It is very difficult to process titanium alloys. Due to the relatively active nature of the metal, argon must be used as protective gas to cover the welding spot or vacuum electronic welding must be used to ensure the reliability of welding. The predecessor of "Striver", "Jiaolong", relied on Russia to help with the processing of titanium alloy cabin. Russian deep-sea submersible is very good, because they have this large forging press and have strong processing capacity of titanium alloy.
Previously, China has developed nearly type Marine corrosion resistant titanium alloy Ti 75, Ti 31, Ti-B19, Ti91, Ti70 and Ti80 of different strength grades. The Ti75 alloy developed by Northwest Institute of Nonferrous Metals has its own intellectual property rights, and has good comprehensive performance with Ti31 alloy, and has been applied in practice. In addition, Ti70 mainly developed by Baoji nonferrous Metal processing plant and Ti91 developed by Northwest Nonferrous Metal Research Institute have good medium strength, high plastic performance, cold processing performance, sound permeability and weldability. These titanium alloys are widely used in ships, submarines and submersibilites.
However, in deep-sea probes, the performance requirements of titanium alloy are higher. The pressure housing of manned submersible is the main provider of buoyancy, and its weight accounts for about 1/5~1/4 of the entire submersible system. The working depth, hydrodynamic characteristics, internal and external arrangement, material availability, cost and manufacturing process should be taken into account in the structural design of the pressure-resistant shell. Therefore, the manufacturing technology of high-strength titanium alloy spherical pressure-resistant shell should be mastered.
The whole sea deep manned submersible is a very difficult engineering equipment, involving design technology, material technology, sealing technology, technology, communication technology, safety technology, integration technology, test technology and so on, each of which is the limit technology, and must be highly safe and reliable.
