Thermomechanical Processing of Metals and Alloys

For commercial products in any industry, their external shapes are the result of hot deformation i.e. hot rolling. The necessary mechanical properties are deduced from the alloy design and through heat treatment after hot-deforma-tion. Thermomechanical processing (TMP) is a technique designed to improve the mechanical properties of materials by controlling the hot-deformation processes, which origi-nally were designed to produce the required external final shape of the product.The first introduction of TMP for commercial production was controlled rolling of C-Mn steel plates of 40kgf/mm2 grade for ship-building in the 1950s. During the World War II, a number of transport ships, so-called 'Liberty' ships suffered from the occurrence of
brittle fractures initiated at welded joints. This inci-dent stimulated the concept of toughness, which is diff-erent from the concept of ductility, and notch toughness became a requirement for ship-building and other structu-ral steel plates. At that time, the concept of ductile-brittle transition temperature through grain refinement was introduced. It was reported that an improvement of
about 10-15°C in the 20J transition temperature could be possible through controlled low temperature hot-rolling process.