Ask A Scientist© Engineering Archive

 >    name         David
 >    status       student
 >    age          40s

 >    Question -   What is the difference between physical properties and
 > mechnical properties of steel?


I am not sure I really follow your question, but I'll see if I can answer
it.  I take it you mean physical properties to be things like mass, melting
point, etc., whereas mechanical properties are things like modulus of
elasticity, hardness, etc.  Both physical and mechanical properties are
going to be dependent on chemical composition.  More carbon, less carbon,
more nickel, less nickel, etc. are going to influence what kind of steel you
have.  That is why you see numbered steels because they represent a certain
composition.  However, mechanical properties can be greatly influenced by
how they are treated during manufacturing.  Steels can be quenched in water
to give one value of hardness, whereas they can be quenched in oil to give a
different value for hardness.  Most of the mechanical properties are
influence on what phase of material is allowed to develop as the steel is
made.  Quenching is just one way to influence phases and grains of a piece
of material.  Heat treating and annealing are just a couple of other ways to
work a metal.
In short, physical properties such as mass and melting point are "kind of"
locked in by the composition of the elements that make up steel, but
mechanical properties can be greatly influenced by how the metal is treated
during its creation.
Hope this helped.

Dr. C. Murphy

=========================================================