A method for reducing the cutting head length of the continuous casting starting slab

Abstract

The present application provides a method for reducing the cutting head length of the continuous casting starting slab. According to the deoxidation system, it is required that the dosage of the deoxidizer for the starting furnace heat be increased by 10 - 30 kg on the original basis, which reduces the oxidizability of the molten steel and reduces the problem of excessive subcutaneous bubbles in the slab caused by overoxidation of the molten steel; it is required that the tundish baking temperature reach above 950 °C and the liquid level of the starting tundish be increased to above 10 - 15 tons, which reduces the problem of excessive subcutaneous bubbles in the slab caused by improper tundish baking; during starting casting, aluminum wire is placed on the inner arc side of the mold to deoxidize the starting slab head, effectively reducing the problem of excessive subcutaneous bubbles in the slab caused by the moisture of the materials used for the stopper ingot; it can effectively reduce the subcutaneous bubbles of the starting slab, improve the internal quality of the starting slab, reduce the cutting head length by more than 80%, reduce the cutting head length to 0.8 - 1.2 m, improve the slab yield, and greatly reduce the cost of the continuous casting process.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking continuous casting, and particularly to a method for reducing the cut head length of the starting casting blank in continuous casting. Background Art

[0002] With the annual increase in the scale of steel investment in China, the steel output has also been released year by year, and the problem of overcapacity in domestic steel has become increasingly prominent. In such a large market environment, cost reduction and efficiency improvement have become important means for each enterprise to survive. As a steel enterprise, in the face of such a severe market situation, cost management is naturally a top priority. In a sense, cost determines the competitiveness of a steel enterprise. On the premise of ensuring the quality of steel products, cost reduction is an effective measure to improve the economic benefits of steel enterprises.

[0003] In bloom continuous casting production, the billet yield is the main economic and technical index to measure the production of the caster. The higher the billet yield, the lower the cost of the continuous caster relatively, and the less waste of the produced billets. The billet yield index is directly related to the tundish residue, the intermediate ladle residue, the cut head, the cut tail, the process scrap, the cut seam loss, and the scale loss, etc. If the continuous casting cost is to be reduced and the billet yield is to be increased, it is necessary to reduce the tundish residue, the intermediate ladle residue, the cut head, the cut tail, the process scrap, and the scale loss, etc. After each casting of the bloom continuous caster, because there are easy-to-occur quality problems such as subcutaneous bubbles in the billet head, the billet head needs to be cut off. The length of the cut billet head is generally controlled at 3.5 - 4 m, resulting in great waste. If the cutting position of the billet head is lower than 3.5 m, due to defects such as subcutaneous bubbles inside the billet, the surface of the rolled material will peel off during the subsequent rolling process, resulting in the rejection of the rolled material. In order to further reduce the cut head length of the starting casting blank, it is necessary to solve the problem of subcutaneous bubbles in the starting casting blank.

[0004] Therefore, how to solve the problem of subcutaneous bubbles in the starting casting blank has become a restrictive link in reducing the cut head length at the start of casting, and reducing subcutaneous bubbles inside the starting casting blank has become a technical problem. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for reducing the cut head length of the starting casting blank in continuous casting.

[0006] To solve the above technical problems, the technical solution proposed by the present invention is as follows:

[0007] A method for reducing the cut head length of the starting casting blank in continuous casting, comprising the following steps carried out in sequence:

[0008] 1) Converter process:

[0009] After the molten steel is smelted and tapped from the converter, according to the composition of the carbon drawing, when the carbon drawing < 0.05%, the dosage of the deoxidizer for the first tapping heat is required to be 0.78 - 0.85 kg / t of molten steel;

[0010] When the carbon drawing ≥ 0.05%, the dosage of the deoxidizer for the first tapping heat is required to be 0.64 - 0.71 kg / t of molten steel;

[0011] 2) Continuous casting process:

