Computer Controlled Plasma Welding Machine
Welding is joining of two pieces of similar metals by heating and adding of a filler material. The welded material may be shielded or unshielded. The shielding material is usually inert gas and it protects the welding process and materials being welded together. Welding processes are coated electrode welding, lo-hydrogen coated electrode welding, Tungsten inert gas welding, or the latest Plasma welding.
Welding process is a high temperature process and the welding zone has to be smaller to protect the parent material and distortion of the job. The welding process may be coated welding electrode, a low hydrogen electrode, a tungsten inert gas welding or the plasma welding. Each one is in increasingly better than the previous one and the parent metal is better protected from being oxidized or from hydrogen related corrosion.
Plasma arc welding (PAW) is an advanced version of the tungsten inert gas (TIG) welding process. TIG welding has a free-burning arc, which is unstable and tends to go in all directions in the low current range. The arc diameter also increases with the current increase. This affects the zone of welding and the total quality of welding. The total input to the work-piece is also increased and the related effects of higher power are evident in the quality of work.
The high temperature of weld zone on the other hand is more concentrated in plasma welding and thus the inputs of welding heat if less and the quality of welding is better. The plasma column is stabilized along the axis of the electrode and is more intense than the TIG-welding arc. The column temperature is 10,000-24,000 degrees K compared to 8,000-18,000 degrees K in case of TIG-welding. (Degrees Kelvin is equal to degrees centigrade plus 273.2)
Add to this a computer control the advantages are increased and the disadvantages are decreased.
The advantages of computer-controlled plasma welding over TIG are,
? It is less sensitive to arc length
? Heat affected zone is reduced and the distortion of work-piece is reduced or eliminated. The reduction of distortion is more evident in low thickness plates rather than high thickness plates.
? High speed welding is possible and this increases the production volumes..
? Recessed electrode reduces the possibility of tungsten inclusions in the weld and can substantially increase the period between electrode dressings resulting in increased life of electrode.
? There is a marked reduction in embitterment of stainless steel by carbides and inter-metallic compounds higher alloys of steel. This is possible due to reduction of welding time.
? The residual stress in work piece is reduced.
? The porosity of welded material is reduced.
? For hard facing, the thickness of hard facing is important. A lower thickness of coating is possible with computer controlled plasma machines. . This reduces the cost of hard facing. This is not possible with TIG welding.
Computer controlled plasma welding can be used in Aerospace and Space Industries, Cryogenics, Foodstuff and Chemical Industries, Machine and Plant Construction, Automobile, Railway, Ship Construction, Tank, Equipment and Pipeline Construction etc.
These machines are made in nearly every country and the competition for such machines is large. The use of computer control makes it suitable for control by a central computer without manual intervention at all. The requirement of human element becomes very less and the production and its quality gets a boost.