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Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

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

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

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

Critical Points
One of the most important means of investigating the properti...

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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

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

Connecting Rods
The material used for all connecting rods on the Liberty engi...

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

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Corrosion
This steel like any other steel when distorted by cold worki...



Knowing What Takes Place






Category: HARDENING CARBON STEEL FOR TOOLS

How are we to know if we have given a
piece of steel the very best possible treatment?

The best method is by microscopic examination of polished and etched
sections, but this requires a certain expense for laboratory equipment
and upkeep, which may prevent an ordinary commercial plant from
attempting such a refinement. It is highly recommended that any
firm that has any large amount of heat treatment to do, install
such an equipment, which can be purchased for from $250 to $500.
Its intelligent use will save its cost in a very short time.

The other method is by examination of fractures of small test bars.
Steel heated to its correct temperatures will show the finest possible
grain, whereas underheated steel has not had its grain structure
refined sufficiently, and so will not be at its best. On the other
hand, overheated steel will have a coarser structure, depending
on the extent of overheating.

To determine the proper quenching temperature of any particular
grade of steel it is only necessary to heat pieces to various
temperatures not more than 20 deg.C. (36 deg.F.) apart, quench in water,
break them, and examine the fractures. The temperature producing
the finest grain should be used for annealing and hardening.

Similarly, to determine tempering temperatures, several pieces
should be hardened, then tempered to various degrees, and cooled
in air. Samples, say six, reheated to temperatures varying by 100 deg.
from 300 to 800 deg.C. will show a considerable range of properties,
and the drawing temperature of the piece giving the desired results
can be used.

For drawing tempers up to 500 deg.F. oil baths of fresh cotton seed
oil can be safely and satisfactorily used. For higher temperature
a bath of some kind of fused salt is recommended.





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