Method for replacing crystallizer casting powder through steel ball bush casting of slab continuous casting machine

Abstract

The invention relates to the field of ferrous metallurgy, in particular to a method for replacing casting powder for steel sleeve casting of a slab continuous casting machine, which is characterized by comprising the following steps: cleaning of casting powder blocks in a crystallizer, control of the residual amount of the casting powder, control of a continuous casting process during replacement of the casting powder, recovery time of the pulling speed of the continuous casting machine to normal, and inspection of sleeve casting blanks.

Description

Technical Field

[0001] The invention relates to the field of iron and steel metallurgy, in particular to a method for replacing protective slag in steel casting of a slab continuous casting machine. Background Art

[0002] Since the emergence of continuous casting technology, efficient continuous casting production has always been the goal pursued by enterprises. With the development of related technologies, the quality of continuous casting refractory materials has been greatly improved, and the number of continuous casting furnaces of continuous casting machines has continued to rise. However, due to the current severe steel market situation, the small number of orders has caused a decrease in the number of continuous casting furnaces of continuous casting machines. The steelmaking process can smelt steels with large differences in composition. At this time, the number of continuous casting furnaces becomes a limiting link. The protective slag used when pouring different steels is also different. However, in the process of steel type overcasting, the protective slag of the corresponding steel type is forced to be replaced. In the process of changing the protective slag, cracks in the casting or production accidents may occur, which will bring certain losses to the enterprise. In order to meet the production needs of overcasting and reduce losses, a method for replacing protective slag for steel type overcasting of slab continuous casting machines was invented. Summary of the invention

[0003] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a method for replacing protective slag during steel casting of a slab continuous casting machine, and the technical solution to the problem is to include the following steps: cleaning of protective slag blocks in the crystallizer, control of the residual amount of protective slag, continuous casting process control during replacement of protective slag, time for the continuous casting machine to return to normal, and inspection of the cast slab; Step 1: Cleaning of protective slag blocks: When the previous furnace of the cast furnace is about to be finished, reduce the amount of mold protective slag added. When the thickness of the protective slag powder layer in the crystallizer is 3-5mm, operate the crystallizer liquid level control button on the operation panel to properly lower the crystallizer liquid level and leak out some slag bars. Use an oxygen tube to clean the protective slag bars and slag blocks until there is no slag block larger than 5mm left. During the cleaning of the protective slag blocks, ensure that the molten steel in the crystallizer is not exposed. Step 2: Control the residual amount of protective slag: After cleaning the protective slag block, use a shovel to scrape off the powder slag layer and part of the sintered layer. The sintered layer is closely related to the viscosity of the protective slag. Ensure that there is no leakage of molten steel during the operation. The area about 100mm away from the narrow surface of the crystallizer does not need to be cleaned. Avoid touching the molten steel during the operation; Step 3: Control the continuous casting process during the replacement of protective slag: After the above conditions are met, reduce the casting speed of the continuous casting machine to the lower limit of the process casting speed, that is, the casting speed corresponding to the minimum quality requirement, and start pouring the next bag of molten steel at the same time; gradually add protective slag corresponding to another steel grade into the crystallizer, and the amount of protective slag added is sufficient to ensure that the sintering layer does not leak red, ensuring the principle of small amounts and multiple times; Step 4: Time for the continuous casting machine to resume normal casting speed: When the amount of molten steel poured from the first ladle reaches about 1 / 3 of the effective volume of the tundish, the normal casting speed of the corresponding steel grade can be gradually restored; Step 5. Inspection of cast ingots: From the time the protective slag is replaced to the time the normal pulling speed is restored, pay attention to the heat flux density of the crystallizer. The heat flux density should be within a reasonable range. When the heat flux density is abnormal, reduce the pulling speed appropriately and maintain the pulling speed until the heat flux density returns to the normal value of the corresponding steel grade. The ingots in the abnormal heat flux period should be taken offline for surface inspection. The surface temperature of the ingot is about 350°C. If there are defects, clean them up in time to avoid surface defects after rolling.

[0004] Preferably, the oxygen tube is made of steel and has an outer diameter of φ5 mm and an inner diameter of φ3 mm.

[0005] The beneficial effects of the present invention are: Through the implementation of the invention, the success rate of steel type casting of slab continuous casting machine has been achieved, the overall production efficiency of continuous casting machine has been improved, and certain benefits have been brought to the enterprise. Through the implementation of the invention, the surface problems of the casting in the casting part area have been improved, the qualified rate of casting quality has been improved, and the foundation for quality improvement has been laid. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION

[0007] The following is combined with Figure 1 The specific implementation modes of the present invention are further described in detail.

