28-09-2016, 03:01 PM
1456638340-Lecture4FerrousMetal.ppt (Size: 2.23 MB / Downloads: 3)
Introduction
Metals form about a quarter of the earth crust by weight
One of the earliest material used dated back to
pre-historic time
Some of the earliest metals used include:
copper, bronze and iron
Stone age Bronze age … ’discovery’ of steel
Industrial Revolution in the 18th century
All metals except gold are generally found chemically
combined with other elements in the form of
oxides and sulphates. Commonly known as ores.
Pure Metals and Alloys
Metal that are not mixed with any other materials are known
as pure metals. Metals listed in the Periodic Table are pure
metals
E.g. Iron (Fe), Copper (Cu) and Zinc (Zn)
Alloys are mixtures of two or more metals formed together
with other elements/materials to create new metals with
improved Mechanical Properties and other properties
of the base metal.
E.g. Brass (Copper and Zinc),
Stainless steel (steel and chromium)
Alloy = metal A + metal B + … + other elements
Ferrous Metals & Non-Ferrous Metals
Ferrous metals are metals that contain iron
E.g. Steel (iron and carbon)
Non-ferrous metals are metals that do not contain iron
E.g. Zinc (pure metal), Bronze (Copper and tin)
(non-ferrous may contain slight traces of iron)
Ferrous Metal = alloy metals that contains iron
( Primary base metal is iron)
Non-ferrous Metal = alloy metals that do not contain iron
Primary base metal does not contain iron)
Extraction of Iron
Iron is found in iron oxide in the earth.
Three primary iron ores: magnetite, haematite, limonite,siderite
Iron is extracted using blast furnace
Steps in extraction of iron
Ores is washed, crushed and mixed with
limestone and coke
The mixture is fed into the furnace and is then melted
Coke(a product of coal, mainly carbon) is
used to convert the iron oxides to iron
Molten iron sinks to bottom of furnace, where it is tapped off from furnace and cast into large ingots called “pigs”…pigs contain high carbon content (4% or so), plus many impurities, such as sulphur and silica which wasn’t removed by the limestone.
Types of Steel
Steel
Low carbon steel (mild steel)
Medium carbon steel
High carbon steel (tool steels)
Cast iron
Alloy Steels
Stainless steel
High speed steel
Low Carbon Steel
Also known as mild steel
Contain 0.05% -0.32% carbon
Tough, ductile and malleable
Easily joined and welded
Poor resistance to corrosion
Often used a general purpose material
Nails, screws, car bodies,
Structural Steel used in the construction industry