Effect of heat treatment on the elevated temperature properties of a 2{1/4}Cr-1Mo submerged arc weldment
2{1/4}Cr-1Mo steels have been used in power and chemical plants for elevated temperature high pressure components since the 1930`s. Recent concerns involving the service of submerged arc (SA) welded steam piping has resulted in the inception of this study. Because welded piping may be either annealed and tempered (A and T), normalized and tempered (N and T) or subcritically postweld heat treated (PWHT), the aim of this study was the determination of the elevated temperature properties of 2{1/4}Cr-1Mo weldments subjected to these heat treatments after welding. The SA weldment fabricated for this study had a difference in chromium content (0.62%) between the base metal (2.07%) and weld metal (2.69%). The significance of this chromium difference was investigated in addition to the determination of stress rupture properties in the different heat treated conditions. Characterization of the microstructure using analytical techniques indicated that the stability of M{sub 2}C type carbides in the ferritic or bainitic microconstituents dictate the elevated temperature properties of the weld metal. Microscopy of the soft ferrite band revealed presence of fine M{sub 2}C type carbides. This soft ferritic region is strengthened by fine acicular M{sub 2}C carbides along with the interactive solid solution hardening effect of molybdenum in ferrite. In addition, adjacent regions which are stronger than the soft zone exert a constraint effect thereby limiting the rupture potential of this zone. Thus, the soft zone did not contribute to creep failure. 120 refs., 44 figs.
- OSTI ID:
- 197646
- Journal Information:
- Bulletin - Welding Research Council, Journal Name: Bulletin - Welding Research Council Journal Issue: 405; ISSN 0043-2326; ISSN WRCBA2
- Country of Publication:
- United States
- Language:
- English
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