BS in Materials Engineering
Materials Engineering Department
High strength, low alloy steel is most commonly utilized in plate or sheet form-with a thickness under 4 in, one unconventional application however, is open die forging where cross-sectional area can be as large as 9.5 in by 11.5 in. When forging to larger section size than one would thermo-mechanically roll sheet steel, a new set of complications, such as variation in microstructure and mechanical properties, arise. This study investigates the heat treatment and processing options needed to negate the inherent microstructural irregularity and Charpy V-Notch (CVN) toughness variation. Intercritical heat treatment—normalizing and then quench and tempering above the AC3, 1750°Fand then again between 1440°F – 1750°F, the AC1 and AC3 respectively, has lessened the CVN toughness variation, increasing the success rate of passing parts in production from 25% to 75%. By controlling cooling rate and section size in this micro-alloyed steel, lower variability was attained.