[0012] Requirements for tundish baking: Bake with low fire for 1 - 1.5 hours, medium fire for 0.5 - 1 hour, high fire for 2 - 2.5 hours, and the inner wall temperature of the tundish is required to be ≥ 950 °C at the end of baking;

[0013] The inner wall of the mold shall be kept dry, and there shall be no residual mold powder. The inner wall of the mold is dry and free of moisture;

[0014] Check and confirm the asbestos cloth, hook head, and cold materials used, and they are required to be dry, rust-free, and oil-free;

[0015] Spread a layer of magnetic separation iron particles with a thickness of 3 - 5 mm above the asbestos cloth;

[0016] Use a roller brush to apply lubricating oil to the inner wall of the mold. It is prohibited to use an oil filling pipe to apply lubricating oil to the inner wall of the mold to prevent excessive oil filling;

[0017] Place 4 - 6 aluminum wires with a diameter of 1.0 - 2.0 mm and a length of 600 - 700 mm evenly on the inner arc side of the mold. The aluminum wires are prohibited from sticking to the inner wall of the mold, and it is prohibited to pick out the aluminum wires during the tapping process;

[0018] Increase the height of the tapping liquid level of the tundish. It is required to start tapping when the molten steel tonnage in the tundish reaches more than 10 - 15 tons;

[0019] During the tapping process, control the addition amount of lubricating oil in the mold, and the flame height is controlled to be 200 - 300 mm higher than the upper opening of the mold.

[0020] Preferably, the flow rate of fuel gas during low-fire baking is 500 - 750 Nm 3 / h, and the baking temperature is 200 °C - 600 °C;

[0021] The flow rate of fuel gas during medium-fire baking is 750 - 850 Nm 3 / h, and the baking temperature is 600 °C - 800 °C;

[0022] The flow rate of fuel gas during high-fire baking is 850 - 950 Nm 3 / h, and the baking temperature is 800 °C - 1100 °C.

[0023] The present invention has achieved the following beneficial technical effects:

[0024] (1). According to the deoxidation system, it is required that the dosage of the deoxidizer for the starting casting heat be increased by 10 - 30 kg on the original basis, effectively reducing the oxidizability of the molten steel and reducing the problem of excessive subcutaneous bubbles in the continuous casting billets caused by overoxidation of the molten steel;

[0025] (2). It is required that the baking temperature of the tundish reaches above 950 °C, and the liquid level of the starting tundish is increased to above 10 - 15 tons, reducing the problem of excessive subcutaneous bubbles in the continuous casting billets caused by improper baking of the tundish;

[0026] (3). During starting casting, place aluminum wire on the inner arc side of the mold to deoxidize the starting billet head, effectively reducing the problem of excessive subcutaneous bubbles in the continuous casting billets caused by the moisture of the materials used for the stopper ingot;

[0027] In the actual production process, using this method can effectively reduce the problem of subcutaneous bubbles in the starting continuous casting billets, improve the internal quality of the starting continuous casting billets, reduce the cut - head length by more than 80%, reduce the cut - head length to 0.8 - 1.2 m, improve the billet yield, and greatly reduce the cost of the continuous casting process. Description of the Drawings

[0028] Figure 1 It is a macro - etch sample at the 0.8 - meter position of the head of the billet prepared by a method for reducing the cut - head length of the starting continuous casting billet provided in Embodiment 1 of the present application. Detailed Embodiments

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The present application provides a method for reducing the cut - head length of the starting continuous casting billet, including the following steps carried out in sequence:

[0031] 1) Converter process:

[0032] After the molten steel is smelted and tapped from the converter, according to the tapping carbon content, when the tapping carbon < 0.05%, it is required that the dosage of the deoxidizer for the starting casting heat be 0.78 - 0.85 kg / t of molten steel;

[0033] When the tapping carbon ≥ 0.05%, it is required that the dosage of the deoxidizer for the starting casting heat be 0.64 - 0.71 kg / t of molten steel;

[0034] 2) Continuous casting process:

