The RSD system for a precise measuring of residual steel in the tundish of continuous casting machines maximizes the yield from the tundish. In case of one steel grade change to another, the system minimizes the intermixing zone in the strand.
Customers of the steel making industry demand ever more specialized grades of steel in combination with increasingly shorter delivery times. Therefore steel plants must produce different grades of steel at increasingly shorter intervals.
During a steel grade change two grades of steel mix in one tundish, resulting in a product of lower quality. The “mixed steel” means unnecessary costs and ought to be reduced to a minimum.
The “residual steel detector”, developed by AMEPA, measures the amount of steel remaining in a tundish so precisely that it can be emptied almost completely before a new grade of steel is poured in. This results in substantial cost savings.
In this application too, sensors and measuring components have to meet strict requirements.
When draining the tundish, no slag flow occurs until a characteristic steel level hcrit relative to the refractory bottom is reached. Below hcrit the probability of a slag carry- over will rise rapidly.
This was verified successfully in field trials for tundishes operating with stopper rod control.
If the residual steel level can be measured accurately enough the tundish can be drained near to h without an increased risk of slag flow.
Towards the end of draining, the measurement of the effective residual steel level by existing level control systems is not accurate enough, with respect to the unknown amount of slag contained in the tundish and the refractory lining wear.
The AMEPA RSD system however measures, by use of an electromagnetic method, the effective steel level with high accuracy.
Alternating currents of multiple frequencies are fed into coils of the sensor, generating eddy currents in the melt above the sensor. The eddy current in the residual steel generates a characteristic signal in the sensor coils. From this the effective steel level is derived.