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Steel Making

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

Annealing In Bone
Steel and cast iron may both be annealed in granulated bone. ...

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

Alloying Elements
Commercial steels of even the simplest types are therefore p...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

A Chromium-cobalt Steel
The Latrobe Steel Company make a high-speed steel without tun...

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

Steel Worked In Austenitic State
As a general rule steel should be worked when it is in the a...

The material used for all gears on the Liberty engine was sel...

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

Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

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

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

Rate Of Absorption


According to Guillet, the absorption of carbon is favored by those
special elements which exist as double carbides in steel. For example,
manganese exists as manganese carbide in combination with the iron
carbide. The elements that favor the absorption of carbon are:
manganese, tungsten, chromium and molybdenum those opposing it,
nickel, silicon, and aluminum. Guillet has worked out the effect
of the different elements on the rate of penetration in comparison
with steel that absorbed carbon at a given temperature, at an average
rate of 0.035 in. per hour.

His tables show that the following elements require an increased
time of exposure to the carburizing material in order to obtain
the same depth of penetration as with simple steel:

When steel contains Increased time of exposure
2.0 per cent nickel 28 per cent
7.0 per cent nickel 30 per cent
1.0 per cent titanium 12 per cent
2.0 per cent titanium 28 per cent
0.5 per cent silicon 50 per cent
1.0 per cent silicon 80 per cent
2.0 per cent silicon 122 per cent
5.0 per cent silicon No penetration
1.0 per cent aluminum 122 per cent
2.0 per cent aluminum 350 per cent

The following elements seem to assist the rate of penetration of
carbon, and the carburizing time may therefore be reduced as follows:

When steel contains Decreased time of exposure
0.5 per cent manganese 18 per cent
1.0 per cent manganese 25 per cent
1.0 per cent chromium 10 per cent
2.0 per cent chromium 18 per cent
0.5 per cent tungsten 0
1.0 per cent tungsten 0
2.0 per cent tungsten 25 per cent
1.0 per cent molybdenum 0
2.0 per cent molybdenum 18 per cent

The temperature at which carburization is accomplished is a very
important factor. Hence the necessity for a reliable pyrometer,
located so as to give the temperature just below the tops of the
pots. It must be remembered, however, that the pyrometer gives
the temperature of only one spot, and is therefore only an aid to
the operator, who must use his eyes for successful results.

The carbon content of the case generally is governed by the temperature
of the carburization. It generally proves advisable to have the
case contain between 0.90 per cent and 1.10 carbon; more carbon
than this gives rise to excess free cementite or carbide of iron,
which is detrimental, causing the case to be brittle and apt to chip.

T. G. Selleck gives a very useful table of temperatures and the
relative carbon contents of the case of steels carburized between
4 and 6 hrs. using a good charcoal carburizer. This data is as


At 1,500 deg.F., the surface carbon content will be 0.90 per cent
At 1,600 deg.F., the surface carbon content will be 1.00 per cent
At 1,650 deg.F., the surface carbon content will be 1.10 per cent
At 1,700 deg.F., the surface carbon content will be 1.25 per cent
At 1,750 deg.F., the surface carbon content will be 1.40 per cent
At 1,800 deg.F., the surface carbon content will be 1.75 per cent

To this very valuable table, it seems best to add the following
data, which we have used for a number of years. We do not know
the name of its author, but it has proved very valuable, and seems
to complete the above information. The table is self-explanatory,
giving depth of penetration of the carbon of the case at different
temperatures for different lengths of time:

Penetration -----------------------------
1,550 1,650 1,800
Penetration after 1/2 hr. 0.008 0.012 0.030
Penetration after 1 hr. 0.018 0.026 0.045
Penetration after 2 hr. 0.035 0.048 0.060
Penetration after 3 hr. 0.045 0.055 0.075
Penetration after 4 hr. 0.052 0.061 0.092
Penetration after 6 hr. 0.056 0.075 0.110
Penetration after 8 hr. 0.062 0.083 0.130

From the tables given, we may calculate with a fair degree of certainty
the amount of carbon in the case, and its penetration. These figures
vary widely with different carburizers, and as pointed out immediately
above, with different alloy steels.

Next: Carburizing Material

Previous: Surface Carburizing

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