Development of structural steels with fire resistant microstructures

This paper is concerned with the design and characterisation of fire resistant steels for building construction. Steel design considerations are discussed. Issues raised include controlling the grain size, properties of substitutional elements, and processing. New experimental fire resistant steels microalloyed with molybdenum and niobium, or tungsten, titanium, and boron have been made and their microstructures and tensile properties characterised. The steels possess satisfactory high temperature strength, owing partly to their relatively large grain sizes compared with conventional steels. The nature of equilibrium precipitation has been calculated using Thermo Calc. Optical microscopy, SEM, TEM, and differential scanning calorimetry have been used to determine the physical characteristics. The strengthening mechanisms observed on the experimental steels of this study could be attributed to secondary formation of fine precipitates, in line with previous observations. MST/4936.