Microalloyed Steel Preforms

An analysis was conducted on two types of microalloyed steel to study their metallurgical, mechanical, and processing characteristics, and also to evaluate the suitability of utilizing these alloys as forgings for small gun tube components. The primary benefit associated with these steels is that optimum properties can be attained by direct quenching from the forging temperature. Presently, typical hot forgings must be thermally treated after forging to obtain desired properties. A test matrix was constructed to facilitate examination of the previously stated characteristics. The criteria included alloy type, heat-treatment temperature, forging reduction, tempering temperature, and bar diameter. Test results were compiled in a mechanical property data base that included hardness, tensile strength and yield strength, impact toughness, and ductile-to-brittle transition temperature. Further evaluation of these data enabled the determination of a desired processing route to achieve optimum properties. Based on the limited drawing specification requirements of only hardness, it was determined that several different processing combinations could yield acceptable results. However, for optimum properties hardness, it was found that section thickness should be limited to one inch or less.