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Steel Making

Carbon In Tool Steel
Carbon tool steel, or tool steel as it is commonly called, us...

Application To The Automotive Industry
The information given on the various parts of the Liberty eng...

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

Separating The Work From The Compound
During the pulling of the heat, the pots are dumped upon a ca...

Crucible Steel
Crucible steel is still made by melting material in a clay or...

Annealing Alloy Steel
The term alloy steel, from the steel maker's point of view, r...

Correction By Zero Adjustment
Many pyrometers are supplied with a zero adjuster, by means ...

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

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

Carbon-steel Forgings
Low-stressed, carbon-steel forgings include such parts as car...

Uses Of The Various Tempers Of Carbon Tool Steel
DIE TEMPER.--No. 3: All kinds of dies for deep stamping, pres...

Manganese
Manganese adds considerably to the tensile strength of steel,...

Knowing What Takes Place
How are we to know if we have given a piece of steel the ver...

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

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

Non-shrinking Oil-hardening Steels
Certain steels have a very low rate of expansion and contract...

Corrosion
This steel like any other steel when distorted by cold worki...

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

Temperatures To Use
As soon as the temperature of the steel reaches 100 deg.C. (...

Tempering Colors On Carbon Steels
Opinions differ as to the temperature which is indicated by t...



Temperatures To Use






Category: HARDENING CARBON STEEL FOR TOOLS

As soon as the temperature of the steel reaches
100 deg.C. (212 deg.F.) the transformation begins, increasing in intensity
as the temperature is raised, until finally when the lower critical
range is reached, the steel has been all changed into the ordinary
constituents of unhardened steels.

If a piece of polished steel is heated in an ordinary furnace, a
thin film of oxides will form on its surface. The colors of this
film change with temperature, and so, in tempering, they are generally
used as an indication of the temperature of the steel. The steel
should have at least one polished face so that this film of oxides
may be seen.

An alternative method to the determination of temper by color is
to temper by heating in an oil or salt bath. Oil baths can be used
up to temperatures of 500 deg.F.; above this, fused-salt baths are
required. The article to be tempered is put into the bath, brought
up to and held at the required temperature for a certain length
of time, and then cooled, either rapidly or slowly. This takes
longer than the color method, but with low temperatures the results
are more satisfactory, because the temperature of the bath can
be controlled with a pyrometer. The tempering temperatures given
in the following table are taken from a handbook issued by the
Midvale Steel Company.

TABLE 23.--TEMPERING TEMPERATURES FOR STEELS
----------------------------------------------------------------------------
Temperature Temperature
for 1 hr. for 8 min.
--------------- Color --------------- Uses
Deg. F.Deg. C. Deg. F.Deg. C.
-----------------------------------------------------------------------
370 188 Faint yellow 460 238 Scrapers, brass-turning tools,
reamers, taps, milling cutters,
saw teeth.
390 199 Light straw 510 265 Twist drills, lathe tools,
planer tools, finishing tools
410 210 Dark straw 560 293 Stone tools, hammer faces,
chisels for hard work, boring
cutters.
430 221 Brown 610 321 Trephining tools, stamps.
450 232 Purple 640 337 Cold chisels for ordinary work,
carpenters' tools, picks, cold
punches, shear blades, slicing
tools, slotter tools.
490 254 Dark blue 660 343 Hot chisels, tools for hot
work, springs.
510 265 Light blue 710 376 Springs, screw drivers.
----------------------------------------------------------------------------

It will be noted that two sets of temperatures are shown, one being
specified for a time interval of 8 min. and the other for 1 hr. For
the finest work the longer time is preferable, while for ordinary
rough work 8 min. is sufficient, after the steel has reached the
specified temperature.

The rate of cooling after tempering seems to be immaterial, and
the piece can be cooled at any rate, providing that in large pieces
it is sufficiently slow to prevent strains.





Next: Knowing What Takes Place

Previous: The Theory Of Tempering



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