The 4500 manned submersible spherical shell development is a key project in china.The manned submersible spherical shell is consisted of two TC4ELI titanium alloy hemispheres,with a total weight of over 4 tons,an inner diameter of 2.1 meters,a wall thickness of 53mm,five observation windows,and a closing weld of about 7 meters long.The project is based on the most cutting-edge technolody in the world,integrating” industry,academia,research and application”,giving full play to the equipment and technology advantages of various domestic industries,and making wide collaborations and great innovations.The Project has made a number of breakthroughs in key technologies such as the melting of large titanium alloy ingots,the forging of large titanium alloy slabs,the development of wide titanium alloy thick plates,the overall molding of titanium alloy hemispheres,the development of special welding wires and narrow-gap welding processes,the electron-beam welding technology of large titanium alloy components,the heat treatment of spheres and the control of processing deformation. Hence it has filled a number of gaps in the field of domestic manned submersibles and titanium alloy research and reached the international advanced level. It possesses completely independent intellectual property rights,which is of great significance in promoting the development of many fields in china,including new materials such as titanium alloys,advanced equipment manufacturing technology ocean development and others. The manned submersible spherical shells have been successfully applied to the “Deep Sea Warrior” manned submersible,realizing the domestication of key components of China’s manned submersible and receiving high recognition from the Party and State leaders.