Hot gas welding is a fabrication process for thermoplastic materials. The process uses a steam of gas, usually air, to heat and melt both the thermoplastic substrate material and the thermoplastic welding rod. A hand-held welding gun consists of an integral blower, a heating element with thermostat and a set of interchangeable nozzles for directing hot gas at the workpiece. The welding rod is used and this is made from the same polymer as the components to be welded.
The temperature of the hot gas stream is typically in the range 200-400°C. With the heated gas directed towards the joint, local melting or softening of the components and filler rod take place. A weld is formed when the joint region and welding rod fuse and then cool to ambient temperature.
Extrusion welding, another process for fabrication in plastics, is used on thick sections. Filler material is separately heated in the barrel of a hand-held extruder. Softened or molten material is extruded through a PTFE die into the joint which has been pre-heated using a hot gas gun mounted on the extruder barrel.
The main advantage of hot gas welding is that the equipment is portable; however, the process can be slow and weld quality is operator dependent. Fabrication of containment vessels and pipework are the main applications.
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