Title: Influence of Sulfur on AlN Precipitation during Cooling after Solidification and Resulting Hot Shortness in Low Carbon Steel
Abstract:The influence of sulfur on AlN precipitation during cooling after solidification and hot ductility was investigated in low carbon aluminium killed steels by means of a Gleeble tester together with che...The influence of sulfur on AlN precipitation during cooling after solidification and hot ductility was investigated in low carbon aluminium killed steels by means of a Gleeble tester together with chemical analysis and analyitical TEM. 1) The precipitation kinetics of AlN is very slow in austenite, but it is promoted with the addition of sulfur. 2) In the steels bearing sulfur, MnS precipitates first in austenite grain boundaries followed by the AlN precipitation, which preferentially takes place on MnS. The following orientation relationship was found between the two precipitates: (1\bar11)MnS\varparallel(0001)AlN, [110]MnS\varparallel[2\bar1\bar10]AlN and [121]MnS\varparallel[10\bar10]AlN. 3) This coherent heterogeneous precipitation was inferred to stem from the fact that the condition for the heterogeneous nucleation, which holds when the contribution of interfacial energy is large, was satisfied due to the relatively low interfacial energy of AlN/MnS as compared with that of γ-Fe/MnS. 4) The embrittlement of slabs during CC-DR (Continuous Casting-Direct Rolling) becomes understandable when the present result of AlN precipitation is superimposed in the convetional time-temperature embrittle curve. Namely, hot ductility becomes poor under the condition of the complex precipitation of MnS and AlN.Read More