EMBRITTLEMENT OF BOLTS MADE OF THE 25Cr2Mo1V STEEL AFTER LONG EXPOSURE AT 540℃
Qu Zhe;Guo Kexin (K. H. Kuo) Institute of Metal Research; Academia Sinica
Cite this article:
Qu Zhe;Guo Kexin (K. H. Kuo) Institute of Metal Research; Academia Sinica. EMBRITTLEMENT OF BOLTS MADE OF THE 25Cr2Mo1V STEEL AFTER LONG EXPOSURE AT 540℃. Acta Metall Sin, 1980, 16(4): 371-487.
Abstract Bolts made of the 25Cr2Mo1V steel become gradually embrittled with increas-ing fraction of intercrystalline fracture after long exposure (more than 40000hours) at 540℃. This is found to be caused by the segregation of phosphorus upto 8 at% at austenitic grain boundaries accompanying the depletion of molybdenumin ferrite down to about 0.3% owing to the formation of a molybdenum-contain-ing carbide Fe_3Mo_3C (M_6C). Reheating of the embrittled bolts to 680℃ removes the segregation of phos-phorous at the grain boundaries and therefore also the intercrystalline embrittle-ment. However, the molybdenum content of ferrite is further lowered to about 0.2%and its scavenging effect for phosphorous is thus greatly lost, therefore the embrit-tling tendency of these bolts during reuse is enhanced. Even after requenchingand tempering, the service life of these bolts is still shortened, owing possibly tothe inhomogeniety of molybdenum in austenite not removed by the reaustenitizingtreatment.
[1] Yu, J. and McMahon, C. J. Jr., The Effects of Composition and Carbide Precipitation on Temper Embrittlement of 2 1/4 CrlMo Steel, Part 1: Effects of P and Sn, 1979 (未发表). [2] Ibid., Part 2: Effects of Mn and Si, 1979 (未发表). [3] Viswanathan, R., Met. Trans., 2 (1971) , 809． [4] McMahon, C. J. Jr., Amer. Soc. Test. Mater., Spec. Tech. Publ. № 407, 1968, p. 127． [5] Handbook of Auger Electron Spectroscopy, 2nd ed., Physics Electronics, Inc., Minnesota, 1976． [6] Barnard, L. and Brook, R., J. Iron Steel Inst., 205 (1967) , 756． [7] Kuo, K. (郭可信), J. Iron Steel Inst., 173 (1953) , 363．
