Mathematical Model of Microstructural Evolution of Hot Rolled Wire Rods for Nb Microalloyed Steels

Wire rods are supplied for end users manufactures of products with increasing complexity and mechanical properties requirements. Demanding end users field applications must provide high yield stress, ductility and, in certain cases, toughness. These properties can be improved simultaneously if appropriate rolling technique and alloy design are used. It has been known for decades in the flat rolling industry that microalloyed steels can be produced achieving requirements just mentioned. The technology, however, is less often seen applied at the long products industry. In order to obtain metallurgical sound products, steelmakers need to run industry scale trials. These, however, are costly, time consuming and results are not always easy to analyze given the number of variables involved. Mathematical models are frequently used in order to reduce plant trials reducing costs. There models already published in the literature suitable for wire rod applications. They are however more concerned with the thermomechanical process than with alloy design. This paper presents a model for wire rod rolling of microalloyed steels in which some consideration to alloy design is taken into account. Predicted and mill trial results were compared. Reasonable agreement was found proving the model to be a valuable tool in both schedule and alloy design.