Abstract: The multi-arc additive manufacturing technology (M-WAAW) represents a crucial new pathway for achieving high-performance and efficient forming of large-scale high-strength steel components. This study simulated the temperature field of straight-wall components during M-WAAM, investigated the organizational characteristics of metal deposition under multiple thermal cycles. It analyzed the organizational performance of components with three different horizontal spacings and explored the mechanism of organizational control in M-WAAM. The research identified four regions in the metal deposition, including solidification zone, coarse grain zone, normalized zone and stable zone. With an increase in the horizontal spacing of the multi-arc torch, the thermal cycle curve exhibits a characteristic of double high-temperature peaks, resulting in increased high-temperature dwell time and decreased average cooling rate of the metal deposition. Specifically, with a spacing of 10 mm, the metal deposition demonstrates the fastest cooling rate, forming a structure composed of martensite and upper bainite, which exhibits the highest strength but relatively poor toughness. With a spacing of 30 mm, the reheating effect of the filling arc decreases the cooling rate, forming a structure composed of ferrite and bainite, leading to decreased strength but increased toughness. Lastly, with a spacing of 50 mm, the slowest cooling rate and longest high-temperature dwell time lead to grain coarsening of the austenite, forminglarger-sized structures with decreased strength and toughness. Therefore, the microstructure control of high strength steel deposited metal can be realized by adjusting the horizontal spacing of arc torch.

Key words: multi-arc additive manufacturing, high-strength steel, temperature field and thermal cycle, microstructural evolution, microstructural control regulations