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Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...

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

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

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

Process Of Carburizing
Carburizing imparts a shell of high-carbon content to a low-...

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Crankshaft
The crankshaft was the most highly stressed part of the entir...

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

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...

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

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

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



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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