Study of Weld Cracking under Various Restraint Conditions

Abstract

The objective of this study was to investigate the root-cracking in welded joints with restraint and to find the suitable welding procedure corresponding with the intensity of restraint.
Large H-type specimen and variable restraint equipment were used to simulate four steps of restraaint, and five kinds of steels were submitted to testing.
The conclusions are as follows:
(1) Welded joint length of at least 150 mm appeared to be necessary for the crack testing from the study of stress distribution of H-type specimen.
(2) The ranges of restraint intensity free from root-cracking were found as shown in Fig. 13. It is noteworthy that the low alloy 50 kg/mm² strength steels have a high crack susceptibility.
(3) Two or three passes welded under 10 minutes intervals are as much efficient as preheating to prevent root-cracking, whereas they have no effect to decrease the restraint stress.