溶接構造物の脆性破壊発生に及ぼす応力除去焼鈍の影響

概要

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Effects of stress-relieving heat treatment on brittle fracture initiation in welded structures are quantitatively discussed in terms or fracture mechanics. The basic concept employed for discussion is that brittle fracture should initiate when tensile yield zone formed ahead of a pre-existing crack attains a critical size depending on the material. The critical zone size as a function of temperature is predictable from Charpy-V transition temperature. Metallurgical information on welding residual stress and Charpy-V data for various conditions of heat treatment is compiled and put into the proposed logical frame of fracture mechanics. There is a divergence of conclusion for every case of steel type. Cases studied are those of an ordinary mild steel, two kinds of quenched-and-tempered high strength steels and a Mn-Mo steel for nuclear pressure vessels.