The Transformation Monitor directly measures the transformation of iron from austenite to ferrite through a real-time, online measurement of the ferrite concentration within the steel as it cools. It uses EMspec technology under license from The University of Manchester, U.K.
The Transformation Monitor breaks with the traditional approach of measuring the surface temperature of the steel on the runout table, a method which is open to error as the temperature reading can be affected—for instance, scale or water on the steel surface will produce a lower reading. In this case, however, the sensor head is constantly washed with water to prevent false signals caused by material on the surface. One or more sensor heads are located under the passline on the runout table. Each water-cooled head is in close proximity to the hot steel and generates a primary magnetic field which interacts with the hot steel, producing a secondary magnetic field that is detected by the sensor head. Austenite has a low magnetic permeability while ferrite has a high magnetic permeability, so the Transformation Monitor exploits this difference to measure the percentage of transformation that has occurred.
The Transformation Monitor measures transformation directly, making it superior to the common approach where modeling is still used to determine the microstructure of the final product by controlling rolling and cooling. This model often relies on parameters that are not exclusively related to microstructure. Given that certain steel grades do not fully transform to ferrite, a more useful measurement is the Transformation Index, a material-dependent measure of the ratio of austenite to ferrite in the final product. The Transformation Monitor can be installed into new and existing mills.