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Steel Making

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

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

The Influence Of Size
The size of the piece influences the physical properties obta...

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

Air-hardening Steels
These steels are recommended for boring, turning and planing...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...

Hardening
The forgings can be hardened by cooling in still air or quen...

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

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

Gears
The material used for all gears on the Liberty engine was sel...

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

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

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



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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