STEEL DEMANDS

Friday's class started off with a documentary film from 1944 on STEEL MANUFACTURING PROCESS at Ohio. 
We could observe how the crude iron ore was molten; combined with coke from bituminous coal in a blast furnace where limestone is shoved.
The molten iron now contains high levels of carbon and is sent to an oxygen char in ladles on wheels. Here hot air is blown into the molten iron at intervals and steel scraps are added. The resultant is molten steel. The steel is then shaped by molds and cooled down before an acid wash that removes surface impurities.

After this process which is the common beginning of all steel productions, the steel is subjected to a variety of further treatment:

COLD ROLLING : makes very thin steel coils
COATING      : makes steel resistant to corrosion
TINNING      : to further reduce the gauge(thickness) and add tin coat
ANNEALING    : makes steel easier to bend and form
TEMPERING    : to add hardness and create surface textures

Because of the high carbon content in steel it is always prone to be corroded by the atmosphere - factors of temperature, humidity, precipitation etc. So GALVANIZATION (coating of zinc) is done by 2 methods :

COLD DIPPING     : matte finish-durable-prevalent use
ELECTRODE METHOD : lustrous finish-less durable-not preferred as much

Now the differences between hot rolled and cold rolled steel

HOT ROLLED : higher temperature-easily molded-cheaper
COLD ROLLED: lower temperature-more surface finishes-expensive

COLD HAMMERING : also called forging causes change of form before re-crystallization 
QUENCHING      : bringing steel to room temperature by pouring water or oil . This forms a layer on the steel surface due to rapid crystallization- promotes ductility

After extending the steel process for desired production and usage
SURFACE FINISHES come into play

BURNISHING           : sliding contact-increases surface smoothness
ACID ETCHING         : coating and removing partially  
ELECTROLYTIC COLORING: shades like red,green,gold and bronze
PAINTING             : only an external coat
ENAMELING            : coated and baked to melt and cure

All I could recollect.

-Veronica





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