A method for dynamically adjusting electromagnetic stirring based on purity of molten steel

Abstract

The application discloses a dynamic adjustment method of electromagnetic stirring based on the purity of molten steel, which comprises the following steps: judging the purity of molten steel according to the thickness of converter slag in a converter and the difference between the total aluminum content and the acid aluminum content in the molten steel; dynamically adjusting the argon flow according to the purity of the molten steel; and dynamically adjusting the stirring current of electromagnetic stirring according to the purity of the molten steel. The application judges the purity of molten steel according to the thickness of converter slag and the aluminum oxide content in the molten steel, and dynamically adjusts the argon flow and the electromagnetic stirring process according to the purity of the molten steel, so as to reduce the inclusions in the molten steel and improve the quality of the slab.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of continuous casting improvement, and particularly relates to an electromagnetic stirring dynamic adjustment method based on the purity of molten steel, and especially to improving the quality of continuous casting slabs in continuous casting steel production. BACKGROUND

[0002] As for the current continuous casting improvement technology, most of them are about electromagnetic stirring equipment, cooling, winding, etc., that is, the current large amount of technology is to explain how to realize electromagnetic stirring, and as for a certain electromagnetic stirring equipment on a fixed crystallizer, the corresponding refined molten steel in the casting process, the suitable crystallizer liquid level setting position, that is, the electromagnetic stirring magnetic field strength applied to the crystallizer, especially the range of the upper end of the crystallizer, is relatively less. For example, patent publication No. CN104690242 A discloses a dynamic control method for the position of electromagnetic stirring at the solidification end of steel continuous casting, which adopts a bidirectional linked list composed of a continuous casting tracking unit to establish a continuous casting dynamic tracking model, to collect continuous casting process parameters in real time, and to calculate continuous casting slab solidification information; by comparing the current electromagnetic stirring position with the optimal electromagnetic stirring position, the required displacement amount of the solidification end electromagnetic stirrer is calculated in real time; this technology theoretically discusses on the caster, but does not give a solution to the problem from the feedback of the quality result of the next process. Patent publication No. CN102554172 A discloses a dynamic control method for slab continuous casting electromagnetic stirrers, characterized in that: (1) a continuous casting primary computer control system continuously collects the steel grade, slab cross-sectional size, molten steel temperature and casting speed of the on-site continuous casting production, and transmits the collected real-time data to a continuous casting secondary computer; (2) the continuous casting secondary computer continuously processes the received various measured data to calculate the solidification shell thickness at the corresponding position of electromagnetic stirring; undoubtedly, this method improves the electromagnetic stirring process on the shell, and the result is only to improve the shell, but does not adjust according to the actual situation of the molten steel.

[0003] In the continuous casting production process, it is necessary to improve the purity of the molten steel. At present, the commonly used method is electromagnetic stirring, which has the following two aspects: 1. Increase the floating efficiency of inclusions. 2. Shell washing, reduce the slag inclusion of solidification front. However, due to the rolling of the molten steel surface in the rolling process, the emulsification of the protective slag is increased, which leads to the rolling of the protective slag, and the rolling of the protective slag defect occurs; especially the magnetic field has the characteristics of middle strong and both ends weak; therefore, the molten steel needs to be refined and improved in the aspects of increasing the floating of non-metallic inclusions and avoiding the rolling of the protective slag. SUMMARY

[0004] To address the aforementioned deficiencies in existing technologies, the purpose of this invention is to provide a method for dynamically adjusting electromagnetic stirring based on the purity of molten steel. This method determines the purity of molten steel based on the converter slag thickness and the alumina content in the molten steel, and dynamically adjusts the argon flow rate and electromagnetic stirring process according to the purity of the molten steel, thereby reducing inclusions in the molten steel and improving the quality of the slab.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for dynamically adjusting electromagnetic stirring based on the purity of molten steel, comprising the following steps:

[0007] S1. The purity of molten steel is determined by the difference between the thickness of the converter slag and the total aluminum and acid aluminum content in the molten steel.

[0008] S2, dynamically adjust the argon gas flow rate according to the purity of the molten steel;

[0009] S3, dynamically adjust the stirring current of the electromagnetic stirrer according to the purity of the molten steel.

