Quantitative Evaluation of Reheat Cracking Susceptibility by in-situ observation and measurement using laser confocal microscope

In the post weld heat treatment (PWHT) process, the reheat cracking which might occur in the weldments of low alloy steels has been a serious problem. So, it is considered to be important to predict the possibility of occurrence of the reheat cracking in these steels. It is however recognized as time consuming procedure to evaluate quantitatively the susceptibility to this type of cracking. In the present study, a new quantitative evaluation method of reheat cracking susceptibility by in-situ observation and measurement using a laser confocal microscope has been proposed. Through this new method, the reheat cracking susceptibility of any kind of steels can been evaluated with the same standard. Moreover, because the position of initial crack can be focused and the critical ductility to initiate crack is measured by in-situ observation, the reheat cracking susceptibility can be evaluate by using only one specimen. So the newly developed method can provide efficient quantitative assessment of the reheat cracking sensitivity with high accuracy.