Pressure vessel made of aluminium for transport and storage of fluids. The vessel comprises two mainly semi-spherical, forged parts (2), that are joined together along their periphery by means of plasma welding. Each semi-spherical part is provided with a boss (4) that is formed under the forging operation, one or both of the bosses may be provided with passing bores (5) having internal threads for attaching a valve/valves thereto. Further, one or both of the bosses may be equipped with external threads for the attachment of protective caps (8), or one protective cap and a support leg.