Swing-groove-free casting method of billet continuous casting machine

Abstract

The invention relates to the technical field of iron and steel smelting, in particular to a square billet continuous casting machine swing-groove-free casting method which comprises the steps that firstly, before casting, a tundish is baked through soft fire, medium fire and big fire; secondly, after baking is completed, 1.3-1.5 kg / flow of casting powder is used for filling a sizing water feeding opening of the tundish; 3, reinforcing the dummy ingot hook by using twisted steel; and fourthly, an oxygen pipe for pouring and drainage of the tundish is fixed in a threaded head fixing mode, and in the pouring process, large-flow oxygen is adopted for drainage. According to the method, the tundish, the dummy ingot hook and the oxygen drainage pipe are pretreated, the flow of drainage oxygen is regulated and controlled, groove-swinging-free casting of the square billet continuous casting machine is achieved, splashing of steel slag is reduced, and the molten steel recovery rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and particularly relates to a method for starting casting without a swing chute for a billet continuous casting machine. Background Art

[0002] In the process of steel production, the methods for solidifying molten steel into a formed shape mainly include the traditional ingot casting method and the continuous casting method. The traditional ingot casting method is to pour liquid molten steel into a pre-made ingot mold, and solidify it under conditions such as natural cooling or water spraying cooling. After the ingot is completely cooled, it is then removed from the ingot mold to obtain a cast billet. The traditional ingot casting method is relatively flexible, can produce castings with complex shapes according to needs, and has low requirements for the fluidity of molten steel. However, the production efficiency and metal yield are relatively low because the ingot needs to be heated, bloomed, etc., and this method consumes a large amount of energy. The continuous casting method, abbreviated as continuous casting, refers to the process of directly obtaining a cast billet by pouring, condensing, and cutting liquid molten steel with a continuous casting machine, and is an intermediate link connecting steelmaking and rolling. Continuous casting omits processes such as demolding, mold dressing, soaking of ingots, and blooming of ingots, significantly improves the production efficiency and metal yield of cast billets, and can effectively reduce energy consumption.

[0003] Starting casting of the tundish is a key link in continuous casting production. To prevent secondary oxidation of the steel flow and ensure the cleanliness of the molten steel, the existing technology usually adopts the method of combined stopper control and submerged nozzle pouring for protective casting during continuous casting. This pouring method has problems such as high refractory cost, short tundish life, short continuous casting time, and low molten steel yield. Continuous casting sizing pouring is a pouring method that does not require stopper control. This pouring method relies on the inner diameter of the nozzle to control the flow rate of molten steel injected into the mold, which not only improves the quality of continuous casting billets but also reduces the refractory cost and equipment spare parts cost. When starting casting of the tundish during continuous casting sizing pouring, generally, a swing chute is first used to divert the molten steel into an overflow basin behind the tundish car. After confirming that the steel flow is circular and strong, the swing chute is then moved to the preparation position, and the molten steel is injected into the mold, and the operator normally starts. The above operations have the following problems: 1. During the process of moving the swing chute, the splashing of steel slag is serious, and there is a safety hazard of scalding personnel; 2. Using the swing chute to divert the molten steel into the overflow basin reduces the molten steel recovery rate and is not conducive to cost control; 3. After the swing chute is used, it is necessary to clean the cold steel by manual oxygen burning and regularly replace the swing chute, which not only increases the labor intensity of the on-site personnel but also has certain safety and environmental protection hazards. Summary of the Invention

[0004] Aiming at the problems that the use of a swing chute in the continuous casting sizing pouring process can cause serious splashing of steel slag, low recovery rate of molten steel and high maintenance cost of the swing chute, the present invention provides a method for starting pouring without a swing chute for a billet continuous caster. By pre-treating the tundish, dummy bar and oxygen drainage pipe, and regulating the flow rate of the drainage oxygen, the billet continuous caster realizes starting pouring without a swing chute, reduces the splashing of steel slag and improves the recovery rate of molten steel.

