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Steel Making

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

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

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

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

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

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

The Electric Process
The fourth method of manufacturing steel is by the electric f...

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

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

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

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

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

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

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

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...



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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