A production process of multi-machine multi-flow gas mist cooling continuous casting machine for realizing heat exchange tundish

Abstract

The application discloses a production process of a multi-machine multi-flow gas mist cooling continuous casting machine for realizing hot exchange tundish, which can reasonably optimize the operation process under the premise of ensuring stable operation of equipment and quality of the casting blank, and can automatically reduce the secondary cooling gas pressure to 0.05MPa after the drawing speed stops through setting a system program, so that the secondary cooling nozzle can be in the state of compressed air cooling under the condition of sharp rise of the ambient temperature, and the cooling speed of the casting blank can be reduced to the maximum extent; the secondary cooling water distribution system is modified, the secondary cooling gas and water are in the automatic state when the drawing speed is greater than 0m / min, the secondary cooling gas is 0.25MPa, and the secondary cooling water is executed according to the water distribution table; the secondary cooling gas and water are in the automatic state when the drawing speed is equal to 0m / min, the secondary cooling gas is 0.05MPa, and the secondary cooling water is executed according to the water distribution table. The production process of the gas mist cooling mode square billet continuous casting machine for realizing quick hot exchange tundish is realized, an effective process method and path are explored for improving the operation rate of the continuous casting machine, and the effect is remarkable.

Description

TECHNICAL FIELD

[0001] The present application relates to a production process of a multi-machine multi-flow gas mist cooling continuous casting machine for realizing hot change tundish. BACKGROUND

[0002] In the metallurgical industry, the continuous casting process is an important process in steel production, and plays a role in connecting the converter and the rolling process. Improving the operation rate of the continuous casting machine actually comprehensively improves the casting speed and the number of continuous casting furnaces under the premise of ensuring the quality of the cast billet. For multi-machine multi-flow square billet continuous casting machines, the core of improving production efficiency is to improve the operation rate. With the progress and development of science and technology in recent years, the service life of the tundish has been further improved, and the replacement of the tundish has become an important constraint on the operation rate of the continuous casting machine. At present, the hot change tundish is usually used to solve this problem. There are many kinds of continuous casting hot change tundish technologies that use water cooling methods, but for multi-machine multi-flow square billet continuous casting machines with gas mist cooling, there are obvious differences between the cooling methods and the water cooling methods, and the failure risk of hot change tundish operation increases significantly, so there are basically no cases of multi-machine multi-flow gas mist cooling continuous casting machines implementing hot change tundish processes.

[0003] Taking a continuous casting machine production line with a hot change tundish as an example, the continuous casting machine has an initial 80T converter, a five-machine five-flow continuous casting machine, an arc of 8 meters, a main production billet type of 150mm*150mm, a cooling method of full-section gas mist cooling, and a casting mode of fixed-diameter casting. If the secondary cooling gas and the cooling water are all stopped during the operation process, the cast billet is in a state of natural cooling, and the ambient temperature around the cast billet will rise sharply. The gas mist nozzle base and the cooling gas and water vertical pipe are connected through a sealing ring, and the sealing ring will melt if the time is too long, causing water and gas leakage at the connection between the base and the vertical pipe, destroying the uniformity of the secondary cooling, and affecting the quality of the cast billet. Therefore, the reasonable treatment of water and gas during hot change is particularly important. Secondly, if the cast billet stays in the crystallizer for too long, the liquid core will shrink, the billet shell will completely separate from the copper plate after shrinking towards the center, and the molten steel will fill the gap during casting, causing the cast billet to be difficult to pull, which may cause production accidents and damage the secondary cooling condition. Therefore, the reasonable control of the hot change time is also very important. If the above key operation points are not handled properly, the tundish hot change will fail, which may cause production interruption and equipment damage, further affecting the operation rate of the continuous casting process.

[0004] Currently, there is no systematic and effective reference to the related technology and discussion of the five-machine five-flow square billet continuous casting machine with fixed-diameter casting mode and gas mist cooling method during the hot change tundish process. The present application solves the problem of hot change tundish by determining the production process method based on the process requirements of the tundish hot change and the key points in the operation process through repeated tests and demonstrations. This process method can effectively improve the operation rate of the continuous casting machine and can be directly used in steel production. SUMMARY

[0005] The present application aims to provide a production process of multi-machine multi-flow gas mist cooling continuous casting machine to realize hot change tundish, which can improve the operation rate of the continuous casting machine under the premise of ensuring the stable and safe operation of the equipment and meeting the quality requirements of the cast slab.

