Method for on-line replacement of tundish in multi-strand continuous casting machine

Abstract

The present application relates to a kind of on-line replacement of intermediate ladle of multiple machine multiple flow continuous casting machine, belong to continuous casting technical field.The technical scheme is: when the liquid level of intermediate ladle drops to 275-325mm, the speed of one or several flows of stopper is not closed is reduced to 1m / min;When the liquid level of intermediate ladle drops to 225-275mm, the liquid level of molten steel in each flow crystallizer is kept at 100mm from the upper mouth of crystallizer;When the liquid level of intermediate ladle drops to 180-225mm, the speed of each flow is all reduced to 0m / min;In each flow crystallizer, connecting rod is placed, so that 40%-50% of connecting rod is immersed in molten steel;Replace new intermediate ladle, and when the liquid level of intermediate ladle reaches 400mm, open pouring each flow by using manual operation stopper in turn, and the speed starts gradually to process requirement from 0.5m / min.The beneficial effects of the present application are: continuous casting steel is realized, the production efficiency of continuous casting machine is improved, and the yield of molten steel is obtained.

Description

Technical Field

[0001] This invention relates to a method for online replacement of intermediate ladles in a multi-machine, multi-strand continuous casting machine, belonging to the field of continuous casting process technology in the metallurgical industry. Background Technology

[0002] With the rapid development of continuous casting technology in my country's steelmaking industry, the continuous casting time in tundishes of continuous casting machines has gradually increased from 10 hours to 18 hours, and now to 26 hours. This extended casting time reduces the cost of producing steel billets through continuous casting and improves worker efficiency. However, even with a longer casting cycle, the limited lifespan of the refractory materials used to manufacture the tundishes necessitates stopping casting and replacing them with new ones once the tundishes reach their end of their service life. Stopping casting and replacing tundishes not only consumes production time but also requires the raw materials necessary for starting casting in the new tundish. More importantly, each tundish replacement generates one tail billet and one head billet, increasing production costs in continuous casting. Summary of the Invention

[0003] The purpose of this invention is to provide a method for online replacement of tundishes in a multi-machine, multi-strand continuous casting machine, thereby achieving continuous steel casting, improving the production efficiency of the continuous casting machine, increasing the steel yield, and solving the problems existing in the background technology.

[0004] The technical solution of this invention is: A method for changing the tundish online in a multi-machine, multi-strand continuous casting machine, comprising the following steps: Step 1: When the last ladle before changing the intermediate tank is half-filled, perform a shut-off test on each flow plug to check whether each flow plug can be closed tightly. Mark one or more flow plugs that cannot be closed tightly. Step 2: After the last ladle before changing the tundish has finished pouring molten steel and the liquid level in the tundish has dropped to 275-325mm, reduce the pulling speed of one or more of the leaky stoppers to 1m / min, while keeping the pulling speed of the other streams unchanged. Step 3: When the liquid level in the intermediate tank drops to 225-275mm, disconnect the drain outlets of each stream in the intermediate tank and keep the liquid level of the molten steel in each crystallizer 80-120mm away from the top of the crystallizer. Step 4: When the liquid level in the intermediate tank drops to 175-225mm, reduce the pull speed of each flow to 0m / min, and at the same time close the stopper rods of all flows. If the stopper rods of one or more flows cannot be closed tightly, use plug cones to block them. Step 5: Place the connecting rod in the crystallizer of each flow, so that 40%-50% of the connecting rod is submerged in the molten steel. Start the pulling speed button for each flow and manually operate the pulling speed so that the liquid level in each crystallizer is 200-300mm away from the bottom of the crystallizer. Press the pulling speed stop button for each flow and set the pulling speed gauge to 0.5m / min. At the same time, fill the area around the connecting rod with cold material. Step Six: Replace with a new intermediate tank, open the ladle sliding nozzle, and wait until the liquid level in the intermediate tank reaches 375-425mm. Then, manually operate the stopper rod to start pouring each stream in sequence. When the liquid level reaches 180-220mm from the top of the crystallizer, start the billet pulling button for each stream. Start the pulling speed from 0.5m / min, stabilize for 2-3 minutes, then increase the pulling speed to 1m / min, stabilize for 7-8 minutes, and then increase the pulling speed to the process requirement. The replacement of the intermediate tank is now complete, and normal production can begin.