[0035] Tundish baking requirements: Bake with low fire for 1 - 1.5 hours, medium fire for 0.5 - 1 hour, high fire for 2 - 2.5 hours. When baking ends, the inner wall temperature of the tundish is required to be ≥950°C;

[0036] The inner wall of the mold shall be kept dry, and there shall be no residual mold powder. The inner wall of the mold is dry and free of moisture;

[0037] Check and confirm the asbestos cloth, hook head, and cold materials used, and they are required to be dry, rust-free, and oil-free;

[0038] Sprinkle a layer of magnetic separation iron particles with a thickness of 3 - 5 mm above the asbestos cloth;

[0039] Use a roller brush to apply lubricating oil on the inner wall of the mold. It is prohibited to use an oil filling pipe to apply lubricating oil on the inner wall of the mold to prevent excessive oil filling;

[0040] Uniformly place 4 - 6 aluminum wires with a diameter of 1.0 - 2.0 mm and a length of 600 - 700 mm on the inner arc side of the mold. The aluminum wires are prohibited from sticking to the inner wall of the mold, and it is prohibited to pick out the aluminum wires during the starting casting process;

[0041] Increase the starting casting liquid level height of the tundish. It is required to start casting when the molten steel tonnage in the tundish reaches 10 - 15 tons or more;

[0042] During the starting casting process, control the addition amount of lubricating oil in the mold, and the flame height is controlled at 200 - 300 mm above the upper opening of the mold.

[0043] In an embodiment of the present application, the flow rate of fuel gas during low - fire baking is 500 - 750 Nm 3 / h, and the baking temperature is 200°C - 600°C;

[0044] The flow rate of fuel gas during medium - fire baking is 750 - 850 Nm 3 / h, and the baking temperature is 600°C - 800°C;

[0045] The flow rate of fuel gas during high - fire baking is 850 - 950 Nm 3 / h, and the baking temperature is 800°C - 1100°C.

[0046] The methods and devices not described in detail in the present invention are all prior arts and will not be elaborated.

[0047] To further understand the present invention, the following describes in detail a method for reducing the cut - head length of the continuously cast starting casting billet provided by the present invention in combination with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0048] Example 1

[0049] A method for reducing the cutting length of the continuous casting starting billet. Taking a 150-ton converter production line as an example, the continuous caster type is an eight-machine eight-strand, 165×165mm square billet continuous caster, and the steel grade is low-carbon alloy steel with the carbon content in the steel controlled at 0.22% - 0.25%. The method includes the following steps carried out in sequence:

[0050] 1) Converter process:

[0051] After the molten steel is smelted and tapped from the converter, the tapping carbon content is 0.1251%. According to the deoxidation system, it is required that the dosage of the deoxidizer for the starting tapping heat be increased by 10 - 30 kg on the original basis, and the actual addition amount of the deoxidizer is 93 kg;

[0052] 2) Continuous casting process:

[0053] The tundish is baked with low fire for 1 hour, medium fire for 0.7 hour, and high fire for 2.5 hours. After the baking is completed, the inner wall temperature of the tundish is 1035℃;

[0054] When baking with low fire, the flow rate of the fuel gas is 600 Nm 3 / h, and the baking temperature is 500℃;

[0055] When baking with medium fire, the flow rate of the fuel gas is 800 Nm 3 / h, and the baking temperature is 700℃;

[0056] When baking with high fire, the flow rate of the fuel gas is 900 Nm 3 / h, and the baking temperature is 1100℃;

[0057] The inner wall of the mold is dry without residual mold powder;

[0058] The asbestos cloth, hook head, and cold materials used are dry, rust-free, and oil-free;

[0059] After stuffing the asbestos cloth, sprinkle a layer of magnetic separation iron particles with a thickness of 3 mm on the upper part;

[0060] Use a roller brush to apply lubricating oil on the inner wall of the mold;

[0061] Place 5 aluminum wires evenly on the inner arc side of the mold. The aluminum wires are strictly prohibited from sticking to the inner wall of the mold. During the starting pouring process, it is strictly prohibited to pick out the aluminum wires;

[0062] When the molten steel tonnage in the tundish reaches 12 tons, the tundish starts pouring;

[0063] During the starting pouring process, control the addition amount of the lubricating oil in the mold, and control the flame height of the burning lubricating oil to be 200 - 300 mm higher than the upper mouth of the mold.

