Abstract
Notched bead bend specimen of Lehigh type was used to evaluate the influence of welding on the notch sensitivity of structural mild steels. The test pieces werc arc welded manually and compared with the unwelded base plates. Some of them were cooled to -10°C and them welded to examine the effects of different welding temperatures. The ductility transition temperatures (Tra or Tφ) were determined by measuring Ghe.bend angle at maximum load (aM) or the lateral contraction below notch (φBN) respectively, and the fracture transition temperature (Trs) was decided by the fracture appearance.
Tests results revealed that Tra and Tφ were seriously raised after arc welding except one killed steel, accompanied by great reductions of aM and φBN. So a considerable danger of susceptibility to crack growth may be said to be present in heat affected zones. On the other hand, TrS was hardly influenced by welding;namely, it was indicated that the transition temperature of welded joint might not rise particularly when a crack, initiated in the heat-affected zone, plopagated into the base plate The increase of hardness was also slight in specimens welded at -10°C, and their transition temperatures were exactly the same as those welded at room temperature.
At the same time, it was proved that there existed satisfactory correlations between transition temperatures of steels determined by various test methods, if they were classified in to the fracture and ductility transition temperature and compared between each group. For example, Trs correlated well to the transition temperature determined by the fracture appearance in the Kahn tear test, and Tra also did so to 15 ft-1bs. transition temperature measured by the V-notched Charpy test.
