Complete notes of the course

Pagina 1

CONVENTIONAL METAL WELDING TECHNOLOGIES Introduction Before discussing and introducing the unconventional processes we need first to study the welding process. Welding is, together a mechanical fixing and bonding, it's a permanent process that can unite two or more parts together. This process is opposed to the non-permanent ones. Permanent joining process of two mechanical components: • Base metal = they are the two pieces to be welded • Filler metal = it is the metal that can be added to the base metal in order to create the joint We can classify the different type of welding depending on the characteristics of the base and the filler metal: • Homogeneous = base metal and filler metal are the same metal • Heterogeneous = base metal and filler metal are different metal • Autogenous = base metal is melte d so the filler metal is optional (to weld the filler metal is not necessary) • Heterogeneous = base metal is melted so the filler metal is compulsory Welding can also be dived in function of the technology used to weld • Fusion welding = fusion and solidifi cation of two faces with or without filler metal (gas or arc fusion) • Brazing = chemical or electrical fusion of filler material only • Resistance welding = mechanical pressure combined with heating of the two faces In general, the different techniques of we lding can be summarised in the following table. Before going in depth on the different techniques it’s useful to study the welding topography and the welding joint types. Another important definition to know before studying the welding i s the definition of weldability: it is the capacity of the material to be welded under imposed fabrication conditions into a specific, suitable designed structure and to perform satisfactorily in intended service. In addition…