Steelmaking.ca Home Steel Making Categories Manufacturing and the Economy of Machinery

Steel Making

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

Crucible Steel
Crucible steel is still made by melting material in a clay or...

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

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

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

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

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

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

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

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

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

Care In Annealing
Not only will benefits in machining be found by careful anne...

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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

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



The Theory Of Tempering






Category: HARDENING CARBON STEEL FOR TOOLS

Steel that has been hardened is generally
harder and more brittle than is necessary, and in order to bring
it to the condition that meets our requirements a treatment called
tempering is used. This increases the toughness of the steel, i.e.,
decrease the brittleness at the expense of a slight decrease in
hardness.

There are several theories to explain this reaction, but generally
it is only necessary to remember that in hardening we quench steel
from the austenite phase, and, due to this rapid cooling, the normal
change from austenite to the eutectoid composition does not have
time to take place, and as a consequence the steel exists in a
partially transformed, unstable and very hard condition at atmospheric
temperatures. But owing to the internal rigidity which exists in
cold metal the steel is unable to change into its more stable phase
until atoms can rearrange themselves by the application of heat.
The higher the heat, the greater the transformation into the softer
phases. As the transformation takes place, a certain amount of heat
of reaction, which under slow cooling would have been released in
the critical range, is now released and helps to cause a further
slight reaction.

If a piece of steel is heated to a certain temperature and held
there, the tempering color, instead of remaining unchanged at this
temperature, will advance in the tempering-color scale as it would
with increasing temperature. This means that the tempering colors
do not absolutely correspond to the temperatures of steels, but the
variations are so slight that we can use them in actual practice.
(See Table 23, page 158.)





Next: Temperatures To Use

Previous: Quenching Tool Steel



Add to Informational Site Network
Report
Privacy
ADD TO EBOOK


Viewed 6617