Influence of Heat Input on Microstructure and Corrosion Resistance of Underwater Wet-Welded E40 Steel Joints
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JMEPEG https://doi.org/10.1007/s11665-020-05160-7
Influence of Heat Input on Microstructure and Corrosion Resistance of Underwater Wet-Welded E40 Steel Joints Jianfeng Wang, Jiangkun Ma, Yibo Liu, Tao Zhang, Shichao Wu, and Qingjie Sun (Submitted February 6, 2020; in revised form August 14, 2020; Accepted September 20, 2020) Heat input has a significant effect on the microstructure and corrosion performance for welded joints. Underwater wet welding (UWW) was applied to high-strength low-alloy steels E40 with different heat inputs. Corrosion performance of the base metal (BM), weld metal (WM), and heat-affected zone (HAZ) was investigated by the electrochemical techniques including electrochemical impedance spectroscopy and potentiodynamic polarization tests emerged in 3.5 wt.% NaCl solution. The results indicated that corrosion resistance of WM decreases with increasing heat input when the welding speed remains constant. Compared with arc voltage and welding current used in UWW, welding speed plays a more important role in the corrosion behavior of WM. The excessive welding speed can cause severe deterioration of corrosion resistance of WM. Meanwhile, the WM indicates the better corrosion resistance than the HAZ and the BM for the sample 2 with a heat input of 2.5 kJ/mm, and the worst corrosion resistance appears in the BM. The critical role of microstructure, grain size, grain boundary and crystal orientation in the corrosion resistance was discussed by optical microscope and electron backscatter diffraction techniques. Keywords
corrosion resistance, EBSD, heat microstructure, underwater wet welding
input,
1. Introduction With the exploitations of marine resources and the application of underwater engineering, underwater welding has become a significant technical means for the maintenance and installation of marine steel structures (Ref 1). Underwater wet welding (UWW) technique can be employed in the aqueous environment without additional auxiliary measures. Hence, it is the most feasible method for welding complex marine structures due to its simple equipment, low cost and convenient operation (Ref 2, 3). The gradual development of UWW process has promoted the quality of the welded joints. It should be noted that the rapid cooling of surrounding water still has a great adverse influence on the UWW process, which will inevitably result in defects of the welded joints such as cracks, pores and slags (Ref 4). Meanwhile, uneven welding thermal cycle of UWW may lead to the changes of chemical Jianfeng Wang, State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, No. 92 West Dazhi Street, Harbin 150001, China; Shandong Provincial Key Laboratory of Special Welding Technology, Harbin Institute of Technology at Weihai, No. 2, West Wenhua Road, Weihai 264209, China; and School of Metallurgy, Northeastern University, Shenyang 110819, China; Jiangkun Ma, Tao Zhang, and Shichao Wu, Shandong Provincial Key Laboratory of Special Welding Technology, Harbin Institute of Technology at Weihai, No. 2,
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