DESIGN TECHNOLOGY
MATERIALS - METAL
FERROUS METALS
Ferrous metals are metals that contain IRON. Iron on its own is of little use as it is very
soft. It is usually ALLOYED with CARBON or other metals. When alloyed with Carbon
we get a range of CARBON STEELS. In the main, the more carbon we add the harder the
Steel becomes and the more brittle it becomes. Mild Steel has a very small amount of
carbon added (0.15-0.35%) and this results in a very workable steel that can be used for
many applications. Mild Steel is the most commonly found steel in use today.
If we require a harder steel, for cutting and drilling, then we add more carbon (0.8 - 1.5%)
to get High Carbon Steel.
If we add chromium, nickel & magnesium in small quantities then we get Stainless Steel.
This is a very useful steel as it does not require any surface treatment as it does not rust. It
is however more expensive to produce than ordinary steels and it is very hard to work.
CAST IRON
MELTING POINT - 1200 C
COMPOSITION - Iron + 3.5% carbon
PROPERTIES - Hard and brittle
USES - Heavy machinery, vices, car engines
HIGH CARBON STEEL
MELTING POINT - 1800 C
COMPOSITION - Iron + 0.8 - 1.5% carbon
PROPERTIES - Very hard and brittle Tools
USES - hammers, chisels
MILD STEEL
MELTING POINT - 1600 C
COMPOSITION - Iron + 0.15-0.35% carbon
PROPERTIES - Tough and malleable, easily joined, general purpose metal
USES - Nails, screws, girders, car bodies, fridges
HIGH SPEED STEEL
MELTING POINT - 1800 C plus
COMPOSITION - Steel + tungsten, chromium, vanadium
PROPERTIES - Extremely hard, cannot be cut by normal means
USES - Machine tools
STAINLESS STEEL
MELTING POINT - 1800 C plus
COMPOSITION - Iron + chromium, nickel & magnesium
PROPERTIES - Does not rust, difficult to work
USES - Sinks, cutlery