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Critical Points
One of the most important means of investigating the properti...

Leeds And Northrup Optical Pyrometer
The principles of this very popular method of measuring tempe...

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

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

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

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

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

Manganese
Manganese adds considerably to the tensile strength of steel,...

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

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

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

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

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

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...



Quenching






Category: CASE-HARDENING OR SURFACE-CARBURIZING

It is considered good practice to quench alloy steels from the pot,
especially if the case is of any appreciable depth. The texture
of carbon steel will be weakened by the prolonged high heat of
carburizing, so that if we need a tough core, we must reheat it
above its critical range, which is about 1,600 deg.F. for soft steel,
but lower for manganese and nickel steels. Quenching is done in
either water, oil, or air, depending upon the results desired.
The steel is then very carefully reheated to refine the case, the
temperature varying from 1,350 to 1,450 deg.F., depending on whether
the material is an alloy or a simple steel, and quenched in either
water or oil.



There are many possibilities yet to be developed with the carburizing
of alloy steels, which can produce a very tough, tenacious austenitic
case which becomes hard on cooling in air, and still retains a
soft, pearlitic core. An austenitic case is not necessarily file
hard, but has a very great resistance to abrasive wear.

The more carbon a steel has to begin with the more slowly will it
absorb carbon and the lower the temperature required. Low-carbon
steel of from 15 to 20 points is generally used and the carbon
brought up to 80 or 85 points. Tool steels may be carbonized as
high as 250 points.

In addition to the carburizing materials given, a mixture of 40
per cent of barium carbonate and 60 per cent charcoal gives much
faster penetration than charcoal, bone or leather. The penetration
of this mixture on ordinary low-carbon steel is shown in Fig. 32,
over a range of from 2 to 12 hr.





Next: Effect Of Different Carburizing Material

Previous: Carburizing Material



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