What are the efficient welding methods for titanium alloy welding?
How to weld titanium alloy efficiently?
Table of Contents
At present, more efficient titanium alloy welding methods are: PAW, LW, LW + MIG and other automatic welding methods.
Preparation before welding
The preparation before welding of titanium alloy is very important.
Cleaning before welding
Before welding, the groove and the titanium alloy surface within 50 mm on both sides of the groove shall be polished with a fine stainless steel wire brush until the metallic luster of the titanium alloy itself is exposed. After grinding, wipe the groove and both sides with clean white silk cloth and acetone to thoroughly remove the oxide film, grease, water, dust and other impurities in the welding area.
Before welding, the pressure of each cylinder should be carefully checked to ensure that all kinds of gas pressure are sufficient. Before PA and l-mig compound welding, the welding machine should be adjusted and checked to ensure that the power supply and wire feeder work normally. During adjustment and inspection, the welding gun can be placed above the full length of the weld
Make sure that the walking mechanism works normally and the welding gun and the weld are in good alignment. Before LW welding, the weld trajectory should be corrected and the NC program should be written.
Welding materials for titanium alloy welding
In plasma arc welding (PAW), the first grade pure argon (≥ 99.99%) is used for the plasma gas, nozzle shielding gas, bracket and back shielding gas; In the process of laser welding (LW), pure helium (≥ 99.99%) is used as side blowing gas, and primary pure argon (≥ 99.99%) is used as trailing cover and back shielding gas; In the compound welding of laser + MIG (LW + MIG), the mixture of (70% He + 30% AR) is used in MIG welding gun.
The base metal of the weldment is TI70 (ti-2.5al-2zr-1fe) α Titanium alloy) and TA5 (ti-4al-0.005b system) α There are two kinds of titanium alloy. All welding materials are made of stainless steel Φ 1.2mm disc welding wire TA10.
Welding method for titanium alloy welding
Plasma arc welding
For the titanium plate with thickness between 2.5 ~ 15mm, when the groove is I-shaped, the small hole method can be used for one-time penetration welding. In order to ensure the stability of the small hole, the size of the air filled groove on the back is 30mm × 30mm. There are many process parameters of paw, when the small hole method is used, it mainly involves nozzle diameter, welding current, ion gas flow, welding speed, protective gas flow and so on. The nozzle diameter used in this welding is 2.5mm, and the current type is DC direct connection (DCEN).
The main process parameters of LW welding are laser power, welding speed, defocusing amount, side blowing gas flow and shielding gas flow. Due to the high welding speed of LW, the process parameters can not be adjusted in the welding process. Therefore, the best combination of parameters should be determined through pre-test before formal welding, and the interlayer temperature during welding should not be greater than 100 ℃.
Laser MIG hybrid welding
In LW-MIG hybrid welding, because there are two heat sources, laser and arc, and each heat source has more process parameters to be adjusted, a lot of experiments are needed to make the laser and arc match harmoniously. For the butt joint of 4mm TI70 plate, the welding process parameters given in Fig. 3 are used, and a well formed single pass full penetration weld is obtained. When welding, the relative position of laser and arc should be adjusted properly.
Inspection after welding
After the completion of welding, the appearance of the weld is inspected and non-destructive testing is carried out. The appearance color of titanium alloy can indicate the degree of weld contamination. Generally, the silver white is well protected, and there is almost no pollution of harmful gases; Light yellow and golden yellow welds have little effect on mechanical properties; Other colors such as blue and gray are not acceptable. Due to the sufficient protection in the high temperature zone, the appearance color of the weld after welding is basically silver white or golden yellow. However, due to the fact that the trailing cover can not be fully secured in the arc starting section, the protection effect at the arc starting section is slightly poor. Under normal conditions, the appearance of the weld after welding is in good condition, and there are no defects such as cracks, lack of fusion, air holes, weld beading, etc.
Source: China Titanium Flange Manufacturer: www.titaniuminfogroup.com