[0005] The technical solution of the present invention is as follows: A method for starting pouring without a swing chute for a billet continuous caster, comprising the following steps: Step 1: Before starting pouring, bake the tundish with small fire, medium fire and large fire respectively to ensure that the temperature of the tundish bottom and the tundish nozzle reaches 1000-1100 °C; Step 2: After baking, fill the sizing upper nozzle of the tundish with protective slag at 1.3-1.5 kg / strand to prevent slag leakage during starting pouring; Step 3: Reinforce the dummy bar with threaded steel bars, and the number of cold materials around the dummy bar is 105-115 pieces, and the cold materials are steel bars; Step 4: Fix the oxygen pipe for tundish starting pouring drainage by means of thread head fixation. During starting pouring, large-flow oxygen drainage is adopted.

[0006] Further, in Step 1, the small fire is such that the flame does not touch the ladle lining, the medium fire is such that the flame just touches the ladle lining, and the large fire is such that the flame directly hits the tundish bottom and returns upward.

[0007] Further, in Step 1, while baking the tundish with large fire, oxygen-enriched baking is started, and the opening ratio of oxygen-enriched baking is 8%-12%, and the opening ratio of oxygen-enriched baking is preferably 10%.

[0008] Further, in Step 1, the baking time of the tundish with small fire is 1-1.5 h, preferably 1 h, the baking time of the tundish with medium fire is 1-1.5 h, preferably 1 h, and the baking time of the tundish with large fire is 2-3 h, preferably 2 h. During the baking of the tundish with large fire, the air volume is 85%-95%.

[0009] Further, in Step 2, the main components of the protective slag are CaO and SiO2, the CaO content in the protective slag is 33 wt%, and the SiO2 content in the protective slag is 28 wt%.

[0010] Further, in Step 3, the diameter of the threaded steel bar is 32-40 mm. The present invention adopts the method of welding the threaded steel bar to the dummy bar to reinforce the dummy bar.

[0011] Further, in Step 3, the strength of the connection between the dummy bar and the molten steel is increased.

[0012] Furthermore, in step 4, when the tundish is opened for pouring and drainage, the opening of the oxygen valve is opened to 75%-85%, preferably 80%, and a large flow of oxygen is used for drainage to avoid the occurrence of molten steel dispersion.

[0013] Furthermore, in step one, before pouring, a negative pressure furnace is used to ignite the fire.

[0014] The beneficial effects of the present invention are: The present invention provides a method for non-swinging slot casting of a square billet continuous casting machine. Before the tundish is cast, the tundish is baked with a low fire, a medium fire and a high fire respectively, so as to remove moisture in the lining material of the tundish, enhance the strength of the lining material of the tundish, reduce the temperature drop of the molten steel in the tundish, and improve the purity of the molten steel and the recovery rate of the molten steel; protective slag is used to fill the sizing upper water inlet of the tundish to prevent the leakage of the casting slag; the ingot hook is reinforced and the amount of cold material around the ingot hook is limited, so that the molten steel can enter the ingot hook area more easily to avoid the situation of starting to pull off; during the casting process, a large flow of oxygen is used for drainage to avoid the situation of molten steel scattering. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0016] Example 1 A method for casting a square billet continuous casting machine without a swing slot comprises the following steps: Step 1: After the tundish is built, first clean the waste refractory materials in the tundish thoroughly. Then, 2 hours before pouring, use a negative pressure furnace to ignite, and use a low fire to bake the tundish for 1 hour, use a medium fire to bake the tundish for 1 hour, and use a high fire to bake the tundish for 2 hours. When baking the tundish with a high fire, start oxygen-enriched baking at the same time. The opening ratio of oxygen-enriched baking is 10%, ensuring that the bottom of the tundish and the water inlet temperature of the tundish reach 1000℃ before pouring. During the baking of the tundish with a high fire, the air volume is 85%. Among them, the low fire is based on the flame not touching the lining, the medium fire is based on the flame just touching the lining, and the high fire is based on the flame rushing directly to the bottom of the tundish and returning upward. After baking, clean the debris in the upper water inlet of the tundish half an hour before pouring to improve the stability of the steel flow when the tundish is poured.

