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

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

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Effect Of A Small Amount Of Copper In Medium-carbon Steel
This shows the result of tests by C. R. Hayward and A. B. Joh...

An Automatic Temperature Control Pyrometer
Automatic temperature control instruments are similar to the ...

Manganese
MANGANESE is a metal much like iron. Its chemical symbol is M...

Corrosion
This steel like any other steel when distorted by cold worki...

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

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

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

Critical Points
One of the most important means of investigating the properti...

Properties Of Alloy Steels
The following table shows the percentages of carbon, manganes...

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

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

Manganese
Manganese adds considerably to the tensile strength of steel,...

Affinity Of Nickel Steel For Carbon
The carbon- and nickel-steel gears are carburized separately...

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

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

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...



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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