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Steel Making

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

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

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Affinity Of Nickel Steel For Carbon
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Testing And Inspection Of Heat Treatment
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High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Molybdenum
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Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

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

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

Protective Screens For Furnaces
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Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

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

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

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

Robert Mushet
Robert (Forester) Mushet (1811-1891), born in the Forest of D...



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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