Plasma keyhole welding offers high integrity welds and high productivity, and finds plenty of applications in industries that manufacture products from stainless and titanium, e.g. welding the linear seams of stainless tanks for storage and transportation, as well as manufacture of tube and pipe.
Full penetration plasma keyhole welds have inherent undercut due to any joint gap and material sag at the keyhole root. A welding camera positioned at the front of the seam may be used to monitor the position of the plasma nozzle relative to the weld seam and observe the melting behavior as the metal flows around the front of the keyhole to the back. Because it is quite difficult to get the balance right in a keyhole pass, a second pass known as a capping pass is used to add material to the top surface, reinforce the weld and eliminate undercut. In the capping pass the plasma torch is modified for a conduction mode type puddle or a second TIG torch is employed to melt filler wire into the conduction mode puddle. A welding camera is also useful in these cases to monitor the melting behavior and checking the wire feed position.
In many plasma arc welding applications, the torch position makes visual monitoring of the weld process by the operator difficult, and a camera can make the operator more effective while improving the operator's ergonomics. In some applications, a camera is located at the rear to visualize the solidification of the keyhole pass and capping pass. In rare applications (e.g. tube mills where the material moves instead of the welding torch) a camera can be located with a view of the penetrating arc at the bottom surface. If the view permits, the user may monitor the size and position of the penetrating arc with machine vision techniques thereby creating a penetration sensor for the plasma keyhole welding process.
The MeltView DART2 and MeltView PIXI provide clear images of plasma keyhole welding, the brightest arc process, at 1920x1080p resolution.
