Effect of Electro Slag Remelting (ESR) on the microstructure and mechanical properties of low carbon bainitic steel

Abstract

It is essential to produce steels free from impurities and inclusions and decrease the segregations as much as possible knowing that the quality of the primary cast steel is a very critical factor influencing its final microstructure and mechanical properties. For this aim, various refinement processes including Electro Slag Remelting (ESR) have been developed to gain high-quality primary steel for subsequent heat treatments and production procedures. This article aims to study the effect of primarily conducted ESR process on microstructural characteristics and final mechanical properties of carbide free low carbon bainitic steels isothermally obtained at 350 and 400◦C. Results indicated that applying the ESR process before the austempering heat treatments was beneficial in steel refinement and production of a clean product free from inclusions. Besides, it has been declared that the amount of the segregation in heat treated material decreased after conducting the ESR process and a much more uniform distribution of alloying elements within the primary austenite could be attained. Uniform primary austenite resulted in finer bainitic ferrites, much more uniform size distribution of bainitic subunits and higher volume fraction of high carbon retained austenite. Finally, it has been shown that higher values of ultimate tensile strength in combination with enhanced elongation and also improved impact toughness properties could be achieved in samples primarily electro-slag remelted.