[0017] Step 2: After baking, use 1.3kg / stream of protective slag to fill the sizing upper water inlet of the tundish (during the production of square billets, the molten steel is pulled out from the square billet continuous casting machine in seven streams, and 1.3kg / stream here means that 1.3kg of protective slag is used for each stream). The main components of the protective slag are CaO and SiO2, with a CaO content of 33wt% and a SiO2 content of 28wt% in the protective slag.

[0018] Step 3: The dummy hook is reinforced with a 32mm diameter threaded steel bar. The reinforced dummy hook is used to complete the dummy work. The number of cold materials around the dummy hook is 110. The cold materials are cut steel bars, one for each. The strength of the connection between the dummy rod and the molten steel is increased by welding threaded steel bars.

[0019] Step 4: Use a wire head to fix the oxygen pipe for the tundish opening and drainage. During the tundish opening and drainage process, open the oxygen valve to 80% and use a large flow of oxygen for drainage.

[0020] The molten steel yield of this embodiment is 99.5%, and no molten steel pulling off or leakage occurs.

[0021] Example 2 A method for casting a square billet continuous casting machine without a swing slot comprises the following steps: Step 1: After the tundish is built, first clean the waste refractory materials in the tundish thoroughly. Then, 2 hours before pouring, use a negative pressure furnace to ignite, and use a low fire to bake the tundish for 1.5 hours, use a medium fire to bake the tundish for 1 hour, and use a high fire to bake the tundish for 3 hours. Turn on the high fire to bake the tundish while turning on the oxygen-enriched baking. The opening ratio of the oxygen-enriched baking is 12%, ensuring that the bottom of the tundish and the water inlet temperature of the tundish reach 1030℃ before pouring. During the high fire to bake the tundish, the air volume is 88%. Among them, the low fire is based on the flame not touching the lining, the medium fire is based on the flame just touching the lining, and the high fire is based on the flame rushing directly to the bottom of the tundish and returning upward. After baking, clean the debris in the upper water inlet of the tundish half an hour before pouring to improve the stability of the steel flow when the tundish is poured.

[0022] Step 2: After baking, fill each sizing water inlet of the tundish with 1.5kg of protective slag (during the production of billets, the molten steel is pulled out from the billet continuous casting machine in seven streams, and 1.5kg / stream here means that 1.5kg of protective slag is used for each stream). The main components of the protective slag are CaO and SiO2, with a CaO content of 33wt% and a SiO2 content of 28wt%.

[0023] Step 3: The dummy hook is reinforced with a 40mm diameter threaded steel bar. The reinforced dummy hook is used to complete the dummy work. The number of cold materials around the dummy hook is 115. The cold materials are cut steel bars, one for each. The method of welding threaded steel bars is used to increase the strength of the connection between the dummy rod and the molten steel.

[0024] Step 4: Use a wire head to fix the oxygen pipe for the tundish opening and drainage. During the tundish opening and drainage process, open the oxygen valve to 85% and use a large flow of oxygen for drainage.

[0025] The molten steel yield of this embodiment is 99.55%, and no molten steel pulling off or leakage occurs.

[0026] Example 3 A method for casting a square billet continuous casting machine without a swing slot comprises the following steps: Step 1: After the tundish is built, first clean the waste refractory materials in the tundish thoroughly. Then, 2 hours before pouring, use a negative pressure furnace to ignite, and use a low fire to bake the tundish for 1.5 hours, use a medium fire to bake the tundish for 1 hour, and use a high fire to bake the tundish for 2.5 hours. Turn on the high fire to bake the tundish while turning on the oxygen-enriched baking. The opening ratio of the oxygen-enriched baking is 8%, ensuring that the bottom of the tundish and the water inlet temperature of the tundish reach 1100℃ before pouring. During the baking of the tundish with a high fire, the air volume is 95%. Among them, the low fire is based on the flame not touching the lining, the medium fire is based on the flame just touching the lining, and the high fire is based on the flame rushing directly to the bottom of the tundish and returning upwards. After baking, clean the debris in the upper water inlet of the tundish half an hour before pouring to improve the stability of the steel flow when the tundish is poured.

