The pressure gas welding is define as, the coalescence body is produced by the heating of weld metal and heat source is some gas of mixture. Then apply the pressure on weld metal to completed the pressure gas welding. Any kind of filler metal is not used in this welding process.
This welding technique is commonly used in sheet metal welding, pipe welding, railroad joining etc.
Any kind of special edge preparation is not required in this type of welding method.