Although the structure design of all-titanium container is similar to stainless steel, due to some special properties of titanium itself, it has its own uniqueness in design and processing. Therefore, when designing the structure, the following points must be paid attention to:
1. When designing the welding structure, the welding part must be convenient for the operation of the hydrogen arc welding tool, and all the welding joint areas at high temperature (above 400 ℃) can be effectively protected.
Titanium can chemically react with almost any element in the molten state, so special protection must be taken during welding and hot working. In order to achieve the purpose of effective protection, the structure and shape of the parts should be simple, and the opening of the nozzle on the casing should be as perpendicular to the axis of the casing as possible, so that the protective fixture can be easily manufactured and the protective effect is better.
2. Strictly avoid the welded structure of mutual fusion of steel and titanium. Since other metals such as iron are melted in the titanium weld, it will form a hard and brittle intermediate metal compound, which greatly reduces the plasticity of the weld. Except for explosive welding and brazing, titanium and steel cannot be welded.
3. The blunt edge clearance of butt welded joints should be appropriate. The blunt edge gap of the butt welded joint of the all-titanium pressure vessel is smaller than that of the steel, which is due to the high melting point, poor thermal conductivity, small heat capacity and high resistivity of titanium, as well as the large fluidity of the weld pool metal.
4. The design of the titanium vessel should ensure the continuity of the structure and the smooth transition of the welded joints, and try to avoid stress concentration.
5. The bending and flanging of titanium parts should adopt a larger bending radius (compared with steel), and a smaller expansion rate should be used when expanding the tube.
6. Industrial pure titanium is prone to crevice corrosion in some media. When designing and handling containers in contact with these media, gaps and stagnation areas should be avoided as much as possible, and crevice corrosion-resistant titanium alloys (such as titanium palladium alloy) or coating.
7. When designing and handling containers in contact with conductive corrosive media, if it is found that contact between titanium and other metals can lead to galvanic corrosion, structural measures should be taken (such as using a third material as a transition layer) or using Anodic protection.
8. When designing equipment that is prone to corrosion, the flow rate of the corrosive medium should be lower than the critical flow rate, and try to avoid sudden changes in flow rate or flow direction; or set up protective baffles at the parts that are prone to corrosion and abrasion.
① When the medium is corrosive or abrasive and ρv2>740kg/(m·s2) or the medium is non-corrosive or non-abrasive, but ρv2>2355kg/(m·s2) (ρ is the density of the medium, kg/m3, v is the material When the linear velocity of the flow, m/s), the anti-shock plate should be installed at the material inlet.
② When the corrosive medium enters the equipment along the tangential direction, or the inlet pipe is facing the wall of the device, and the distance between them is less than 2 times the outer diameter of the pipe, a protective plate should be installed.