[0006] The technical scheme adopted by the present application is a production process of multi-machine multi-flow gas mist cooling continuous casting machine to realize hot change tundish,

[0007] 1) By setting the system program, the secondary cooling gas pressure is automatically reduced to 0.05MPa after the pulling speed stops. In this way, the secondary cooling nozzle can be in a compressed air cooling state in the case of a sharp rise in ambient temperature, and the cooling speed of the cast slab can be maximally reduced;

[0008] 2) Modify the secondary cooling water distribution system. When the pulling speed is greater than 0m / min, the secondary cooling gas and water are in an automatic state, the secondary cooling gas is 0.25MPa, and the secondary cooling water is executed according to the water distribution table. When the pulling speed is 0m / min, the secondary cooling gas and water are in an automatic state, the secondary cooling gas is 0.05MPa, and the secondary cooling water is executed according to the water distribution table;

[0009] The production steps of the process on a five-machine five-flow continuous casting machine are as follows: the arc of the continuous casting machine is 8 meters, the main production slab type is 150*150mm, the cooling method is full-section gas mist cooling, and the casting mode is fixed-diameter casting,

[0010] A, preparation of tools for hot change tundish and routine inspection;

[0011] B, tundish baking: the baking temperature of the tundish reaches 1100-1200℃;

[0012] C, temperature condition of molten steel: the end-point temperature of the casting is controlled to 1620-1630℃, and the tundish temperature is ensured to be within 1570-1580℃;

[0013] Operation process:

[0014] ① Ensure that the pulling speed before stopping is not less than 2.4m / min to avoid that the connecting piece cannot be added into the crystallizer after the tundish car leaves the casting position;

[0015] ② Before the last furnace stops casting, open the casting furnace on the rotary table, and prepare the tundish at the waiting position. After the ladle casting is completed, a special person measures the liquid level in the tundish, and when the liquid level in the tundish drops to below 250mm, informs the tundish operator to operate the hydraulic cylinder to insert the blind plate to block the flow;

[0016] ③ After the tundish car leaves, a designated person operates the handheld device to start the casting speed. The tundish worker adds the connector and uses a ruler to measure the position of the billet shell. The casting speed is stopped when the distance from the top is 500mm. The size, shape, and insertion depth of the tundish connector are the key points of this operation. The tundish connector is 800mm long and uses φ32mm threaded steel. Both ends use 8cm long φ32mm threaded steel. The whole connector is in the shape of "I". It is inserted into the liquid surface for 400mm to increase the connection length and the force-bearing area. This prevents the billet from breaking off at the connection due to excessive time interval, which could lead to a production accident and failure of hot tundish exchange.

[0017] ④ After adding the guide rod, clean the slag adhering to the four walls of the crystallizer to prevent the semi-solidified molten steel from being rolled into the slag and causing slag leakage. Add cold material, which is φ10 HPB300 coiled steel bar, cut into 20-25cm lengths. During the addition of cold material, the cold material should be placed vertically in the crystallizer to avoid bridging and scratching the copper tubes of the crystallizer. The amount of cold material added should be about 15cm above the top of the crystallizer, piled in the middle in a mushroom shape to protect the head of the guide rod. If the cold material is too thick, it may not melt quickly due to the emergence time and will not be able to protect the head of the guide rod. If the cold material is too thin, it will melt quickly and will also not be able to protect the head of the guide rod.

[0018] ⑤ Casting Operation: Move the spare tundish to the casting position. After alignment, pull open the ladle. When the liquid level in the tundish is >600mm, measure the temperature and start casting. Start casting from both sides simultaneously. The flow sequence is 1 / 5-3-2 / 4. Use a φ13mm slider to ensure that the surface time in the crystallizer is >10s. Ensure that the cold material in the crystallizer can be fully melted and increase the thickness of the billet shell at the joint. Control the starting speed to below 1.6m / min to avoid breakage accidents caused by increased resistance to billet pulling at the moment of start-up due to fast starting speed.

[0019] ⑥ After the cast billet joint enters the straightening machine, it enters normal production mode;

[0020] ⑦ The entire heat exchange intermediate batch time should be controlled within 10 minutes.

[0021] Invention Implementation Results: Following the above process flow, the results are compared below:

[0022]

[0023] (1) After 6 months of continuous testing, the success rate of hot-changing tundish in continuous casting was 100%, and the success rate of single-strand casting was 100%. This increased the system's production rate by 2.5%.

[0024] (2) The temperature of the steel is reduced by 40-50℃, saving 5kw.h / ton of electricity, and saving 5600kw.h of electricity per month.

