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Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...

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

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

Martien was probably never a serious contender for the honor ...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

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

The Thermo-couple
With the application of the thermo-couple, the measurement of...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

Vanadium has a very marked effect upon alloy steels rich in c...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...



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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