Three-way argon flow control method for ultra-low carbon steel continuous casting tundish

Abstract

The invention discloses an ultra-low carbon steel continuous casting tundish three-way argon flow control method which comprises the following steps: after a target pulling speed is reached in a casting process, controlling the three-way argon flow according to the section size of a crystallizer: the section of the crystallizer is less than or equal to 1300mm, the argon flow of a stopper rod is controlled to be 4-5L / min, the argon flow of an upper nozzle is controlled to be 3-4L / min, and the argon flow between plates is controlled to be 5-7L / min; the section of the crystallizer is 1,300-1,500 mm, the argon flow of a stopper rod is controlled to be 5-6 L / min, the argon flow of an upper nozzle is controlled to be 4-5 L / min, and the argon flow between plates is controlled to be 6-8 L / min; the section of the crystallizer is larger than or equal to 1500 mm, the argon flow of a stopper rod is controlled to be 6-7 L / min, the argon flow of an upper nozzle is controlled to be 5-6 L / min, and the argon flow between plates is controlled to be 7-9 L / min. According to the method, through reasonable control over the three-way argon flow of the tundish, the fluctuation of the molten steel level of the crystallizer is small, the continuous casting stability of ultra-low carbon steel is effectively improved, the cleanliness of a submersed nozzle and molten steel is improved, the inclusion defect of a casting blank is remarkably reduced, and the continuous casting castability and the molten steel quality are effectively guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of continuous casting, in particular to a three-way argon flow control method for ultra-low carbon steel continuous casting tundish. BACKGROUND

[0002] As the last metallurgical vessel in the continuous casting production process, the three-way argon of the tundish is mainly blown into the tundish stopper, the upper nozzle and the plate to prevent secondary oxidation of the molten steel during pouring, and to effectively remove inclusions in the molten steel by forming argon bubbles to change the flow behavior, collision adhesion, wake carrying and other ways of the molten steel.

[0003] Ultra-low carbon steel has [C] ≤ 30ppm, such as IF steel and automobile outer plate steel, which has high requirements for the purity of molten steel. Since [Al] in the steel is easy to generate secondary oxidation reaction to form inclusions such as Al2O3, which gathers at the stopper head, the inner wall of the submerged nozzle and other parts to fall off, resulting in the appearance of inclusions defects such as points and lines on the surface of hot-rolled and cold-rolled plates in the later process. Therefore, how to prevent the secondary oxidation of the molten steel in the tundish during pouring, ensure the floating of small particle inclusions in the molten steel, and prevent the clogging of the submerged nozzle to form large particle inclusions, has important significance for improving the quality of the casting blank.

[0004] Chinese patent application with publication number CN117340209A provides a surface defect control method and system for automobile outer plate, which adjusts the three-way argon flow of the tundish according to the liquid level fluctuation, and replaces the submerged nozzle according to the rising trend of the stopper or the liquid level fluctuation; but the control value is a fixed value, which is not distinguished according to different sections, and the control is not described in detail. Chinese patent application with publication number CN119747635A provides a continuous casting method for improving the meniscus fluctuation of ultra-low carbon IF steel crystallizer, which adopts stopper argon flow of 3.0-5.5L / min, upper nozzle argon flow of 3.5-6.5L / min, and inter-plate argon flow of 5.0-9.5L / min; this method also does not classify in detail according to the section, and does not mention the different argon flow sizes and control specific processes of the stopper and the upper nozzle, so the applicability is not strong. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a three-way argon flow control method for ultra-low carbon steel continuous casting tundish, which effectively improves the pouring stability of ultra-low carbon steel continuous casting.

