Method for increasing the service life of a tundish

Abstract

The application relates to a method for prolonging the service life of a tundish, which comprises the following steps: S1: in the ladle steelmaking production, calcium cored wire is fed in batches to a refining furnace and a vacuum furnace; S2: the end-point sulfur content of a converter is controlled to be below 0.005%; S3: after the composition and temperature of molten steel are adjusted, the calcium cored wire is fed in the refining process; S4: the excessive Al2O3 and sulfides in the molten steel are promoted to float up through argon soft stirring operation, and the floated Al2O3 and sulfides are removed; S5: the molten steel after the refining process enters a vacuum process to perform cyclic degassing; S6: after the cyclic degassing, 150-200 meters of calcium cored wire is fed again; and S7: when the molten steel is continuously cast to 9-12 furnaces, the submerged entry nozzle is replaced. Through the method for adjusting the calcium treatment process and reducing the production of low-melting-point calcium aluminate to inhibit the erosion of a stopper, and the measure of replacing the submerged entry nozzle on line in the casting process, the service life of the tundish is prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steelmaking, and particularly relates to a method for prolonging the service life of a tundish. BACKGROUND

[0002] The service life of the tundish is closely related to the stability of the long nozzle of the ladle, the tundish stopper and the submerged nozzle of the crystallizer. In the continuous casting process, the erosion control of the tundish stopper and the submerged nozzle is the key to realizing high reliability continuous casting. The stopper, as the controller of the tundish steel flow channel, is installed in the tundish, and through the cooperation of the stopper and the flow control area of the tundish upper nozzle bowl, the flow of the steel into the crystallizer is accurately controlled, which is matched with the drawing speed to ensure the stability of the liquid level of the steel in the crystallizer, and the safe shutdown is realized at the end of the tundish casting. Therefore, the condition of the stopper plays a crucial role in the smoothness of the entire casting process. However, during the use of the tundish stopper, especially when producing calcium-treated steel, the head erosion affects the control of the steel flow, and in severe cases, it leads to the loss of control of the steel flow and the stoppage of the continuous casting. At the same time, the erosion of the calcium-treated steel to the slag line position of the submerged nozzle easily leads to the thinning and porosity of the nozzle wall, which also affects the service life of the tundish. In actual production, the service life of the tundish does not exceed 600 minutes, which adversely affects the production cost and quality.

[0003] Based on the above problems, it is necessary to provide a method for prolonging the service life of a tundish. SUMMARY

[0004] The purpose of the present application is to provide a method for prolonging the service life of a tundish to prolong the service life of the tundish.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] A method for prolonging the service life of a tundish, comprising the steps of:

[0007] S1: In the production of ladle steelmaking, batch feeding of calcium cored wire is carried out in the two processes of refining furnace and vacuum furnace;

[0008] S2: The sulfur content at the end of the converter is controlled to be below 0.005%;

[0009] S3: In the refining process, after the composition and temperature of the molten steel are adjusted, the calcium cored wire is fed;

[0010] S4: The excess Al2O3 and sulfides in the molten steel are promoted to float up by argon soft stirring operation, and the floated Al2O3 and sulfides are removed;

[0011] S5: After the refining process, the molten steel enters the vacuum process for cyclic degassing;

[0012] S6: After the degassing, 150-200 meters of calcium cored wire is fed again;

[0013] S7: The submerged entry nozzle is replaced when the molten steel is continuously cast for 9-12 heats.

[0014] Preferably, in the method for prolonging the service life of the tundish, in step S7, the submerged entry nozzle is replaced when the molten steel is continuously cast for 10-12 heats.

[0015] Preferably, in the method for prolonging the service life of the tundish, in step S7, the submerged entry nozzle is replaced when the molten steel is continuously cast for 9-10 heats.

[0016] Preferably, in the method for prolonging the service life of the tundish, in step S7, the temperature of the molten steel is controlled within a preset temperature range before the submerged entry nozzle is replaced.

[0017] Preferably, in the method for prolonging the service life of the tundish, in step S7, the casting superheat is increased and precisely controlled at 29±3℃ when the molten steel is continuously cast for 9-12 heats.

[0018] Preferably, in the method for prolonging the service life of the tundish, in step S1, 300-400 meters of calcium cored wire is fed in batches to the refining furnace and the vacuum furnace for 180-ton ladle steelmaking production.

[0019] Preferably, in the method for prolonging the service life of the tundish, in step S3, 150-200 meters of calcium cored wire is fed after the composition and temperature of the molten steel are adjusted, and the amount of the 150-200 meters of calcium cored wire is less than that of the 300-400 meters of calcium cored wire.

