How should pure titanium pipes be welded?

Titanium alloy pipe welding is usually on-site all-position welding, which is much more difficult than stainless steel pipe welding. The weld area of ​​titanium and its alloys above 400°C must be protected because its chemical properties are particularly active and can easily absorb harmful gases. , leading to material performance degradation and even cracks. Therefore, special attention should be paid to the following matters when welding:

When welding titanium and its alloy pipes, the selection of welding materials is basically based on the principle of equal strength. When a suitable welding material cannot be found, the method of cutting it from the base metal can be used; and the selection of argon gas will directly affect the welding seam. The hardness and toughness also have a significant impact on the occurrence of welding cracks, so it is required to use high-purity argon (99.99%) (especially pure titanium).

The titanium tube should be cut and broken using cold processing methods, and it should not be overheated and discolored. Use a grinding wheel or stainless steel wire wheel to polish the internal and external surfaces of the groove to a metallic luster within a range of not less than 20mm. Use a scraper to trim the burrs on the groove and then polish it smooth to avoid hanging cloth wires during cleaning. bending titanium pipe / Gr23 Ti-6Al-4V ELI Titanium Tube / Grade 7 Ti-0.2Pd Titanium Tube

The quality of cleaning directly affects the occurrence of welding cracks and pores. It is usually pickled (3% HF + 35% HNO3 + H2O) first, then rinsed with clean water, finally dried, and wiped with acetone or alcohol before welding. The cleaned welding joint must be welded immediately and not more than 4 hours, otherwise it needs to be cleaned again. Do not use rubber gloves when cleaning. Use white cotton gloves instead.

The protection of the welding area is very important when welding titanium alloy pipes. It is similar to the welding of stainless steel pipes, but the requirements for gas protection are more stringent. The filling of argon in the pipe must continue until the end of the welding, and it cannot stop until the temperature of the welding area drops below 350°C; The outer front argon protection uses a large-diameter nozzle and an extended hood. In order to improve the protection effect, the hood does not end when the welding is completed. The air supply must be stopped and the hood must be removed after the temperature drops below 200°C.