Comparison of Microstructure and Toughness of Simulated CGHAZs between V-N-Ti, V-Ti And Nb-Ti Microalloyed Steels
For the purpose of obtaining the suitable alloy system for high heat input welding of the hull structure steels, the SHCCT, microstructure evolution and CGHAZ toughness under the different weld cooling times were investigated. The results indicate that increasing nitrogen based on V-Ti steel led the SHCCT to upper and left. The V-N-Ti steel can obtain the best CGHAZ toughness compared the others and is suitable for high welding cooling times. Increasing nitrogen promoted the formation of V(C, N) and TiN, lowered the coarsening rate of (Ti,V)(C,N) at the same time. The austenite size refined and V(C, N) formed accelerated the ferrite transformation of V-N-Ti steel. The finer polygonal ferrite of V-N-Ti steel is the key to guarantee good CGHAZ toughness for V-N-Ti steel. The detrimental effect of the free nitrogen on the toughness can be partly remedied by finer polygonal ferrite.
V-N-Ti microalloyed steel, coarse-grained heat affected zone, microstructure, impact toughness, ferrite, phasetransformation.
Ruizhen Wang (1), Zhongran Shi (2), Qingfeng Wang (2), Caifu Yang (1), Hang Su (1)
(1) Central Iron & Steel Research Institute, No.76 Xueyuan Nanlu, Haidian District, Beijing, China, 100081
(2) Yanshan University, No.438 Western Hebei Street, Qinghuangdao, Heibei, China, 066004
Vanadium Microalloyed Steels: A Symposium in Memory of Michael Korchynsky, MS&T14, 12-16 October 2014, Pittburgh, PA, USA.