[0006] To solve the above technical problems, the technical solution adopted by the present application is: after the target casting speed is reached during pouring, the three-way argon flow is controlled according to the size of the crystallizer section: when the crystallizer section ≤ 1300mm, the stopper argon flow is controlled to be 4-5L / min, the upper nozzle argon flow is controlled to be 3-4L / min, and the inter-plate argon flow is controlled to be 5-7L / min. The crystallizer section is 1300-1500mm, the argon flow rate of the stopper is controlled to be 5-6L / min, the argon flow rate of the upper nozzle is controlled to be 4-5L / min, and the argon flow rate between the plates is controlled to be 6-8L / min. The crystallizer section is greater than or equal to 1500mm, the argon flow rate of the stopper is controlled to be 6-7L / min, the argon flow rate of the upper nozzle is controlled to be 5-6L / min, and the argon flow rate between the plates is controlled to be 7-9L / min.

[0007] Further, after the target casting speed is reached in the pouring process, the argon back pressure of the stopper and the argon back pressure of the upper nozzle are both controlled to be 0.2-0.5Mpa, and the argon back pressure between the plates is greater than or equal to 0.1Mpa.

[0008] Further, the argon flow rate of the stopper is greater than the argon flow rate of the upper nozzle by 0.5-1.5L / min.

[0009] Further, when the continuous casting ladle is being baked, the argon flow rate of the stopper is controlled to be 6-7L / min, the argon flow rate of the upper nozzle is controlled to be 5-6L / min, and the argon flow rate between the plates is controlled to be 7-9L / min; when the pouring is started, the argon flow rate of the stopper is controlled to be 4-5L / min, the argon flow rate of the upper nozzle is controlled to be 3-4L / min, and the argon flow rate between the plates is controlled to be 5-7L / min.

[0010] Further, in each continuous casting furnace, the argon flow rate of the stopper is increased by 0.1-0.15L / min compared to the previous furnace, and the argon flow rate of the upper nozzle is increased by 0.1-0.15L / min compared to the previous furnace.

[0011] The beneficial effects produced by the above technical solution are that, by reasonable control of the three-way argon flow rate of the tundish, the liquid level of the crystallizer is stable and has small fluctuations, the pouring stability of the ultra-low carbon steel continuous casting is effectively improved, the submerged entry nozzle and the cleanliness of the molten steel are improved, the inclusion defects of the cast slab are significantly reduced, and the occurrence rate of the inclusion defects of the cast slab is reduced from 5.6% of the conventional method to less than 2.6%; the continuous casting has good pouring stability and a clean submerged entry nozzle, which effectively ensures the castability of the continuous casting and the quality of the molten steel. BRIEF DESCRIPTION OF DRAWINGS

[0012] The application will be further described in detail below with reference to the drawings and specific embodiments.

[0013] Figure 1 is a liquid level fluctuation curve diagram of the steel liquid of the crystallizer in Example 1; Figure 2 is a clean appearance diagram of the plate inter-plate cylindrical region of the submerged entry nozzle of the tundish in Example 1; Figure 3 is a clean appearance diagram of the discharge hole of the submerged entry nozzle of the tundish in Example 1; Figure 4is a liquid surface fluctuation curve of a continuous casting mold of the steel liquid of Example 2; Figure 5 is a clean topography of a plate inter-cylindrical region of a submerged entry nozzle of a continuous casting tundish of the steel liquid of Example 2 at the end of the continuous casting of the fourth furnace; Figure 6 is a clean topography of a discharge hole of a submerged entry nozzle of a continuous casting tundish of the steel liquid of Example 2 at the end of the continuous casting of the fourth furnace; Figure 7 is a liquid surface fluctuation curve of a continuous casting mold of the steel liquid of Example 3; Figure 8 is a clean topography of a plate inter-cylindrical region of a submerged entry nozzle of a continuous casting tundish of the steel liquid of Example 3 at the end of the continuous casting of the fourth furnace; Figure 9 is a clean topography of a discharge hole of a submerged entry nozzle of a continuous casting tundish of the steel liquid of Example 3 at the end of the continuous casting of the fourth furnace. DETAILED DESCRIPTION

[0014] The three-way argon flow control method for the ultra-low carbon steel continuous casting tundish includes the following steps: (1) Continuous casting tundish stage: control the argon flow of the stopper 6-7 L / min, the argon flow of the upper nozzle 5-6 L / min, and the argon flow of the inter-plate 7-9 L / min; during this process, the three-way argon flow is controlled according to the large flow, which can effectively prevent the secondary oxidation of the stopper, the upper nozzle and other refractory materials during high-temperature tundish baking.

