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Steel Making

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

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

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

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

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

Annealing
There is no mystery or secret about the proper annealing of d...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Manganese
Manganese adds considerably to the tensile strength of steel,...

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...



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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