[0010] Preferably, in step S1, with a converter slag thickness of 65 mm and a difference of 90 ppm between the total aluminum and acid aluminum content in the molten steel as a benchmark, the purity of the molten steel is defined as "poor" when the converter slag thickness d > 65 mm and the difference of w between the total aluminum and acid aluminum content in the molten steel > 90 ppm; the purity of the molten steel is defined as "medium" when the converter slag thickness d satisfies: 50 mm < d ≤ 65 mm and the difference of w between the total aluminum and acid aluminum content in the molten steel satisfies: 50 < w ≤ 90 mm; and the purity of the molten steel is defined as "good" when the converter slag thickness d ≤ 50 mm and the difference of w between the total aluminum and acid aluminum content in the molten steel ≤ 50 ppm.

[0011] Preferably, in step S2, with the argon gas flow rate of the stopper rod at 10 L / min as a baseline, when the purity of the molten steel is defined as "poor", the argon gas flow rate is increased to 15-18 L / min; when the purity of the molten steel is defined as "medium", the argon gas flow rate is the baseline value; and when the purity of the molten steel is defined as "good", the argon gas flow rate is adjusted to 5-6 L / min.

[0012] Preferably, in step S3, with the stirring current of the electromagnetic stirrer being 500-550A as a reference, when the purity of the molten steel is defined as "poor", the stirring current is adjusted to 700-750A; when the purity of the molten steel is defined as "medium", the stirring current is adjusted to 500-550A; and when the purity of the molten steel is defined as "good", the stirring current is adjusted to 200-300A.

[0013] The electromagnetic stirring dynamic adjustment method based on the purity of molten steel has the following beneficial effects:

[0014] 1. The electromagnetic stirring dynamic adjustment method based on the purity of molten steel judges the purity of molten steel according to the thickness of converter slag and the content of aluminum oxide in molten steel, and dynamically adjusts the argon flow and the electromagnetic stirring process according to the purity of molten steel, so as to reduce the inclusions in molten steel and improve the quality of slab.

[0015] 2. According to the basic principle of metallurgical slag in metallurgical physical chemistry and the function of removing inclusions and bubbles by electromagnetic stirring, and in combination with the current continuous casting production process, the argon flow and the current of electromagnetic stirring are dynamically adjusted in combination with the purity of molten steel, the three are matched with each other, the inclusions in molten steel are increased to float up, and at the same time, the protective slag is avoided from being involved in molten steel, so as to improve the quality of continuous casting slab. BRIEF DESCRIPTION OF DRAWINGS

[0016] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments with reference to the following drawings:

[0017] Figure 1 The figure is a definition diagram of the purity of molten steel in the electromagnetic stirring dynamic adjustment method based on the purity of molten steel. DETAILED DESCRIPTION

[0018] In order to better understand the above technical solutions of the present application, the technical solutions of the present application will be further described below in combination with embodiments.

[0019] In the converter steelmaking process, refining treatment is carried out for temperature adjustment and alloying. The continuous casting in the steelmaking plant is the last process, which completes the transformation from liquid to solid. In the continuous casting process, the molten steel is solidified in the crystallizer. In order to prevent the molten steel from being oxidized and the temperature from being too low, protective slag needs to be added for heat insulation and heat preservation. However, the protective slag is on the surface of the molten steel, and will be captured by the solidified shell due to the action of electromagnetic stirring. For different casting machines and different electromagnetic stirring equipment, optimization needs to be carried out after a period of production. Since most of the magnetic fields are several pairs of electromagnetic group windings, under the action of alternating current, the magnetic field is alternately generated, so that the force acting on the liquid surface pushes the liquid surface to rotate, thereby playing a stirring role.

[0020] However, when the purity of molten steel is high and the inclusions are few, the argon gas of the stopper does not need to be too much. Generally, the argon gas of the continuous casting stopper is used to avoid the accumulation of inclusions in the molten steel, especially the accumulation of aluminum oxide in the water gap, which causes the adhesion of the water gap and the stopper, and the role is to flush the inclusions. If the amount of argon gas is too large, the bubbles will adhere to the slab, and various defects will be produced in the rolling process, causing the quality of the slab to decrease.

[0021] Therefore, the application proposes an electromagnetic stirring dynamic adjustment method based on the purity of molten steel, which specifically comprises the following steps.

