In order to reduce the cost and increase the operating rate of the continuous casting machine, when the tundish reaches the service life, it is necessary to carry out the hot-swapping operation of the tundish. During the hot-swapping of the tundish, the casting billet drawing speed is stopped, and the casting billet is still in continuous spraying In the cooling state, if the heat exchange time of the bale is too long, it is likely that the slab is cooled too much, which makes the slab hard and causes stagnation, interrupts production, and may even cause a frozen slab accident. At present, there is a hot-swapping operation for the tundish in the CCM of the steel plant, but there is no specific description of the control range of each operation.
This article aims at the continuous casting of slabs in steel mills and the pulling speed during the hot exchange of the tundish, which makes the slab continuously cooled by spraying, resulting in excessive hardening of the slab cooling and production problems in the slab. The method improves the success rate of heat exchange and the operation rate of continuous casting machine, reduces the labor intensity, and plays an active role in demonstrating energy saving and consumption reduction of enterprises.
The purpose of this method is to improve the success rate of the heat exchange of the continuous casting machine, control the heat exchange time of the tundish within 5 minutes, reduce the cost and improve the operation rate. The following are the specific contents:
Step1 The ladle waiting time is 5-10min, the ladle reaches the continuous casting platform temperature 1590-1600°C;
Step2 The pulling speed of the tundish molten steel is reduced by one gear every 20 seconds, and the pulling speed is reduced to 0. 3m/min within 8min;
Step3 Measure the liquid level of the tundish. When the liquid level of the tundish is 300-500mm, drive the standby tundish to the heat exchange preparation area. When the tundish stops pouring, move the standby tundish and the pouring tundish to the other side start simultaneously on the side;
Step4 After the spare tundish car is opened to the pouring position, quickly install the red hot immersion nozzle (the bake time of the immersion nozzle is 2h longer), adjust the position of the tundish car so that the immersion nozzle is in the middle of the crystallizer, and install the blind plate After that, adjust the height of the tundish car to ensure that the bottom of the immersion nozzle is 150-180mm away from the upper mouth of the crystallizer;
Step5 When the tundish is ready, the ladle is opened, after pouring 10 tons of molten steel, 150-200kg of covering agent is added to the tundish, and the temperature of the open tundish is measured, which requires> 1550°C;
Step6 When the ladle is poured 20 tons, the tundish starts pouring, and the tundish molten steel is poured into the crystallizer;
Step7 After the pouring of the tundish, the emergence time is controlled at 80-120S. When the molten steel in the crystallizer reaches 115-125mm from the bottom of the immersion nozzle, that is, the molten steel has not passed the immersion nozzle, the pulling start operation is carried out, and the pulling speed after starting 0. 3m/min, 0. 3m/min pulling speed is maintained for 1min, and then the pulling speed is increased to the normal value of 0.9m/min; from the first tundish stop to the start of the second tundish, the time is controlled at 4 -5min.
The operation points of the present invention: coordinate the rhythm of molten steel, control the time of molten steel preparation ladle and reach the temperature of continuous casting platform, control the speed drop time and control the liquid level height of tundish; Simultaneously start the standby tundish and the pouring tundish at the same time. After the standby tundish is opened to the pouring position, the submerged nozzle is quickly installed and centered. After the blind plate is installed, the large tundish is poured; from the first tundish The total pouring time from the pouring stop to the replacement of the tundish is controlled within 5min; this method shortens the hot exchange time of the tundish as much as possible to avoid the stagnation phenomenon caused by the excessive cooling time of the casting slab, and demonstrates the technological progress.
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