Internal expansion equipment by external circumference welding catering for diameters ranging between 200mm and 1100mm and thicknesses between 0.5 and 3mm of pressed bottoms on stainless steel tubes using a TIG procedure. The basic operation consists in locking both the bottom and the tube being used on a special copper expander which adheres all around the circumference. In this phase, while the pieces are properly locked in position and gauged to adapt to the nominal diameter, they are made to rotate and the circumference welding takes place. Once the welding has been completed, the welding head rotates to facilitate unloading and release of the finished piece after the centre has withdrawn.