Correlation of Weld Microstructures with Fracture Toughness of 18% Nickel (250) Grade Maraging Steel

摘要

A program designed to obtain a correlation between fracture toughness and microstructural features of 18% nickel maraging steel plate weldments prepared by various techniques has been partially completed. Results of this study have shown that the center-of-theweld possesses the lowest fracture toughness for all weldments and that the welding techniques giving rise to successively decreasing weldment fracture toughness may be listed as follows: Big Tig, Tig, Mig, and submerged-arc. Macrostructural and microstructural examinations of typical weldments, as well as examination of macro-topographies and micro-topographies of fractures of weldments prepared by these four techniques, have shown that submerged-arc weldments present lower resistance to crack travel than do the weldments of the multi-pass inert gas shield arc techniques. In addition, the embrittling and cracking problem in submerged-arc weldments have been tentatively associated with the formation of an ordering AlTi phase. (Author)