[0008] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0009] Example 1, citing the production of peritectic steel and medium carbon steel on a 230mm×1650mm specification continuous casting machine for casting, the peritectic steel is cast in the front of the casting, and the medium carbon steel is cast in the back, and the weight of the molten steel in the ladle is 150 tons; Step 1: When there is 50±3 tons of molten steel remaining in the last ladle of peritectic steel, stop adding peritectic steel protection slag to the crystallizer; Step 2: As the molten steel continues to be poured, the protective slag in the crystallizer is gradually consumed. When there is about 20±2 tons left in the ladle, the powder slag inside the crystallizer has been almost consumed. Operate the crystallizer liquid level control button on the operation panel to appropriately lower the crystallizer liquid level, leak out some slag bars, use an oxygen tube to clean the slag bars and slag blocks in the crystallizer, and use a shovel to shovel away the powder slag layer and part of the sintering layer. The sintering layer is closely related to the viscosity of the protective slag. Do not clean the area about 80mm away from the narrow surface of the crystallizer. Ensure that the molten steel is not exposed during the cleaning period; Step 3: After the casting of peritectic steel is completed and the first batch of medium carbon steel is poured, the pulling speed is reduced to 0.85m / min; Step 4: After the medium carbon steel is poured, gradually add medium carbon steel protection slag into the crystallizer in small amounts and multiple times; Step 5: The weight of the molten steel in the ladle is 150 tons, and the weight of the effective volume of the middle ladle is 45±2 tons. When the weight of the molten steel in the ladle reaches 100±2 tons, the pulling speed is increased by 0.05m / min every 3 minutes, and gradually increased to 1.2m / min; Step 6: From the time the mold slag is replaced to the time the normal casting speed is restored, the heat flux density of the crystallizer is paid attention to. The heat flux density is maintained at 1.2±0.15MW / m2, and there is no large fluctuation in the heat flux density. The ingots are allocated according to the process and put into storage; Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for replacing mold slag in steel casting of a slab continuous casting machine, characterized in that: The following steps are involved: Cleaning of mold slag blocks, control of residual mold slag, continuous casting process control during mold slag replacement, time for continuous casting machine casting speed to return to normal, and inspection of cast billets; Step 1: Cleaning of protective slag blocks: When the previous furnace of the cast furnace is about to be finished, reduce the amount of mold protective slag added. When the thickness of the protective slag powder layer in the crystallizer is 3-5mm, operate the crystallizer liquid level control button on the operation panel to properly lower the crystallizer liquid level and leak out some slag bars. Use an oxygen tube to clean the protective slag bars and slag blocks until there is no slag block larger than 5mm left. During the cleaning of the protective slag blocks, ensure that the molten steel in the crystallizer is not exposed. Step 2: Control the residual amount of protective slag: After cleaning the protective slag block, use a shovel to scrape off the powder slag layer and part of the sintered layer. The sintered layer is closely related to the viscosity of the protective slag. Ensure that there is no leakage of molten steel during the operation. The area about 100mm away from the narrow surface of the crystallizer does not need to be cleaned. Avoid touching the molten steel during the operation; Step 3: Control the continuous casting process during the replacement of protective slag: After the above conditions are met, reduce the casting speed of the continuous casting machine to the lower limit of the process casting speed, that is, the casting speed corresponding to the minimum quality requirement, and start pouring the next bag of molten steel at the same time; gradually add protective slag corresponding to another steel grade into the crystallizer, and the amount of protective slag added is sufficient to ensure that the sintering layer does not leak red, ensuring the principle of small amounts and multiple times; Step 4: Time for the continuous casting machine to resume normal casting speed: When the amount of molten steel poured from the first ladle reaches about 1 / 3 of the effective volume of the tundish, the normal casting speed of the corresponding steel grade can be gradually restored; Step 5. Inspection of cast ingots: From the time the protective slag is replaced to the time the normal pulling speed is restored, pay attention to the heat flux density of the crystallizer. The heat flux density should be within a reasonable range. When the heat flux density is abnormal, reduce the pulling speed appropriately and maintain the pulling speed until the heat flux density returns to the normal value of the corresponding steel grade. The ingots in the abnormal heat flux period should be taken offline for surface inspection. The surface temperature of the ingot is about 350°C. If there are defects, clean them up in time to avoid surface defects after rolling.

2. The method for replacing mold slag for steel grades in a slab continuous casting machine according to claim 1, characterized in that: The oxygen tube is made of steel and has an outer diameter of φ5 mm and an inner diameter of φ3 mm.

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