[0020] The method for prolonging the service life of the tundish has the advantages that the erosion of the stopper is inhibited by adjusting the calcium treatment process to reduce the generation of low-melting-point calcium aluminate, and the service life of the tundish is prolonged by replacing the submerged entry nozzle online during the casting process. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a flowchart of the method for prolonging the service life of the tundish according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present application, but not to limit the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings for the convenience of description, rather than all the structures.

[0023] As Figure 1As shown, the embodiment discloses a method for prolonging the service life of a tundish, which comprises the following steps:

[0024] S1: In the steel ladle steelmaking production, calcium cored wire is fed in batches in the two processes of a refining furnace and a vacuum furnace;

[0025] S2: The sulfur content at the end point of the converter is controlled to be below 0.005%, so as to create conditions for reducing inclusions;

[0026] S3: After the composition and temperature of the molten steel are adjusted in the refining process, a small amount of calcium cored wire is fed in;

[0027] S4: The excess Al2O3 and sulfides in the molten steel are promoted to float up through argon soft stirring operation, and then the floated Al2O3 and sulfides are removed, so that the purity of the molten steel is preliminarily improved;

[0028] S5: The molten steel after the refining process enters a vacuum process to perform cyclic degassing;

[0029] S6: After the cyclic degassing, 150-200 meters of calcium cored wire is fed again, so that the Al2O3 inclusions in the molten steel are thoroughly removed;

[0030] S7: When the molten steel is continuously cast to 9-12 furnaces, the submerged entry nozzle is replaced.

[0031] As a preferred scheme, in step S7, when the molten steel is continuously cast to 10-12 furnaces, the submerged entry nozzle is replaced. Or as a preferred scheme, in step S7, when the molten steel is continuously cast to 9-10 furnaces, the submerged entry nozzle is replaced.

[0032] In step S7, before the submerged entry nozzle is replaced, the temperature of the molten steel is accurately controlled in a preset temperature range, so as to ensure that the time of continuous casting of the molten steel is synchronized with the service life of the tundish.

[0033] In step S7, when the molten steel is continuously cast to 9-12 furnaces, the casting superheat is increased and accurately controlled at 29±3℃;

[0034] In step S1, for 180-ton steel ladle steelmaking production, 300-400 meters of calcium cored wire is fed in batches in the two processes of a refining furnace and a vacuum furnace; further, in step S3, after the composition and temperature of the molten steel are adjusted, 150-200 meters of a small amount of calcium cored wire is fed in;

[0035] The embodiment prolongs the service life of the tundish by adjusting the calcium treatment process, reducing the method of producing low-melting-point calcium aluminate to inhibit the erosion of the stopper, and cooperating with the measure of replacing the submerged entry nozzle online during the casting process.

[0036] The calcium treatment process is adjusted from the original vacuum furnace one-time calcium wire feeding process to the refining furnace and vacuum furnace batch feeding of small amount of calcium wire process. Through improving the cleanliness of molten steel and the calcium wire batch feeding process, the erosion speed of the stopper and the submerged entry nozzle can be effectively slowed down.

[0037] In this embodiment, the fast-changing submerged entry nozzle is used, and the molten steel is continuously poured into 10-12 furnaces to replace the submerged entry nozzle. The temperature of the molten steel during the replacement period is precisely controlled in advance to ensure that the service life of the tundish is extended from 600 minutes to 840 minutes.

[0038] Factors affecting the service life of the tundish: causes of stopper and submerged entry nozzle erosion:

[0039] Because the aluminum deoxidized steel must remove excess oxygen from the molten steel during production, high melting point Al2O3 inclusions (melting point 2054℃) inevitably exist in the steel, which is in a solid state at the pouring temperature (1500-1600℃) and is easily accumulated at the tundish nozzle to cause blockage. In industrial production, calcium wire is added to the aluminum deoxidized molten steel in the vacuum furnace process for calcium treatment, which can change the morphology of aluminum oxide inclusions, generate 12CaO·7Al2O3 low melting point (1455℃) intermediate phase, and is beneficial to the aggregation and floating of inclusions, so that a large amount of deoxidation products are removed from the molten steel before entering the tundish, improving the cleanliness of the steel, reducing the blockage of the tundish nozzle, and ensuring the smoothness of continuous casting. In addition, calcium treatment can ensure that the calcium-sulfur ratio in the molten steel meets the production requirement of greater than 1.5, prevent the formation of manganese sulfide and other inclusions to pollute the molten steel, and avoid the decline of the internal quality of the product.

