Feb_March_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 2 0 2 0 JOINING WEATHERING-STEEL PLATE USING ULTRANARROW- GAP LASER WELDING WITH FILLER WIRE A novel approach in the field of narrow gap laser welding produces superior weld joint quality, especially the configuration of weld toe, which has a positive effect on fatigue life. Yumo Jiang, Yong Zhao, Shengchong Ma, Yuhang Duan, and Keng Yan Lab of Advanced Welding Technology, Jiangsu University of Science and Technology, Zhenjiang Jiangsu, China Fig. 1 — Filler-wire feeding module. G rade SMA490BW weathering steel, a low-carbon nickel-chromium steel (JIS G 3114: 0.18 max C, 0.45-0.75 Cr, 0.05-0.30 Ni) with high strength and corrosion resistance is widely used in structures such as rail- way vehicles, bridges, and buildings [1-3] . Currently, laser welding is increasing- ly used to join such materials where the weld joint is made only of the base metal without any filler materials. Laser welding offers many advantages, such as high penetration-to-width ratio; high welding speed, which improves production efficiency; low heat in- put; and minimal thermal deformation compared with traditional arc-welding technology [2,4-9] . However, autogenous laser welding is very sensitive to the weld-groove gap and the single-pass penetration of weld beam is highly de- pendent on the maximum power; thus, the method is not suitable for welding thick plate [10,11] . Over the past few years, ultra- narrow-gap laser welding with filler wire has gained interest for welding any plate thickness (theoretically), requir- ing only about 20% of the volume of fill- er material required using traditional arc welding. In addition, the metallur- gy and mechanical properties of the weld can be greatly improved by intro- ducing filler wire [11,12-15] . However, laser welding with filler wire involves more process parameters than other welding technologies, which increases the diffi- culties of application and the tendency to produce defects. Zhang, et al. [16] in- vestigated the preclusion of fusion de- fects and process optimization for thick plate laser welding with filler wire. They achieved a sound weld when the sur- face of filling metals was concave, while lack of fusion occurred if the surface was convex. The authors investigated fiber- laser welding with filler wire of 16-mm (0.63 in.) thick SMA490BW plate. Joint quality was evaluated by microstruc- tural examination and mechanical test- ing. The study was aimed at providing a technical and metallurgical refer- ence for the application of laser weld- ing with filler wire in the manufacturing industry. EXPERIMENTAL WORK SMA490BW steel plate was ma- chined into 300 mm × 260 mm × 16 mm base metal and 1.2-mm diameter 55CNH (≤0.10 C, 0.30-0.90 Cr, 0.20-0.60 Ni)