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Steel Making

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

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The simplest carburizing substance is charcoal. It is also th...

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

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

Hardness Testing
The word hardness is used to express various properties of me...

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

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

Brown Automatic Signaling Pyrometer
In large heat-treating plants it has been customary to mainta...

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In order to give definite information concerning furnaces, fu...

Crankshaft
The crankshaft was the most highly stressed part of the entir...

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

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

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

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

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...



The Effect Of Tempering On Water-quenched Gages






Category: HARDENING CARBON STEEL FOR TOOLS

The following information has been supplied by Automatic and Electric
Furnaces, Ltd., 6, Queenstreet, London, S. W.:

Two gages of 3/4 in. diameter, 12 threads per inch, were heated
in a Wild-Barfield furnace, using the pyroscopic detector, and
were quenched in cold water. They were subsequently tempered in a
salt bath at various increasing temperatures, the effective diameter
of each thread and the scleroscope hardness being measured at each
stage. The figures are in 10,000ths of an inch, and indicate the
change + or - with reference to the original effective diameter
of the gages. The results for the two gages have been averaged.

TABLE 24.--CHANGES DUE TO QUENCHING
----------------------------------------------------------------
After Tempering temperature, degrees Centigrade
Thread quenching-----------------------------------------
220 260 300 340 380 420
---------------------------------------------------------
1 +25 +19 +17 +15 +13 +11 +11
2 +18 +12 +11 + 9 + 6 + 5 + 5
3 +12 + 6 + 5 + 3 0 0 0
4 +10 + 4 + 4 + 2 ... 0 - 1
5 + 9 + 4 + 4 + 2 0 0 0
6 + 9 + 4 + 3 + 2 0 0 0
7 +10 + 5 + 5 + 3 + 2 + 1 + 2
8 + 8 + 4 + 3 + 2 0 0 + 1
9 + 9 + 4 + 3 + 2 + 1 + 1 + 1
10 + 9 + 5 + 5 + 3 + 2 + 2 + 2
11 + 7 + 4 + 4 + 2 + 1 + 1 + 1
12 + 9 + 5 + 5 + 5 + 4 + 4 + 3

Scleroscope 80 70 70 62 56 53 52
----------------------------------------------------------------

Had these gages been formed with a plain cylindrical end projecting
in front of the screw, the first two threads would have been prevented
from increasing more than the rest. The gages would then have been
fairly easily corrected by lapping after tempering at 220 deg.C. Practically
no lapping would be required if they were tempered at 340 deg.C. There
seems to be no advantage in going to a higher temperature than
this. The same degree of hardness could have been obtained with
considerably less distortion by quenching directly in fused salt. It
is interesting to note that when the swelling after water quenching
does not exceed 0.0012 in., practically the whole of it may be
recovered by tempering at a sufficiently high temperature, but when
the swelling exceeds this amount the steel assumes a permanently
strained condition, and at the most only 0.0014 in. can be recovered
by tempering.





Next: Tempering Colors On Carbon Steels

Previous: Tempering Round Dies



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