A 370mm super-thick slab intermediate ladle butt joint production method

Abstract

The application discloses a butt joint method for a 370mm super-thick slab tundish and belongs to the technical field of iron and steel production. The method comprises the following steps: preparing work before tundish butt joint, tundish butt joint and preventive measures for possible accidents of tundish butt joint. The method can simplify production organization, stabilize the connection of the front and rear slabs, eliminate the breakout of the crystallizer caused by the poor connection of the solidification connection, reduce the shutdown frequency of the continuous casting machine, improve the operation rate of the super-thick slab continuous casting machine, reduce the production cost and improve the economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, in particular to a 3700mm super-thick slab tundish butt joint production method. BACKGROUND

[0002] Due to the complex product species of continuous casting super-thick slab, it is necessary to frequently stop and replace the continuous casting tundish. The replacement of the continuous casting tundish of the super-thick slab production line needs to be stopped for more than 2 hours, directly reducing the continuous casting production operation rate and increasing the production cost.

[0003] The super-thick slab with a thickness of 370mm is thicker than the medium-thick slab continuous casting machine, and the butt joint operation process is basically the same, but due to the thicker thickness, more time is needed for solidification to achieve stable connection of the front and rear solidification, and it is easy to cause the solidification to separate after starting due to poor solidification connection, resulting in molten steel leakage from the crystallizer, causing huge economic loss and bringing great difficulty to production operation. SUMMARY

[0004] In order to overcome the defects of the prior art, the present application provides a 370mm super-thick slab tundish butt joint method, which specifically adopts the following technical scheme:

[0005] A 370mm super-thick slab tundish butt joint production method, characterized in that it comprises the following steps:

[0006] (I) Preparation before tundish butt joint

[0007] (1) Confirm the production plan and tundish butt joint time;

[0008] (2) Bake the tundish more than 5 hours in advance, the tundish baking temperature is 1200±50℃, and the nozzle baking temperature is ≥900℃;

[0009] (3) After the second-to-last furnace of the previous group production is poured, the temperature of the first furnace of the butt joint group is controlled according to the upper limit, and the ladle is controlled to remain for 2 minutes of pouring time to the platform to prevent the first furnace from being too cold and causing sticking and pad rod;

[0010] (4) Check the tundish car running area and track for obstacles;

[0011] (5) Prepare the flow plate, pressure rod, measuring rod, drill, cutting gun, 350mm long flow plate tube and other tools, and prepare 3-4 bent oxygen pipes on both sides of the crystallizer cover plate, with a bend of about 30cm;

[0012] (6) Notify the relevant equipment maintenance personnel to the pouring platform 30 minutes before butt joint, and have a person in the main control room and the electrical room respectively and carry a intercom to prevent the need to perform the roll gap lifting, motor power-off reset operation;

[0013] (II) The butt joint of the tundish

[0014] (1) At the end of the pouring of the last ladle of the upper group, the first ladle is guided to the platform, the sliding nozzle oil cylinder is installed, the slag detection line is connected, and the ladle cover is covered;

[0015] (2) After the pouring of the upper group is completed, the ladle rotating platform is rotated to the horizontal position in the east-west direction; the mechanical hand is returned to the preparation position to replace the protective sleeve, and then the measurement of the molten steel depth in the tundish is prepared;

[0016] (3) After the ladle pouring is completed, the slag in the crystallizer begins to melt, and when the slag is red, if the slag is not enough, 15 tons of tundish is added to the opening pouring slag to perform the molten steel surface insulation operation in the crystallizer. When the blind plate is walked, 2 bags of opening pouring slag are added to the east and west sides of the crystallizer, covering the molten steel surface;

[0017] (4) When the tundish tonnage is left with 20 tons, the drawing speed is reduced, and the drawing speed is reduced by 5% for every 2 tons of molten steel in the tundish, and the molten steel depth in the tundish is measured;

[0018] (5) When the tundish tonnage is 12 tons, the drawing speed is reduced to 0.5 m / min, and the tundish is walked;

[0019] (6) When the tundish tonnage is 30 tons, the standby baking tundish is checked, the water nozzle quick change oil cylinder is closed, and the upper limit position signal of the tundish baking device is confirmed to be activated;

[0020] (7) The automatic stop rod is used, and after the stop rod is closed, the dead plug opening degree is manually lifted up, and the blind plate operation, the "creep" button and the "butt joint" button are pressed;