[0015] (2) Pouring and lifting speed stage: when the tundish is ready to be poured, control the argon flow of the stopper 4-5 L / min, the argon flow of the upper nozzle 3-4 L / min, and the argon flow of the inter-plate 5-7 L / min, and the continuous casting machine is normally poured and the speed is lifted.

[0016] (3) Stable speed stage: after the target speed is reached during pouring, control the argon back pressure of the stopper and the argon back pressure of the upper nozzle to be 0.2-0.5 Mpa, and the argon back pressure of the inter-plate to be ≥0.1 Mpa, always ensure that the argon flow of the stopper is 0.5-1.5 L / min larger than the argon flow of the upper nozzle, and the small section is controlled according to the lower limit and the large section is controlled according to the upper limit; in order to avoid the inclusion of the stopper head and the inner wall of the nozzle adhering and gathering and then falling into the molten steel to cause inclusion defects, the three-way argon flow is adjusted immediately after the target speed is reached, and the three-way argon flow of the first heat is controlled according to the size of the mold section as follows: if the mold section is ≤1300 mm, control the argon flow of the stopper 4-5 L / min, the argon flow of the upper nozzle 3-4 L / min, and the argon flow of the inter-plate 5-7 L / min; if the mold section is 1300-1500 mm, control the argon flow of the stopper 5-6 L / min, the argon flow of the upper nozzle 4-5 L / min, and the argon flow of the inter-plate 6-8 L / min; If the cross section of the crystallizer is greater than or equal to 1500 mm, the argon flow rate of the stopper is controlled to be 6-7 L / min, the argon flow rate of the upper nozzle is controlled to be 5-6 L / min, and the argon flow rate between the plates is controlled to be 7-9 L / min.

[0017] In the continuous casting process, the three-way argon flow rate in the tundish is increased by 0.1-0.15 L / min for each casting process compared with the previous casting process, and the argon flow rate of the stopper is increased by 0.1-0.15 L / min.

[0018] If the submerged nozzle is replaced, the three-way argon flow rate and back pressure of the first furnace after replacement are controlled according to the three-way argon flow rate before the replacement of the submerged nozzle.

[0019] If the cross section of the crystallizer is greater than or equal to 1500 mm, the argon flow rate of the stopper is controlled to be 6-7 L / min, the argon flow rate of the upper nozzle is controlled to be 5-6 L / min, and the argon flow rate between the plates is controlled to be 7-9 L / min.

[0020] When the argon flow rate is adjusted, the argon flow rate of the upper nozzle in the tundish is first adjusted to ensure that the crystallizer liquid surface around the submerged nozzle is slightly bubbled and turned over, and the bubble diameter is controlled to be 5-10 mm; then the argon flow rate of the stopper is adjusted, so that the argon flow rate of the stopper is greater than the argon flow rate of the upper nozzle by 0.5-1.5 L / min, so that the crystallizer liquid surface at a distance of 150-200 mm from the submerged nozzle on both sides is slightly bubbled and turned over, and the bubble diameter is controlled to be 5-10 mm; finally, the argon flow rate between the plates is adjusted.

[0021] Example 1: Production of ultra-low carbon steel DC06, the cross section of the crystallizer is 1300 mm, and the working process of the three-way argon flow rate control method in the tundish is as follows: First, before the production of the ultra-low carbon steel DC06 continuous casting process, open the three-way argon flow rate switch in the tundish, and open the flow rate to the maximum, the argon flow rate of the stopper is 7 L / min, the argon flow rate of the upper nozzle is 6 L / min, and the argon flow rate between the plates is 9 L / min. When the tundish is ready for pouring, adjust the three-way argon flow rate to the minimum, the argon flow rate of the stopper is 4 L / min, the argon flow rate of the upper nozzle is 3 L / min, and the argon flow rate between the plates is 5 L / min, and the continuous casting machine is normally started.

