Abstract:The high temperature plasticity of the laser butt welding plate and LBW/SPF technology for Inconel718 superalloy with ultra-fine grain were investigated. The results showed that when the tensile direction is vertical to laser welding seam, the maximum elongation is 400.6% at temperature of 950 ℃ with initial strain rate of 3.1×10^-4 s^-1. When the tensile direction is parallel to laser welding seam, the maximum elongation is 164.0% at temperature of 965 ℃ with initial strain rate of 6.2×10^-4 s^-1.At the temperature of 950~980 ℃,the laser butt welding plate has good plasticity in free bulging state. The relative bulging height is higher than 1.0. The laser welding problem of multi-sheet cylinder sandwich structure is settled through clamp apparatus which has internal stay of diametral variation. The laser penetration welding parameters are the power of 1 200 W, welding speed of 1 200 mm/min, defocusing amount of -1 mm, shield gas flow rate of 0.6 L/min. The parameters for superplastic forming are the temperature of 965 ℃, pressure of 4.2 MPa, time of 130 min. The multi-sheet cylinder sandwich structure by LBW/SPF composite technology has good shape, uniform wall thickness distribution, the high symmetry of internal structure.