1. Preparation before welding
The surface quality of welds and wires has great influence on the mechanical properties of welds, so it must be cleaned strictly.Mechanical cleaning and chemical cleaning can be used for iron plate and titanium wire.
1.1 mechanical cleaning of welding parts with low quality requirements or difficult pickling can be wiped with fine sandpaper or stainless steel wire brush, but it is best to scrape titanium plate with cemented carbide yellow to remove oxidation film.
1.2 chemical cleaning.Before welding, the specimen and welding wire can be pickling, pickling liquid can be used hf5% +HNO335% water melt.After pickling, rinse with clean water, dry and weld immediately.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, the part in contact with the fixture and the titanium plate.
2, the selection of welding equipment titanium and titanium alloy gold tungsten plate argon arc welding should choose the dc argon arc welding power source with the characteristics of external descent, high-frequency arc initiation, and delay the time of gas transfer not less than 15 seconds, to avoid the welding suffered from oxidation, pollution.
3. 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 <0.001%.When the pressure in the argon cylinder drops to 0.981mpa, it should be stopped to prevent the quality of the welded joint from being affected.In principle should choose and base metal composition of the same titanium wire, sometimes in order to hold the high weld metal plasticity, also can choose the strength of the base metal slightly lower than the wire.
4. Gas protection and welding temperature: in order to prevent the welding joints from being polluted by harmful gases and elements at high temperature, necessary welding protection and temperature control must be carried out on the welding area and welds, and the temperature should be below 250℃.The main methods of protection and temperature control are as follows: 1.The other is to be filled with protective gas in the welded tube.The shielding gas is argon, whose purity should be ≥ 99.99%.The flux of shielding gas shall meet the welding technical requirements
5. Selection of welding parameters
5.1 titanium alloy welding wire.The grade of filler wire should be selected according to the base material, generally using the principle of homogeneity with the base material, sometimes in order to improve the plasticity of the joint, can also choose to base material less alloyed degree of the wire.Wire diameter should be selected according to base material thickness
5.2 tungsten electrode.It is best to choose cerium tungsten pole, its diameter according to the thickness of titanium alloy tube wall, generally in 1.0 ~ 3.0mm, tungsten extreme should be ground into 30 ~ 45 degree cone.
6, groove form selection principle to minimize the number of welding layers and welding metal.With the increase of the number of welding layers, the cumulative suction placement of the welds increased, which affected the performance of the welding joint. In addition, the welding pool size of titanium and titanium alloy was larger, so the specimen was ordered with v-type 70-80 ° groove.
In order to reduce welding deformation, positioning welding is carried out before welding. Generally, the distance of positioning welding is 100~150mm, and the length is 10~ 15mm.The welding wire, welding process parameters and gas protection conditions used in positioning welding shall be the same as those used in welding joints.Clearance 0~2mm, blunt edge 0~1.0mm.
Contact Person: Mr. Chang