[0005] In step five, the cold material filling around the connecting rod is threaded steel.

[0006] The threaded steel filling around the connecting rod is made of 15-20 pieces of 14mm diameter threaded steel cut into 150mm lengths.

[0007] In step one, it is also necessary to prepare the new intermediate tundish to be replaced and the ladle to be poured into the new intermediate tundish, and ensure that the temperature of the molten steel in the ladle is 60 degrees higher than the temperature of the molten steel in the ladle during normal pouring.

[0008] The beneficial effects of this invention are: by using different methods to control the pouring of each stream according to the usage of each flow plug, the time for changing the tundish online is saved, ensuring successful continuous pouring of each stream, achieving continuous steel casting, improving the production efficiency of the continuous casting machine, increasing steel yield, and reducing production costs. Detailed Implementation

[0009] A method for changing the tundish online in a multi-machine, multi-strand continuous casting machine, comprising the following steps: Step 1: When the last ladle before changing the intermediate tank is half-filled, perform a shut-off test on each flow plug to check whether each flow plug can be closed tightly. Mark one or more flow plugs that cannot be closed tightly. Step 2: After the last ladle before changing the tundish has finished pouring molten steel, and the liquid level in the tundish has dropped to 275-325mm, reduce the pouring speed of one or more flows that are not properly closed by the stopper rod to 1m / min, while keeping the pouring speed of the other flows unchanged. Step 3: When the liquid level in the intermediate tank drops to 225-275mm, disconnect the drain outlets of each stream in the intermediate tank and keep the liquid level of the molten steel in each crystallizer 80-120mm away from the top of the crystallizer. Step 4: When the liquid level in the intermediate tank drops to 175-225mm, reduce the pull speed of each flow to 0m / min, and at the same time close the stopper rods of all flows. If the stopper rods of one or more flows cannot be closed tightly, use plug cones to block them. Step 5: Place the connecting rod in the crystallizer of each flow, so that 40%-50% of the connecting rod is submerged in the molten steel. Start the pulling speed button for each flow and manually operate the pulling speed so that the liquid level in each crystallizer is 200-300mm away from the bottom of the crystallizer. Press the pulling speed stop button for each flow and set the pulling speed gauge to 0.5m / min. At the same time, fill the area around the connecting rod with cold material. Step Six: Replace with a new intermediate tank, open the ladle sliding nozzle, and wait until the liquid level in the intermediate tank reaches 375-425mm. Then, manually operate the stopper rod to start pouring each stream in sequence. When the liquid level reaches 180-220mm from the top of the crystallizer, start the billet pulling button for each stream. Start the pulling speed from 0.5m / min, stabilize for 2-3 minutes, then increase the pulling speed to 1m / min, stabilize for 7-8 minutes, and then increase the pulling speed to the process requirement. The replacement of the intermediate tank is now complete, and normal production can begin.

[0010] In this embodiment, the online replacement of the intermediate tundish on a twelve-strand continuous casting machine is used as an example for illustration.

[0011] The twelve-strand continuous casting machine adopts a double tundish casting mode, with one tundish casting six strands. The ladle holds 150 tons of molten steel, grade HRB400E, with the following composition: C: 0.21-0.25; SI: 0.20-0.60; Mn: 1.20-1.60; P, S: ≤0.045; normal casting temperature 1570℃. o -1590 o The ladle pouring time is 40 minutes, and the billet size is 150mm×150mm.

