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Steel Making

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

Silicon
SILICON is a very widespread element (symbol Si), being an es...

Machineability
Reheating for machine ability was done at 100 deg. less than ...

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

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

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

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

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

High Speed Steel
For centuries the secret art of making tool steel was handed ...

Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...



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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