Developing a Technology for Rolling Low-Alloy Steel Plates by Modeling the Structure-Forming Processes

Controlled rolling is widely recognized as an effective means of improving the properties of steels. However, its use requires powerful rolling equipment and steels of optimum chemical composition. The technology need not be used when the requirements for the rolling operation are less stringent - other rolling regimes executed at higher temperatures can be used. That makes it possible to obtain strong rolled products having satisfactory toughness without incurring additional costs for heat treatments such as normalization. Among the other technologies that can be used are normalizing rolling (NR) and controlled recrystallization rolling (CRR). The processes CRR and normal are fairly similar to one another: deformation occurs at relatively high temperatures in both cases, in order to refine the grains. However, CRR is one of the heat treatments for which no precise temperature range is specified for deformation above the temperature at which austenite recrystallization ends. In addition, CRR entails additional steps to optimize the technology (for example, the semifinished product must be heated to a temperature no higher than the temperature at which intensive austenite grain growth begins; also accelerated cooling is required after deformation) and optimize the chemical composition of the steel (use of the alloying system C-Mn-V-Ti-N) in order to obtain the best results. The specifics of the normalization regime are determined by the structure and properties of the metal and depend in large part on the thickness of the rolled product. The goal of our study was to determine the feasibility of obtaining a favorable fine-grained structure and a prescribed set of properties in low-alloy steels subjected to high-temperature deformation and subsequent cooling (accelerated cooling or cooling in air).