[0012] This online intermediate tank replacement method includes three steps: preparation before replacement, online replacement, and post-replacement maintenance. These three steps are performed sequentially and seamlessly to complete the replacement in the shortest possible time, ensuring successful continuous casting for all flows. The specific implementation plan is as follows: I. Preparations before changing the intermediate tank

[0013] 1. Preparation of intermediate tank cars and intermediate tanks (1) Before the intermediate tank car goes online, check whether its walking mechanism is normal, whether its lifting and centering mechanisms are working properly, and whether there are foreign objects on the track between the intermediate tank car and the pouring position. (2) After the intermediate tank car is placed on the intermediate tank seat, first check the pouring condition of the intermediate tank working layer, whether the working layer surface is flat and the thickness is uniform, whether the pre-heating is uniform, and whether the working surface is scratched when the intermediate tank is taken out; manually operate the 12 flow plug rod mechanism to check whether it is flexible, check whether the screws on the cross arm of the plug rod are tight, and ensure that each flow plug rod is in the center of the drain outlet. 2. Baking in the intermediate pan (1) Baking of refractory material in intermediate tank: Baking of intermediate ladle for 6 hours, intermediate tank temperature required to be greater than 1000℃, intermediate tank nozzle baking for 4 hours, temperature greater than 800℃; (2) During the baking process of the intermediate tank, pay attention to the position of the stopper rod of each flow at the drain outlet. If any deviation is found, adjust and correct it in time. The stopper rod of each flow should be in the center of the drain outlet. Check the tightness of the screws on the cross arm of the stopper rod. If any looseness is found, tighten them in time. 3. Preparation of materials and tools The materials and tools needed to replace the intermediate tank mainly include plugging cones, connecting rods, intermediate tank covering agent, intermediate tank protective slag, continuous temperature measuring tubes, protective sleeves, oxygen burning tubes, oxygen belts, etc. These materials and tools should be prepared in sufficient quantities and placed in the designated locations. II. Online replacement of intermediate tank

[0014] 1. After the last ladle of steel is poured before the tundish is replaced, the tundish should maintain its original liquid level. After 20 minutes of pouring, a sealing test should be performed on the 12 flow stoppers to check if each flow stopper can be closed tightly. Mark any flow stoppers that cannot be closed tightly. For example, if flow stoppers 1, 4, and 7 are found to be unable to close tightly, simultaneously prepare the ladle for the new tundish to be poured at the furnace front and refining processes. The molten steel temperature should be 60°C higher than the usual pouring temperature. O For example, during normal production, the temperature from the ladle holder to the ladle turret is 1570°C. o -1590 o When changing the intermediate tank online, the temperature from the ladle holder to the ladle rotary table is 1630°C. o -1650 o And according to the established procedure, it is placed on the receiving arm of the ladle rotatable table; 2. After the ladle has finished pouring molten steel and the liquid level in the tundish has dropped to 300mm, the pouring speed of the streams that are not properly closed by the stopper rod should be reduced to 1m / min. The automatic addition of protective slag switch for each stream crystallizer should be turned off, and manual slag addition should be carried out as needed. 3. When the liquid level in the intermediate tank drops to 250mm, disconnect the drain outlets of each flow in the intermediate tank and operate the stopper rod mechanism of all flows to keep the liquid level of molten steel in each flow crystallizer 100mm away from the top of the crystallizer. 4. When the liquid level in the intermediate tank drops to 200mm, the pulling speed of all flows is reduced to 0m / min. At the same time, the stoppers of all flows are closed. The flow whose stoppers cannot be closed tightly are plugged with plug cones. 5. Place a connecting rod in the crystallizer of each flow, with 40%-50% of the connecting rod submerged in the molten steel. Start the pulling speed button for each flow and manually operate the pulling speed to make the liquid level in each crystallizer 200-300mm from the bottom of the crystallizer. Add 15-20 pieces of cold material, which are 14 threaded steel cut into 150mm long sections. The amount of cold material should fill the area around the connecting rod. At the same time, stop the secondary cooling water and stop the external spray water on the tensioning and straightening. 6. After driving away the tundish car, lift the tundish baking device and drive the new tundish car to the pouring position. Use the lateral movement mechanism on the tundish car to align the outlets of each flow on the tundish with the crystallizer openings of each flow. Install the dried ladle long nozzle, place it inside the tundish, and place it on the outlet of the sliding nozzle. According to the machine operator's instructions, open the ladle sliding nozzle. When the tundish weighs 15 tons or the liquid level in the tundish reaches 400mm, manually operate the stopper rod to start pouring each flow in sequence. When the liquid level reaches 200mm from the top of the crystallizer, start the pulling speed of each flow at 0.5m / min. After stabilizing for 2-3 minutes, increase the pulling speed to 1m / min. After stabilizing for 7-8 minutes, increase the pulling speed to 2.7m / min. After the billet of this pouring is pulled out of the straightening machine, return to automatic mode and install the 12 outlets of the tundish to complete the replacement of the tundish. III. Maintenance after replacing the intermediate tank

