THE STRENGTH AND PLASTICITY OF BASE-METAL HAZ OF WELDED JOINT OF 3CRO7MOO3 AND 2CRO6MOO1V1.2NI STEELS AT ELEVATED-TEMPERATURE AND THEIR RELATIONSHIP WITH REHEAT AND UNDERCLAD CRACKING

The article presents the results of mechanical tests of 3CrO7MoO3V and 2CrO6Mo O1V1.2Ni steels and their simulated HAZ at 20 degrees C and a t elevated temperatures. The kinetics of precipitation hardening was a lso studied. The results of study of microstructural transformations a re compared with the results of tests of mechanical properties. The ch anges in mechanical properties in dependence on the time and level of thermal effect are explained on the basis of Ashby's model of deformat ion of plastically inhomogenous matters. The results suggest that for the known precipitation kinetics of the secondary phase in a given ste el it is possible to predict the qualitative changes in the strain har dening coefficient and material plasticity according to the value of H olomon-Jeffe's parameter.