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Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

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

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

Carburizing Material
The simplest carburizing substance is charcoal. It is also th...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

Forging High-speed Steel
Heat very slowly and carefully to from 1,800 to 2,000 deg.F....

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

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

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...

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

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

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

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



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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