[0022] When the casting speed of the continuous casting machine is increased from 0 m / min to 0.8 m / min, the three-way argon flow rate is quickly adjusted, the argon flow rate of the upper nozzle is first adjusted to 4 L / min and the back pressure is 0.2 Mpa, to ensure that the crystallizer liquid surface around the submerged nozzle is slightly bubbled and turned over, the argon flow rate of the stopper is secondly adjusted to 5 L / min and the back pressure is 0.2 Mpa, to ensure that the crystallizer liquid surface at a distance of 150-200 mm from the submerged nozzle on both sides is slightly bubbled and turned over, and the bubble diameter is 5 mm, and finally the argon flow rate is adjusted to 7 L / min and the back pressure is 0.1 Mpa.

[0023] When the second furnace of the casting sequence was started, the argon flow rate of the stopper was increased to 5.1 L / min, and the argon flow rate of the upper nozzle was 4.1 L / min. With the increase of the number of continuous casting furnaces, the argon flow rate of the stopper and the upper nozzle was increased by 0.1 L / min for each additional furnace. At the end of the casting sequence, the liquid surface of the crystallizer of the entire casting sequence was stable, as shown in Figure 1 The appearance of the submerged nozzle at the end of the fourth furnace was changed, as shown in Figure 2 , Figure 3 The degree of cleanliness was shown.

[0024] Example 2: Production of ultra-low carbon steel DC04, the cross section of the crystallizer was 1400 mm, and the working process of the three-way argon flow control method of the tundish was as follows: First, before the production of the ultra-low carbon steel DC04 continuous casting, the three-way argon flow switch of the tundish was opened, and the flow rate was opened to the maximum, the argon flow rate of the stopper was 6 L / min, the argon flow rate of the upper nozzle was 5 L / min, and the argon flow rate between the plates was 9 L / min. When the tundish was ready to be opened, the three-way argon flow rate was adjusted to the minimum, the argon flow rate of the stopper was 4 L / min, the argon flow rate of the upper nozzle was 3 L / min, and the argon flow rate between the plates was 5 L / min, and the continuous casting machine was normally opened.

[0025] When the casting speed of the continuous casting machine was increased from 0 m / min to 0.8 m / min, the three-way argon flow rate was quickly adjusted. First, the argon flow rate of the upper nozzle was adjusted to 4.5 L / min, and the back pressure was 0.3 MPa, to ensure that the steel liquid surface around the submerged nozzle of the crystallizer was slightly foamed and stirred, and the bubble diameter was 8 mm. Secondly, the argon flow rate of the stopper was adjusted to 5.5 L / min, and the back pressure was 0.3 MPa, to ensure that the steel liquid surface at a distance of 150-200 mm from the submerged nozzle on both sides of the crystallizer was slightly foamed and stirred, and the bubble diameter was 8 mm. Finally, the argon flow rate was adjusted to 6.5 L / min, and the back pressure was 0.1 MPa.

[0026] When the second furnace of the casting sequence was started, the argon flow rate of the stopper was increased to 5.6 L / min, and the argon flow rate of the upper nozzle was 4.6 L / min. With the increase of the number of continuous casting furnaces, the argon flow rate of the stopper and the upper nozzle was increased by 0.12 L / min for each additional furnace. At the end of the casting sequence, the liquid surface of the crystallizer of the entire casting sequence was stable, as shown in Figure 4 The appearance of the submerged nozzle at the end of the fourth furnace was changed, as shown in Figure 5 , 6 The degree of cleanliness was shown.

