Preparation before welding

It is best to divide a separate area at the titanium welding site, and non professionals are not allowed to enter to protect the cleanliness of the area. All welding personnel should wear clean work clothes, knitted gloves or thin sheepskin gloves, and cotton gloves are not allowed. When entering the tank for welding, shoes should be covered with shoe covers.
The inner and outer surfaces of the groove and its sides within 50mm, as well as the surface of the welding wire, should be cleaned of oil stains, and mechanical methods such as fine files, austenitic stainless steel wire brushes, milling cutters, etc. should be used to remove oxide films, burrs, and surface defects. The cleaning tools should be dedicated and kept clean; After mechanical cleaning, the surface should be degreased with sulfur-free acetone or ethanol before welding. It is strictly prohibited to use chloride solvents such as trichloroethylene and carbon tetrachloride, and cotton fibers should not be attached to the groove surface. According to the technical requirements, a "phenanthrene" test was conducted on the welding environment before welding, and a "iron ion" contamination test was conducted around the weld seam. Only after passing the test can welding be carried out.
The quality of cleaning directly affects the occurrence of welding cracks. When the cleaning quality is poor, a gray white suction layer will be formed on the surface of the base material and welding wire, leading to the formation of welding cracks and pores. Therefore, the following points should be noted during cleaning: ① Use acid cleaning first. The pickling solution is 2% -4% HF+30% -40% HNO3+H2O (residual). Finally, rinse with clean water and blow dry. Before welding, wipe with acetone or alcohol Welding wire generally needs to undergo dehydrogenation treatment after acid washing, and then be degreased with acetone before welding It is strictly prohibited to use oxide degreasing Rubber gloves should not be worn during cleaning to prevent the reaction between rubber and degreasing solvent, which may cause porosity in the weld seam The cleaned weld must be welded immediately and should not be left for a long time (generally not exceeding 4 hours), otherwise it needs to be cleaned again according to the previous steps.
The protective cover used during titanium welding is very important. A skilled welder without a good protective cover, even if the weld seam is beautifully welded and all oxidation and discoloration occur after welding, this weld seam is still unqualified and will be scrapped.