Thermo-mechanical processing and microstructure of microalloyed steel bar and wire rod products

Abstract

Microalloyed steels exhibit superior mechanical properties in the as-processed condition without requiring further heat treatments. This has been achieved by thermo-mechanical (TM) processing these steels with micro-additions (ranging from 10-3 % to 10-1 %) of carbonitride formers, notably niobium, vanadium, titanium, zirconium, and boron. They offer an array of steels for fabricators and end users to lower cost while maintaining or improving product performance. This paper reviews the role that the microalloying elements play in bar and rod mill processing, and how they influence the evolution of the microstructure of austenite and ferrite during thermo-mechanical or controlled rolling schedules. It also examines the future requirements which include a better understanding of fabricators and end-user requirements, computer-aided system for analysing thermo-mechanical processing, innovative strategies in alloy design and thermo-mechanical treatments, and prediction of properties in the final products. © 1995.