Embrittlement in the Weld Metal of High Purity 30Cr-2Mo Steel
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概要
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The factors which influence the toughness in the weld metal of a high purity 30Cr-2Mo steel were studied. A charpy impact test was performed on the weld metals with nitrogen and oxygen of various levels in order to elucidate the roles of these elements in a brittle fracture of the steel. Contributions of other factors which might be causes of embrittlement in the weld metal e.g., 475℃ mebrittlement, grain coarsening, σ-phase embrittlement, were also investigated. As the result, it was found that the main cause of the embrittlement in the weld metal by conventional TIG method was pick-up of nitrogen during welding. In the case of the nitrogen content in the weld metal increasing more than about 100ppm by pick-up during welding, disc-like Cr_2N precipitates on {001} planes in the matrix. Consequently, the embrittlement is induced in the weld metal by the precipitation hardening. In addition to this, disc-like Cr_2N also causes the embrilltement by lowering energy for a cleavage fracture due to its precipitating on {001} planes where the cleavage fracture occurs. 475℃ embrilltement is induced in the weld metal in the welding process. However, its influence is not so large, i.e., this is observed as a rise in the transition temperature of several degrees during single pass TIG welding. Grain size does not significantly influence the toughness of the weld metal and σ-phase embrittlement is not inducea in the welding process.
- 社団法人溶接学会の論文
- 1980-10-01
著者
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IKAWA Hiroshi
Osaka Univ., Faculty of Engineering
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NAKAO Yoshikuni
The Osaka Institute of Technology
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NISHIMOTO Kazutoshi
The Osaka Institute of Technology