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Steel Making

The Forging Of Steel
So much depends upon the forging of steel that this operation...

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

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

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

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

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

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

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

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

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

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

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...



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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