PREDICTION OF TENSILE PROPERTIES OF INTERCRITICAL HEAT-AFFECTED ZONE

The tensile properties of the intercritical heat affected zone of stru ctural steels have been examined using the weld thermal simulation tec hnique. The investigation includes one normalised C-Mn steel, one norm alised and one rapidly cooled low carbon microalloyed steel, and two q uenched and tempered high strength low alloy steels. Depending on the base plate strength, high strength values with corresponding low ducti lity may be obtained at rapid cooling rates (DELTAt8/5 < 5 s, where DE LTAt8/5 is the time to cool the weld from 800 to 500-degrees-C). With increasing cooling time, the yield strength was reduced to a level bel ow that of the respective base plate, with an associated improvement i n ductility. In contrast, the tensile strength was higher than the ini tial base metal strength, independent of weld cooling time and chemica l composition of the steel. Both theoretical and empirical equations h ave been combined to predict the strength of the intercritical heat af fected zone from the volume fraction of martensite-austenite islands, the Vickers hardness, the strain hardening exponent, the weld cooling time between 800 and 500-degrees-C, and the peak temperature. A compar ison of measured and calculated values shows that both the yield stren gth and the tensile strength can be predicted with relatively high acc uracy.