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

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

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

The Forging Of Steel
So much depends upon the forging of steel that this operation...

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...

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

Hardening
Steel is hardened by quenching from above the upper critical....

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

Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Conclusions
Martien was probably never a serious contender for the honor ...

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

Annealing Work
With the exception of several of the higher types of alloy s...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

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

Bessemer Process
The bessemer process consists of charging molten pig iron int...

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

Steel Can Be Worked Cold
As noted above, steel can be worked cold, as in the case of ...



Care In Annealing






Category: HEAT TREATMENT OF STEEL

Not only will benefits in machining be found
by careful annealing of forgings but the subsequent troubles in
the hardening plant will be greatly reduced. The advantages in
the hardening start with the carburizing operation, as a steel of
uniform and fine grain size will carburize more uniformly, producing
a more even hardness and less chances for soft spots. The holes in
the gears will also close in more uniformly, not causing some
gears to require excessive grinding and others with just enough
stock. Also all strains will have been removed from the forging,
eliminating to a great extent distortion and the noisy gears which
are the result.

With the steels used, for the heat-treated gears, always of a higher
carbon content, treatment after forging is necessary for machining, as
it would be impossible to get the required production from untreated
forgings, especially in the alloy steels. The treatment is more
delicate, due to the higher percentage of carbon and the natural
increase in cementite together with complex carbides which are
present in some of the higher types of alloys.

Where poor machining conditions in heat-treated steels are present
they are generally due to incomplete solution of cementite rather
than bands of free ferrite, as in the case of case-hardening steels.
This segregation of carbon, as it is sometimes referred to, causes
hard spots which, in the forming of the tooth, cause the cutter
to ride over the hard metal, producing high spots on the face of
the tooth, which are as detrimental to satisfactory gear cutting
as the drops or low spots produced on the face of the teeth when
the pearlite is coarse-grained or in a banded condition.

In the simpler carburized steels it is not necessary to test the
forgings for hardness after annealing, but with the high percentages
of alloys in the carburizing steels and the heat-treated steels
a hardness test is essential.

To obtain the best results in machining, the microstructure of the
metal should be determined and a hardness range set that covers
the variations in structure that produce good machining results.
By careful control of the heat-treating operation and with the aid
of the Brinell hardness tester and the microscope it is possible
to continually give forgings that will machine uniformly and be
soft enough to give desired production. The following gives a few
of the hardness numerals on steel used in gear manufacture that
produce good machining qualities:

0.20 per cent carbon, 3 per cent nickel, 1-1/4; per cent
chromium--Brinell 156 to 170.

0.50 per cent carbon, 3 per cent nickel, 1 per cent chromium--Brinell
179 to 187.

0.50 per cent carbon chrome-vanadium--Brinell 170 to 179.





Next: The Influence Of Size

Previous: Temperature For Annealing



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