A study of chromium, its common alloys, uses and extraction
Citation preview
1. METALS An indepth Study of Chromium By Ben DeBortoli, Joe
McDonogh & Tim Chow
2. Chromiums use through history
Chromiums most common use throughout history has been the
production of various ferrous alloys (alloys containing iron) with
the most common by far being the alloy ferrochromium
Chromium is also used to make:
3. paint up to the 1980s 4. Elevators 5. Escalators 6. Barbeques
7. AeroplaneFrames 8. And many other things 9. Activity & Ease
of Refinement
In relation to Chromiums uses:
Chromium does not react easily; it possesses passivation, which
makes it highly unreactive
It does not corrode or oxidise easily
Therefore it is used to build & plate things to protect
them from corrosion and oxidation
Chromium ore (chromite) has a high abundance, and chromium is
easy to extract
The relative ease of refinement allows chromium to be widely
used
10. Extraction Process of Chromium
Chromium is extracted commercially from chromite (chromium
oxide), which is found naturally
Chromite has the formula Cr 2 O 3
Chromium is extracted using the Thermite Process in which a
reduction/oxidation reaction takes place with aluminium
Chromite (chromium oxide) reacts with aluminium. The chromite
is reduced to form pure chromium, and the aluminium is oxidised to
form aluminium oxide
Cr 2 O 3(s)+ 2Al (s)Al 2 O 3(s)+ 2Cr (s)
Chromite 11.
Energy input involved:
The Thermite Process requires substantial heat energy
This energy drives the reaction
In turn the reaction produces a substantial amount of heat
Therefore energy input is necessary to successfully extract
chromium from its ore
Extraction Process of Chromium A typical thermite reaction 12.
Common Alloys of Chromium
Chromoly:
- A Range of low alloy steels
- Advantage over aluminium is more tensile strength and
malleability
- Disadvantage to aluminium is extra weight and does not resist
corrosion asstainless steel does
- Used in bicycle frames and race-car roll cages
Chromel:
- Made up of roughly 90% nickel and 10% chromium
- resists high temperatures (1100C) and high
tensilestrength
- used to make positive conductors for a type of temperature
sensor know as a thermocouple
Chromel A:
-Variation of Chromel, contains 80% nickel and 20 % chromium
and has high resistance to corrosion, high temperatures and
oxidation
13. Common Alloys of Chromium
Stellite:
- Formed from a variety of cobalt-chromium alloys designed to
wear resistance
- Completely non-corrosive and non-magnetic
- Cuts things at high temps
- Expensive to produce due to extreme durablity, done by
grinding rather than cutting
- used in saw teeth, hard facing, acid-resistant machine parts,
improved quality of poppet valves, valve seats and internal
combustion engines greatly. Also used in M60 machine guns, starting
from the chamber as well as jet turbine engine blades
Ferrochrome:
- This alloy of chromium is 50%-70% chromium, alloyed with
iron
- 80% of ferrochrome is used in the production of stainless
steel
- Usually used in areas of specialist productions like
engineering. A high Cr to Fe ratio is needed and minimum amounts of
other elements such as Sulfur, Phosophorus and titanium are
important
- This production is done in small furnices rather than
large
Ferrochrome 14. Common Alloys of Chromium
Stainless Steel:
- Most common alloy which chromium is present in
- Resistance to heat, malleable, resistance to corrosion, cost
effective and resistance to water and oxidation
- Many different types due to the ease amounts of each metal
can be varied
-Core metals are chromium, iron, aluminium and titanium
-Stainless steel is used to make cutlery, cooking utensils,
pots and pans, furniture, shelters, subway trains, fuel and
chemical containers, piping and much more
15. Availability of Metals
The availability of metals has increased in the past 200
years
This is due to:
The discovery of more ores and metals
Advances in technology
It is easier to locate ore bodies now than 200 years ago
New processes to extract metals from their ores have been
discovered, eg the Bayer Process
The industrial revolution
Mass production and extraction of metals began
Due to these advances, it is easier to extract and produce
metals. Therefore their availability has increased as these
advances are made
16. The Recycling of Chromium
Chromium is currently not recycled on the large scale due
to:
The abundance of chromium ores and their ability to satisfy
human needs for many hundreds of years
The relative ease associated with extracting chromium
However in the future a need may arise to recycle
chromium:
as chromium ores become depleted
as energy conservation becomes more of an issue
But in the short term and at present there is no need to
recycle chromium