[0064] For the continuously cast billets produced by the process method described in Example 1, one macrostructure sample was taken at the position of 0.8 m to analyze the internal quality of the continuously cast billets. No subsurface blowholes were found, and the macrostructure samples are as shown in the appendix Figure 1 and the grading results are as shown in Table 1 below:

[0065] Table 1 Macrostructure sample grading table at the position of 0.8 m at the head of the continuously cast billets prepared in Example 1

[0066] Flow number Central porosity Central segregation Shrinkage cavity Corner crack Subsurface crack Intermediate crack Central crack Subsurface blowhole Inclusion 1 1 0.5 0 0 0 0 0 0 0.5 2 0.5 0 0.5 0 0.5 0 0 0 0.5 3 0.5 0 0.5 0 0 1 0 0 0.5 4 0 0.5 0 0 0.5 1 1 0 0.5 5 0 0.5 0 0 0.5 1 0 0 0.5 6 0 0 1 0 0 0.5 0 0 1 7 1.5 0 0 0 0 0 0 0 0.5 8 0.5 0.5 0 0.5 0 0.5 0 0 0.5

[0067] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for reducing the cut head length of the continuous casting starting billet, characterized in that, It includes the following steps carried out in sequence: 1) Converter process: After the molten steel is smelted and tapped in the converter, according to the composition of the carbon drawing, when the carbon drawing < 0.05%, the dosage of the deoxidizer for the starting tapping heat is required to be 0.78 - 0.85 kg / t of molten steel; When the carbon drawing ≥ 0.05%, the dosage of the deoxidizer for the starting tapping heat is required to be 0.64 - 0.71 kg / t of molten steel; 2) Continuous casting process: Requirements for tundish baking: Bake with low heat for 1 - 1.5 hours, medium heat for 0.5 - 1 hour, high heat for 2 - 2.5 hours, and the inner wall temperature of the tundish is required to be ≥ 950 °C at the end of baking; The flow rate of fuel gas during low-temperature baking is 500 - 750 Nm 3 / h, and the baking temperature is 200℃ - 600℃; The flow rate of the fuel gas during medium-fire baking is 750 - 850 Nm 3 / h, and the baking temperature is 600°C - 800°C; The flow rate of fuel gas during high-temperature baking is 850 - 950 Nm 3 / h, and the baking temperature is 800℃ - 1100℃; The inner wall of the mold shall be kept dry, and there shall be no residual mold powder. The inner wall of the mold is dry and free of moisture; Check and confirm the asbestos cloth, hook head, and cold materials used, and they are required to be dry, rust-free, and oil-free; Sprinkle a layer of magnetic separation iron particles with a thickness of 3 - 5 mm above the asbestos cloth; Use a roller brush to apply lubricating oil to the inner wall of the mold. It is prohibited to use an oil filling pipe to apply lubricating oil to the inner wall of the mold to prevent excessive oil filling; Evenly place 4 - 6 aluminum wires with a diameter of 1.0 - 2.0 mm and a length of 600 - 700 mm on the inner arc side of the mold. The aluminum wires are prohibited from sticking to the inner wall of the mold, and the aluminum wires are prohibited from being picked out during the starting tapping process; Raise the starting tapping liquid level height of the tundish, and it is required to start tapping when the molten steel tonnage in the tundish reaches more than 15 tons; During the starting tapping process, control the addition amount of lubricating oil in the mold, and the flame height of the burning lubricating oil is controlled to be 200 - 300 mm higher than the upper opening of the mold.

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