3. Metallurgical phenomena and their consequences

A brief review of the principles of the various welding processes shows that a certain number of metallurgical phenomena may come into play; their list, taking all processes together, is as follows:

• phenomena due to temperature variations :

  • melting and processing of the liquid bath,

  • solidification,

  • allotropic transformations,

  • dilatation ;

• environmental phenomena :

  • action of the atmosphere,

  • pollutant actions ;

• inclusion phenomena.

In this section, we take a closer look at these phenomena.