Influence of coiling on microstructural evolution and mechanical properties of strip-cast low-carbon low-niobium steel

As-cast low-carbon low-niobium steels fabricated by direct strip casting (DSC) were treated by simulated coiling in the lab. Coiling temperatures were carefully selected: (1) 900 °C (in the austenite); (2) 700 °C (during the austenite-to-ferrite transformation); (3) 650 °C (in the ferrite). Optical microscopy and transmission electron microscopy were used to examine the microstructure constituents and the precipitates. Mechanical properties were evaluated by Vickers macrohardness measurements. The results show that coiling treatment has a strong influence on the final microstructure and mechanical properties, thus highlighting the necessity to carefully design the coiling treatment. In addition, the differences in hardness for the three coiling temperatures derive from a complex combination of different strengthening mechanisms.