Brittle Fracture Initiation and Arresting Characteristics of Sheet Plate

Abstract

Recently, the demand for constructing welded structures for low temperature materials such as LPG, LMG, liquid oxygen and nitrogen has increased. Low temperature structural steels such as aluminum killed steel (QT), 2.5, 3.5 and 9% Ni steels have been employed for these structures. The brittle fracture initiation and arresting characteristics of these steels are very important for their application. It is wellknown that the thinner plate has the lower transition temperature on account of the decreased triaxiality and the improved metallurgical factors such as the fine grain and the lower finishing temperature, etc.
In this paper, thin mild steel plates or sheets were investigated to evaluate the brittle fracture initiation and the arresting characteristics by using the large size tests such as the deep notch test, the welded and notched wide plate test and the ESSO test with temperature gradient.
Two scmikilled steels and two killed steels 3.2 mm thick were tested. The brittle faacture characteristics of plate in the directions parallel and nomal to rolling were investigated.
From the results of these large size tests, the excellent notch toughness or brittle fracture initiation and arresting characteristics were proved. In addition, the effect of welding residual stress on brittle fracture initiation characterestics was discussed.