[0021] (8) After the tundish car starts to rise, the liquid surface slowly descends, at this time, the stirring operation is not needed, if the gap of the crystallizer narrow surface billet shell is relied on, a slight stirring of the molten steel and slag in the crystallizer is performed with a bent blowing oxygen pipe, so that a small amount of molten steel can fill the gap, and after the liquid surface descends, the large slag shell is broken in time, and the molten steel liquid surface is kept liquid;

[0022] (9) After the tundish car walks to the pouring position, it is quickly centered left and right, front and back, and two people cooperate to insert the tundish nozzle into the molten steel; at the same time, the other pouring worker compresses the test rod and lifts it up tightly, and confirms the pouring after the confirmation. At this time, the east and west ends stop stirring at the same time, and the flow blocking plate and flow blocking paper tube are put in;

[0023] (10) The distance between the molten steel liquid surface after the blind plate is struck and the upper opening of the crystallizer is measured, and the height reaches 200 mm, the straightening operation is stopped, the new and old steel shell is ensured to have enough cooling time and reaches the drawing strength;

[0024] (11) When the tundish molten steel weight reaches 10 tons, the stopper is opened, the middle flow is poured, and the starting time is controlled at 60S-80S according to the section and the height of the liquid surface;

[0025] (12) After starting, the speed is increased according to the docking speed system, the starting speed is fixed to 0.1 m / min, the speed is increased to 0.2 m / min when the docking blank length is 0.1 m, the speed is increased to 0.3 m / min when the docking blank length is 0.2 m, and then the speed is increased to the scheduled speed.

[0026] The tundish docking production method of the 370mm super-thick slab can simplify production organization, stabilize the connection of the front and rear ends of the slab, eliminate the occurrence of molten steel leakage caused by poor solidification connection and decoupling of the slab, reduce the number of continuous casting machine downtime, improve the operation rate of the super-thick slab continuous casting machine, reduce production costs, and improve economic benefits. Using the method of the application, the change group time can be saved by 180 minutes each time, and the output can be increased by 820 tons. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the following will describe the embodiments of the present application in detail.

[0028] Embodiment 1

[0029] A tundish docking production method of a 370mm super-thick slab, specifically comprising the following steps:

[0030] 1. Preparation before tundish docking

[0031] (1) Confirm the production plan and tundish docking time;

[0032] (2) Bake the tundish 5 hours or more in advance, control the tundish baking temperature at 1200±50℃, and the nozzle baking temperature ≥900℃;

[0033] (3) After the second-to-last furnace molten steel of the previous group production is poured, the first furnace ladle temperature of the docking group is controlled according to the upper limit, which is about 2 minutes of remaining pouring time of the ladle to the platform, to prevent the first furnace molten steel temperature from being reduced too much to cause sticking, pad rod and other abnormal conditions;

[0034] (4) Check the tundish car running area and track for obstacles;

[0035] (5) Prepare the flow baffle, pressure rod, measuring rod, drill, cutting gun, and flow baffle paper tube (350mm long) for use, and prepare 3-4 bent oxygen pipes on the east and west sides of the crystallizer cover plate, with a bend of about 30cm;

[0036] (6) 30 minutes before docking, inform the relevant equipment maintenance personnel to the casting platform, the main control room and the electrical room have a person and carry a intercom, in case of need to perform the roll gap, motor power reset operation (normal pull straightening force 3000KN or so before docking).

[0037] 2, tundish docking

[0038] (1) the normal command of the upper group of tail furnace pouring end of the first furnace ladle to the platform, and install the sliding nozzle cylinder, connect the slag detection line, cover the ladle cover;

[0039] (2) after the upper group of tail furnace pouring, rotate the ladle rotary table to the horizontal position (east-west direction); put the manipulator back to the preparation position to replace the protective sleeve, and then prepare to measure the depth of molten steel in the tundish;

[0040] (3) when the ladle pouring is finished, the crystallizer starts to slag, and when the slag is red, if the slag is not enough, add it, when the tundish tonnage is 15 tons, add the opening pouring slag to the surface of the molten steel in the crystallizer, and when the car is punched, add 2 bags of opening pouring slag (10 kg / bag) to the east and west sides of the crystallizer, covering the surface of the molten steel;

[0041] (4) when the tundish tonnage is left 20t, appropriately reduce the pulling speed, and specifically according to the tundish molten steel volume, reduce the pulling speed by 5% for every 2 tons;

[0042] (5) when the tundish tonnage is 12t, the pulling speed is reduced to 0.5m / min, and then according to the quantity of the rod, the liquid level of the tundish is about 250mm, and the car is driven;

[0043] (6) when the tundish tonnage is 30t, check the standby baking tundish, close the nozzle quick change cylinder, and confirm that the upper limit position signal of the tundish baking device is activated;

