Titanium alloy has low density, high specific strength, good corrosion resistance, low thermal conductivity, non-toxic and non-magnetic, weldable;Widely used in aviation, aerospace, chemical industry, petroleum, electric power, medical, construction, sporting goods and other fields.
The commonly used welding methods of titanium and titanium alloy include argon arc welding, submerged arc welding, vacuum electron beam welding and so on.
The surface quality of welded parts and titanium wire has a great influence on the mechanical properties of welded joints, so it must be cleaned strictly.
1) for welding parts with low welding quality requirements or difficult pickling by mechanical cleaning, use fine sandpaper or stainless steel wire brush to wipe, but it is best to scrape titanium plate with hard alloy yellow to remove oxide film.
2) chemical cleaning: the specimen and welding wire can be pickled before welding. HF (5%) +HNO3 (35%) water melt can be used as the pickling solution.Rinse with clean water after pickling and weld immediately after drying.Or use acetone, ethanol, carbon tetrachloride, methanol and other materials to wipe the groove of titanium plate and its two sides (within 50mm each), the surface of welding wire, the part of jigs in contact with titanium plate.
3) welding equipment selection: argon arc welding power source with external characteristics and high frequency arc initiation should be selected for titanium and titanium alloy tungsten plate, and the delay of gas transmission time should be no less than 15 seconds to avoid oxidation and pollution of welding parts.
4) selection of welding materials: the purity of argon should be no less than 99.99%, the dew point should be below -40℃, and the total mass fraction of impurities should be 0.001%.When the pressure in the argon bottle drops to 0.981MPa, the use should be stopped to avoid affecting the quality of the welded joint.
5) gas protection and welding temperature: in order to prevent the welding joint from being polluted by harmful gases and elements at high temperature, the welding area and welding seam must be protected and controlled by necessary welding protection and temperature, and special protective towing hood should be used for all-round protection, and the temperature should be below 250℃.
1. During manual argon arc welding, minimum Angle (10~15°) should be kept between wire and welding parts.The welding wire is fed into the pool smoothly and evenly along the front end of the pool. The end of the welding wire shall not be moved out of the argon gas protection zone.
2. During welding, the welding gun basically does not swing horizontally. When it is needed to swing, the frequency should be low and the swing amplitude should not be too large to avoid affecting the protection of argon.
3. When arc breaking and weld ending, the welding gun can be removed only when the weld and the metal in the heat affected area are cooled to below 350℃.
Weld and heat affected zone surface color
1. Weld area
Silver white, light yellow (first, second, third weld allowed);Dark yellow (second and third weld allowed);Gold purple (third-grade weld allowed);Deep blue (first, second and third welding seams are not allowed).
2. Heat affected zone
Silver white, light yellow (first, second, third weld allowed);Dark yellow, gold purple (second and third welding seam allowed);Dark blue (grade iii weld allowed).