A control method for improving the number and quality of continuous casting furnaces for straight-up steel grades

Abstract

The present invention discloses a control method for improving the number and quality of continuous casting and pouring furnaces of straight-up steel grades, which belongs to the field of steel production and specifically comprises the following steps: (1) adopting a corrosion-resistant reinforced stopper rod for continuous casting tundish casting, wherein the rod head material of the corrosion-resistant reinforced stopper rod comprises the following components in percentage by mass: FC: 8-12%, MgO: 10-14%, and the remainder Al2O3, and the sum of the above components is 100%; (2) reducing the inner diameter of the tundish nozzle of the continuous casting tundish and controlling the inner diameter of the tundish nozzle to φ25mm; (3) adopting a corrosion-resistant extended external immersed nozzle, wherein the length of the nozzle is controlled to be 740±3mm, the slag line wall thickness is 30mm, and the ZrO2 content in the slag line material is 75-83%; the method enhances corrosion resistance by optimizing the stopper rod head and nozzle material, and the control method effectively increases the number of continuous casting furnaces and reduces the amount of scrap.

Description

Technical Field

[0001] The invention relates to a control method for improving the number and quality of continuous casting furnaces, in particular to a control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, and belongs to the field of steel production. Background Art

[0002] As competition in the steel industry becomes increasingly fierce, reducing processes and increasing production costs and efficiency have become key issues that steel mills need to address.

[0003] The continuous casting machine with large cross-sections such as 250*350 adopts refining technology to produce Q195 steel strip, Q195-1, Q235B-2, bulb-flat A and other steel grades. The molten steel treatment cycle is long, and the refining power consumption and refractory costs are high. The continuous casting machine with small cross-sections of 150*150 adopts refining and light treatment technology to produce nuclear power rebar varieties such as HRB400-9 and HRB500E-2. The overall cost is high, which affects the competitiveness of the products.

[0004] However, low-carbon steel grades such as Q195 steel strip are produced using the direct-flow process, and the oxygen content of the molten steel is unstable: when the oxygen content is high, the stopper rod is severely eroded during the pouring process, the flow control is unstable, and the number of continuous pouring furnaces is small; when the oxygen content is low, aluminum inclusions cannot float up effectively, the liquid level of the molten steel fluctuates greatly during the pouring process, and many castings are scrapped.

[0005] HRB400-9 and other nuclear power rebars have high C, Si, and Mn contents, large amounts of added alloys, and narrow Ceq requirements. The direct-acting process cannot achieve stable control of temperature and composition, and an urgent problem needs to be solved on site.

[0006] The current patent CN108570532B is a method for improving the quality of straight-through steel grades and the stopper rod flow control time. The method controls the reasonable oxygen level of the molten steel by optimizing the converter steel-tapping deoxidation system, without refining to obtain an oxygen level below 40ppm. At the same time, it extends the stopper rod flow control time, reduces the waste billets caused by liquid level fluctuations during the casting process, and reduces the occurrence of flow stoppage accidents caused by stopper rod loss of control. It does not involve improvements in the size of stopper rods and nozzle materials to solve the problem of improving the number and quality of continuous casting furnaces of straight-through steel grades.

[0007] Therefore, developing a control method for increasing the number and quality of continuous casting furnaces for straight-up steel grades that can overcome the above defects has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a control method for improving the number and quality of continuous casting furnaces for straight-up steel grades. By optimizing the plugger rod head and nozzle material to enhance corrosion resistance, this control method effectively increases the number of continuous casting furnaces and reduces the amount of waste billets.

[0009] In order to solve the above technical problems, the present invention provides a control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, which specifically includes the following steps:

[0010] (1) The continuous casting tundish pouring adopts a corrosion-resistant reinforced stopper rod, and the rod head material of the corrosion-resistant reinforced stopper rod includes the following components in terms of mass percentage:

[0011] FC: 8-12%, MgO: 10-14%, the balance is Al2O3, the sum of the above components is 100%;

[0012] (2) Reduce the inner diameter of the tundish nozzle of the continuous casting ladle and control it to φ25mm;

[0013] (3) An anti-corrosion extended external submerged nozzle is used. The length of the nozzle is controlled at 740±3 mm, the slag line wall thickness is 30 mm, and the slag line material includes the following components by mass percentage: ZrO2: 75-83%, FC: 10-16%, Al2O3: 6-15%, and the sum of the above components is 100%.

[0014] The technical solution further defined in the present invention is:

[0015] Furthermore, in the aforementioned control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, the bulk density of the rod head is 2.65 g / cm 3 , porosity 16%, compressive strength 30.2MPa, flexural strength 8.5MPa.

[0016] In the aforementioned control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, the rod head material of the corrosion-resistant reinforced stopper rod includes the following components by mass percentage:

[0017] FC: 11.8%, MgO: 12.1%, the balance is Al2O3: 76.1%.

[0018] In the aforementioned control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, the slag line material includes the following components by mass percentage: ZrO2: 78%, FC: 14%, Al2O3: 8%, and the sum of the above components is 100%.

[0019] The beneficial effects of the present invention are:

[0020] The present invention improves the inner diameter of the tundish water inlet, reducing it from φ30mm to φ25mm, thereby improving the flow control capability.

