Mold Level Automatic Measurement System

Overview

The automatic control for the molten steel level of the mold is one of the key technologies of continuous casting production. It is very important to reduce the labor intensity of workers, improve production efficiency, improve the quality and output of casting billet, reduce overflow and breakout of steel and improve the management level of steelmaking and continuous casting.

The molten steel is poured into the mold. In order to prevent overflow, the molten steel level must be kept stable. Otherwise, during the casting process, if the level will fluctuate too much, and slag will be involved, forming surface slag inclusion on the surface of the casting billet, affecting the quality of the billet. The test points out that the relationship between the level fluctuation and the depth of casting billet surface slag inclusion is as follows:

The experience has shown that surface slag inclusions can be eliminated when the level fluctuation is within ±10mm. At the same time, if the level fluctuation is more than 10mm, the rate of longitudinal cracks on the casting billet surface is 30%. It means that the level fluctuation directly affects the surface quality of the casting billet.



The function and software implementation

In order to overcome these disturbances, the mold level control strategy adopts PID control. And on the basis of PID control, self-adaptive correction and feedforward control are introduced to form an advanced control system. The level control is the main loop, and there is a proportional gain of the main loop controller. According to the self-adaptive correction of the mold width change and feedforward compensation of casting speed, so as to further reduce and eliminate liquid level fluctuations caused by mold width adjustment and casting speed changes.

In order to reduce the frequent action of the stopper, the system adopts the intergarting time change of the controller, and automatically selects a longer intergarting time when the molten steel level fluctuates lightly. And the system will choose a shorter intergrating time when molten steel level fluctuates greatly. Thereby, the fluctuation of the controlled object caused by the frequent action of the stopper rod is suppressed.

In the signal processing of molten steel level gauge, an appropriate filtering link is added and the vibration frequency synchronous filter is used for filtering processing, which can overcome the interference of mold vibration frequency and amplitude variation.