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Steel Making

Composition And Properties Of Steel
It is a remarkable fact that one can look through a dozen tex...

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

The Electric Process
The fourth method of manufacturing steel is by the electric f...

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

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

Tool Or Crucible Steel
Crucible steel can be annealed either in muffled furnace or b...

Molybdenum
Molybdenum steels have been made commercially for twenty-five...

Pickling The Forgings
The forgings were then pickled in a hot solution of either ni...

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

High-chromium Or Rust-proof Steel
High-chromium, or what is called stainless steel containing f...

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

Correction For Cold-junction Errors
The voltage generated by a thermo-couple of an electric pyrom...

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

Case-hardening Treatments For Various Steels
Plain water, salt water and linseed oil are the three most co...

Carburizing Low-carbon Sleeves
Low-carbon sleeves are carburized and pushed on malleable-ir...

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

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

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

Rate Of Cooling
At the option of the manufacturer, the above treatment of gea...

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



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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