The machinability of abrasion resistant AR450 steel was examined using industrial steel samples obtained for different process routings including: EAF vs. BOF steelmaking and steady state vs. non-steady state casting conditions. Samples for machinability testing were cut from fully processed AR450 plate samples and a fixed volume machining test was conducted to measure the progressive flank wear of the machining tool during machining evaluations. Machining chip analysis, tool wear measurements, tool surface analysis and microstructural characterization of the steel were performed to investigate factors affecting the machinability of each steel sample. Metallography and cross section hardness testing confirmed the presence of a martensitic microstructure for all samples tested. Automated SEM/EDX analysis was employed to characterize the non-metallic inclusions present in the steel. Non-metallic inclusions were observed to have a significant influence on the machinability of AR450 steel.