Fig. 1. Change process of droplet with radius of 0.9 mm entering keyhole of molten pool at different moments。 (a) t=39.2 ms; (b) (t+3) ms; (c) (t+4) ms

Fig. 2. Change process of droplet with radius of 0.6 mm entering keyhole of molten pool at different moments。 (a) t=39.2 ms; (b) (t+3) ms; (c) (t+4) ms

Fig. 3. Longitudinal cross-sectional flow field of molten pool with droplet radius of 0.9 mm at different moments。 (a) t=39.2 ms; (b) (t+3) ms; (c) (t+4) ms

Fig. 4. Longitudinal cross-sectional flow field of molten pool with droplet radius of 0.6 mm at different moments。 (a) t=39.2 ms; (b) (t+3) ms; (c) (t+4) ms

Fig. 5. Change of liquid metal flow velocity at point A in front of keyhole wall