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Steel Making

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

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

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

Effect Of Different Carburizing Material
[Illustrations: FIGS. 33 to 37.] Each of these different p...

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

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

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

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

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

Quenching Tool Steel
To secure proper hardness, the cooling of quenching of steel ...

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

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

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

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

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

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

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...

Annealing To Relieve Internal Stresses
Work quenched from a high temperature and not afterward tempe...



A Chromium-cobalt Steel






Category: HIGH-SPEED STEEL

The Latrobe Steel Company make a high-speed steel without tungsten,
its red-hardness properties depending on chromium and cobalt instead
of tungsten. It is known as P. R. K-33 steel. It does not require
the high temperature of the tungsten steels, hardening at 1,830 to
1,850 deg.F. instead of 2,200 deg. or even higher, as with the tungsten.

This steel is forged at 1,900 to 2,000 deg.F. and must not be worked
at a lower temperature than 1,600 deg.F. It requires soaking in the
fire more than the tungsten steels. It can be normalized by heating
slowly and thoroughly to 1,475 deg.F., holding this for from 10 to 20
min. according to the size of the piece and cooling in the open
air, protected from drafts.

A peculiarity of this steel is that it becomes non-magnetic at or
above 1,960 deg.F. and the magnetic quality is not restored by cooling.
Normalizing as above, however, restores the magnetic qualities. This
enables the user to detect any tools which have been overheated,
with a horseshoe magnet.

It is sometimes advantageous to dip tools, before heating for hardening,
in ordinary fuel or quenching oil. The oil leaves a thin film of
carbon which tends to prevent decarbonization, giving a very hard
surface.

For other makes of high-speed steel used in lathe and planer tools
the makers recommend that the tools be cut from the bar with a
hack saw or else heated and cut with a chisel. The heating should
be very slow until the steel reaches a red after which it can be
heated more rapidly and should only be forged at a high heat. It
can be forged at very high heats but care should be taken not to
forge at a low heat. The heating should be uniform and penetrate
clear to the center of the bar before forging is begun. Reheat
as often as necessary to forge at the proper heat.

After forging cool in lime before attempting to harden. Do not
attempt to harden with the forging heat as was sometimes done with
the carbon tools.

For hardening forged tools, heat slowly up to a bright red and
then rapidly until the point of the tool is almost at a melting
heat. Cool in a blast of cold, dry air. For large sizes of steel,
cool in linseed oil or in fish oil as is most convenient. If the
tools are to be used for finishing cuts heat to a bright yellow
and quench in oil. Grind for use on a sand wheel or grindstone
in preference to an emery or an artificial abrasive wheel.

For hardening milling and similar cutters, preheat to a bright
red, place the cutter on a round bar of suitable size, and revolve
it quickly over a very hot fire. Heat as high as possible without
melting the points of the teeth and cool in a cold blast of dry
air or in fish oil.

Light fragile cutters, twist drills, taps and formed cutters may
be heated almost white and then dipped in fish oil for hardening.
Where possible it is better to give an even higher heat and cool
in the blast of cold, dry air as previously recommended.





Next: Suggestions For Handling High-speed Steels

Previous: Heat Treatment Of Punches And Dies Shears Taps Etc



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