JSS 1. TOPIC 9. PROCESSING OF MATERIALS- metals

 Metal is processed from a natural solid mineral found beneath the earth called iron-ore. In its natural state iron-ore contains a lot of impurities which is removed through smelting.

Blast furnace: The blast furnace is a smelting (heating or burning) plant used for changing iron – ore into pig –iron. To smelt iron – ore in the blast furnace, other chemicals like coke (which serves as fuel) and limestone (which removes impurities) are added to the iron – ore so that most of the impurities may be removed. Eg.

Pig – iron:  Pig –iron is derived from iro n- ore. It is the product,  derived from the blast furnace. Further processing of pig – iron gives birth to steel. The furnace used for this purpose is called “Bessemer Converter”.eg.

Bessemer Converter: This is the furnace used for smelting pig – iron into steel by further burning off of impurities in the right percentage. Since steel are categorized into three categories, the Bessemer converter is used for this purpose. Eg.

Other Methods: Other furnaces used for smelting iron – ore into steel are:

The basic oxygen furnace:

The electric furnace :  for producing cast iron products

The open-hearth furnace:  is one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel

This three methods listed above make use of iron oxide at high temperature (1600⁰   C)  to remove impurity.

Bessemer Converter

Electric Arc Furnace

                                                               Classification of Steel

Steel is produced from pig – iron. However  pig – iron contains 3 to 5% of carbon. This percentage of carbon is too high for any steel since the metal will be too weak for any engineering work.

The three basic elements of steel are ferrite (pure iron), cementite and pearlite.

                                                       Classes of steel

Low Carbon Steel: The content of  carbon In a low carbon steel is about 0.05% - 0.3%. it contains mostly ferrite. It has low tensile strength and is used for car bodies and light structures.

Medium Carbon Steel: This class of steel mainly contains cementite. This property makes medium carbon steel hard and ad of great strength. It is mainly used in making lighter springs and power transmission devices. The carbon con tent is about 0.3% - 0.6%.

High Carbon Steel: This is the steel that contains mostly pearlite. It is usually very hard and it is used for making cutting tools like files, punches, chisels, dyes, etc.

Class Work

What is iron – ore?

How is pig – iron produces from iron – ore

What is the bessemer converter used for?

ASSIGNMENT

Draw the following, fully labeled

Blast furnace

Bessemer converter

Open – hearth furnace 

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