[0044] (7) adopt automatic rod closing, manually lift the dead plug opening degree after closing the rod, and simultaneously punch the blind plate operation, simultaneously press "creep", and simultaneously press the "docking" button;

[0045] (8) after the tundish car starts to lift, the liquid level will slowly decrease, at this time, there is no need to stir the flow, if you observe the shrinkage gap of the crystallizer narrow surface billet shell, you can use the bent blowing oxygen pipe to slightly stir the molten steel and slag in the crystallizer, the amplitude should not be too large, ensure that there is a small amount of molten steel to fill the gap, and at the same time, if there is a large piece of slag shell after the liquid level decreases, it should be broken in time, but remember not to stir the molten steel liquid surface greatly, and keep the molten steel liquid surface liquid;

[0046] (9) After the tundish car walks to the pouring position, it is quickly centered left and right and front and back. Two people cooperate and listen to the command to insert the tundish nozzle into the molten steel (insert 1 cm above the side hole from the liquid level to the nozzle, or fully insert); at the same time, the other pouring worker compresses the test bar and lifts it up tightly. After the machine length is confirmed, the master informs the ladle worker to start pouring. At this time, the two ends stop stirring at the same time, and the flow stop plate and flow stop paper tube are put in;

[0047] (10) Measure the distance between the liquid level of the drawn molten steel and the upper opening of the crystallizer after the blind plate is punched. Stop the straightening operation when the height reaches 200 mm. If the system does not have a stop straightening function, do not perform the butt joint. The target ensures that the new and old steel shells have enough cooling time and reach the drawing strength;

[0048] (11) When the tundish molten steel weight reaches 10 t, open the stopper, and start pouring. The start time is controlled at 60S-80S according to the cross section and the height of the liquid level;

[0049] (12) After starting, the speed is increased according to the butt joint speed system. The starting speed is fixed at 0.1 m / min. At this time, the master starts to read the billet length. When the butt joint billet length is 0.1 m, the speed rises to 0.2 m / min. When the butt joint billet length is 0.2 m, the speed rises to 0.3 m / min. Then, according to the "pouring speed specification", the speed is increased to the specified speed;

[0050] 3. Preventive measures for possible accidents during tundish butt joint

[0051] (1) The low speed time is long during butt joint, the straightening force is large, the straightening roller alarms, the billet does not move, and the billet stagnation accident is caused.

[0052] ① Pay attention to the change of the straightening force during production. When the straightening force exceeds 4500KN, raise the roll gap of the horizontal section by 3mm before butt joint to reduce the straightening force;

[0053] ② Grasp the time nodes of each link of the butt joint operation, and try to shorten the butt joint time and the production time of low speed;

[0054] ③ When the straightening force of a single straightening roller in the inner arc reaches 250KN during the butt joint process, the straightening roller should be manually lifted to avoid the straightening roller alarm. When the straightening roller alarms, the master should promptly confirm and restore the alarm straightening roller (when more than 3 straightening rollers alarm, the straightening should be stopped first, and then the alarm straightening roller should be confirmed and restored before starting the straightening again).

[0055] ④ When the actual speed displayed on the OS1 dial fluctuates frequently, it can be determined that the billet has stopped moving at this time, and the straightening roller on the primary picture must have an alarm. Prompt the master to reset the straightening roller in time;

[0056] ⑤If the casting blank still does not move, the hot blank pressure of the horizontal section 10-18# section pull straightening roll can be converted into the dummy bar pressure, and the roll gap of the large reduction section 12-18# is lifted by 5mm. At this time, if the blank still does not move, immediately stop pouring.

[0057] (2) The gap between the blank shell and the copper plate of the mold during butt joint may cause a leakage accident.

[0058] ①Strictly control the time from the end of tundish pouring to the start of the next ladle pouring within 5 minutes to avoid serious shrinkage of the tail blank.

[0059] ②After the tundish is moved, the flow must be fully stirred, especially the narrow face of the mold, to ensure that the steel flow continuously hits the narrow copper plate, so that the gap between the blank shell and the narrow copper plate is within 5mm.

[0060] ③Check whether there is residual steel in the four corners of the mold before and after butt joint, otherwise it should be removed in time. If it cannot be removed in time, the pulling speed after butt joint should be 0.2m / min lower than the specified speed. When the butt joint blank exits the fan-shaped section, observe whether the shape of the four corners of the blank is normal. If it is normal, it can be increased to the normal pulling speed. If there are continuous pits and obvious steel leakage, reduce the pulling speed to the minimum speed, and stop pouring when the furnace is poured.

