Effect of Ca on the evolution of inclusions and the formation of acicular ferrite in Ti–Mg killed EH36 steel

Abstract

The characteristics of inclusions and the formation of acicular ferrite (AF) in Ti-Mg-Ca killed EH36 steel were researched. Typical inclusions in the Ca-free samples were MgO•Al 2 O 3 + MnS and pure MgO•Al 2 O 3 . With the addition of Ca, MgO•Al 2 O 3 was modified into Mg-Ca-Al-O , which promoted MnS precipitating on those inclusions. Mg-Ca-Al-O+MnS/MnS-CaS was the nucleus of AF. While pure MgO•Al 2 O 3 was inert for nucleation of AF. Therefore, the percentage of AF increased to 21% in the steel with 0.0017% Ca. However, 0.0051% Ca led to a rise of CaS content in the inclusions. Probability of AF nucleation on the inclusions was reduced due to high lattice mismatch between CaS and α-Fe. Area fraction of AF in the steel with 0.0051% Ca decreased while that of ferrite side plates increased. It is appropriate when the content of Ca is 0.0017% in this study.

Effects of Ti/N Ratio on Coarse-Grain Heat-Affected Zone Microstructure Evolution and Low-Temperature Impact Toughness of High Heat Input Welding Steel

“…If high heat input welding technology is adopted, thick steel can be welded in one pass to greatly improve welding efficiency. Therefore, it has gradually become a trend to develop steel suitable for high heat input welding technology to replace traditional steel [3,4].…”