Effect of small amounts of cerium on impact toughness and tensile properties of industrial Al-killed steel Q355D

The influence of cerium (Ce) on the mechanical properties of industrial steel was meaningful. And inclusions, grains, impact toughness, and tensile properties of industrial aluminium-killed Q355D were investigated by adding varying amounts of Ce. It was found that (i) inclusion of the sample without Ce was mainly manganese sulphide (MnS) and Al 2 O 3 -Mn(Ca)S, inclusion of the sample with adding 0.0017% Ce was mainly MnS- and Ce-based inclusions of CeAlO 3 –Ce 2 O 2 S–CaS, and inclusion of the sample with adding 0.0025% Ce was mainly MnS- and Ce-based inclusions of CeAlO 3 –Ce 2 S 3 –Mn(Ca)S; (ii) the number of MnS inclusions had decreased and shortened by increasing Ce. Meanwhile, Ce-based inclusions moved in the direction of decreasing size by increasing Ce; (iii) the grains were refined by adding Ce. In particular, fine acicular ferrite was formed by adding 0.0017% Ce; and (iv) the low-temperature impact toughness was best, and yield strength was the highest for the sample with adding 0.0017% Ce, which was attributed to the contribution of fine acicular ferrite and Ce 2 O 2 S inclusion.