초록
In order to evaluate the proper fracture strength of microstructures in a steel weldment, smaller size loading ball than used for a conventional small punch(CSP) testing is required due to regional limitation on constitutive structures. In this study, the minimized loading ball(${\varphi}1.5mm$) and bore diameter of lower die(${\varphi}3mm$) were designed for an advanced small punch(ASP) test. The results obtained from the ASP test were compared with those from a CSP testing for a X20CrMoV121 steel weldment. It was found that the ASP test clearly showed the microstructural dependance on fracture strength and ductile-brittle transition behavior of the weldment. In the ASP test, especially, the cracks tend to initiate for various directions within hemispherical indentation region of an objective structure in SP test. This indicates that the evaluation of more proper fracture strength for F.L+CGHAZ, FGHAZ and ICHAZ can be performed by means of the ASP test in a steel weldment.