FORGING.--Gently warm the steel to remove any chill, is particularly desirable in the winter, then heat slowly and carefully to a scaling heat, that is a lemon heat (1,800 to 2,000 deg.F.), and forge uniformly. Reheat the tool for further forgi... Read more of Lathe And Planer Tools at Steel Making.caInformational Site Network Informational
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Highly Stressed Parts
The highly stressed parts on the Liberty engine consisted of ...

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

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...

For Milling Cutters And Formed Tools
FORGING.--Forge as before.--ANNEALING.--Place the steel in a ...

Nickel
Nickel may be considered as the toughest among the non-rare a...

Heat Treatment Of Punches And Dies Shears Taps Etc
HEATING.--The degree to which tools of the above classes shou...

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

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

Care In Annealing
Not only will benefits in machining be found by careful anne...

The Pyrometer And Its Use
In the heat treatment of steel, it has become absolutely nece...

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

Heating
Although it is possible to work steels cold, to an extent de...

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

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

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

Crankshaft
The crankshaft was the most highly stressed part of the entir...

Protectors For Thermo-couples
Thermo-couples must be protected from the danger of mechanica...

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

Annealing Of Rifle Components At Springfield Armory
In general, all forgings of the components of the arms manufa...



Tempering Colors On Carbon Steels






Category: HIGH-SPEED STEEL

Opinions differ as to the temperature which is indicated by the
various colors, or oxides, which appear on steel in tempering.

The figures shown are from five different sources and while the
variations are not great, it is safer to take the average temperature
shown in the last column.

TABLE 25.--COLORS, TEMPERATURES, DEGREES FAHRENHEIT
----------------------------------------------------------
A B C D E Average
----------------------------------------------------
Faint yellow 430 430 430 430 430 430
Light straw 475 460 450 ... 450 458
Dark straw 500 500 470 450 470 478
Purple (reddish) 525 530 520 530 510 523
Purple (bluish) ... 555 550 550 550 551
Blue 575 585 560 580 560 572
Gray blue ... 600 ... 600 610 603
Greenish blue ... 625 ... ... 630 627
----------------------------------------------------------

TABLE 26.--ANOTHER COLOR TABLE
----------------------------------------------------------
Degrees
Fahrenheit High temperatures judged by color
---------------------------------------------------------
430 Very pale yellow
460 Straw-yellow
480 Dark yellow
500 Brown-yellow > Visible in full daylight
520 Brown-purple
540 Full purple
560 Full blue
600 Very dark blue /
752 Red heat, visible in the dark
885 Red heat, visible in the twilight
975 Red heat, visible in the daylight
1,292 Dark red
1,652 Cherry-red
1,832 Bright cherry-red
2,012 Orange-red
2,192 Orange-yellow
2,372 Yellow-white
2,552 White welding heat
2,732 Brilliant white
2,912 Dazzling white (bluish-white)
----------------------------------------------------------

These differences might easily be due to the difference in the light
at the time the colors were observed. It must also be remembered
that even a thin coating of oil will make quite a difference and
cause confusion. It is these possible sources of error, coupled
with the ever present chance of human error, that makes it advisable
to draw the temper of tools in an oil bath heated to the proper
temperature as shown by an accurate high-temperature thermometer.

Another table, by Gilbert and Barker, runs to much higher temperatures.
Beyond 2,200 deg., however, the eye is very uncertain.

TABLE 26.--COLORS FOR TEMPERING TOOLS
-----------------------------------------------------------------------
Approximate
color and Kind of tool
temperature
----------------------------------------------------------------------
Yellow Thread chasers, hollow mills (solid type) twist drills
430 to 450 deg.F. centering tools, forming tools, cut-off tools, profile
cutters, milling cutters, reamers, dies, etc.
----------------------------------------------------------------------
Straw-yellow Thread rolling dies, counterbores, countersinks. Shear
460 deg.F. blades, boring tools, engraving tools, etc.
----------------------------------------------------------------------
Brown-yellow Taps, Thread dies, cutters, reamers, etc.
500 deg.F.
----------------------------------------------------------------------
Light purple Taps, dies, rock drills, knives, punches, gages, etc.
530 deg.F.
----------------------------------------------------------------------
Dark purple Circular saws for metal, augers, dental and surgical
550 deg.F. instruments, cold chisels, axes.
----------------------------------------------------------------------
Pale blue Bone saws, chisels, needles, cutters, etc.
580 deg.F.
----------------------------------------------------------------------
Blue Hack saws, wood saws, springs, etc.
600 deg.F.
-----------------------------------------------------------------------





Next: High Speed Steel

Previous: The Effect Of Tempering On Water-quenched Gages



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