1.5 mm and 0.7 mm Invar sheets are lap-jointed by pulsed tungsten inert gas（pulsed TIG） welding in overhead position.The macro morphology

microstructure and mechanical properties of the lap joints are investigated. The results show that when the peak current increase

the characteristic dimensions Laand P obviously increase and R rarely change. The weld metal（WM） zone is composed of coarse austenitic columnar crystal with cellular substructure

and the heat affected zone（HAZ） is composed of coarse equiaxial crystal. The plane grained region and partial melting region constitute the bond

which is the weakest region in the joint.Microhardness tests reveal that the microhardness value of HAZ is less than that of WM and base metal. The maximum tensile shear force of all samples is approximately 4 300 N

and all fractures are located in bond.