The characterisation of irregular austenitic grain growth in micro-alloyedforging steels by linear analysis

A method of evaluating the austenitic microstructure of micro-alloyed forgi ng steels during preheating is presented. The measurement of the austenitic grain size is carried out by semi-automatic linear analysis on a suitably prepared specimen. A method of evaluating the chord length distribution of such microstructures is demonstrated on a number of specimens of the steel 27Mn-SiVSG heat treated at temperatures from 1000 to 1350 degreesC. By comp arison with Poisson-Voronoi Mosaics, an uniformity factor can be derived fr om the linear analysis data as a quantitative determination of irregular gr ain growth. For the type of steel chosen, the range of temperature over whi ch irregular grain growth occurs is determined to be from 1100 to 1250 degr eesC.