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Two tool steels designated M 2 (based on Fe-0 . 8C-4Cr-5M o-7W-2V) and A2 (based on Fe-1 . 0C-5Cr-1M o-V, all wt-%) were preheated and rolled in three passes to a total reduction of 50% in the range 880 to 1150 C in which alloy carbides are dissolved to varying degree. The rate of isothermal transformation was determined by dilatometry for undeformed or deformed austenite related to annealing at 880 C or rolling from 1150 C preheat for steel M 2 and thermomechanical processing (TM P ) at 980 C for steel A2. The deformation accelerates the transformation to pearlite, but the high solution temperature retards it so that the net effect in hot rolled M 2 (1150 C) is retardation relative to annealed (880 C). In A2, TM P at 980 C results in acceleration compared to simply heat-treated and thus a reduction in hardenability. Carbide precipitation prior to the pearlite transformation is also enhanced by the deformation. The nal hardness of the deformed steels is much greater than that of heat-treated steels.

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