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Steel Making

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

The Theory Of Tempering
Steel that has been hardened is generally harder and more br...

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

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Restoring Overheated Steel
The effect of heat treatment on overheated steel is shown gra...

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

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

Preventing Carburizing By Copper-plating
Copper-plating has been found effective and must have a thick...

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

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

Short Method Of Treatment
In the new method, the packed pots are run into the case-har...

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

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

Lathe And Planer Tools
FORGING.--Gently warm the steel to remove any chill, is parti...

The Thermo-couple
With the application of the thermo-couple, the measurement of...

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

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

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...



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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