Automatic control of molten steel level in copper mould tube

Why is the automatic control of the molten steel level of copper mould tube necessary?
If manual pouring is performed, the molten steel level of copper mould tube will fluctuate widely, which will also cause slag inclusion and slag entrapment. The rapid change of the drawing speed causes uneven cooling, which affects the surface quality of copper mould tube casting billet. The automatic control of copper mould tube and the molten steel surface has a small fluctuation in the drawing speed, which overcomes the shortcomings of manual pouring, thereby improving the quality of the cast slab.

There are four commonly used methods for copper mould tube molten steel level detection system: source type, eddy current type, infrared type and electromagnetic type.

The isotope radiation source is used, and the scintillation crystal receiver is used to receive the radiation that changes with the height of the molten steel liquid level, thereby detecting the liquid level height.

The electromagnetic signal in the eddy current sensor generates an eddy current on the surface of the molten steel. The eddy current generates an induction signal in the sensor coil. The magnitude of the eddy current changes with the distance from the surface of the molten steel to the sensor. Suitable for slabs and rectangular blanks with large cross-sections.

The vertical suspension of the eddy current sensor is installed above the copper pipe mouth of the mold and cooled by compressed air. There is no need to modify the mold, because it is restricted by the installation conditions, the eddy current type cannot be applied to the small section continuous casting machine.

It is suitable for the open pouring method without protective slag. It is susceptible to moisture, smoke, etc. At present, this method is rarely used.

The sensor is installed on the copper plate mould, and the sensing surface is flush with the inner surface of the copper plate. The sensor emits electromagnetic signals and receives the returned eddy current. Its intensity is proportional to the molten steel level. The basic principle is similar to the eddy current type, but the installation method is different. (The eddy current type mounts the sensor hanging above copper mould tube mouth, while the electromagnetic type mounts the sensor on the mold copper plate).

Suitable for slabs and large-section rectangular billets. Compared with the eddy current type, the electromagnetic type eliminates the need to move the sensor every time the tundish is replaced, but it is expensive.

In order to ensure the surface quality of copper mould tube casting billet, it is very important to carry out the molten steel level detection and automatic and stable control.