[0025] (3) Reduce the waste product quantity of opening and stopping, the waste blank quantity can save 27.4 tons per month, and the blank forming rate of continuous casting blank is improved from 98.75% to 98.94%.

[0026] The new process designed by the present application can reasonably optimize the operation process under the premise of ensuring the stable operation of equipment and the quality of the casting blank, realize the production process of the bloom continuous casting machine with the quick hot change tundish of the gas mist cooling mode by setting the new two-cooling gas and two-cooling water mode, designing the new connecting piece and the layout of the cold material addition, ensuring the opening and sprouting time, and controlling the starting speed, and an effective process method and path are explored for improving the operation rate of the continuous casting machine, and the effect is remarkable. DETAILED DESCRIPTION

[0027] A production process for realizing a hot change tundish of a multi-machine multi-flow gas mist cooling continuous casting machine,

[0028] 1) By setting the system program, the two-cooling gas pressure is automatically reduced to 0.05 MPa after the pulling speed stops, so that the two-cooling nozzle can be in the state of compressed air cooling under the condition of rapid rise of the ambient temperature, and the cooling speed of the casting blank can be reduced to the maximum;

[0029] 2) Modify the two-cooling water distribution system, when the pulling speed is greater than 0 m / min, the two-cooling gas and water are in an automatic state, the two-cooling gas is 0.25 MPa, and the two-cooling water is executed according to the water distribution table; when the pulling speed is 0 m / min, the two-cooling gas and water are in an automatic state, the two-cooling gas is 0.05 MPa, and the two-cooling water is executed according to the water distribution table;

[0030] The production steps of the present process on a five-machine five-flow continuous casting machine are as follows: the arc of the continuous casting machine is 8 meters, the main production blank type is 150*150 mm, the cooling mode is full-section gas mist cooling, and the casting mode is constant-diameter casting,

[0031] A, preparation of tools for hot change tundish and routine inspection;

[0032] B, tundish baking: the baking temperature of the tundish reaches 1100-1200 DEG C;

[0033] C, temperature condition of molten steel: the end-point temperature of the steel is controlled to 1620-1630 DEG C, and the tundish temperature is ensured to be within 1570-1580 DEG C;

[0034] Operation process:

[0035] ① Ensure that the pulling speed before stopping is not less than 2.4 m / min, so that the connecting piece can be added into the crystallizer after the tundish car leaves the casting position;

[0036] ② Before the last furnace is stopped, the furnace is turned on and the trolley is prepared in the waiting position. After the ladle is finished, a special person measures the liquid level in the tundish. When the liquid level in the tundish drops to below 250mm, the tundish worker is notified to operate the hydraulic cylinder to drive in the blind flange to block the flow.

[0037] ③ After the tundish car leaves, a designated person operates the handheld device to start the casting speed. The tundish worker adds the connector and uses a ruler to measure the position of the billet shell. The casting speed is stopped when the distance from the top is 500mm. The size, shape, and insertion depth of the tundish connector are the key points of this operation. The tundish connector is 800mm long and uses φ32mm threaded steel. Both ends use 8cm long φ32mm threaded steel. The whole connector is in the shape of "I". It is inserted into the liquid surface for 400mm to increase the connection length and the force-bearing area. This prevents the billet from breaking off at the connection due to excessive time interval, which could lead to a production accident and failure of hot tundish exchange.

[0038] ④ After adding the guide rod, clean the slag adhering to the four walls of the crystallizer to prevent the semi-solidified molten steel from being rolled into the slag and causing slag leakage. Add cold material, which is φ10 HPB300 coiled steel bar, cut into 20-25cm lengths. During the addition of cold material, the cold material should be placed vertically in the crystallizer to avoid bridging and scratching the copper tubes of the crystallizer. The amount of cold material added should be about 15cm above the top of the crystallizer, piled in the middle in a mushroom shape to protect the head of the guide rod. If the cold material is too thick, it may not melt quickly due to the emergence time and will not be able to protect the head of the guide rod. If the cold material is too thin, it will melt quickly and will also not be able to protect the head of the guide rod.

[0039] ⑤ Casting Operation: Move the spare tundish to the casting position. After alignment, pull open the ladle. When the liquid level in the tundish is >600mm, measure the temperature and start casting. Start casting from both sides simultaneously. The flow sequence is 1 / 5-3-2 / 4. Use a φ13mm slider to ensure that the surface time in the crystallizer is >10s. Ensure that the cold material in the crystallizer can be fully melted and increase the thickness of the billet shell at the joint. Control the starting speed to below 1.6m / min to avoid breakage accidents caused by increased resistance to billet pulling at the moment of start-up due to fast starting speed.

