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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

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

Impact Tests
Impact tests are of considerable importance as an indication ...

Carbon Steels For Different Tools
All users of tool steels should carefully study the different...

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

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

Introduction Of Carbon
The matter to which these notes are primarily directed is the...

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

Blending The Compound
Essentially, this consists of the sturdy, power-driven separa...

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

Machineability
Reheating for machine ability was done at 100 deg. less than ...

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

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

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

Heat Treatment Of Gear Blanks
This section is based on a paper read before the American Gea...

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

Making Steel Balls
Steel balls are made from rods or coils according to size, st...

Pyrometers For Molten Metal
Pyrometers for molten metal are connected to portable thermoc...

Composition Of Transmission-gear Steel
If the nickel content of this steel is eliminated, and the pe...



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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