Steelmaking.ca Home Steel Making Categories Manufacturing and the Economy of Machinery

Steel Making

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

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Quality And Structure
The quality of high-speed steel is dependent to a very great ...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

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

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

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

Nickel
Nickel may be considered as the toughest among the non-rare a...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

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

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

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

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

Machineability
Reheating for machine ability was done at 100 deg. less than ...

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

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

The Electric Process
The fourth method of manufacturing steel is by the electric f...



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



Add to Informational Site Network
Report
Privacy
ADD TO EBOOK


Viewed 5584