[0021] This invention improves the stopper rod tip material to enhance its oxidation resistance and corrosion resistance. During stopper rod machining, machining allowances are reduced to 8-12 mm (the ultimate goal is 0 mm), and machining accuracy can reach 1 mm (the ultimate goal is 0 mm, i.e., no machining). This reduces secondary damage during stopper rod machining, ensures the integrity of the rod tip slurry particles, and improves oxidation resistance and corrosion resistance. The tundish nozzle improves flow control capabilities, and the external submerged nozzle improves corrosion resistance and service life. The overall effect can effectively increase the number of continuous casting furnaces and reduce the amount of scrap. This invention optimizes the materials of the rod tip and nozzle to enhance corrosion resistance. This enhanced corrosion resistance of the refractory material prolongs the casting time, thereby increasing the number of continuous casting furnaces. It also reduces molten steel corrosion of the refractory material and the introduction of refractory dispersed matter into the molten steel, thereby improving the purity and other quality levels of the molten steel. Reducing the inner diameter of the tundish nozzle improves flow control capabilities, reduces molten steel level fluctuations, and thus reduces scrap caused by excessive liquid level fluctuations. It also reduces the possibility of slag entanglement during fluctuations, thereby improving the internal quality of the steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of the structure of the corrosion-resistant reinforced stopper rod used in an embodiment of the present invention;

[0024] Figure 3 This is a schematic structural diagram of the corrosion-resistant, elongated externally mounted submerged nozzle used in an embodiment of the present invention. DETAILED DESCRIPTION Example 1

[0025] This embodiment provides a control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, the process of which is as follows: Figure 1 As shown, the specific steps include:

[0026] (1) The continuous casting tundish pouring adopts corrosion-resistant reinforced stopper rods such as Figure 2 The specific components and properties of the stopper rod head are shown in Table 1;

[0027] Table 1 Parameters of the plug head

[0028]

[0029] Table 1 shows that the rod head made of this material effectively improves the compressive and flexural strength of the rod head material and enhances its corrosion resistance to molten steel. Compared with existing technologies, the MgO content is reduced and the Al2O3 content is increased. Al2O3 has higher compressive and flexural strengths at high temperatures. For example, a micro-expansion castable with an Al2O3 content of 68% achieves a compressive strength of 60 MPa and a flexural strength of 9 MPa at 1400°C. In contrast, MgO has lower compressive and flexural strengths. For example, pure magnesium oxide has a melting point of 2800°C, but its compressive and flexural strengths are far lower than those of Al2O3, indicating its poor structural stability at high temperatures. These data show that under the same temperature conditions, Al2O3 exhibits higher compressive and flexural strengths, which is due to its higher chemical stability and crystal structure strength.

[0030] (2) Reduce the inner diameter of the tundish nozzle from φ30mm to φ25mm;

[0031] (3) Use erosion-resistant extended external submerged nozzles such as Figure 3 As shown, the length of the nozzle is controlled at 740±3 mm, the slag line wall thickness is 30 mm, and the slag line material includes the following components by mass percentage: ZrO2: 78%, FC: 14%, and Al2O3: 8%.

[0032] The total design length is extended from 710mm to 740±3mm, the slag line wall thickness is increased by 5mm, the ZrO2 content of the slag line in the external submerged nozzle is increased by 3-5%, the material has enhanced corrosion resistance, and double slag line operation is adopted during production to increase the number of continuous casting furnaces and reduce the amount of waste billets when changing the nozzle.

[0033] After adopting the above method, the number of continuous casting furnaces and the amount of scrap are as follows: the number of continuous casting furnaces for large-section direct-on steel grades such as Q195 steel strips of 250*300 is increased from 12 furnaces / group to 17 furnaces / group; the number of continuous casting furnaces for small-section direct-on steel grades such as 150*150 is increased from 21 furnaces / group to 25 furnaces / group; the amount of scrap for large-section direct-on steel grades such as Q195 of 250*300 is reduced to 6.57 tons / group, which is 11.56 tons / group less than before the improvement; the amount of scrap for small-section direct-on steel grades such as 150*150 is reduced to 2.98 tons / group, which is 9.98 tons / group less than before the improvement.

[0034] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A control method for improving the number and quality of continuous casting furnaces for straight-up steel grades, characterized in that: The specific steps include: (1) The continuous casting tundish pouring adopts a corrosion-resistant reinforced stopper rod, and the rod head material of the corrosion-resistant reinforced stopper rod includes the following components in terms of mass percentage: FC: 8-12%, MgO: 10-14%, the balance is Al2O3, the sum of the above components is 100%; (2) Reduce the inner diameter of the tundish nozzle of the continuous casting ladle and control it to φ25mm; (3) Use an anti-corrosion extended external submerged nozzle, the length of the nozzle is controlled at 740±3mm, and the slag line wall thickness is 30mm; The slag line material includes the following components by mass percentage: ZrO2: 75-83%, FC: 10-16%, Al2O3: 6-15%, and the sum of the above components is 100%.

2. The control method for improving the number and quality of continuous casting furnaces for straight-up steel grades according to claim 1 is characterized in that: The rod head material of the corrosion-resistant reinforced stopper rod comprises the following components by mass percentage: FC: 11.8%, MgO: 12.1%, the balance is Al2O3: 76.1%.

3. The control method for improving the number and quality of continuous casting furnaces for straight-up steel grades according to claim 1 is characterized in that: The bulk density of the rod head is 2.65 g / cm 3 , porosity 16%, compressive strength 30.2MPa, flexural strength 8.5MPa.

4. The control method for improving the number and quality of continuous casting furnaces for straight-up steel grades according to claim 1 is characterized in that: The slag line material includes the following components by mass percentage: ZrO2: 78%, FC: 14%, Al2O3: 8%, and the sum of the above components is 100%.

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