Important Metal Processes
Welding
It is process for joining similar metals by melting and fusing the base metals as well as the filler metal. Welding is usually used with ferrous-based metals such as steel and stainless steel. The temperature range of welding is 800ºC - 1635ºC. Welded joints are the strongest of joints. Used in joining iron rods and plates in construction, heavy engineering.
Brazing
It is a process in which two close-fitting parts are joined by using a filler material which is heated above its melting point and distributed in the gap by capillary action. A chemical cleaning agent known as flux is used to prevent oxidation of metals being heated. Temperature range for brazing is above 450ºC. Usually used for joints in household utensils and thin sheets of metal where welding is not suitable.
Soldering
It is a process similar to brazing but the filler material is of much lower melting point. The filler material, solder is an alloy of tin and lead. Temperature range for soldering is below 450ºC. Soldered joints are the weakest of the three viz welding, brazing and soldering. Used in joining electronic components on printed circuit boards.
Electroplating
It is process in electric current is used to deposit ions of a metal on another. Thus chromium may be used to plate iron bars. Electroplating is usually done to prevent corrosion of the base metal or for decorative purpose. Shining parts of automobiles, cycles etc are electroplated with chromium.
Smelting
It is a process of extracting a metal from its ore by heating the ore beyond its melting point. Flux is used in the process to remove the slag
Annealing
It is a process in which a metal is heated to a specific temperature and then cooled slowly in order to make the metal soft enough for easy cutting and shaping.
Hardening
It is a process in which a metal is heated to a specific temperature and then cooled suddenly in order to make the metal hard. This also makes the metal brittle or easy to break.
Tempering
It is a process in which a hardened metal is heated to a specific temperature and then cooled slowly in order to make the metal tough enough for use as cutting or abrading tool. Tools such as drills, chisels, files etc. are hardened and tempered.
Galvanisation
It is a process in which a protective zinc coating is applied on iron to prevent it from rusting.