Evaluation of Welds Exhibiting Large Scatter in Charpy Toughness Using the Reference Temperature

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Abstract
Conformance tests carried out on 7018 M weld wire revealed that some lots exhibited excessive scatter in Charpy toughness. A test program was conducted to determine if the fracture behavior of the welds was significantly influenced by the occasional low Charpy values. Charpy and tensile data were collected on welds made from lots of 7018 M wire that failed conformance testing. Fracture toughness tests were also conducted to characterize the fracture performance in the transition temperature region. A baseline for acceptable fracture behavior was established based on fracture toughness and Charpy data from 70-series weld wires that are typically used in the same, or similar, applications. The reference temperature of the 7018 M weld was determined to be -72.1°C (-97.7°F), which was well below the baseline of -45°C (-49°F). Therefore, the 7018 M weld was shown to have equal or better fracture toughness than the baseline at any temperature. Consequently, the large scatter in Charpy toughness was not indicative of poor fracture performance.