Dynamic fracture toughness properties of a 9Cr1Mo weld from instrumented impact and drop-weight tests

Abstract

This paper reports the RT NDT and K Id results obtained from instrumented impact and drop-weight tests of 9Cr1Mo welds. RT NDT results for welds prepared using electrodes of diameter 2–5, 3–15 and 4 mm agree within 5K, the respective values being 264, 269 and 268K. For all the three welds, 269K can be taken as the conservative RT NDT. The procedures presented in this paper enable estimation of reasonably conservative values of K Id from instrumented impact test of unprecracked Charpy V-notch specimens. For the range of temperatures 193–303K, the lower bound K Id estimates obtained for the 9Cr1Mo welds are higher than the ASME K IR curve; hence, the ASME K IR curve will give conservative K Id values for the welds of this 9Cr1Mo steel in the above temperature range; at higher temperatures, the applicability of the ASME K IR curve to the welds of the present 9Cr1Mo steel needs verification/validation. Microcleavage fracture stress or cleavage fracture strength, σ f, estimated for the 9Cr1Mo welds is about 2160 MPa and is much lower than the 2550–2850 MPa reported for a normalised and tempered 9Cr1Mo plate material.