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Steel Making

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

High Speed Steel
For centuries the secret art of making tool steel was handed ...

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

Molybdenum steels have been made commercially for twenty-five...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

MANGANESE is a metal much like iron. Its chemical symbol is M...

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Chromium when alloyed with steel, has the characteristic func...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

SULPHUR is another element (symbol S) which is always found i...

Tungsten, as an alloy in steel, has been known and used for a...

The Modern Hardening Room
A hardening room of today means a very different place from ...

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

Steel Worked In Austenitic State


As a general rule steel should
be worked when it is in the austenitic state. (See page 108.) It
is then soft and ductile.

As the steel is heated above the critical temperature the size of
the austenite crystals tends to grow rapidly. When forging starts,
however, these grains are broken up. The growth is continually
destroyed by the hammering, which should consequently be continued
down to the upper critical temperature when the austenite crystals
break up into ferrite and cementite. The size of the final grains
will be much smaller and hence a more uniform structure will result
if the mother austenite was also fine grained. A final steel
will be composed of pearlite; ferrite and pearlite; or cementite
and pearlite, according to the carbon content.

The ultimate object is to secure a fine, uniform grain throughout
the piece and this can be secured by uniform heating and by thoroughly
rolling it or working it at a temperature just down to its critical
point. If this is correctly done the fracture will be fine and
silky. Steel which has been overheated slightly and the forging
stopped at too high a temperature will show a granular fracture.
A badly overheated or burned steel will have iridescent colors
on a fresh fracture, it will be brittle both hot and cold, and
absolutely ruined.

Next: Steel Can Be Worked Cold

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