Flow velocity and two phase flow measurement
in steel production
AMEPA GmbH, Jülicher Straße 320, D-52070 Aachen
Steel is and remains one of the most important manufacturing materials. The requirements regarding material characteristics and purity are constantly rising. The steel production process requires therefore an increasing effort regarding process control. Flow related influences on quality - positive and negative - have become a topic of great interest in the last years.
During the course of steel production the steel is poured several times from one vessel into another. But the slag which arises during each step of the process must not be transferred into the next vessel. Here electromagnetic slag detection systems have been successfully implemented. Equipped with high temperature sensors they detect the entrainment of slag into the discharged steel stream accurate and with high sensitivity. The amount of carried over slag is significantly reduced.
In the case of continuous casting the molten steel is poured from a tundish into a water cooled copper mould. The steel flow in the mould has an important influence on steel cleanliness. A lot of water model studies and computer simulations dealt with this problem. During the last years also several flow measuring techniques were developed and tested to determine the steel flow under production conditions. Most of them use a kind of a ceramic probe that is immersed into the steel.
A system that is able to monitor the flow velocity under production conditions was tested at Thyssen Krupp Stahl in Dortmund as well as in other steel plants. The electromagnetic sensors are mounted behind the walls of the mould. They consist of permanent magnets and sensitive receiver probes.
Metal flow measurements were carried out at a laboratory mould model using a kind of Woods metal and it was shown that the flow velocities were in close correspondence with results achieved with a conventional flow meter.
The steel plant operation of this flow monitoring system has shown significant correlation between casting parameters and mould flow pattern. Especially the influence of submerged nozzle position, nozzle outlet angle and argon rate have been investigated and the inclusion rate in a series of cold rolled strips has been correlated with the monitored mould flow pattern.
The results led to suggestions for improvements of the casting equipment.