MICROSTRUCTURE AND TOUGHNESS OF THE SIMULATED WELDING HEAT AFFECTED ZONE IN X100 PIPELINE STEEL WITH HIGH DEFORMATION RESISTANCE
NIE Wenjin, SHANG Chengjia, YOU Yang, ZHANG Xiaobing, Sundaresa Subramanian
1) School of Material Science and Technology, University of Science and Technology Beijing, Beijing 100083
2) Chief Engineer Office, Jiangsu Shagang Group, Zhangjiagang 215625
3) Department of Materials and Engineering, McMaster University, Hamilton, Canada, L8S4M1
Cite this article:
NIE Wenjin SHANG Chengjia YOU Yang ZHANG Xiaobing Sundaresa Subramanian. MICROSTRUCTURE AND TOUGHNESS OF THE SIMULATED WELDING HEAT AFFECTED ZONE IN X100 PIPELINE STEEL WITH HIGH DEFORMATION RESISTANCE. Acta Metall Sin, 2012, 48(7): 797-806.
Abstract A single welding thermal-cycles with different heat inputs (8, 16, 20, 25, 30 and 50 kJ/cm) were simulated by Gleeble 3800 to study the correlation of toughness, hardness and microstructure in heat affect zone (HAZ) of the X100 pipeline steel with multi-phases and 0.10\%Nb (mass fraction). The microstructures of the CGHAZ in HAZ were characterized by means of OM, SEM and EBSD, and mechanical properties were tested. The results show that for a low heat input of less than 20 kJ/cm, the microstructure is lath bainite or acicular ferrite structure with high-density of large-angle boundaries (≧15o), which exhibits good Charpy impact toughness. However, for a large heat input over 25 kJ/cm, the uniformity of prior austenite grains becomes worse, the M/A constituents and the granular bainite (GB) are coarsening, and the amount of large-angle boundaries decreases with the increase of heat input. The results of the instrumented Charpy impact test and the observation of fracture surfaces on the specimens indicate that the cracks are induced near the coarse M/A constituents and the large-angle boundaries can remarkably restrict crack propagations. Therefore, in order to ensure a strong match between the HAZ and the base metal, and the resistance to hydrogen induced delayed damage because of high hardness of HAZ, the heat input energy should be about between 15 and 20 kJ/cm.
[2] Shang C J, WangX X, Liu Q Y, Fu J Y. Int Seminar on Welding of Pipline Steel, Arasa, Brazil: December, 2011
[3] Miao C L, Shang C J, Cao J P, Wang X M, He X L. Iron Steel, 2009; 44: 62
(缪成亮, 尚成嘉, 曹建平, 王学敏, 贺信莱. 钢铁, 2009, 44: 62)
[4] Miao C L, Shang C J, Zhang G D, Sunbrainmani S. Mater Sci Eng, 2010; A527: 4985
[5] Miao C L, Shang C J, Wang X M, Zhang L F, Subramanian S V. Acta Metall Sin, 2010; 46: 5419
(缪成亮, 尚成嘉, 王学敏, 张龙飞, Subramanian S V. 金属学报, 2010; 46: 5419)
[6] Miao C L, Shang C J, Zhang G D, Zhu G H, Zurob H, Subramanian S V. Front Mater Sci China, 2010; 4: 197
[7] Nie W J, Shang C J, Guan H L,Zhang X B, Chen S H. Acta Metall Sin, 2012; 48: 298
(聂文金, 尚成嘉, 关海龙, 张晓兵, 陈少慧. 金属学报, 2012; 48: 298)
[8] Shang C J. Technology Forum on High Grade Pipeline Steels for Oil & Gas Industry–New Challenges for Steels from Strategic Demand of Exploration and Transportation of Oil & Gas, Beijing, Chinese Society for Metals (CSM), 2011: 55)
