Case Study of Steel Forgings Involving Heat Treatment

Engineering materials, mostly steel, are heat treated under controlled sequence of heating and cooling to alter their physical and mechanical properties to meet desired engineering applications. In this study we did research on formation of bainite patches i.e. acicular ferrite cementite matrix on normalizing heat treatment. Desired microstructure for SAE 8622 steel BP shaft is uniformly distributed fine pearlite. To solve the problem three way approaches are followed. First is software based using JMatPro to get cooling curves like CCT and TTT transformation curve second heat transfer laws and unsteady state heat transfer equation to get the actual cooling curve followed by sample and then validating both two by practical heat treatment operation and result analysis. In my work effect of sample size on microstructure is studied while performing same heat treatment operation. After studying all these it is concluded that gear blank of SAE 8622 steel with desired microstructure cannot be achieved by normalizing heat treatment. To achieve this microstructure isothermal transformation is to be used. By using CCT curve raw data from JMatPro and time temperature relation of sample while cooling calculated using heat transfer equation with the help of Microsoft Excel is clubbed on origin software to see the exact cooling curve followed by sample helps in optimizing heat treatment operation to be done. Selected heat treatment is performed on sample and desired results are obtained.