Abstract
The effects of welding condition on fracture toughness of electron beam welded joint were examined in 2.3GPa grade 18%Ni maraging steel for rocket motor case. In addition, the possibility of toughening by the thermomechanical treatment was investigated. Main results are summarized as follows ; (1) Because the aging precipitates were not solution, when it was kept to aging temperature range before the solution treatment at 1073K for 4ks, the fracture toughness was decreased at either welding condition. (2) In the sample which the welding heat input was the lowest, the fracture toughness was decreased markedly. (3) The fracture toughness is improved by the subzero treatment before heat treatment.