[0040] ⑥ After the cast billet joint enters the straightening machine, it enters normal production mode;

[0041] ⑦ The entire heat exchange intermediate batch time should be controlled within 10 minutes.

Claims

1. A multi-machine multi-flow gas mist cooling continuous casting machine realizes the production process of hot exchange tundish, characterized in that: 1) by setting the system program, the secondary cooling gas pressure is automatically reduced to 0.05 MPa after the drawing speed stops, so that the secondary cooling nozzle is in the state of compressed air cooling in the case of rapid rise of ambient temperature, and the cooling speed of the casting blank is reduced to the maximum; 2) modify the secondary cooling water distribution system, when the drawing speed is greater than 0 m / min, the secondary cooling gas and water are in an automatic state, the secondary cooling gas is 0.25 MPa, and the secondary cooling water is executed according to the water distribution table; when the drawing speed is 0 m / min, the secondary cooling gas and water are in an automatic state, the secondary cooling gas is 0.05 MPa, and the secondary cooling water is executed according to the water distribution table; The production steps are as follows: the cooling mode is full-section gas mist cooling, and the casting mode is constant-diameter casting, A, preparation of tools for hot exchange tundish and routine inspection; B, tundish baking: the baking temperature of the tundish reaches 1100-1200℃; C, the temperature of molten steel: the end point temperature of the casting is controlled to 1620-1630℃, and the tundish temperature is ensured to be within 1570-1580℃; Operation process: ① Ensure that the drawing speed before stopping is not less than 2.4 m / min to avoid that the connecting piece cannot be added into the crystallizer after the tundish car leaves the casting position; ② Before the last furnace stops casting, open the casting furnace on the rotary table, and prepare the tundish at the waiting position. After the ladle casting is completed, a special person measures the liquid level in the tundish, and when the liquid level in the tundish is below 250 mm, the tundish worker is informed to operate the hydraulic cylinder to insert the blind plate to block the flow; ③ After the tundish car leaves, a special person operates the hand-operated device to start the drawing speed, the tundish worker adds the connecting piece, measures the shell position with a ruler, and stops the drawing speed when the distance from the upper port is 500 mm. The size, shape and insertion depth of the tundish connecting piece are the key points of this operation. The tundish connecting piece is 800 mm long, uses φ32 mm threaded steel, and uses φ32 mm threaded steel with a length of 8 cm at both ends. The whole is in the shape of "H" type, is inserted into the liquid surface by 400 mm, increases the connection length and stress area, avoids the breakage of the casting blank from the connection due to too long interval time, and causes production accidents to cause the failure of hot exchange tundish; ④ After the guide rod is added, the slag skin adhered to the four walls of the crystallizer is cleaned to prevent the semi-solid molten steel from being rolled into the slag skin to cause rolling slag and leakage of molten steel. Cold material is added. The cold material is φ10 HPB300 round steel bar, which is cut into steel bars with a length of 20-25 cm. During the addition of the cold material, the cold material is vertically placed in the crystallizer and cannot form a bridge to avoid scratching the copper pipe of the crystallizer by the cold strip. The addition amount of the cold strip is appropriate to be about 15 cm above the upper port of the crystallizer, and the middle is stacked into a mushroom shape to protect the head of the guide rod. If the cold material is too thick, it may not melt quickly due to the time of emergence, and cannot protect the head of the guide rod. If the cold material is too thin, it can also melt quickly and cannot protect the head of the guide rod. ⑤Pouring operation: the standby ladle is opened to the pouring position, the ladle is pulled away after the alignment is completed, the temperature is measured after the liquid level of the ladle is greater than 600mm, and the pouring is started. The two sides are poured at the same time, the flow sequence is 1 / 5-3-2 / 4, the pouring slider uses a φ13mm slider, the surface time in the crystallizer is ensured to be greater than 10s, the cold charge in the crystallizer is ensured to be fully melted, the billet shell thickness at the joint is increased, and the starting speed is controlled to be below 1.6m / min to avoid the increase of the billet resistance in the starting moment due to the fast starting speed, and the breakage accident; ⑥After the casting billet joint enters the puller-straightener, the normal production mode is entered; ⑦The time of the whole hot-changing tundish is controlled to be within 10min.

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