Fig. 1. Clamp schematic for ultra-thin sheet

Fig. 2. Appearances of weld defects with poor clamping under different laser powers. (a) P=600 W; (b) P=800 W; (c) P=1000 W

Fig. 3. Schematic of deformation of bottom copper plate and gap under heat conditon

Fig. 4. Weld appearances when SUS304 is under copper sheet. (a) P=2200 W; (b) P=2300 W

Fig. 5. (a) Good overall appearance of weld; (b) weld morphology obtained by microscope

Fig. 6. (a) Appearance of welding joint with SUS304 corroded; (b) microstructure of zone 1; (c) microstructure of zone 2; (d) microstructure of zone 3; (e) microstructure of zone 4; (f) appearance of welding joint with copper corroded; (g) microstructure of zone 5

Fig. 7. EDS results of welding joint. (a) Cu distribution in weld; (b) Fe distribution in weld; (c) content fluctuation curves of Cr, Mn, Fe, Ni and Cu in upper weld along horizontal direction; (d) content fluctuation curves in weld along longitudinal direction; (e) detailed content fluctuation curves of Fe and Cu in Fig. 7(c)

Fig. 8. Distribution curves of weld microhardness. (a) Lateral microhardness; (b) vertical microhardness

Fig. 9. (a) Tensile strengths under different laser powers; (b) morphology of tensile fracture obtained by electronic microscope

Fig. 10. (a) Position of tensile fracture; (b) microstructure of fracture position