Fig. 1. Schematic diagram of experimental equipment

Fig. 2. Schematic diagram of spectral stratification scanning in different directions
(a): X direction; (b): Y direction

Fig. 3. Calibration of characteristic spectral lines

Fig. 4. Two typical droplet transition modes
(a): Slag column transition; (b): Liquid bridge transition

Fig. 5. Skeleton diagram of Ar Ⅱ 480.602 02 nm

Fig. 6. Distribution of arc temperature field in X direction
(a): Tungsten axis coincides with cladding layer center; (b): Tungsten axis is shifted to the left by 1 mm from cladding layer center

Fig. 7. Distribution of arc temperature field in Y direction

Fig. 8. Current signal

Fig. 9. Welding voltage at different position between tungsten axis and cladding layer center
(a): Tungsten axis coincides with cladding layer center; (b) Tungsten axis is shifted to the left by 1mm from cladding layer center

Fig. 10. Schematic diagram of heat source model

Fig. 11. Thin-walled part
(a): Straight; (b): Inclined