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Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

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

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

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

Annealing Method
Forgings which are too hard to machine are put in pots with ...

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

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

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

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

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

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

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

Impact Tests
Impact tests are of considerable importance as an indication ...

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

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

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



Testing And Inspection Of Heat Treatment






Category: HEAT TREATMENT OF STEEL

The hard parts of the
gear must be so hard that a new mill file does not bite in the
least. Having passed this file test at several points, the gears go
to the center-punch test. The inspector is equipped with a wooden
trough secured to the top of the bench to support the gear, a number
of center punches (made of 3/4-in. hex-steel having points sharpened
to an angle of 120 deg.) and a hammer weighing about 4 oz. With
these simple tools, supplemented by his skill, the inspector can
feel the depth and quality of the case and the condition of the
core. The gears are each tested in this way at several points on
the teeth and elsewhere, the scrap gear being also subjected to
the test. Finally, the scrap gear is securely clamped in the
straightening press shown in Fig. 57. With a 3-1/2-lb. hammer and
a suitable hollow-ended drift manipulated by one of Sandow's
understudies, teeth are broken out of the scrap gear at various
points. These give a record confirming the center-punch tests,
which, if the angle of the center punch is kept at 120 deg. and
the weight of the hammer and blow are uniform, is very accurate.

After passing the center-punch test the ends of the teeth are peened
lightly with a hammer. If they are too hard, small particles fly
off. Such gears are drawn in oil at a temperature of from 300 to
350 deg.F., depending on their hardness. Some builders prefer to have
the extreme outer ends of the teeth drawn somewhat lower than the
rest. This drawing is done on gas-heated red-hot plates, as shown
at A in Fig. 58.



Nickel steel, in addition to all the tests given to carbon steel,
is subjected to a Brinell test. For each steel, the temperature
and the period of treatment are specific. For some unknown reason,
apparently like material with like treatment will, in isolated
cases, not produce like results. It then remains for the treatment
to be repeated or modified, but the results obtained during inspection
form a valuable aid to the metallurgist in determining further
treatment.





Next: Temperature Recording And Regulation

Previous: Affinity Of Nickel Steel For Carbon



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