Optimization of hot-metal working of austenitic stainless steels

Abstract

The present paper ends the series of industrial research performed by the author with regard to the heating optimization of the austenitic stainless ingots. Austenitic stainless steels possess the best thermal shock resistance properties at low temperatures and the best resistance to elevated temperatures, with versatile demands in the economy. For all stainless steel grades, the best hot workability is obtained when the structure of the steel at the hot-metal working temperature consists of a single phase. Small quantities of ferrite can be tolerated in the structure of the austenitic and martensitic steels as well as small quantities of austenite in the structure of ferritic steels, but these have to be maintained within certain limits, either through an appropriate change of the chemical composition of the steel, or through the control of the hot-metal working temperature. Therefore, the research observes the evolution of the structure during the heating of austenitic stainless steels, stating the soaking zone favourable for reducing the existing content of ferrite down to values that do not worsen the plasticity. Based on the conducted research, a new heating technology was designed, resulting in the reduction of the heating duration and a high efficiency in terms of the dissolution and spheroidization of the residual ferrite in the basic austenitic structure.