Welding is any metal joining process wherein coalescence is produced by heating the metal to suitable temperatures, with or without the application of pressure and with or without the use of filler metals.
Metals are divided into two classes, ferrous and nonferrous.
Ferrous metals are those in the iron class and are magnetic in nature. These metals consist of iron, steel, and alloys related to them.
Nonferrous metals are those that contain either no ferrous metals or very small amounts. These are generally divided into the aluminum, copper, magnesium, lead, and similar groups.