Method for improving purity of tundish molten steel

Abstract

The invention relates to a method for improving the purity of tundish molten steel, and belongs to the technical field of continuous casting pouring processes in the metallurgical industry. According to the technical scheme, the method comprises the steps that firstly, a plurality of blowing devices (1) facing the interior of the tundish are arranged in the circumferential direction of the side wall of the tundish; secondly, before casting is started, argon is blown into the tundish through a blowing device (1), air in the tundish is exhausted, and an argon atmosphere is formed; and thirdly, after casting is started, after the liquid level of the molten steel in the tundish exceeds the height of the blowing device (1), argon continues to be blown into the tundish, and the molten steel in the tundish is stirred through the argon blown into the tundish in different directions. The argon blowing device has the beneficial effects that air in the tundish can be discharged before casting to form an argon atmosphere, argon is continuously blown into the tundish after the height of molten steel exceeds the height of the blowing device after casting, the argon blown into the tundish in different directions stirs the molten steel, inclusions in the molten steel are promoted to float upwards and enter a covering agent above the molten steel level, and the molten steel is prevented from entering the covering agent. The purpose of reducing inclusions in the molten steel is achieved.

Description

Technical Field

[0001] The invention relates to a method for improving the purity of molten steel in a tundish, and belongs to the technical field of continuous casting technology in the metallurgical industry. Background Art

[0002] With the high-end development of the equipment manufacturing industry, the requirements for steel performance and purity are getting higher and higher. The continuous casting process is a key process for quality control. In the continuous casting production process, tundish pouring is an important link in the continuous casting process to control the purity, which has an important impact on the purity control of subsequent products. At the same time, the high content of inclusions in the molten steel and the poor purity of the molten steel may also cause the tundish immersion nozzle to be blocked, causing production accidents and affecting the smooth production. Therefore, in the continuous casting production process, how to do a good job of protecting the pouring, reduce the secondary oxidation of the molten steel, and improve the purity of the molten steel is crucial.

[0003] Traditional continuous casting protective pouring includes argon blowing at the ladle nozzle, argon blowing at the integral immersion nozzle or immersion nozzle, mold protection slag, and covering agent in the tundish. Some steel mills blow argon to the impact zone of the tundish before pouring, and use the tundish cover to blow argon to the pouring zone of the tundish during the steel pouring process to prevent secondary oxidation of molten steel. However, the argon blowing effect of the tundish cover on the pouring zone is not ideal, and the residual oxygen content in the tundish is high, which cannot play a good protective pouring effect. If you want to ensure that the residual oxygen in the tundish is reduced to a sufficiently low level, the amount of argon required is very large, which will greatly increase the cost.

[0004] How to continue to improve the protective pouring effect of continuous casting on the basis of traditional protective pouring, reduce the inclusion content in molten steel, improve the purity of continuous casting molten steel, and produce products that meet higher purity requirements has become an urgent problem to be solved by various steel companies.

[0005] Patent CN214601907U "Argon Blowing Protection Tundish Cover" discloses an argon blowing protection tundish cover, which belongs to the technical field of tundish covers in steel smelting enterprises, including a steel structure, a tundish cover refractory, a side cover plate and an argon blowing pipe. The tundish cover refractory is arranged inside the steel structure, and a plurality of side cover plates are fixedly connected to the side wall of the tundish cover refractory, so as to seal the tundish cover refractory. A plurality of argon blowing pipes are arranged inside the tundish cover refractory, and the gas outlet of the argon blowing pipe is arranged at the bottom of the tundish cover refractory, and the argon blowing pipe is connected to the external argon gas. Among them, the present invention can effectively form an argon protective layer on the liquid surface of the molten steel in the tundish, which plays the effect of protecting the molten steel and reducing the oxidation of the molten steel. At the same time, the argon pipe is pre-buried in the refractory material of the tundish cover to prevent the molten steel from splashing onto the pipe and causing burning, and also to prevent the slag from blocking the pipe mouth. At the same time, the layout is simple, which solves the safety hazard of personnel arranging the pipe during production, thereby ensuring the purity of the molten steel and improving the quality of the casting. However, the blowing of argon on the tundish cover must ensure that the residual oxygen in the tundish is sufficiently low, and the required amount of argon is very large, resulting in a substantial increase in production costs.

