This chapter describes some welding processes that permit lower temperatures than those normally required for other common joining processes. These processes are brazing and soldering, whose concept is based on filling the gap between the two metals to be welded with filler metals that are melted with an external source. Solidification results in a strong joint. The chapter also describes thermal cutting processes, permanent and nonpermanent mechanical fasteners, and joining methods for plastic materials. Thermal cutting processes include oxygen cutting, electric-arc cutting, and plasma-arc cutting. Metals and nonmetals are sprayed by being melted or softened and are then swept away at high speed and atomized in a jet of air or gas. Surfacing or hard-facing is a process of welding wear- or corrosion-resistant metal on a part to make it serviceable or to rebuild or repair it. Braze welding, also called bronze welding, is like fusion welding, in that a filler is melted and deposited in a groove, fillet, plug, or slot between two pieces to make a joint. Brazing is the name given a group of welding operations in which a nonferrous filler metal melts at a temperature below that of the metal joined, but is heated above 427° C (800° F). Soldering or soft soldering is the process of joining metals by means of alloys that melt between 177–371° C (350–700° F). Mechanical fasteners include permanent and nonpermanent means of fastening. Adhesive bonding is used to create a permanent joint between two surfaces.
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