Classification of Metals
1.0 What is Metal ?
Metal is a class of substance characterized by high electrical and thermal conductivity as well as by malleability, ductility and high reflectivity if light.
1.1 Classification of metal
Metals are classified as follows-
A) Ferrous metal- Ferrous metals are those whose primary constituent element is iron. It may be in Divalant (Fe2+) or Trivalant (Fe3+) form. Example- Steel, Cast iron etc.
B)Non-ferrous metal- Non-Ferrous metals are those which don't have Iron its primary constituent element. Example- Nickel and its alloys, Aluminum and its alloys etc.
1.2 Ferrous metals and its alloys
Depending upon the percentage of Iron, carbon and other alloying element ferrous metals are classified as follows:
A) Steel- Steel s an Iron-Carbon alloy containing carbon up to 2.1% max.
B) Cast-Iron- Cast Iron is also Iron carbon alloy that contain carbon more than 2.1%.
A.1) Based on Carbon and alloying element percentage steels are classified as follows-
A 1.1) Carbon steel- Carbon steel are those in which main alloying element is carbon. It also contains other alloying elements like Mn (<1.6%), Si (<0.6%), Cu (<0.6%). Based on carbon percentage of carbon steels are classified as follows
A1.1.1) Low carbon Steel- This types steel contains carbon petcentage up to 0.3%. If carbon percentage lies between 0.15% - 0.3% it is called as Mild Steel.
A1.1.3) High carbon Steel- If the carbon percentage is more than 0.8% then that steel is known as high carbon steel.
A.2) Alloy Steel- Steel is called alloy steel if Mn >1.65%, Si > 0.6% and Cu >0.6%. It is further classified into two types.
A.2.1) Low alloy steel- If the total alloy content is less than 8% then it is classified as low alloy steel.
A.2.2) High alloy steel- If the total alloy content is more than 8% then steel is classified as high alloy steel.
A 3) Stainless Steel- Stainless steel is high alloy steel contain major alloying elements as chromium and Nickel. The percentage of chromium and nickel present in the metal determine phase to be formed and based on these stainless steels are classified as follows:
a) Austenitic steel
b) Ferritic steel
c) Martensitc steel
d) Duplex steel
e) Precipitation hardening steel
|
Family |
Weldability |
Ductility |
High
temperature resistance |
Common
Grade |
|
Austenitic
steel |
High |
High |
High |
304,310,316 |
|
Ferritic
Steel |
Low |
Medium |
High |
430 |
|
Martensitic |
Low |
Low |
Low |
410,420 |
|
Duplex |
High |
Medium |
Low |
2205 |
|
Precipitation
hardening |
Low |
Medium |
Low |
630 |
A.4) Tool Steel- Tool steel contains various amounts of tungsten, molybdenum, cobalt, and vanadium to increase the heat resistance and durability of the metal. Tools steel is divided into six group.
a) Water-hardening
b) Cold-work
c) Shock-resisting
d) High-speed
e) Hot-work
f) Special purpose
B) Cast Iron- Cast iron, an alloy of iron that contains more than 2.1% C, along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace.
|
Type |
Nature
of Graphite |
Ductility |
|
White
cast iron |
Not present |
Negligible |
|
Grey
Cast iron |
Flake |
Negligible |
|
Malleable
C.I. |
Flake to nodular |
Present |
|
Nodular
C.I. |
Nodular |
Present |
|
Compact
graphite C.I. |
Worm like |
Present |
Non-ferrous metals are alloys or metals that do not contain any appreciable amount of iron. All pure metals are non-ferrous elements, except for iron(Fe). Non-ferrous metals are mainly used due to the properties as given below:
a) Easy to fabricate (including machinability, casting and welding)
b) High corrosion resistance
c) Good thermal and electrical conductivity.
There is a great verity of non-ferrous alloys available in the market, but the most commonly used non-ferrous metals are Nickel, copper and aluminum and their alloys.
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