Titanium welding generally adopts tungsten inert gas welding (TIG) method, but in order to speed up the welding speed and improve work efficiency, it is advantageous to use the molten electrode inert gas shielded welding (MIG) method of electrode wire self-fusion. However, due to the low thermal conductivity of titanium, when the titanium electrode wire is energized due to arc heat and Joule heat, the welding wire is flammable, making the arc length longer, and titanium is easy to oxidize and nitride, so it must be protected with argon gas. In this way, no oxide will be formed on the surface of the substrate, but it will cause the cathode point to be unstable and the arc to be unstable, which will eventually lead to a snake shape of the MIG weld. When the butt welding plate is less than 5 mm thick, it is very difficult to ensure a sufficient amount of deposition under the condition of not welding through. To this end, the method of shortening the arc length during MIG welding of titanium is discussed. At the same time, a new welding method is proposed to increase the amount of deposition by moving the welding torch to obtain a good weld.
Fix the CCD camera behind the welding torch to photograph the shape of the weld pool and the welding pit after welding to obtain information such as the change of the weld pool width and the weld seam width. In order to control the arc length, a welding power source with nonlinear characteristics is used. The power supply voltage varies nonlinearly according to the size of the welding current, so that the voltage and welding current between the welding torch and the substrate are in a pulse waveform, which is controlled by the arc itself. Keep the arc length substantially constant. The current value suitable for the power supply was tested. CCD camera observation shows that when 70 A welding current is used, the arc is unstable; when 300 A welding current is used, the arc is stable, so the peak current is adjusted to 300 A. In the case of one pulse of the pulse current waveform, it is best to drop one droplet from the electrode wire. Therefore, in order to maintain a short arc length, the pulse width of the peak current is adjusted to 2.5 ms. When the pulse MIG method is used for butt welding of 1 mm thick pure titanium plates, in order not to cause welding penetration, the wire feed speed is adjusted to 100 mm/s and the welding speed is adjusted to 16.6 mm/s. At this time, the observation of the CCD camera shows that when the current is at the base value of the pulse current, the arc will shift, and the amount of welding is insufficient. To this end, a folding-back welding method that moves the welding gun forward and backward during welding is proposed. The scheme of advancing the welding torch by 22 mm and then retreating by 12 mm was tested. The average welding speed was 15 mm/s, sufficient deposition was obtained, and the welding seam was good.