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Steel Making

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

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

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

Piston Pin
The piston pin on an aviation engine must possess maximum res...

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

Compensating Leads
By the use of compensating leads, formed of the same materia...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

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

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

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

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

Sulphur
SULPHUR is another element (symbol S) which is always found i...



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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