Rafael Coura Giacomin¹, Bryan Webler¹; ¹Carnegie Mellon University

The 3rd generation of Advanced High-Strength Steels (AHSS) is being developed to obtain good combinations of strength and ductility for automotive applications. These grades contain higher levels of manganese, silicon, and/or aluminum than many other steels. Although they exhibit excellent strength and ductility after appropriate processing, they are challenging to produce using existing steel production methods. One of the major challenges has been cracking of continuously cast slabs. This work examined microstructure-property relations in as-cast steels to identify the reasons for this cracking. Failed production slabs were examined and several laboratory heats were produced to vary chemical composition. Laboratory heat compositions were 0.2wt.%C, 2.5-3.0wt.%Mn and 0.5-3.0wt.%Si. Charpy V-Notch tests were used as a measure of toughness for all samples. Grades with higher silicon exhibited the lowest toughness due to a network of thin allotriomorphic ferrite at prior austenite grain boundaries.