[0022] S1, judging the purity of molten steel according to the thickness of converter slag in the converter and the difference between the total aluminum and acid aluminum content in the molten steel;

[0023] Specifically, the purity of molten steel is judged according to the actual situation of the molten steel. First, the pollution degree of the ladle slag to the molten steel is determined by the thickness of the converter slag, and the purity of the molten steel is determined by the thickness of the converter slag. Second, the purity of the molten steel in the converter is determined by the actual composition refined from the molten steel, and the purity of the molten steel is determined by the difference between the total aluminum and acid aluminum content in the molten steel. Combined Figure 1 As shown in the specific embodiment, the thickness of the converter slag is 65mm, and the difference between the total aluminum and acid aluminum content in the molten steel is 90ppm as a reference. When the thickness of the converter slag d> 65mm, and the difference between the total aluminum and acid aluminum content in the molten steel w> 90ppm, it is defined that the molten steel is polluted, and the purity of the molten steel is defined as "poor". When the thickness of the converter slag d satisfies: 50< d≤ 65mm, and the difference between the total aluminum and acid aluminum content in the molten steel w satisfies: 50< w≤ 90mm, the purity of the molten steel is defined as "medium". When the thickness of the converter slag d≤ 50mm, and the difference between the total aluminum and acid aluminum content in the molten steel w≤ 50ppm, the purity of the molten steel is defined as "good".

[0024] S2, dynamically adjusting the argon flow according to the purity of the molten steel;

[0025] Specifically, the argon flow is dynamically adjusted according to the purity of the molten steel. When the purity of the molten steel is defined as "good", the amount of argon is reduced, when the purity of the molten steel is defined as "poor", the flow of argon is increased to flush the accumulation of inclusions in the water gap and the stopper. Taking the argon flow of the stopper as 10L / min as a reference, when the purity of the molten steel is defined as "poor", the argon flow of the stopper is increased to 15-18L / min; when the purity of the molten steel is defined as "medium", the argon flow of the stopper is increased to the reference value, i.e. 10L / min; when the purity of the molten steel is defined as "good", the argon flow of the stopper is adjusted to 5-6L / min.

[0026] S3, dynamically adjusting the stirring current of electromagnetic stirring according to the purity of the molten steel.

[0027] Specifically, the stirring current of the electromagnetic stirring is dynamically adjusted in combination with different molten steel conditions; when the purity of the molten steel is defined as "poor", the stirring current intensity of the electromagnetic stirring is increased to improve the removal effect of inclusions floating, when the purity of the molten steel is defined as "good", the stirring current intensity of the electromagnetic stirring is reduced to save energy; taking the stirring current of the electromagnetic stirring as 500-550 A as a reference, when the purity of the molten steel is defined as "poor", the stirring current is adjusted to 700-750 A; when the purity of the molten steel is defined as "medium", the stirring current is adjusted to the reference range, i.e. 500-550 A; when the purity of the molten steel is defined as "good", the stirring current is adjusted by 200-300 A.

[0028] By the above method, the cold rolling inclusions (calculated according to weight) of the final continuous casting slab are controlled to be less than 5%, so that the slag entrapment defect occurrence rate (calculated according to the number of slab blocks) of the continuous casting slab is reduced to less than 3%.

[0029] The electromagnetic stirring dynamic adjustment method based on the purity of molten steel according to the present application is further described below in combination with specific examples.

[0030] Example 1

[0031] In this example, a certain steel plant produces a furnace of steel on a certain day, and the molten steel continuous casting process is adjusted by the following method:

[0032] I. Determine the purity of the molten steel according to the actual situation of the molten steel: first measure the pollution degree of the ladle slag to the molten steel from the thickness of the converter slag. Take the thickness of the converter slag as the reference to determine the pollution degree of the incoming molten steel, and take the thickness of the converter slag as 65 mm and the difference between the total aluminum and acid aluminum content in the molten steel as 90 ppm as the reference. When the thickness of the converter slag d> 65 mm and the difference w between the total aluminum and acid aluminum content in the molten steel> 90 ppm, it is defined that the incoming molten steel is polluted, and the purity of the molten steel is defined as "poor"; when the thickness of the converter slag d satisfies: 50

[0033] II. Adjust the argon flow according to the purity of the molten steel. The purity of the molten steel of this furnace is low, i.e. the purity of the molten steel is defined as "poor", and the argon flow needs to be increased to 18 L / min.

[0034] 3. Dynamically adjust the electromagnetic stirring current according to different molten steel conditions. The purity of the molten steel in this furnace is low, that is, the purity of the molten steel is defined as "poor". Increase the current stirring intensity to improve the effect of removing inclusions by flotation; adjust the electromagnetic stirring current to 700A.

