Micro tension controlled rolling
Micro tension controlled rolling (MTCR) is an advanced technology for the production of high-strength, high- ductility strip. It combines the advantages of cold rolling and conventional hot rolling, allowing for the production of thinner and longer strip with a guaranteed surface quality. The process is suitable for a wide range of materials, including plain carbon and alloy steels, titanium alloys, and stainless steels.
In MTCR, stainless steel strip is first heated to around 800–900 °C. This high temperature is necessary in order to attain a ductile microstructure. Once the strip is heated, it is placed in a mill with a relatively large (2000–3000 N/mm2), yet constant, vertical tension. This is done by maintaining a vertical force on the strip, thus providing minimal internal stresses. At these temperatures, if the strip were allowed to cool to ambient before rolling, it would result in a brittle cracking along either the shear plane or longitudinal direction.
As the strip is being rolled, the temperature of the heated strip is maintained by passing water over it. In addition, a vertical roller is positioned and maintained on the strip to maintain a high precision of rolling. This allows for the strip to maintain the necessary tension throughout the entire rolling process.
The vertical roller also allows for a higher strip speed. This is due to the contributions of the vertical tension and the increases in the strip’s attainable yield strength. In addition, due to the controlled and constant tension, the strip is able to suffer greatly reduced stress concentrations on the rollers, reducing the possibility of rolling defects such as scratches, peeling, and cracks.
The process also offers a high degree of grain refinement which results in improved ductility and formability. The use of high temperatures and a steady rolling process means that during the rolling process, dynamic recrystallization occurs. This is a process during which the microstructure of the strip is refined, resulting in a more homogeneous environment within the metal.
Overall, the MTCR process is an efficient and flexible method of producing thin steel strip with a guaranteed surface quality. It is ideal for the production of high-strength, high-ductility strip, and is also suitable for a wide variety of materials, including plain carbon and alloy steels, titanium alloys, and stainless steels. It is also beneficial for its ability to produce strips that have improved ductility and formability thanks to the dynamic recrystallization process. With the help of the high precision rolling techniques, the process can be used to create strips that are thinner and longer than conventional hot rolling methods. The result is a process that is cost-effective and reliable, making it an excellent choice for steel strip manufacturers.
