Except for the Soviet MIR I and MIR II, which use steel […]
Except for the Soviet MIR I and MIR II, which use steel, the contemporary manned spherical shells with deep dives are all made of titanium. Moreover, the 6000-meter-class "Russia" and "Consul" developed by Russia also use titanium. alloy. Although the technical characteristics of the large-depth manned submersibles designed by various countries are different, the choice of titanium alloy for the manned spherical shell is the same. The selected titanium alloys are Ti64 (Ti-6Al-4V) and Ti6211 (Ti-6Al-2Nb-1Ta-0.8Mo) two medium-strength titanium alloys. After the United States later abandoned Ti6211 titanium alloy and chose Ti64 ELI (exra-low-interstitial) titanium alloy, the material of the current large-depth manned spherical shell is all Ti64 (ELI). Compared with steel materials, titanium alloys have excellent seawater corrosion resistance, including resistance to static corrosion and dynamic corrosion under cyclic loading conditions, and are more suitable for marine applications. In addition, titanium alloy also has a higher specific strength. As a spherical shell material, it can greatly reduce the weight of the spherical shell and increase its effective load. Therefore, titanium alloy has a unique advantage as a large-depth manned spherical shell material.