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Ebbw Vale And The Bessemer Process
After his British Association address in August 1856, Besseme...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

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

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

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

Compensating Leads
By the use of compensating leads, formed of the same materia...

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

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

Annealing Work
With the exception of several of the higher types of alloy s...

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

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

Heat Treatment Of Milling Cutters Drills Reamers Etc
THE FIRE.--Gas and electric furnaces designed for high heats ...

Properties Of Steel
Steels are known by certain tests. Early tests were more or l...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

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

Annealing
ANNEALING can be done by heating to temperatures ranging from...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...



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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