African Fusion March 2018

shape and distribution patterns gives an overall higher Vickers hardness and lower impact toughness than the HPAW joint.  Conclusions In this paper, Weldox 960 AHSS plates of 12mmthicknesswere readily butt-welded in a single pass using the HPAW process. Compared with multi-pass GMAW, HPAW showed a higher welding speed and did not require pre- or post-weld heat treatments. From the experimental results and discussions, the following conclusions could be drawn: (1) The heat input of the HPAW process was calculated and compared with GMAW. It is shown that the overall heat input of HPAW in this research was 12.64 kJ/cm, while the GMAW process gave an overall heat input of 34.04 kJ/cm. The lower heat input of HPAW contributed to a smaller post-weld deformation of the AHSS plate. (2) The uniaxial tensile strength and elongation of HPAWwas almost same as those of the GMAW and base metal. The impact toughness of the weldmetal and HAZ of the HPAW joint produced in this research was lower than those of GMAW joint, while the micro Vickers hardness values of the weld metal and HAZ of the HPAW joint were higher. (3) Larger amounts of lath martensite, as well as the smaller width and parallel distribution patterns of the laths, were found in the grain of the weld metal and HAZ in the HPAW joint. This amount of martensite and its distribution pat- terns were due to the short t 8/5 period, which results in a quenching effect in the weld metal and HAZ during the cooling of weld seam. This finally led to higher hardness

Figure 5. Microstructures of the heat affect zone of the welding joints with (a) GMAW and (b) HPAW. [mark top row of two pics (a) and bottom row (b)]. values and lower impact toughness of the HPAW joints. Extracted fromthe proceedings of IIW2017 International Confer- ence, June, 29-30, Shanghai, P.R. China. ©IIW June 2017. References [1] U Dilthey and H Keller. Process of Lasers Manufacturing (2001), 453-465. [2] TP Diebold and CE Albright. Welding Journal, 1984,63-6: 18-24. [3] G Song and Z Luo. Optics and lasers in Engineering , 2011, 49: 82-88. [4] Z Liu, MKutsuna and L Sun. Journal of the JapanWelding Society, 2006, 24-1: 17-25. [5] ZLiu,GXuandMKutsuna.JournaloftheJapanWeldingSociety,2007,25-2:254-260. [6] I Dykhno and R Davis. The Fabricator. 2006,11: 60-62. [7] NDahotre and S Harimkar. Laser fabrication andmachining of materials. New York: Springer; 2008.

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