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Carburizing By Gas
The process of carburizing by gas, briefly mentioned on page ...

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

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

Take Time For Hardening
Uneven heating and poor quenching has caused loss of many ve...

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

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

Critical Points
One of the most important means of investigating the properti...

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

Tungsten
Tungsten, as an alloy in steel, has been known and used for a...

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

Double Annealing
Water annealing consists in heating the piece, allowing it to...

Hardening Carbon Steel For Tools
For years the toolmaker had full sway in regard to make of st...

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

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

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

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

Detrimental Elements
Sulphur and phosphorus are two elements known to be detrimen...

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

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

The Effect
The heating at 1,600 deg.F. gives the first heat treatment w...



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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