Influence of Al deoxidation on the formation of acicular ferrite in steel containing La

The formation of acicular ferrite (AF) in steel containing Lanthanum (La) with different contents of Aluminum (Al) has been investigated. It has been found that the amount of AF in La treated steel killed by Al is less than the one with little content of Al. The reasons are as follows: first, Al can change the type of La-containing inclusions and may reduce the effectiveness of La inclusion to induce the nucleation of AF. second, Al can make the cooling rate range of AF nucleation narrower in La treated steel. What's more, Al can increase the decomposition temperature of austenite, and all these make AF formation difficult. In this study, the content of Al should be controlled to less than 0.018 wt% to obtain a more effective inclusion to induce the formation of AF.