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

Annealing
There is no mystery or secret about the proper annealing of d...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

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

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

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

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

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

Heating
Although it is possible to work steels cold, to an extent de...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...

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

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

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

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

Care In Annealing
Not only will benefits in machining be found by careful anne...



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.





Next: Hints For Tool Steel Users

Previous: Temperatures To Use



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