Notch Toughness and Mechanical Properties of Synthetic Heat-Affected Zone Microstructures of Quenched and Tempered Steels

Abstract

Weldability as related to the heat-affected zones of the quenched and tempered steels, 2H (HT 60), were evaluated by means of V-Charpy impact and round bar tensile tests of synthetic HAZ specimens.
Firstly, the effect of peak temperatures of termal cycles, 500, 650, 750, 900, 1100, 1300 and 1400°C, on the impact and mechanical properties of synthetic HAZ specimens were obtained.
According to the tensile tests; softened zones have been observed in two locations, that is, the tempered and recrystallized zones. From V-Charpy tests, however, it was assured that these softened zones did not give any adverse effect on the notch toughness of these steels.
Furthermore, the effect of the rate of cooling followed by thermal cycles from a peak temperature of 1300°C, were examined. The toughness of the coarse-grained HAZ microstructures were increased with the increase of the rate of cooling, while the tensile ductilities were decreased on the contrary. Then, these properties were intimately related to the transformation products.
Finally, it was mainly concluded that the toughness and tensile ductilities were generally satisfactory and then should have about the same as those of the ordinary high strength steels usually employed.