Titanium alloy has the advantages of low density, high specific strength, good corrosion resistance, low thermal conductivity, non-toxic and non-magnetic, weldable, etc.Widely used in aviation, aerospace, chemical, petroleum, electric power, medical, construction, sporting goods and other fields.
Common welding methods for titanium and titanium alloys include argon arc welding, submerged arc welding, vacuum electron beam welding, etc
The surface quality of welds and wires has great influence on the mechanical properties of welds.
To the welding quality requirements of low or acid pickling difficult welding parts for mechanical cleaning, the use of fine sandpaper or stainless steel wire brush to wipe, but it is best to use hard and golden to scrape off the oxide film on the titanium plate.
Chemical cleaning: specimens and welding wires can be pickling before welding, pickling solution can be treated with 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 titanium plate groove and its two sides (each 50mm), the surface of welding wire, fixture and titanium plate contact part.
Selection of welding equipment: tig and tig alloy tungsten plates shall be dc tig power source with external characteristics and high frequency arc initiation, and gas transmission delay time not less than 15 seconds to avoid oxidation and pollution of the welding part.
Welding material selection: the purity of argon gas shall not be lower than 99.99%, the dew point shall not be lower than -40℃, and the total mass fraction of impurities shall be 0.001%.When the pressure of the argon cylinder drops to 0.981mpa, stop the machine so as not to affect the quality of the welded joint.
Gas shielded welding temperature: in order to prevent harmful gases and polluting elements from welding joints at high temperatures, necessary butt welding welding protection and temperature control areas and welds must be fully protected with special protection covers.Its temperature should be below 250℃
For manual argon arc welding, the minimum Angle (10-15°) between the wire and the weld shall be maintained.The welding wire is evenly sent into the molten pool along the front end of the molten pool, and the end of the welding wire should not be removed from the argon protection area.
When welding, the welding gun does not swing to the transverse direction. When it needs to swing, the frequency is low and the swing amplitude should not be too large to prevent the protection of argon gas.
After completion of the arc and weld, continue argon protection until the weld metal and heat-affected zone are cooled below 350℃, and remove the welding gun.
Weld surface color and heat affected zone
Silver white, light yellow (first, second and third class welding is allowed);Deep yellow (second and third class welding is allowed);Gold violet (three stage welding is allowed);Dark blue (first, second and third grade welds are not allowed).
Silver white, light yellow (first, second and third class welding is allowed);Deep yellow, gold and purple (grade 2 and grade 3 welds allowed);Dark blue (three class welding is allowed).