[0006] Patent CN111992680B "A device and control method for argon blowing protection pouring in a middle ladle" includes an argon gas supply system, which includes an argon gas source, a gas supply pipe, a hose, a connecting pipe, a gas permeable brick and a plug. The argon gas source is connected to the gas supply pipe, and the two ends of the hose are respectively connected to the gas supply pipe and the connecting pipe. One end of the connecting pipe is embedded in the side wall of the middle ladle, and one end of the gas permeable brick is embedded in the side wall of the middle ladle and docked with one end of the connecting pipe. The other end of the connecting pipe extends into the middle ladle, and the top and end are covered with the refractory material. The height of the bottom surface of the gas permeable brick is higher than the height of the overflow trough, and the plug is configured with the other end of the connecting pipe. The whole device of the present invention has a simple structure and is easy to install, and can realize the protection pouring of the middle ladle. In this method, the gas permeable brick is located above the liquid level of the molten steel, similar to the argon blowing of the cover plate of the middle ladle, and can only form a protective atmosphere above the liquid level of the molten steel. Similarly, the amount of argon required to achieve sufficiently low residual oxygen is very large, which increases the cost.

[0007] Patent CN204171347U "A device for full protection pouring of tundish" has circular ring tubes embedded in the inner sides of the bottom edges of the pouring hole, the baking hole, and the stopper hole. The circular ring tubes are connected to the argon blowing pipe to blow argon gas, which can effectively reduce the entry of air from the pouring hole, baking hole, and stopper hole, quickly replace the air in the tundish, prevent secondary oxidation of molten steel, improve the cleanliness of molten steel, and ultimately improve the quality of the ingot. This device also forms a protective atmosphere above the molten steel surface. Similarly, in order to achieve sufficiently low residual oxygen, the amount of argon gas required is very large, which increases the cost. Summary of the invention

[0008] The purpose of the present invention is to provide a method for improving the purity of molten steel in a tundish, which can discharge the air in the tundish before pouring to form an argon atmosphere. When pouring, the molten steel enters the argon atmosphere of the tundish, does not contact the air during the process, and does not cause secondary oxidation of the molten steel, thereby solving the problems existing in the background technology.

[0009] The technical solution of the present invention is: A method for improving the purity of molten steel in a tundish is performed according to the following steps: Step 1: Arrange a plurality of blowing devices toward the inside of the middle package along the circumferential direction of the side wall of the middle package; Step 2: Before pouring, use a blowing device to blow argon into the tundish to exhaust the air in the tundish and form an argon atmosphere; Step 3: After pouring, when the liquid level of the molten steel in the tundish exceeds the height of the blowing device, continue to blow argon into the tundish. The argon gas blown in from different directions stirs the molten steel in the tundish to promote the floating of inclusions in the molten steel, reduce the inclusions in the molten steel, and thus improve the purity of the molten steel.

[0010] The height of the plurality of blowing devices arranged along the circumferential direction of the side wall of the middle ladle and directed toward the interior of the middle ladle is located at a middle position of the height of the molten steel level in the middle ladle.

[0011] The number of the plurality of blowing devices arranged along the circumferential direction of the side wall of the middle package and directed toward the interior of the middle package is 6-12 and is evenly distributed.

[0012] The plurality of blowing devices arranged along the circumferential direction of the side wall of the middle package and directed toward the interior of the middle package are made of magnesia refractory material and include a diffused air-permeable block, an air inlet block and a joint connected together.

[0013] The MgO in the magnesia refractory material is ≥85%.

[0014] The included angle α between the blowing direction of the blowing device and the horizontal plane is 5-10 degrees.

[0015] The argon pressure of the blowing device is 0.4-0.6MPa, and the flow rate is 30-50L / min.

[0016] The beneficial effects of the present invention are: the air in the tundish can be discharged before pouring to form an argon atmosphere, and the molten steel enters the argon atmosphere of the tundish during pouring, and does not contact the air during the process, and does not cause secondary oxidation of the molten steel. After the height of the molten steel exceeds the height of the blowing device after pouring, argon continues to be blown into the tundish, and the argon blown in from different directions stirs the molten steel, promoting the inclusions in the molten steel to float up into the covering agent above the molten steel surface, thereby achieving the purpose of reducing the inclusions in the molten steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the present invention; Figure 2 It is a schematic diagram of the blowing device of the present invention; In the figure: blowing device 1, middle bag 2, molten steel A, working layer B, permanent layer C, steel shell D, diffused air block a, body b, air inlet block c, joint d. DETAILED DESCRIPTION

[0018] The present invention will be further described below by way of examples with reference to the accompanying drawings.

