A Study for Prevention of Stress-Relief Cracking

Study on Stress Relief Heat Treatment of HT80 (Report 2)

Abstract

The mechanism as to why stress-relief craking originates has been investigated from the standpoint of the residual stress.
The results were obtained as follows :
(1) The stress-relief cracking which occurs at the toes of the back side is closely related with the residual stress perpendicular to the weld line. Cracks arise when the residual stress exceeds 50 kg/mm², whereas they do not appear at all under less than 50 kg/mm².
(2) In order to prevent the stress-relief cracking, it is advisable to select groove shapes and depositing methods with less than 50 kg/mm² of the residual stress.
(3) Whether or not the stress-relief cracking is caused is decided by the relation between the fracture stress of welded joints at the elevated temperature and the residual stress to the weld line after the stress-relieving.