of the mass of the aluminum element in the slag to calculate the amount of slag under the converter. Since the Al2O3 content in the slag at the end of converter blowing fluctuates, the burnout, aluminum content and Al2O3 content in the slag also fluctuate, and the calculation accuracy is low.

[0007] The existing technologies all require slag sampling for testing and use the components in the slag to predict the amount of slag, which involves certain safety risks, high costs and poor accuracy. At the same time, due to the lag in the measurement results, it cannot meet the needs of argon blowing for refining low-carbon aluminum killed steel smelting.

[0008] The existing technology lacks an effective method for predicting the amount of slag in converter tapping, and cannot meet the smelting needs of argon-blown refining of low-carbon aluminum killed steel. Summary of the invention

[0009] The purpose of the present invention is to provide a method for controlling the amount of slag under the converter during steel tapping of low-carbon aluminum-killed steel refined by argon blowing, mainly to solve the technical problems of potential safety hazards, high cost, poor accuracy and hysteresis in the existing method for measuring the amount of slag under the converter during steel tapping; the method of the present invention meets the smelting needs of argon-blown refined low-carbon aluminum-killed molten steel.

[0010] The technical solution adopted by the present invention is a method for controlling the amount of slag discharged from a converter during argon blowing refining of low-carbon aluminum killed steel, comprising the following steps:

[0011] 1) Control of the molten steel smelting process, using top and bottom combined blowing converter smelting, at the end of converter blowing, the product of the mass percentage of carbon in the molten steel and the mass percentage of dissolved oxygen in the molten steel is 0.0016-0.0024; using an auxiliary gun to detect the molten steel temperature and the oxygen content in the molten steel, w[O] in the molten steel at the end of converter blowing is 0.03%-0.08%, and the converter blowing is completed when the molten steel temperature at the end of converter blowing is 1620-1660°C;

[0012] 2) Steel quenching control: at the end of converter blowing, the bottom blowing gas supply intensity is controlled to 0.08-0.15Nm 3 / (min·t), stir for 2 to 3 minutes, and then tap the steel immediately; during the quenching process of the molten steel, the amount of slag under the converter is calculated according to Formula 1:

[0013]

[0014] In formula 1, m 渣 is the amount of slag in the converter, in kilograms; Q 公称容量 is the nominal capacity of the converter, in tons; D0 is the initial diameter of the converter tapping hole, in mm; n is the number of furnaces currently in use at the converter tapping hole; T is the temperature of the molten steel at the end of the converter blowing, in °C; R is the slag basicity at the end of the converter blowing, which is w(CaO) / w(SiO2), where w(CaO) and w(SiO2) are the mass percentages of CaO and SiO2 in the slag at the end of the converter blowing, respectively, in %; w (TFe) is the mass percentage of total iron in the slag at the end of converter blowing, which is 92.51×w[O] 0.54, the unit is %; w[O] is the mass percentage content of dissolved oxygen in molten steel at the end of converter blowing, the unit is %;

[0015] 3) The converter tapping control adopts automatic tapping, slide plate slag blocking and infrared automatic slag judgment control. When slag is detected at the end of tapping, the slide plate mechanism is immediately closed.

[0016] Furthermore, in step 1), when the oxygen blowing amount is 70% to 80% of the total oxygen amount, the auxiliary lance is used to detect the molten steel temperature and the carbon content in the molten steel, and the oxygen lance position is controlled to be the reference lance position, and the reference lance position is: H0+H0*(0.2 to 0.3), H0 is the height of the molten steel surface in the converter; the effect is good.

[0017] In step 1), when the oxygen blowing amount is 85% to 95% 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*(0.1 to 0.2), H0 is the height of the molten steel surface in the converter; the effect is good.

[0018] The technical solution of the present invention is based on the following research and experiments of the applicant:

[0019] 1. The present invention controls the converter smelting process and molten steel calming, promotes the slag-gold reaction in the converter to tend to equilibrium, calculates the mass percentage content of total iron in the converter blowing end slag by using the mass percentage content of dissolved oxygen in the converter blowing end molten steel, and further combines the converter blowing end molten steel temperature and the converter blowing end slag basicity to obtain the influence relationship of the converter blowing end slag physical properties on the converter steel tapping slag amount; wherein, the higher the converter blowing end molten steel temperature and the higher the mass percentage content of total iron in the converter blowing end slag, the smaller the viscosity of the slag and the more the converter slag amount; and the higher the converter blowing end slag basicity, the greater the slag viscosity and the less the converter slag amount.

[0020] 2. The present invention utilizes a steel-making process of automatic steel-making, slide plate slag blocking and infrared automatic slag judgment, so that the human influencing factors of slag discharge during steel-making are controlled, and the influence relationship of the inner diameter of the converter steel-making port on the amount of slag discharged during steel-making of the converter is obtained; wherein, the larger the initial diameter of the converter steel-making port, the more slag discharged by the converter; as the number of times the steel-making port is used increases, the inner diameter of the steel-making port gradually expands, and the amount of slag discharged by the converter gradually increases; data statistical analysis shows that when w[O] in the molten steel at the end of converter blowing is 0.03-0.08% and the temperature is 1620-1660°C, the inner diameter of the steel-making port increases by 0.15 mm per furnace on average.

