PSI - Issue 30

Pavel Zhilin et al. / Procedia Structural Integrity 30 (2020) 209–215 Pavel Zhilin et al. / Structural Integrity Procedia 00 (2020) 000–000

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The use of conventional equipment consisting of unified units (a double-head welding tractor or a welding head, a welding head and a semiautomatic machine, a welding tractor and a semiautomatic machine, two semi-automatic machines, a GTAW manual torch with a wire feed channel, an automatic GTAW head with an insulated contact tube, etc.) enable to implement of the welding or surfacing processes with minimal capital costs. Simultaneously with an increase in labor productivity, the number of workers is reduced, the quality of welds is improved due to decreasing the penetration depth and the ratio of the base and filling metals. Deposition with various combinations of surfacing materials having different properties reduces the consumption of electricity and flux, as well as the number of weld beads and filling passes. Also, it decreases HAZ dimensions and heat input into the base metal. In addition, the appearance of the weld beads becomes better, sanitary and hygienic conditions at workplaces are improved. An advanced programmable welding power source enables to control the GTAW process, as well as heating and feeding AFW to the weld pool. Synchronous pulsed welding and heating current modes can be used to improve the weld quality or to facilitate out-of-position welding. The important parameters of the modes are pulse current, wire heating current, wire feed speed, arc length, and vibration parameters. Hot wire GTAW significantly improves deposition performance compared to the cold wire process. While cold wire GTAW enable to form a weld at a speed of about 20 cm/min, welding speed reaches 80…100 cm/min for the automatic hot wire GTAW process. As a result, welding time is reduced, narrower HAZ is formed, filler wires with the base metal mixing and risk of hot cracking are decreased such as presented by Makarov and Yakushin (2014).

Fig. 7. The hot-wire GTAW facility.

Fig. 8. The average transverse shrinkage for different GTAW methods (plates from the 0.8%C-15%Cr-5%Ni-2%Cu-1%Ti-0.7%Si heat resistant steel of different thicknesses).

Fig. 9. The three-layer hot-wire deposition on equipment parts for subsea hydrocarbon production.

Fig. 10. The terminal for presetting of hot-wire parameters.