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

Heavy Forging Practice
In heavy forging practice where the metal is being worked at...

Shrinking And Enlarging Work
Steel can be shrunk or enlarged by proper heating and cooling...

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

Classifications Of Steel
Among makers and sellers, carbon tool-steels are classed by g...

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

Conclusions
Martien was probably never a serious contender for the honor ...

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...

Heating
Although it is possible to work steels cold, to an extent de...

The Packing Department
In Fig. 56 is shown the packing pots where the work is packe...

Hardening
Steel is hardened by quenching from above the upper critical....

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

Nickel
Nickel may be considered as the toughest among the non-rare a...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

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

A Satisfactory Luting Mixture
A mixture of fireclay and sand will be found very satisfactor...

Refining The Grain
This is remedied by reheating the piece to a temperature slig...

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

Pyrometry And Pyrometers
A knowledge of the fundamental principles of pyrometry, or th...



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.





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Previous: Tempering Round Dies



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