Before the 1980s, controlled rolling technology was not perfect, the process was very complex and confusing, and the role of microalloying was elusive depending on the controlled rolling system.
The concept of austenite adjustment was proposed in the mid-1990s, which hit the mark. In the early stage of hot deformation in the rough rolling stage, there is recrystallization of austenite and the precipitation of niobium, which pave the way for the finishing rolling stage. The ultimate goal of preparation and deformation in the finishing rolling stage is to obtain austenite grains of suitable size.
The second meaning of austenite adjustment is that in order to obtain fine ferrite grain size after γ/α phase transformation, a high ferrite nucleation rate and a low grain growth and crystallization rate are required.
For this reason, the importance of the deformation of the non-γ-recrystallized zone has been theoretically analyzed, and two types of controlled rolling processes, high-temperature recrystallization controlled rolling (RCR) and low-temperature conventional controlled rolling (CCR), have been summarized, as shown in Figure 1 Show.
The former type must enlarge the window between soaking temperature and T95, while the latter type needs to enlarge the range between T5 and final rolling temperature. Niobium-containing stainless steel is very conducive to CCR controlled rolling.