Effect of Heat Treatment for Statical and Dynamical Fracture Toughness of 2 1/4Cr-1Mo Steel Weldments

Abstract

Dynamic fracture toughness K_Id is generally considered as one of the most important mechanical properties, but it is not so easy to obtain K_Id. While statical fracture toughness is easily obtained comparatively. If the relation between K_Ic, and K_Id can be cleared, it may be very useful for engineering. In this paper, the temperature dependence of K_Ic, and K_Id of 2 1/4Cr-lMo steel weld joint were investigated at both states of as weld and as heat treated. Furthermore, the correlations between Charpy impact value C_v and K_Ic, K_Id were studied. Main results obtained are as follows.
(1) K_Ic, and K_Id values as weld state are considerably low, and their increasing ratios as temperature rise are little. But by heat treatment, the former are improved remarkably and the latter are increased.
(2) The temperature dependence curves of K_Id are located at the temperatures which shifted parallelly those of K_Ic, to their higher sides. The amounts of shifts determined by the section transition temperatures of C_v tests are over a range of 74-84°C.
(3) The temperature dependence curves of K_Ic, K_Id and C_v are shifted to lower sides by heat treatment. The amounts of shifts determined by the transition temperatures show some differences between the locations of weld joint, but coincide considerably well so far as any one location concerns.
(4) The formula representing the correlation between C_v and K_Ic, K_Id are presented.