[0040] The tundish stopper is aluminum-carbon (Al2O3-C), and the head contains about 40% Al2O3. In addition to the denaturation and floating of Al2O3 in the molten steel by calcium treatment, excessive [Ca] and [CaO] will form a large amount of low melting point calcium aluminate with Al2O3 in the stopper matrix flowing into the molten steel and slag, resulting in the loss of Al2O3 in the head of the stopper, and ultimately causing the erosion of the head of the stopper. The submerged entry nozzle has the same problem, and calcium treated molten steel will accelerate the erosion.

[0041] For 180-ton ladle steel production, the specific measures to improve the service life of the tundish are:

[0042] 1) Adjust the calcium treatment process of pipeline steel, feed 400-500 meters of calcium cored wire in a single time in vacuum furnace, and optimize to feed 300-400 meters of calcium cored wire in batches in two processes of refining and vacuum. That is, control the sulfur content at the converter endpoint of pipeline steel to be less than 0.005%, to provide conditions for reducing sulfur-based oxide inclusions. After the composition and temperature of the molten steel are adjusted in the next refining process, feed 150-200 meters of small amount of calcium cored wire, promote the floating removal of excess Al2O3 and sulfides in the molten steel through argon soft stirring operation, and preliminarily improve the purity of the molten steel. After the refining is completed, the molten steel will enter the next vacuum process, and 150-200 meters of calcium cored wire is fed again after circulating degassing, so that the Al2O3 inclusions in the molten steel are removed more thoroughly.

[0043] 2) The fast-changing submerged entry nozzle is used, the molten steel is continuously cast to 9-10 furnaces, the submerged entry nozzle is replaced, the temperature of the molten steel during the replacement is precisely controlled in advance, and the continuous casting time of the molten steel is synchronized with the service life of the tundish. In the continuous casting production process, when the molten steel is continuously cast to 9-10 furnaces, the pouring superheat must be increased and precisely controlled at 29±3℃, so as to reduce the influence of the water nozzle panel on the cold steel and the argon sealing effect.

[0044] After the two processes of feeding calcium cored wire in batches and replacing the submerged entry nozzle are adopted in the embodiment, the problems of calcium treatment steel stopper and submerged erosion are effectively improved, and the service life of the tundish is prolonged from 600 minutes to 840 minutes

[0045] Obviously, the above embodiments of the application are only examples for clearly illustrating the application, and are not intended to limit the implementation modes of the application. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the application. It is unnecessary and impossible to enumerate all the implementation modes. Any modification, equivalent substitution and improvement made within the spirit and principle of the application shall be included in the protection scope of the claims of the application.

Claims

1. A method for improving the service life of an intermediate batch, characterized in that, Including the following steps: S1: In ladle steelmaking, calcium cored wire is fed into the refining furnace and vacuum furnace in batches. S2: Control the sulfur content at the converter endpoint to be below 0.005%; S3: In the refining process, after the composition and temperature of the molten steel are adjusted, calcium cored wire is fed in; S4: The argon gas soft stirring operation promotes the floating of excess Al2O3 and sulfides in the molten steel, thereby removing the floating Al2O3 and sulfides. S5: After the refining process, the molten steel enters the vacuum process for circulation and degassing; S6: After degassing, feed in another 150-200 meters of calcium-coated thread; S7: When molten steel is continuously poured to 9-12 heats, replace the submerged entry nozzle; In step S7, when the molten steel is continuously poured into 9-12 heats, the pouring superheat is increased and precisely controlled at 29±3℃; In step S1, for the 180-ton ladle steelmaking production, 300-400 meters of calcium cored wire are fed into the refining furnace and vacuum furnace in batches; In step S3, after the composition and temperature of the molten steel are adjusted, 150-200 meters of calcium-coated wire are fed in, and the amount of 150-200 meters of calcium-coated wire is less than 300-400 meters of calcium-coated wire.

2. The method for improving the service life of intermediate batches according to claim 1, characterized in that: In step S7, when molten steel is continuously poured into 10-12 heats, the submerged entry nozzle is replaced.

3. The method for improving the service life of intermediate batches according to claim 1, characterized in that: In step S7, when the molten steel is continuously poured to 9-10 heats, the submerged entry nozzle is replaced.

4. The method for improving the service life of intermediate batches according to claim 1, characterized in that: In step S7, before replacing the submerged nozzle, the temperature of the molten steel is controlled within a preset temperature range.

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