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

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

Nickel-chromium
A combination of the characteristics of nickel and the charac...

Using Illuminating Gas
The choice of a carburizing furnace depends greatly on the fa...

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

Annealing Work
With the exception of several of the higher types of alloy s...

Hardening High-speed Steels
We will now take up the matter of hardening high-speed steels...

Placing The Thermo-couples
The following illustrations from the Taylor Instrument Compan...

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

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

High Speed Steel
For centuries the secret art of making tool steel was handed ...

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

Hardening
The forgings can be hardened by cooling in still air or quen...

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

Standard Analysis
The selection of a standard analysis by the manufacturer is t...

Preparing Parts For Local Case-hardening
At the works of the Dayton Engineering Laboratories Company, ...

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

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

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

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

Mushet And Bessemer
That Mushet was "used" by Ebbw Vale against Bessemer is, perh...



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 2814