| Inferior drawability of AISI4135 steel rod is sometimes due to the presence of hard constituents such as bainite and martensite in the microstructure of as-hot rolled state. The amount of hard phases can be minimized by controlled rolling, thus refining the austenite grains, which, in turn, shift the CCT diagram towards shorter times. For the same cooling rate, the austenite to ferrite-plus-pearlite transformation is accordingly enhanced. In conducting numerous hot torsion tests, equations describing the recrystallization behavior of AISI4135 steel during hot deformation were developed in order to find the best condition for grain refinement. Austenite grain sizes predicted by the equations are in good agreement with data from commercial rod rolling. |
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