VIEW THE MOBILE VERSION of www.steelmaking.ca Informational Site Network Informational
Privacy
   Home - Steel Making - Categories - Manufacturing and the Economy of Machinery

Steel Making

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

Chrome-nickel Steel
Forging heat of chrome-nickel steel depends very largely on ...

Heat Treatment Of Lathe Planer And Similar Tools
FIRE.--For these tools a good fire is one made of hard foundr...

Hardness Testing
The word hardness is used to express various properties of me...

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

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

Heat-treating Equipment And Methods For Mass Production
The heat-treating department of the Brown-Lipe-Chapin Company...

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

Steel For Chisels And Punches
The highest grades of carbon or tempering steels are to be re...

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

Heating Of Manganese Steel
Another form of heat-treating furnace is that which is used ...

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

Steel Before The 1850's
In spite of a rapid increase in the use of machines and the ...

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

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

Complete Calibration Of Pyrometers
For the complete calibration of a thermo-couple of unknown e...

Drop Forging Dies
The kind of steel used in the die of course influences the he...

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

Plant For Forging Rifle Barrels
The forging of rifle barrels in large quantities and heat-tre...

Phosphorus
PHOSPHORUS is an element (symbol P) which enters the metal fr...



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



Add to del.icio.us Add to Reddit Add to Digg Add to Del.icio.us Add to Google Add to Twitter Add to Stumble Upon
Add to Informational Site Network
Report
Privacy
SHAREADD TO EBOOK


Viewed 2908