[0061] (3) After the butt joint is poured, the stopper pad is lost, and the steel flow is out of control, which may cause a mold overflow accident.

[0062] ①The baking temperature of the tundish must meet the technical requirements, especially the baking quality of the upper nozzle of the tundish must be guaranteed to avoid cold shutdown during pouring.

[0063] ②When checking the standby baked tundish, it must be carefully confirmed whether there are sundries on the rod head and around the upper nozzle of the tundish, otherwise it should be cleaned in time.

[0064] ③Confirm that the nozzle quick-change oil cylinder is completely closed before butt joint.

[0065] ④When the tundish is poured, the middle flow must be poured, and the test rod is performed when the molten steel submerges the side hole of the nozzle. If the stopper is found to be unable to close, it should be lifted immediately. At this time, the pull straightening can be started appropriately in advance (but the breakout time must be greater than or equal to 30s), but the pulling speed is not allowed to be forcibly increased. When the molten steel surface rises to the position of the width adjustment groove, it is uncontrollable and the blind plate should be punched in time to move the tundish.

[0066] In addition to the above embodiments, the present application can also have other implementation manners. Any technical solution formed by equivalent substitution or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A method for producing tundishes for 370mm extra-thick slabs, characterized in that, Includes the following steps: (a) Preparations before intermediate package docking (1) Confirm the production plan and intermediate package docking time; (2) Bake the intermediate bread more than 5 hours in advance. The baking temperature of the intermediate bread is 1200±50℃, and the baking temperature of the sprue is ≥900℃. (3) After the second to last heat of molten steel produced by the previous group is poured, the temperature of the first heat of the docking group is controlled at the upper limit. The temperature is controlled to be on the platform with 2 minutes remaining in the pouring time of the ladle, so as to prevent the temperature of the first heat of molten steel from dropping too much, which may cause sticking and padding. (4) Check that there are no obstacles in the area where the chartered vehicle travels and on the track; (5) Prepare baffles, pressure bars, measuring rods, chisels, cutting torches, and 350mm long baffle paper tubes. Prepare 3-4 bent oxygen blowing tubes on the east and west sides of the crystallizer cover plate, with bends of about 30cm. (6) Notify the relevant equipment maintenance personnel to come to the casting platform 30 minutes in advance. There should be dedicated personnel in the main control room and electrical room who are equipped with walkie-talkies in case it is necessary to perform operations such as lifting the roller gap or resetting the motor power trip. (ii) Intermediate package docking (1) During the final stage of casting of the upper tail furnace, the normal command connects the first furnace ladle to the platform, installs the sliding water nozzle cylinder, connects the slag detection line, and covers the ladle. (2) After the upper tail furnace is finished, rotate the ladle turntable to a horizontal position in the east-west direction; put the robot back to the ready position to replace the protective sleeve, and then prepare to measure the depth of molten steel in the tundish. (3) After the ladle pouring is completed, slag begins to form in the crystallizer until the slag turns red. If there is not enough slag, it should be added. When the tundish tonnage is 15 tons, start pouring slag is added to keep the surface of the molten steel in the crystallizer warm. When the car is running and the blind plate is installed, add 2 bags of start pouring slag to the east and west sides of the crystallizer to cover the surface of the molten steel. (4) When the tundish tonnage is 20t remaining, start to reduce the casting speed. For every 2 tons of molten steel reduced in the tundish, the casting speed is reduced by 5%, and the depth of molten steel in the tundish is measured. (5) When the tundish tonnage reaches 12t, the pulling speed is reduced to 0.5m / min, and the tundish liquid level is 250mm when the machine is running; (6) When the tundish tonnage reaches 30t, check the standby baking tundish, close the water inlet quick change oil cylinder, and confirm that the upper limit signal of the tundish baker is activated. (7) Use automatic rod closing. After closing the rod, manually raise the dead stop rod opening while simultaneously operating the blind plate, pressing the "creep" button and the "docking" button. (8) After the ladle car in the casting position starts to be lifted, the liquid level drops slowly. At this time, there is no need to stir the flow. If the narrow face of the billet shell of the crystallizer shrinks the gap, use the bent oxygen pipe to gently stir the molten steel and slag in the crystallizer to ensure that a small amount of molten steel fills the gap. If there are large pieces of slag shell after the liquid level drops, they should be broken in time to keep the molten steel liquid level liquid. (9) After the tundish car moves to the pouring position, quickly align it left, right, front and back. When lowering the tundish, two people work together to insert the tundish nozzle into the molten steel. At the same time, another steel pourer compresses the test bar and lifts it up to tighten. After confirmation, start pouring. At this time, both ends stop stirring and put in the baffle plate and baffle