Influence of composition and processing variables on mechanical properties of As-cast C-Mn cast steels

The influence of chemical composition and foundry processing variables on the properties of C-Mn cast steels in the as-cast condition has been evaluated. This new class of as-cast steels differs significantly from conventional cast steels that are used only after heat treatment. Control of both composition and cooling late is necessary to provide consistent as-cast microstructures and properties. In this study, 20 alloys with variations in base carbon and manganese levels were produced to investigate the important effect of composition on the properties of as-cast steels. Vanadium additions, as well as the effects of pouring temperature, hot shakeout and chill castings, were also evaluated. Quantitative metallography was used to establish the influence of microstructure on as-cast properties in the as-cast condition. Compositions with 0.16-0.18% C and 1.2-1.6% Mn had the best combination of mechanical properties. As-cast tensile strengths ranged from 50-90 ksi (350-610 MPa), yield strengths ranged from 25-45 ksi (170-310 MPa) and tensile elongation ranged from 20-40%. Rapid transformation cooling rates from hot shakeout improved tensile properties without sacrificing ductility. Further improvements in properties were achieved with 0.08% vanadium additions. Yield strength values as high as 64 ksi (440 MPa) were achieved for low-cai-bon content, vanadium alloyed as-cast steels subjected to hot shakeout.