Fig. 1. Laser processing device for the inner face of small-bore tube. (a) Main structure; (b) ring-shape focal spot; (c) processing for the tube

Fig. 2. Optical path structure of laser processing device for the inner face of small-bore tube

Fig. 3. Appearance of remelted layer in inner face of tube

Fig. 4. Microstructures of remelted layer in inner face. (a) Longitudinal section; (b) transversal section

Fig. 5. Appearances of remelted layers obtained at different scanning times. (a) Three times; (b) four times; (c) five times; (d) six times

Fig. 6. Penetration of remelted layers obtained at scanning speed of 2 mm/s

Fig. 7. Appearances of remelted layers obtained at different scanning speeds. (a) 1 mm/s; (b) 2 mm/s; (c) 3 mm/s

Fig. 8. Penetration of remelted layer obtained at different scanning speeds