[0015] 1. Turn on the secondary cooling water and simultaneously turn on the external spray water on the tensioning and straightening equipment; 2. Check the steel pulling situation after the flow plug control and pulling speed control are switched to automatic control, and adjust the individual parameters according to the molten steel level in the crystallizer.

[0016] 3. Turn on the automatic slag addition switch for each flow to automatically add protective slag to each flow crystallizer.

Claims

1. A method for online replacement of tundishes in a multi-machine, multi-strand continuous casting machine, characterized in that: Follow these steps: Step 1: When the last ladle before changing the intermediate tank is half-filled, perform a shut-off test on each flow plug to check whether each flow plug can be closed tightly. Mark one or more flow plugs that cannot be closed tightly. Step 2: After the last ladle before changing the tundish has finished pouring molten steel, and the liquid level in the tundish drops to 275mm-325mm, reduce the pouring speed of one or more flows that are not properly closed by the stopper rod to 1m / min, while keeping the pouring speed of the other flows unchanged. Step 3: When the liquid level in the intermediate tank drops to 225mm-275mm, disconnect the drain outlets of each stream in the intermediate tank and keep the liquid level of the molten steel in each crystallizer 80mm-120mm away from the top of the crystallizer. Step 4: When the liquid level in the intermediate tank drops to 180mm-225mm, reduce the pull speed of each flow to 0m / min, and at the same time close the stopper rods of all flows. If the stopper rods of one or more flows cannot be closed tightly, use plug cones to block them. Step 5: Place the connecting rod in the crystallizer of each flow, so that 40%-50% of the connecting rod is submerged in the molten steel. Start the casting speed button for each flow and manually operate the casting speed so that the liquid level in each crystallizer is 200-300mm away from the bottom of the crystallizer. Press the casting speed stop button for each flow and set the casting speed gauge to 0.5m / min. At the same time, fill the area around the connecting rod with cold material. Step Six: Replace with a new intermediate tank, open the ladle sliding nozzle, and wait until the liquid level in the intermediate tank reaches 375-425mm. Then, manually operate the stopper rod to start pouring each stream in sequence. When the liquid level reaches 180-220mm from the top of the crystallizer, start the billet pulling button for each stream. Start the pulling speed from 0.5m / min, stabilize for 2-3 minutes, then increase the pulling speed to 1m / min, stabilize for 7-8 minutes, and then increase the pulling speed to the process requirement. The replacement of the intermediate tank is now complete, and normal production can begin.

2. The method for online replacement of tundish in a multi-machine, multi-strand continuous casting machine according to claim 1, characterized in that: In step five, the cold material filling around the connecting rod is threaded steel.

3. The method for online replacement of tundish in a multi-machine, multi-strand continuous casting machine according to claim 1, characterized in that: In step one, it is also necessary to prepare the new intermediate tundish to be replaced and the ladle to be poured into the new intermediate tundish, and ensure that the temperature of the molten steel in the ladle is 60 degrees higher than the temperature of the molten steel in the ladle during normal pouring.