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Steel Making

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

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

Corrosion
This steel like any other steel when distorted by cold worki...

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

Hardening
The forgings can be hardened by cooling in still air or quen...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Quenching
It is considered good practice to quench alloy steels from th...

Connecting Rods
The material used for all connecting rods on the Liberty engi...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

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

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...



Chromium






Category: ALLOYS AND THEIR EFFECT UPON STEEL

Chromium when alloyed with steel, has the characteristic function
of opposing the disintegration and reconstruction of cementite.
This is demonstrated by the changes in the critical ranges of this
alloy steel taking place slowly; in other words, it has a tendency
to raise the Ac range (decalescent points) and lower the Ar
range (recalescent points). Chromium steels are therefore capable
of great hardness, due to the rapid cooling being able to retard
the decomposition of the austenite.

The great hardness of chromium steels is also due to the formation
of double carbides of chromium and iron. This condition is not
removed when the steel is slightly tempered or drawn. This additional
hardness is also obtained without causing undue brittleness such as
would be obtained by any increase of carbon. The degree of hardness
of the lower-chrome steels is dependent upon the carbon content,
as chromium alone will not harden iron.

The toughness so noticeable in this steel is the result of the
fineness of structure; in this instance, the action is similar
to that of nickel, and the tensile strength and elastic limit is
therefore increased without any loss of ductility. We then have
the desirable condition of tough hardness, making chrome steels
extremely valuable for all purposes requiring great resistance
to wear, and in higher-chrome contents resistance to corrosion.
All chromium-alloy steels offer great resistance to corrosion and
erosion. In view of this, it is surprising that chromium steels
are not more largely used for structural steel work and for all
purposes where the steel has to withstand the corroding action
of air and liquids. Bridges, ships, steel building, etc., would
offer greater resistance to deterioration through rust if the
chromium-alloy steels were employed.

Prolonged heating and high temperatures have a very bad effect upon
chromium steels. In this respect they differ from nickel steels,
which are not so affected by prolonged heating, but chromium steels
will stand higher temperatures than nickel steels when the period
is short.

Chromium steels, due to their admirable property of increased hardness,
without the loss of ductility, make very excellent chisels and
impact tools of all types, although for die blocks they do not give
such good results as can be obtained from other alloy combinations.

For ball bearing steels, where intense hardness with great toughness
and ready recovery from temporary deflection is required, chromium
as an alloy offers the best solution.

Two per cent chromium steels; due to their very hard tough surface,
are largely used for armor-piercing projectiles, cold rolls, crushers,
drawing dies, etc.

The normal structure of chromium steels, with a very low carbon
content is roughly pearlitic up to 7 per cent, and martensitic
from 8 to 20 per cent; therefore, the greatest application is in
the pearlitic zone or the lower percentages.





Next: Nickel-chromium

Previous: Nickel



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