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Steel Making

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

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

Typical Oil-fired Furnaces
Several types of standard oil-fired furnaces are shown herew...

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

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

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

Lathe And Planer Tools
TO FORGE.--Gently warm the steel to remove any chill is parti...

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

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

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

The Effect Of Tempering On Water-quenched Gages
The following information has been supplied by Automatic and ...

Protective Screens For Furnaces
Workmen needlessly exposed to the flames, heat and glare from...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

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

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Heat Treatment Of Axles
Parts of this general type should be heat-treated to show the...

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

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



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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