Quantitative study on yield point phenomenon of low carbon steels processed by compact endless casting and rolling

Abstract

Compact endless cast and rolling mill (CEM) is an innovative process to manufacture a hot-rolled steel strip by combining casting and hot-rolling processes. However, the yield point phenomenon (YPP) of low carbon steel strip-processed by CEM induces a negative effect in the steel product and an additional post-process is required to remove the YPP. In this study, the influence of the dislocation density and the grain interior solute atoms on the yield point elongation (YPE) of low carbon steels were quantitatively investigated using 3-dimensional atom probe tomography analysis and X-ray convolutional multiple whole profile fitting. The YPE of low carbon steel is suppressed as the dislocation density increases and carbon atom content decreases. Because the dislocation density of low carbon steel by the CEM process is increased by lowering the processing temperature, the yielding behavior of the CEM products can be eliminated without any additional post-processing. The quantitative study on the carbon/dislocation density and YPP of low carbon steel not only represents the theoretical basis of the role of carbon-dislocation interaction on YPP but also provides an effective solution to optimize the CEM process for superior products.