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Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Furnace Data
In order to give definite information concerning furnaces, fu...

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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

The Modern Hardening Room
A hardening room of today means a very different place from ...

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

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

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Judging The Heat Of Steel
While the use of a pyrometer is of course the only way to hav...

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

Heat-treating Department
The heat-treating department occupies an L-shaped building. ...

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...

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

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...



Refining The Grain






Category: CASE-HARDENING OR SURFACE-CARBURIZING

This is remedied by reheating the piece to a temperature slightly
above the critical temperature of the case, this temperature
corresponding ordinarily to that of steel having a carbon content
of 85 points, When this is again quenched, the temperature, which
has not been high enough to disturb the refined core, will have
closed the grain of the case and toughened it. So, instead of but
one heat and one quenching for this class of work, we have three
of each, although it is quite possible and often profitable to
omit the quenching after carburizing and allow the piece or pieces
and the case-carburizing box to cool together, as in annealing.
Sometimes another heat treatment is added to the foregoing, for
the purpose of letting down the hardness of the case and giving
it additional toughness by heating to a temperature between 300 deg.
and 500 deg.. Usually this is done in an oil bath. After this the piece
is allowed to cool.

It is possible to harden the surface of tool steel extremely hard
and yet leave its inner core soft and tough for strength, by a
process similar to case-hardening and known as pack-hardening.
It consists in using tool steel of carbon contents ranging from
60 to 80 points, packing this in a box with charred leather mixed
with wood charcoal and heating at a low-red heat for 2 or 3 hr.,
thus raising the carbon content of the exterior of the piece. The
article when quenched in an oil bath will have an extremely hard
exterior and tough core. It is a good scheme for tools that must
be hard and yet strong enough to stand abuse. Raw bone is never
used as a packing for this class of work, as it makes the cutting
edges brittle.





Next: Case-hardening Treatments For Various Steels

Previous: The Quenching Tank



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