[0019] See attached Figure 1 , 2 A method for improving the purity of molten steel in a tundish is performed according to the following steps: Step 1: a plurality of blowing devices 1 are arranged along the circumferential direction of the side wall of the middle package and directed toward the inside of the middle package; Step 2: Before pouring, use the blowing device 1 to blow argon into the middle bag to exhaust the air in the middle bag and form an argon atmosphere; Step 3: After pouring, when the liquid level of the molten steel in the middle ladle exceeds the height of the blowing device 1, continue to blow argon into the middle ladle. The argon gas blown in from different directions stirs the molten steel in the middle ladle, promotes the floating of inclusions in the molten steel, reduces the inclusions in the molten steel, and thus improves the purity of the molten steel.

[0020] In this embodiment, refer to the attached Figure 1 , 2 The middle package 2 is composed of molten steel A, working layer B, permanent layer C, and steel shell D. The blowing device 1 is made of magnesia refractory material, wherein MgO≥85%, and it comprises a diffused gas-permeable block a, a body b, an air intake block c, and a joint d. The body b is provided with an air intake block c and a diffused gas-permeable block a. The diffused gas-permeable block a can prevent the molten steel from flowing into the blowing device and causing blockage. The other end of the air intake block c is provided with a joint d connected to the argon gas box through a hose.

[0021] The method for improving the purity of molten steel in the tundish is specifically operated according to the following steps: (1) During the construction of the permanent layer of the tundish, the installation position of the blowing device 1 is reserved on the circumferential direction of the side wall of the tundish. The number of the blowing devices 1 is 6-12, which is selected according to the volume of the tundish. The height of the blowing devices 1 is located at a position of about 50% of the height of the steel liquid level in the tundish, and they are symmetrically distributed. The angle α between the blowing direction of the blowing devices 1 and the horizontal plane is 5-10 degrees. (2) Before the permanent layer of the middle package is baked, the blowing device 1 is installed on the side wall of the middle package and embedded in the permanent layer of the middle package, and the gap is sealed with high temperature resistant material; (3) After the permanent layer of the middle bag is baked, the working layer of the middle bag is tied, and the side end surface of the blowing hole of the blowing device 1 is flush with the surface of the working layer of the middle bag; (4) Before the tundish is ready for pouring, connect the argon box to the blowing device 1 through a hose, open the argon box valve to blow argon into the tundish, and exhaust the air in the tundish; (5) The pressure of argon is 0.4-0.6MPa and the flow rate is 30-50L / min; (6) During the steel pouring process, when the height of the molten steel exceeds the height of the blowing device, argon gas blown in from different directions stirs the molten steel, promoting the inclusions in the molten steel to float up into the covering agent above the steel liquid surface, thereby reducing the inclusions in the molten steel.

Claims

1. A method for improving the purity of molten steel in a tundish, characterized in that: Follow these steps: Step 1: Arrange a plurality of blowing devices (1) along the circumferential direction of the side wall of the middle package and directed toward the interior of the middle package; Step 2: Before pouring, use the blowing device (1) to blow argon gas into the middle bag to exhaust the air in the middle bag and form an argon atmosphere; Step 3: After pouring begins, when the level of the molten steel in the tundish exceeds the height of the blowing device (1), argon gas is continuously blown into the tundish. The argon gas blown in from different directions stirs the molten steel in the tundish, thereby promoting the floating of inclusions in the molten steel, reducing the inclusions in the molten steel, and thus improving the purity of the molten steel.

2. A method for improving the purity of molten steel in a tundish according to claim 1, characterized in that: The height of the plurality of blowing devices (1) arranged along the circumferential direction of the side wall of the middle ladle and directed toward the interior of the middle ladle is located at a middle position of the height of the molten steel level in the middle ladle.

3. A method for improving the purity of molten steel in a tundish according to claim 2, characterized in that: The number of the plurality of blowing devices (1) arranged along the circumferential direction of the side wall of the middle package and directed toward the interior of the middle package is 6 to 12 and are evenly distributed.

4. A method for improving the purity of molten steel in a tundish according to claim 3, characterized in that: The plurality of blowing devices (1) arranged along the circumferential direction of the side wall of the middle bag and directed toward the interior of the middle bag are made of magnesia refractory material and include a diffused air-permeable block (a), an air inlet block (c) and a joint (d) connected together.

5. A method for improving the purity of molten steel in a tundish according to claim 4, characterized in that: The MgO in the magnesia refractory material is ≥85%.

6. A method for improving the purity of molten steel in a tundish according to claim 1, characterized in that: The included angle α between the blowing direction of the blowing device (1) and the horizontal plane is 5-10 degrees.

7. A method for improving the purity of molten steel in a tundish according to claim 6, characterized in that: The argon pressure of the blowing device (1) is 0.4-0.6 MPa, and the flow rate is 30-50 L / min.

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