What is continuous casting automation?

Continuous casting automation is an automatic control process that directly casts molten steel into billets of various specifications through a continuous casting device. Compared with the traditional steel mould ingot casting method, it can save the steel mould ingot casting device and the expensive blooming device and has the advantages of saving energy, improving product quality and yield, and reducing costs. Generally, the yield of molten steel can be increased by 6 to 10%, the energy consumption per ton of billet can be saved by 50 to 80 kilograms of standard coal, the workshop area can be saved by about 50%, and the weight of equipment can be reduced by about 30%. It can also shorten the production cycle and improve labour conditions.

The continuous casting automatic control system mainly consists of production management level computers, process control level computers, equipment control computers, various automatic detection instruments and hydraulic devices. It can complete 7 control functions: tundish tank and mould liquid level control; mould slag filling amount control; secondary cooling water control; billet drawing speed control; slab optimal cutting length control; slab tracking and operation Control; automatic casting and stop control of continuous casting machine.

 

continuous casting automation, continuous casting

 

1. Liquid level control of continuous casting automation

 

1) Liquid level control includes two aspects: intermediate tank liquid level control and crystallization liquid level control.

 

The former is to control the molten steel level in the tundish tank within a certain range to stabilize the pressure of the molten steel injected into the crystallizer and create conditions for crystallizer liquid level control. Usually, the molten steel level in the intermediate tank is measured indirectly by weighing method or directly by electromagnetic induction method and controlled.

The latter is to control the molten steel level in the crystallizer within a certain range to ensure stable heat exchange of the molten steel in the crystallizer and form a good and uniform shell. The liquid level is usually controlled by using a hydraulic device to control the amount of molten steel flowing through the sliding port of the intermediate tank. Crystallizer liquid level detection includes the isotope method, thermocouple method, eddy current method, electromagnetic induction method, laser method ultrasonic method, etc.

 

2) Control of the amount of mould powder loaded

 

In order to prevent the oxidation of molten steel in the mould and reduce the friction between the slab and the surface of the mould, a certain thickness of protective slag is usually covered on the surface of the molten steel in the mould. It also plays a role in stabilizing heat dissipation on the surface of the molten steel. The amount of mould flux added is controlled by measuring the thermal radiation on the mould flux layer.

 

3) Secondary cooling water control

 

After the continuous casting billet is pulled out of the mould, its shell is thin and there is still molten steel in the middle. It still needs to be sprayed with water to continue cooling. This is secondary cooling. The amount of secondary cooling water is usually controlled based on the steel type, billet thickness, and drawing speed. The main device in the secondary cooling water volume adjustment system is a microcomputer, which uses the heat conduction equation of the steel billet as a mathematical model and uses the billet surface temperature as a feedback signal to control the secondary cooling water volume. Proper control of secondary cooling water volume can avoid cracks in the cast slab. Therefore, secondary cooling water control is a key link in the defect-free slab production process.

 

2. Casting speed control

 

The casting speed is determined based on the steel type, billet size, molten steel temperature and output requirements. The continuous casting production process requires that the casting speed be kept constant to ensure stable heat exchange of the slab. There is a speed adjustment system on the tension and levelling machine to ensure stable tensioning speed. When the liquid level in the mould exceeds the upper limit and the liquid level adjustment system cannot be adjusted, the pulling speed needs to be accelerated to prevent the molten steel from overflowing; similarly, if the molten steel in the mould is lower than the lower limit, the pulling speed needs to be slowed down to prevent steel leakage. When these two situations occur, an alarm will be issued and corresponding handling will be done.

 

3. Optimal cutting length control

 

The continuous cast billet is cut into lengths for rolling. To avoid short billets at the end and increase the yield of molten steel, the optimal cutting length can be calculated based on the billet size, molten steel volume, drawing speed and the allowable billet length range. Correction can be made at the later stage of ingot casting to ensure that the final billet length is appropriate.

 

4. Cast slab tracking and operation control

 

Track the billet, record its storage location and quantity, and print a number on the billet so that there is production data for the billet during rolling. The billet tracking and operation control system consists of billet detectors and microcomputers. The stacking location and original data of each slab are stored in the computer. When a certain slab is needed, it can be found out from the computer at any time and notified to the crane driver, who will send it to the next process according to the address. Since the continuous casting billet has not been completely solidified before the straightening rollers, the mechanical strength is very small. To avoid cracks caused by external forces, it is necessary to detect the openings of each support roller and the straightening roller in time and adjust them to the appropriate size.

Detection methods in the modern continuous casting production process are gradually being improved, such as billet crust thickness detection, leakage prediction, molten steel slag inclusion alarm, online detection of billet surface defects, etc. The realization of these projects will greatly improve the accuracy of continuous casting process control. Further improvement of the mathematical model of heat conduction in cast slabs will also improve the yield of defect-free cast slabs. The new continuous casting and rolling process is a good way to save energy, so it is necessary to ensure that continuous casting produces defect-free slabs. Continuous casting computer control is the means to achieve this goal. The continuous casting and rolling process will gradually replace the method of reheating the slab after cooling. Craftsmanship.

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