paper tube. (10) After the blind plate is installed, measure the distance between the molten steel surface and the top of the crystallizer. Stop the straightening operation when the height reaches 200mm to ensure that the old and new molten steel billet shells have sufficient cooling time to form and reach the billet strength. (11) When the weight of molten steel in the ladle reaches 10t, open the stopper rod and start pouring in the middle of the flow. The start time is controlled between 60s and 80s depending on the height of the cross section and the liquid level. (12) After starting, increase the speed according to the docking speed system. The starting speed is fixed at 0.1m / min. When the docking billet length is 0.1m, the speed is increased to 0.2m / min. When the docking billet length is 0.2m, the speed is increased to 0.3m / min. Then increase the speed to the specified speed. (III) Preventive measures for possible accidents during intermediate package docking (1) When docking, the low pulling speed time is long and the pulling force is too large, the pulling roller alarm is triggered, the billet does not move, and the billet stagnation accident is caused. ① During production, pay attention to the changes in tension leveling force. When the tension leveling force exceeds 4500KN, raise the roll gap of the horizontal section by 3mm before docking to reduce the tension leveling force. ② Grasp the time nodes of each step of the docking operation, and shorten the docking time and the production time at low speed as much as possible; ③ During the docking process, when the tension force of a single tension roller on the inner arc reaches 250KN, manually lift the tension roller to avoid tension roller alarm; when tension roller alarm, promptly confirm and restore the alarmed tension roller. ④ When the actual casting speed displayed on the OS1 dial fluctuates frequently, the billet has stopped moving. The straightening roller on the first-level screen will definitely have an alarm. Reset the straightening roller in time to confirm. ⑤ If the billet still does not move, change the hot billet pressure of the horizontal section 10-18# pull straightening rollers to the ingot rod pressure, and raise the gap of the large pressing section 12-18# rollers by 5mm. If the billet still does not move at this time, stop casting immediately. (2) If the gap between the billet shell and the copper plate of the crystallizer is too large during the docking process, it may cause a steel leakage accident; ① Strictly control the time from the end of the intermediate pouring to the start of the next large pouring within 5 minutes to avoid severe shrinkage of the tail billet; ② After the tundish moves along, the flow must be thoroughly agitated, especially the narrow face of the crystallizer, to ensure that the steel flow continuously hits the narrow copper plate, and the gap between the billet shell and the narrow copper plate is within 5mm. ③ Before and after docking, check the four corner seams of the crystallizer for any residual steel and remove it promptly. If it is not removed in time, the casting speed after docking should be 0.2 m / min lower than the specified casting speed. After the docked billet exits the fan-shaped section, observe whether the shape of the four corners of the billet is normal. If it is normal, the casting speed can be increased to the normal speed. If continuous pits appear and there is obvious molten steel seepage, reduce the casting speed to the minimum speed and stop casting when the furnace is finished. (3) After the casting process begins, the stopper rod and the pad rod are used to prevent the steel loss from being controlled, which may cause the crystallizer to overflow with steel. ① The baking temperature of the tundish must meet the process requirements, especially the baking quality of the tundish top nozzle must be guaranteed to avoid cold steel forming when pouring begins; ② When inspecting the loaves of bread ready for baking, be sure to carefully check the loaf head and the area around the sprue for any debris; otherwise, clean them promptly. ③ Before docking, confirm that the quick-change hydraulic cylinder at the sprue is completely closed; ④ When pouring from the tundish, it is essential to ensure that pouring begins in the middle of the flow. When the molten steel submerges the side hole of the nozzle, a test bar should be performed. If it is found that the stopper bar cannot be closed completely, the stopper bar should be lifted in time. The straightening process should be started earlier and the emergence time should be ≥30 seconds. However, the pulling speed should not be forcibly increased. When the molten steel level rises to the position of the width adjustment channel, the blind flange should be applied in time and the machine should be moved.

2. The method for producing tundish joints of 370mm extra-thick slabs as described in claim 1, characterized in that, When the machine is running and the blind plate is being installed, add two bags of starter slag to each of the east and west sides of the crystallizer. Each bag of starter slag weighs 10 kg.

3. The method for producing tundish joints of 370mm extra-thick slabs as described in claim 1, characterized in that, Insert the tundish nozzle to the molten steel surface, 1 cm from the top edge of the nozzle side hole, or fully insert the tundish nozzle.

4. The method for producing tundish joints of 370mm extra-thick slabs as described in claim 1, characterized in that, When more than three straightening rollers alarm, stop straightening first, and restart straightening only after confirming that the alarmed straightening rollers have recovered.