How to weld titanium?

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titanium: Titanium alloy has low density, high specific strength, good corrosion resistance, low thermal conductivity, non-toxic, non-magnetic, and weldable ； Widely used in aviation, aerospace, chemical industry, petroleum, electric power, medical care, construction, sporting goods and other fields. Commonly used welding methods for titanium and titanium alloys include: Argon arc welding, submerged arc welding, vacuum electron beam welding, etc. Preparation before welding The surface quality of the weldment and titanium welding wire has a great impact on the mechanical properties of the welded joint and must be strictly cleaned. 1) Mechanical cleaning of weldments that do not require high welding quality or are difficult to pickle can be wiped with fine sandpaper or a stainless steel wire brush, but it is best to scrape the titanium plate with carbide yellow to remove the oxide film. 2) Chemical cleaning: The test piece and welding wire can be pickled before welding. The pickling liquid can be aqueous solution of HF (5%) + HNO3 (35%). Rinse with clean water after pickling, and weld immediately after drying. Or use acetone, ethanol, carbon tetrachloride, methanol, etc. to wipe the groove of the titanium plate and its two sides (within 50mm each), the surface of the welding wire, and the parts in contact between the tool fixture and the titanium plate. 3) Selection of welding equipment: For argon arc welding of titanium and titanium alloy tungsten plates, a DC argon arc welding power source with external characteristics and high-frequency arc ignition should be used, and the gas delivery time should be delayed not less than 15 seconds to avoid oxidation and contamination of the weldment. 4) Selection of welding materials: The purity of argon should be no less than 99.99%, the dew point should be below -40°C, and the total mass fraction of impurities should be 0.001%. When the pressure in the argon cylinder drops to 0.981MPa, use should be stopped to prevent affecting the quality of the welded joints. 5) Gas protection and welding temperature: When titanium pipe joints are welded, in order to prevent the welded joints from being contaminated by harmful gases and elements at high temperatures, necessary welding protection and temperature control must be carried out on the welding area and welds, and a special protective shield should be used for all-round protection, and its temperature should be below 250°C. Picture 2) Operation essentials 3) 1. When manual argon arc welding, the angle between the welding wire and the weldment should be kept as small as possible (10~15°). The welding wire is fed into the molten pool smoothly and evenly along the front end of the molten pool, and the end of the welding wire must not be moved out of the argon gas protection zone. 2. When welding, the welding gun basically does not swing laterally. When it needs to swing, the frequency should be low and the swing amplitude should not be too large to prevent it from affecting the protection of argon gas. 3. When the arc is broken and the weld is finished, the argon gas protection must be continued until the weld and the metal in the heat-affected zone have cooled to below 350°C before the welding gun can be removed. Surface color of weld and heat-affected zone 1. Silvery white and light yellow in weld area (allowed for first-, second- and third-grade welds) ； Dark yellow (allowed for second and third level welds) ； Golden purple (allowed for level 3 welds) ； Dark blue (not allowed for Level 1, Level 2, and Level 3 welds). 2. The heat-affected zone is silvery white and light yellow (allowed for first-, second- and third-level welds) ； Dark yellow, golden purple (allowed for level 2 and 3 welds) ； Dark blue (allowed for level 3 welds).