SCHINDLER Ivo VSB - Technical University

Optimization of the Rolling Speed at Hot Forming of Iron Aluminide of the Type Fe-40at.%Al

Co-authors ŠUMŠAL Václav, FABÍK Richard

Iron aluminides are of interest due to their excellent high temperature oxidation–corrosion resistance in aggressive environments. They are potential replacements for high temperature steels. The iron-based composition ensures relative cheapness, while the high aluminium content leads to significant density reduction in comparison with commercial steels. It was considered as a structural material without any possibility of forming. The casting process has been used as the only processing technology of this material. A special hot flat rolling technology for such material was developed in laboratory conditions. The particular sample with extremely coarse-grained cast microstructure is placed into the special protection capsule, prepared by welding of the sheet from steel X6Cr17. The capsule should prevent surface transverse cracking of the hot rolled casting since the direct contact of the cold work rolls with the surface of the iron aluminide and thus principle cooling of the surface of the rolled material is eliminated. Previous experiments provided us valuable information on influence of rolling temperature and magnitude of individual reductions on technological formability of iron aluminide, and on possibility of grain refinement by repeated recrystallization. The last stage of research was focused on optimization of the rolling speed. Plastometric experiments revealed favourable influence of low strain rate on hot plasticity. Physical and computer simulations showed, however, that very low rolling speed led to an excessive cooling of surface layers of the specimen by heat removal into the working rolls, which resulted in massive surface cracking even under protective capsule.