[0027] Step 2: After baking, fill each sizing water inlet of the tundish with 1.4kg of protective slag (during the production of billets, the molten steel is pulled out from the billet continuous casting machine in seven streams, and 1.4kg / stream here means that 1.4kg of protective slag is used for each stream). The main components of the protective slag are CaO and SiO2, with a CaO content of 33wt% and a SiO2 content of 28wt%.

[0028] Step 3: The dummy hook is reinforced with a 36mm diameter threaded steel bar. The reinforced dummy hook is used to complete the dummy work. The number of cold materials around the dummy hook is 105. The cold materials are cut steel bars, one for each. The strength of the connection between the dummy rod and the molten steel is increased by welding threaded steel bars.

[0029] Step 4: Use a wire head to fix the oxygen pipe for the tundish opening and drainage. During the tundish opening and drainage process, open the oxygen valve to 75% and use a large flow of oxygen for drainage.

[0030] The molten steel yield of this embodiment is 99.6%, and there is no phenomenon of molten steel breakage or leakage.

[0031] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention.

Claims

1. A method for starting casting without a swing chute in a bloom continuous casting machine, characterized in that, It includes the following steps: Step 1: Before starting casting, bake the tundish with low fire, medium fire and high fire respectively to ensure that the temperature of the tundish bottom and the tundish nozzle reaches 1000 - 1100 °C; Step 2: After baking, fill the sizing upper nozzle of the tundish with 1.3 - 1.5 kg / strand of powder to prevent slag leakage during starting casting; Step 3: Reinforce the dummy bar with threaded steel bars, and the number of cold materials around the dummy bar is 105 - 115; Step 4: Fix the oxygen pipe for tundish starting casting drainage by means of thread head fixing. During starting casting, drain with a large flow of oxygen.

2. The method for starting casting without a swing chute for a billet continuous casting machine according to claim 1, characterized in that, In Step 1, the low fire is such that the flame does not touch the lining, the medium fire is such that the flame just touches the lining, and the high fire is such that the flame directly hits the tundish bottom and returns upward.

3. A method for starting casting without a swing chute in a billet continuous caster, characterized in that, In Step 1, start oxygen-enriched baking while baking the tundish with high fire, and the opening ratio of oxygen-enriched baking is 8% - 12%.

4. A method for starting casting without a swing chute in a bloom continuous casting machine, characterized in that, In Step 1, the baking time of the tundish with low fire is 1 - 1.5 h, the baking time of the tundish with medium fire is 1 - 1.5 h, and the baking time of the tundish with high fire is 2 - 3 h.

5. The method for starting casting without a swing chute in a bloom continuous caster according to claim 1, characterized in that, In Step 2, the main components of the powder are CaO and SiO2.

6. The method for starting casting without a swing chute for a bloom continuous casting machine according to claim 1, characterized in that, In Step 3, the diameter of the threaded steel bar is 32 - 40 mm.

7. The method for starting casting without a swing chute for a bloom continuous caster according to claim 1, characterized in that, In Step 3, increase the strength of the connection between the dummy bar and the molten steel.

8. The method for starting casting without a swing chute in a billet continuous caster according to claim 1, characterized in that, In Step 4, open the oxygen valve to 75% - 85% when draining the tundish at the start of casting.

9. The method for starting casting without a swing chute for a bloom continuous caster according to claim 1, characterized in that, In Step 1, use a negative pressure furnace to ignite before starting casting.