| Microalloyed Steels (MA) steels typically develop adequate hardness and fatigue strength on cooling directly from forging temperatures without any secondary post-forging heat treatment. But the impact strengths are lower than conventional quenched and tempered steels.;In this dissertation the material related background on MA steels is reviewed. The results observed in isothermal upset tests of two typical MA steels are reported. Flow stress and processing-microstructure relationships are developed. Further, the results from pancake and complex forging trials are reported along with process-microstructure-property relationships. The effects of forging parameters, especially forging temperature cooling rate and strain, on microstructure and mechanical properties are examined in detail.;Further, a knowledge based computer system has been designed and developed using the relationships developed in the isothermal upset tests and the pancake forging trials. The results from the complex forging trials were used to verify the computer system.;In this dissertation a methodology for improving the process design sequence in hot forging is proposed with the use of systems to present the designer with concurrent knowledge of the resulting microstructure and properties. |
