Informational Site NetworkInformational Site Network
Privacy
 
   Home - Steel Making - Categories - Manufacturing and the Economy of Machinery

Steel Making

Cutting-off Steel From Bar
To cut a piece from an annealed bar, cut off with a hack saw,...

Oil-hardening Steel
Heat slowly and uniformly to 1,450 deg.F. and forge thorough...

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

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

Surface Carburizing
Carburizing, commonly called case-hardening, is the art of pr...

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

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

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

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

Silicon
SILICON is a very widespread element (symbol Si), being an es...

Rate Of Absorption
According to Guillet, the absorption of carbon is favored by ...

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

Calibration Of Pyrometer With Common Salt
An easy and convenient method for standardization and one whi...

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

Temperature For Annealing
Theoretically, annealing should be accomplished at a tempera...

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

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

Hardening
Steel is hardened by quenching from above the upper critical....

Sulphur
Sulphur is another impurity and high sulphur is even a greate...

Placing Of Pyrometers
When installing a pyrometer, care should be taken that it re...



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 2034