Influence of Low Temperature Thermomechanical Treatment on Some Properties of High Alloy Tool Steels

The modification of mechanical properties (maximum bending strength and deflection, hardness and impact strength) of tool steels whose primary alloying elements are either chromium, tungsten, tungsten and molybdenum, or chromium and molybdenum by low temperature thermomechanical treatment (LTTMT) by rolling with deformations up to 20 percent and extrusion with 60 percent deformation has been investigated. The high chromium tool demonstrated the greatest consistent improvements in strength (40 percent) and deflection (55 percent) for LTTMT over conventional heat treatment. The influence of the LTTMT process on the microstructure of the chromium and tungsten steels is investigated by fractography using a scanning electron microscope. The tungsten steel and the extrusion process yielded a finer distribution of hard particles in the ductile matrix than did the chromium steel and rolling.