![Table 1 and tensile properties in the transverse direction of 593 MPa for the yield strength (YS), 652 MP for the ultimate tensile strength (UTS) and 28% for the elongation. The laser equipment consisted of an IPG Photonics 5 kW continuous wave solid-state Yb-fibre laser (YLR-5000) equipped with an ABB robot. A collimation lens of 150 mm, a focal lens of 250 mm and a fiber diameter of 200 µm were employed to produce a nominal focusing spot diameter of 0.33 mm. The laser beam was positioned on the top surface of the work-piece and calibrated at 5 kW. All experiments were conducted at a defocusing distance of -2 mm and the maximum laser power (5 kW) in “laser leading” mode that enabled a maximum welding speed of 1.5 m/min for full penetration. It is noteworthy that the laser head was inclined 5° from the vertical position to avoid any damage to the equipment from laser beam reflection. Due to the lack of matching or compatible filler material for HSLA-80 steel [2,7], AWS ER70S-6 wire with a diameter of 1.14 mm (0.045") was used (Table 1). A DC pulsed Fronius MAG arc was placed on the work-piece top surface with a distance of 2 mm from the laser beam. The angle between the electrode axis and the work-piece surface was 55°. To protect the molten weld pool during welding, the top surface of the work-piece was shielded using a mixture of 96% Ar and 4% O2 that was fed through a MAG nozzle at a flow rate of 23.6 L/min (50 cfh), while the bottom surface was shielded using a mixture of 50% He and 50% Ar at a flow rate of 9.44 L/min (20 cfh). The HLAW process was developed to achieve full penetration in the 9.1-mm thick HSLA-80 steel plates using a butt joint configuration with a Ygroove. The bevel angle used was approximately 30º. The root size was 6 mm. The joint gap at the root was varied from 0 to 0.3 mm. The nominal wire feed rate (WFR) was calculated based on the groove volume to be filled. To explore the possibility of improving the surface quality, higher WFRs were used to compensate for the metal loss caused by spatter and evaporation. Table 2 lists the main processing parameters used. The HI was calculated using an arc efficiency of 0.84 [4].](/figures/table-1-and-tensile-properties-in-the-transverse-direction-2nccgyr9.webp)
Q2. What are the future works mentioned in the paper "Hybrid fiber laser: arc welding of thick section high strength low alloy steel" ?
Hence for 9. 1-mm thick HSLA-80 steel, the maximum joint gap should be limited to 0. 2 mm for the Y-groove butt configuration used and further work is needed to improve the process stability at wider root gap sizes, which are usually present during assembly of long and thick plates. In addition, future work is needed to control the underfill defect and evaluate the mechanical properties including tensile, impact and fatigue. Thus, for a given plate thickness, a combination of higher laser power and welding speed to give a lower HI and higher cooling rate may potentially be effective in eliminating the HAZ softening.