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Hardening
The forgings can be hardened by cooling in still air or quen...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

Tempering Round Dies
A number of circular dies of carbon tool steel for use in too...

S A E Heat Treatments
The Society of Automotive Engineers have adopted certain heat...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

Suggestions For Handling High-speed Steels
The following suggestions for handling high-speed steels are ...

Application Of Liberty Engine Materials To The Automotive Industry
The success of the Liberty engine program was an engineer...

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

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

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

Annealing
There is no mystery or secret about the proper annealing of d...

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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

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

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

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

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

The Thermo-couple
With the application of the thermo-couple, the measurement of...



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

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