Electromagnetic Slag Detection Machine

Slag-free transfer of molten steel is critical for prime or scrap and for profit or loss in producing high-quality steels. Regardless of whether it is for furnaces, ladles, or distributors: Large quantities of slag must never be transferred to the next vessel. The ESD Electromagnetic Slag Detection, positioned at the ladle bottom, sounds an alarm when slag flows through and automatically sends a signal to close the slide gate.

The sensor is installed in the outlet opening of the pot and through a transmitter installed in the field, it sends the characteristics of the melt passing through the passage of the pot to the terminal board and the slag detection system in the control room. This sensor works based on magnetic field and voltage induction from primary to secondary. The primary coil is excited by an AC electric current, generated by the slag detection system. The voltage of the secondary winding depends on the type of material passing through the bottle outlet. Therefore, the molten steel creates a different voltage compared to the induced voltage during the passage of slag, and the slag detection system reveals this difference.

Slag Detection System

The slag detection system compares the signal received from the secondary sensor with the primary excitation signal and displays the slag percentage in terms of the standard current of 20-4mA in its output. There is also an LED string installed in front of the device that shows the percentage of slag at any moment.             
Also, the Slag Set-Point reference value is set with two keys on the front of the device, and the reference value is displayed on the left LED string.

As soon as the amount of slag at the bottle outlet reaches the Slag Set-Point percentage, a Normally Open relay contact is activated and closed. This contact is sent both to the foundry control system, to the command to close the melt exit slide gate, and to the local panel and siren in the foundry operator's pulpit. This contact can be connected to a PLC system or any desired system.            
The standard current output of 4-20mA, which shows the percentage of slag as a continuous value, is active during the whole process of emptying the bottle, which displays the percentage of slag and sends it to the control system and PLC. The analog output channel of the slag detection system can be connected to any standard analog input channel.

Performance Test

At different stages of designing and manufacturing the machine and its sub-sections, tests were carried out in the casting unit of Esfahan's Mobarakeh Steel Company. After completing the construction steps and making the final settings, in March 2023, the final functional test in this unit was successfully performed on casting machine No. 3.

Structure and Main Components of System

Advantages

• Product quality increases due to the automatic prevention of slag entering the production products in the casting line
• Increasing productivity and reducing the production cost due to clogging of shroud's path and cleaning tundish from slag
• Eliminate human error (which is unavoidable in a manual system)