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Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

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

Crankshaft
The crankshaft was the most highly stressed part of the entir...

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

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

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

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

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

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

Impact Tests
Impact tests are of considerable importance as an indication ...

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

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

Bessemer Process
The bessemer process consists of charging molten pig iron int...

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

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



Case-hardening Treatments For Various Steels






Category: CASE-HARDENING OR SURFACE-CARBURIZING

Plain water, salt water and linseed oil are the three most common
quenching materials for case-hardening. Water is used for ordinary
work, salt water for work which must be extremely hard on the surface,
and oil for work in which toughness is the main consideration. The
higher the carbon of the case, the less sudden need the quenching
action take hold of the piece; in fact, experience in case-hardening
work gives a great many combinations of quenching baths of these
three materials, depending on their temperatures. Thin work, highly
carbonized, which would fly to pieces under the slightest blow if
quenched in water or brine, is made strong and tough by properly
quenching in slightly heated oil. It is impossible to give any
rules for the temperature of this work, so much depending on the
size and design of the piece; but it is not a difficult matter to
try three or four pieces by different methods and determine what
is needed for best results.

The alloy steels are all susceptible of case-hardening treatment;
in fact, this is one of the most important heat treatments for such
steels in the automobile industry. Nickel steel carburizes more
slowly than common steel, the nickel seeming to have the effect
of slowing down the rate of penetration. There is no cloud without
its silver lining, however, and to offset this retardation, a single
treatment is often sufficient for nickel steel; for the core is not
coarsened as much as low-carbon machinery steel and thus ordinary
work may be quenched on the carburizing heat. Steel containing
from 3 to 3.5 per cent of nickel is carburized between 1,650 and
1,750 deg.F. Nickel steel containing less than 25 points of carbon,
with this same percentage of nickel, may be slightly hardened by
cooling in air instead of quenching.

Chrome-nickel steel may be case-hardened similarly to the method just
described for nickel steel, but double treatment gives better results
and is used for high-grade work. The carburizing temperature is the
same, between 1,650 and 1,750 deg.F., the second treatment consisting
of reheating to 1,400 deg. and then quenching in boiling salt water,
which gives a hard surface and at the same time prevents distortion
of the piece. The core of chrome-nickel case-hardened steel, like
that of nickel steel, is not coarsened excessively by the first
heat treatment, and therefore a single heating and quenching will
suffice.





Next: Carburizing By Gas

Previous: Refining The Grain



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