[0035] Through the above adjustments, the inclusions in the continuously cast slabs produced by this furnace steel are controlled to below 4% (by weight), thereby reducing the defect rate of the continuously cast slabs (by weight) to below 2.5% (by number of slabs).

[0036] Example 2

[0037] In this embodiment, a steel plant produces one furnace of steel on a certain day, and the continuous casting process of molten steel is adjusted in the following way:

[0038] I. Determining the purity of molten steel based on its actual condition: First, the thickness of the converter slag is used to measure the degree of contamination of the molten steel by the ladle slag. Using a certain converter slag thickness as a benchmark, the degree of contamination of the incoming molten steel is determined. In a 350-ton converter, with a converter slag thickness of 65mm and a difference of 90ppm between the total aluminum and acid aluminum content in the molten steel as benchmarks, if the converter slag thickness d > 65mm and the difference w between the total aluminum and acid aluminum content in the molten steel > 90ppm, the incoming molten steel is defined as contaminated, and the purity of the molten steel is defined as "poor"; if the converter slag thickness d satisfies: 50 < d ≤ 65mm, and the difference w between the total aluminum and acid aluminum content in the molten steel satisfies: 50 < w ≤ 90mm, the purity of the molten steel is defined as "medium"; if the converter slag thickness d ≤ 50mm and the difference w between the total aluminum and acid aluminum content in the molten steel ≤ 50ppm, the purity of the molten steel is defined as "good". During a certain production day, the slag thickness was 30mm, which did not exceed the benchmark, and the alumina content in the molten steel (the difference between total aluminum and acid aluminum) was 20ppm. The purity of the molten steel was good, that is, the purity of the molten steel was defined as "good".

[0039] 2. Adjust the argon flow rate according to the purity of the molten steel. When the purity of the molten steel in this furnace is good, that is, when the purity of the molten steel is defined as "good", adjust the argon flow rate of the stopper rod to 5L / min, and dynamically adjust the argon flow rate.

[0040] 3. Adjust the electromagnetic stirring current dynamically according to different molten steel conditions. When the purity of the molten steel in this furnace is good, that is, when the purity of the molten steel is defined as "good", adjust the electromagnetic stirring current to 200A~300A.

[0041] Through the above adjustments, the inclusion content of the continuously cast slabs produced by this furnace steel is controlled to below 3.5% (by weight), thereby reducing the defect rate of the continuously cast slabs to below 4% (by number of slabs).

[0042] Those skilled in the art should recognize that the above-described embodiments are merely intended to illustrate the present application, but not to limit the present application, and any changes or modifications to the above-described embodiments within the spirit and principle of the present application will fall within the scope of the claims of the present application.

Claims

1. A method for dynamically adjusting electromagnetic stirring based on the purity of molten steel, characterized in that, Includes the following steps: S1. The purity of molten steel is determined by the difference between the thickness of the converter slag and the total aluminum and acid aluminum content in the molten steel. S2, dynamically adjust the argon gas flow rate according to the purity of the molten steel; S3, dynamically adjust the stirring current of the electromagnetic stirrer according to the purity of the molten steel. In step S1, using a converter slag thickness of 65 mm and a difference of 90 ppm between the total aluminum and aluminate content in the molten steel as benchmarks, the purity of the molten steel is defined as "poor" when the converter slag thickness d > 65 mm and the difference of w between the total aluminum and aluminate content in the molten steel > 90 ppm; the purity of the molten steel is defined as "medium" when the converter slag thickness d satisfies: 50 mm < d ≤ 65 mm and the difference of w between the total aluminum and aluminate content in the molten steel satisfies: 50 ppm < w ≤ 90 ppm; and the purity of the molten steel is defined as "good" when the converter slag thickness d ≤ 50 mm and the difference of w between the total aluminum and aluminate content in the molten steel ≤ 50 ppm. In step S2, with an argon gas flow rate of 10 L / min as a baseline, when the purity of the molten steel is defined as "poor," the argon gas flow rate is increased to 15–18 L / min; when the purity of the molten steel is defined as "medium," the argon gas flow rate remains at the baseline value; and when the purity of the molten steel is defined as "good," the argon gas flow rate is adjusted to 5–6 L / min. In step S3, with the stirring current of the electromagnetic stirrer being 500-550 A as a benchmark, when the purity of the molten steel is defined as "poor", the stirring current is adjusted to 700-750 A; when the purity of the molten steel is defined as "medium", the stirring current is adjusted to 500-550 A; and when the purity of the molten steel is defined as "good", the stirring current is adjusted to 200-300 A.

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