[0021] Compared with the prior art, the present invention has the following positive effects: 1. The method of the present invention has high control accuracy, no additional cost, strong applicability, no hysteresis, and no high-temperature operation risk; the parameters used in the method are the nominal capacity of the converter, the initial diameter of the steel outlet, the number of furnaces currently in use at the steel outlet, the mass percentage content of dissolved oxygen in the molten steel at the end of converter blowing, the molten steel temperature at the end of converter blowing, and the slag basicity at the end of converter blowing, all of which can obtain accurate values ​​before the converter taps. 2. The method of the present invention can accurately guide the converter smelting argon blowing refining of low-carbon aluminum killed steel. DETAILED DESCRIPTION

[0022] The present invention is further illustrated below in conjunction with specific embodiments 1 to 5.

[0023] 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. Among them, embodiments 1-2 are SPHC steels; embodiments 3-4 are SPHD steels; and embodiment 5 is Q195L steel. The production method includes: converter smelting, argon blowing treatment of molten steel at 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 3.

[0024] Table 1 Converter smelting control parameters of the embodiment of the present invention

[0025]

[0026] Table 2 Parameters of molten steel calming and converter tapping in the embodiment of the present invention

[0027]

[0028]

[0029] Table 3 Prediction and application parameters of slag amount at steel tapping in the embodiment of the present invention

[0030]

[0031] Note that the weight percentage of CaO in the desulfurized lime in Table 3 is ≥85%; the weight percentage of the chemical composition of the aluminum slag is: Al: 25-30%, CaO: 30-35%, Al2O3: 30-35%, and the others are ≤5; 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 %.

[0032] When the present invention produces SPHC steel, SPHD steel and Q195L steel 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 and converter tapping process control, effectively supports the dynamic adjustment of the amount of desulfurized lime and aluminum slag added in the tapping process, improves the control accuracy of key quality characteristics of ladle top slag, effectively reduces the total oxygen content of molten steel, and improves the cleanliness of molten steel.

[0033] The slag amount predicted by the method of the present invention supports the dynamic adjustment of the amount of desulfurized lime and aluminum slag added, so that the control stability of the calcium-aluminum ratio and the total iron content of the ladle top slag is greatly improved; as shown in Table 3, the calcium-aluminum ratio of Examples 1-5 is stably controlled to be 0.95-1.25, and the total iron content is stably controlled to be 1.50-3.80%, and the total oxygen content of the molten steel is further stably controlled to be 0.0014-0.0019%, with an average of 0.0016%.

[0034] 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 controlling the amount of slag discharged from a converter during argon blowing refining of low-carbon aluminum killed steel, characterized in that: The method comprises the following steps: 1) Control of the molten steel smelting process, using top and bottom combined blowing converter smelting, at the end of converter blowing, the product of the mass percentage of carbon in the molten steel and the mass percentage of dissolved oxygen in the molten steel is 0.0016-0.0024; using an auxiliary gun to detect the molten steel temperature and the oxygen content in the molten steel, w[O] in the molten steel at the end of converter blowing is 0.03%-0.08%, and the converter blowing is completed when the molten steel temperature at the end of converter blowing is 1620-1660°C; 2) Steel quenching control: at the end of converter blowing, the bottom blowing gas supply intensity is controlled to 0.08-0.15Nm 3 / (min·t), stir for 2 to 3 minutes, and then tap the steel immediately; during the quenching process of the molten steel, the amount of slag under the converter is calculated according to Formula 1: In formula 1, m 渣 is the amount of slag in the converter, in kilograms; Q 公称容量 is the nominal capacity of the converter, in tons; D0 is the initial diameter of the converter tapping hole, in mm; n is the number of furnaces currently in use at the converter tapping hole; T is the temperature of the molten steel at the end of the converter blowing, in °C; R is the slag basicity at the end of the converter blowing, which is w(CaO) / w(SiO2), where w(CaO) and w(SiO2) are the mass percentages of CaO and SiO2 in the slag at the end of the converter blowing, respectively, in %; w (TFe) is the mass percentage of total iron in the slag at the end of converter blowing, which is 92.51×w[O] 0.54 , the unit is %; w[O] is the mass percentage content of dissolved oxygen in molten steel at the end of converter blowing, the unit is %; 3) The converter tapping control adopts automatic tapping, slide plate slag blocking and infrared automatic slag judgment control. When slag is detected at the end of tapping, the slide plate mechanism is immediately closed.

2. The method for controlling the amount of slag at the tapping of a converter for argon-blown refining of low-carbon aluminum-killed steel as claimed in claim 1, characterized in that: In step 1), when the oxygen blowing amount is 70% to 80% of the total oxygen amount, the auxiliary lance is used to detect the molten steel temperature and the carbon content in the molten steel, and the oxygen lance position is controlled to be the reference lance position, and the reference lance position is: H0+H0*(0.2 to 0.3), where H0 is the height of the molten steel surface in the converter.

3. The method for controlling the amount of slag at the tapping of a converter for argon-blown refining of low-carbon aluminum-killed steel as claimed in claim 1, characterized in that: In step 1), when the oxygen blowing amount is 85% to 95% 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*(0.1 to 0.2), where H0 is the height of the molten steel surface in the converter.

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