This change in the characteristics is due to the
fact that carbon diffuses into the iron while cooling changing the overall crystalline structure.
In 1908, Harry Brearley, a 36-year old English
metallurgist, who left school at the age of 12. Became an expert in metals through self-study and
night school. In 1912, Brearley was had the
chance to go to the Brown Firth Research Laboratory in Sheffield, England, to research ways to
eliminate erosion, caused by bullet firing, in gun
barrels.
It briefly came that when a bullet is fired from a
gun, it is pushed through the barrel by the miniature explosion which takes place in the chamber.
Therefore friction occurs between the bullet and
special made grooves in the barrel causing the
bullet to spin, increasing the accuracy of the bullet. This friction caused by the bullet, causes the
barrel to get deformed,
causing the barrel to be
bigger for the bullet,
causing inaccuracy. A
harder metal that could
resist higher temperatures what was needed
for the new barrel design.
As Brearly was one of
the researchers who
were assigned for that mission, he spent months
experimenting to reach a better alloy; yet, none of
his alloys was strong enough to handle the heat
and erosion of the barrel. Disappointed, Brearley
threw all his failing alloys in a junk pile. About a
year later Brearley was looking through this junk
pile when he found that all the alloys have rusted
out except for one of his samples, which was as
bright as new steel. This sample had 12% chromium, hence the erosion did not exist. Chromium
has high affinity for oxygen, that forms a protective layer on the surface of the steel. This layer is
incredibly thin, this microscopic layer clings tightly
to the steel. So that the steel is no Ё