Metal-Ferrous,Non Ferrous,Alloys And Types Of Steel
Metal is produced from iron ore which is dug from the ground.The mineral ore mined from the ground usually contains impurities in the form of non-metallic compounds called gangue.
The extraction process of metal differs from metal to metal.However,all ores are invariably reduced,at high temperatures,to metals with the aid of combustible reducing agents.
In the production of iron,example,the improved ironmite,magnetite or haematite ore is mixed with limestone and melted by burning coke in a blast furnace.
The metal produced by this and similar reactions is called pure metal. It has generally poor physical,magnetic and electrical properties.Some other elements or metals are added to it to improve these properties. That means the metal so produced a mixture of two or more metals. A mixture of two or more metals is called alloying metals or elements.
The product of the blast furnace is pig iron. Carbon is introduced into the iron to give properties lacking in pure iron. The new product is called steel. Steel is usually produced in special furnaces such as cupola,electric arc,bessemer converter,open hearth. Apart from carbon,some of the more common alloying elements are nickel,silicon,manganese,chromium,tungsten,molybdenum and titanium.
Various types of steel are produced in the furnace,depending on the type of scrap-metal fed in and the type and quantity of the alloying elements added.
For example,if traces of other alloying elements are added to iron containing up to 0.3% carbon,the steel produced is low-carbon steel ;between 0.3% and 0.6% carbon,the steel is medium-carbon steel;while between 0.6% and 0.9% carbon, high carbon steel is the product.
Tool steel has between 0.9% and 1.4% carbon steel with silicon content greater than 0.5%, together with some other alloying elements. This is called alloy steel. It has superior properties to plain carbon steel. Such qualities as strength,hardness,corrosion-resistance and wear-resistance are usually added to steel by alloying elements
HOW PLAIN CARBON STEEL ARE APPLIED
The following below are the ways in which plain carbon steel are applied:
Low-carbon steel: This type of steel is applied in the production of screws,structural steel,nails,rivets,sheets for automobile bodies.This type of steel also has 0.1% to 0.3% of carbon.
Medium-carbon steel: This type of steel is applied in the production of bearings,axles,rails,locomotive tyres,wire ropes.This steel has 0.3% to 0.6% of carbon
High-carbon: This type of steel is applied in the production of punches,hammers,saws,screwdrivers,and chisels.This type of steel contains 0.6% to 0.9% of carbon
Tool: This type of steel is applied in the production of axles,knives,files,drills and tapes.This type of steel contains 0.9% to 1.4% of carbon.
Cast iron: This type of steel is applied in the production of automobile cylinders and pistons,water main pipes and dies.This type of steel contains 2.5% to 3.9% of carbon.
Wrought : This type of steel is applied in the production of nails,welding fittings barbed wire.wrought contains 3.9% to 4.3% of carbon.
The most widely used non-ferrous materials are the alloys of copper,aluminium,tin,magnesium,lead and zinc.Other less widely used are gold,silver,platinum,cobalt,cadmium,beryllium,tantalum,zirconium and molybdenum. Most of the non-ferrous metals conduct heat and electricity and are difficult to weld.They have attractive colours and are easily formed into shapes.
FORMING OF METALS
Ferrous and non-ferrous metals can be made into different forms by one of the two board methods:
In Forming processes,solid metals are heated to high temperatures and then compelled to assume a pre-determined shape by the application of force. Examples of forming processes are gorging,extrusion,rolling,drawing,hot-pressing and spinning. Soft metals such as lead may be formed into shape without application of heat.This is usually referred to as cold forming.
For casting, metals are cast into shapes from the molten state.Casting may be done in many ways;these includes: pressure die-casting,chill casting,investment casting and sand casting.