[0027] Example 3: Production of ultra-low carbon steel DC03, the cross section of the crystallizer was 1500 mm, and the working process of the three-way argon flow control method of the tundish was as follows: First, in the ultra-low carbon steel DC03 continuous casting ladle production before baking, open the three-way argon flow switch, the flow is opened to the maximum, stopper argon flow 7L / min, 6L / min, 9L / min. When the end of baking preparation for casting, the three-way argon flow to the minimum, stopper 5L / min, 4L / min, 7L / min, continuous casting machine normal casting.

[0028] The casting speed of the continuous casting machine is increased from 0m / min to 0.8m / min, and the three-way argon flow is adjusted rapidly. First, adjust the argon flow of the upper water inlet to 5L / min and the back pressure to 0.5Mpa, ensure that the surrounding one circle of the submerged entry nozzle is slightly bubbling and the bubble diameter is 10mm. Second, adjust the argon flow of the stopper to 6L / min and the back pressure to 0.5Mpa, ensure that the distance between the two sides of the submerged entry nozzle is 150-200mm, and the bubble diameter is 10mm. Finally, adjust the argon flow to 7L / min and the back pressure to 0.1Mpa.

[0029] When the second furnace of the casting is cast, increase the argon flow of the stopper to 6.1L / min and the upper water inlet to 5.1L / min. With the increase of the continuous casting furnace, the argon flow of the stopper and the upper water inlet increases by 0.15L / min for each increase of 1 furnace. At the end of the casting, the liquid level of the mold is stable as shown in the following figure Figure 7 The fourth furnace is replaced with a submerged entry nozzle with the following appearance Figure 8 , 9 The degree of cleanliness is shown in the following figure.

Claims

1. A method for controlling the flow rate of three-channel argon gas in a tundish for continuous casting of ultra-low carbon steel, characterized in that, After the casting process reaches the target casting speed, the flow rate of three argon gases is controlled according to the cross-sectional size of the crystallizer: for crystallizer cross-sections ≤1300mm, the flow rate of argon gas to the stopper rod is controlled at 4-5L / min, the flow rate of argon gas to the upper water inlet is controlled at 3-4L / min, and the flow rate of argon gas between plates is controlled at 5-7L / min. The crystallizer has a cross-section of 1300-1500 mm, and the argon flow rate is controlled at 5-6 L / min for the stopper rod, 4-5 L / min for the upper water inlet, and 6-8 L / min for the interplate. The crystallizer has a cross-section ≥1500mm, and the argon flow rate is controlled at 6-7L / min for the stopper rod, 5-6L / min for the upper water inlet, and 7-9L / min for the interplate.

2. The method for controlling the flow rate of three-channel argon gas in the tundish of ultra-low carbon steel continuous casting according to claim 1, characterized in that: After the target casting speed is reached during the casting process, the argon back pressure of the stopper rod and the argon back pressure of the upper water inlet are both controlled at 0.2-0.5 MPa, and the argon back pressure between the plates is ≥0.1 MPa.

3. The method for controlling the flow rate of three-channel argon gas in the tundish of ultra-low carbon steel continuous casting according to claim 1, characterized in that: The argon flow rate of the stopper rod is 0.5 to 1.5 L / min greater than the argon flow rate of the inlet.

4. The method for controlling the flow rate of three-channel argon gas in the tundish of ultra-low carbon steel continuous casting according to claim 1, characterized in that: During the continuous casting ladle baking process, the argon flow rate of the stopper rod is controlled at 6-7 L / min, the argon flow rate of the upper water inlet is controlled at 5-6 L / min, and the argon flow rate between the plates is controlled at 7-9 L / min; during the casting process, the argon flow rate of the stopper rod is controlled at 4-5 L / min, the argon flow rate of the upper water inlet is controlled at 3-4 L / min, and the argon flow rate between the plates is controlled at 5-7 L / min.

5. A method for controlling the flow rate of three-channel argon gas in a tundish for continuous casting of ultra-low carbon steel according to any one of claims 1-4, characterized in that: For each consecutive furnace run, the argon flow rate at the stopper rod and the argon flow rate at the water inlet are increased by 0.1–0.15 L / min compared to the previous run.

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