The connection of heat exchange pipe and tube plate
Considering the requirements of connection strength, tightness, resistance to crack corrosion, and ease of manufacturing and processing, the connection between heat exchange pipe and pipe plate are generally constructed with expansion joint and sealing welding. Due to the large ratio of buckling strength of titanium and its alloy, relatively low elongation and thin pipe wall, it is easy to crack at the pipe end when expanding.
Compared with ordinary pipe expansion joint, titanium pipe with smaller gap and lower pipe expansion rate should be selected, and the length of pipe protruding from the pipe plate surface should be strictly controlled, so as to reduce the thinning of pipe end and prevent cracks. When sealing welding, the welding position of tube plate and tube end shall be cleaned strictly, the height of tube end protruding from the tube plate shall be controlled, and automatic or semi-automatic argon arc self-fusion welding without adding welding wire shall be adopted.
Selection of titanium welding materials
There are two types of titanium welding materials available. One is to cut titanium strips directly from the titanium base material and use them as welding materials for titanium after polishing, pickling, and other processes. The other is to use titanium welding wire, namely TA10 and TA2.
In vacuum salt production, the liquid surface fluctuation of the evaporation tank is to ensure the smooth inner wall of the tank, and the welding structure is adopted. The welding structure between the titanium insert strip and the titanium cladding layer is non-permeable, and this structure has strict requirements on manufacturing, and the welding seam is fragile. This part should be considered in the design of the ground after a production, the whole lifting, so as to facilitate the manufacture of welding. At the same time, the equipment should have enough rigidity so that the deformation of the equipment during transportation and installation will not lead to cracks of titanium welding seams.
Non-contaminated titanium surface
Titanium is a metal with excellent corrosion resistance, but it is also a delicate metal. According to the relevant information, the cleanliness of titanium surface and even handprints can affect the quality of welding. The corrosion resistance of titanium can be greatly reduced by iron pollution, improper welding process and welding specification, and without the reliable protection of high purity argon gas.
In the whole manufacturing process, the operation should be strictly in accordance with the manufacturing procedures of titanium materials, especially pay attention to the protection of titanium surface and welding quality, so as not to reduce the excellent corrosion resistance of titanium. In the process of titanium equipment manufacturing, although many protective measures have been taken, it is difficult to achieve a large area of titanium surface completely pollution-free in practice. After the equipment is finished, pickling the titanium surface is absolutely necessary.
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