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Instructions For Working High-speed Steel
Owing to the wide variations in the composition of high-speed...

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

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

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Carbon Tool Steel
Heat to a bright red, about 1,500 to 1,550 deg.F. Do not ham...

High-carbon Machinery Steel
The carbon content of this steel is above 30 points and is ha...

Cyanide Bath For Tool Steels
All high-carbon tool steels are heated in a cyanide bath. Wi...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

Hardening High-speed Steel
In forging use coke for fuel in the forge. Heat steel slowly ...

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

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

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

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

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

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Nickel-chromium
A combination of the characteristics of nickel and the charac...

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

The Influence Of Size
The size of the piece influences the physical properties obta...

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...



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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