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Steel Making

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

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

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

The Penetration Of Carbon
Carburized mild steel is used to a great extent in the manufa...

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

The Care Of Carburizing Compounds
Of all the opportunities for practicing economy in the heat-t...

Annealing
There is no mystery or secret about the proper annealing of d...

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

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

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

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

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

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

Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer
For extremely high temperature, the optical pyrometer is lar...

Gas Consumption For Carburizing
Although the advantages offered by the gas-fired furnace for ...

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

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

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

William Kelly's Air-boiling Process
An account of Bessemer's address to the British Association w...

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



Knowing What Takes Place






Category: HARDENING CARBON STEEL FOR TOOLS

How are we to know if we have given a
piece of steel the very best possible treatment?

The best method is by microscopic examination of polished and etched
sections, but this requires a certain expense for laboratory equipment
and upkeep, which may prevent an ordinary commercial plant from
attempting such a refinement. It is highly recommended that any
firm that has any large amount of heat treatment to do, install
such an equipment, which can be purchased for from $250 to $500.
Its intelligent use will save its cost in a very short time.

The other method is by examination of fractures of small test bars.
Steel heated to its correct temperatures will show the finest possible
grain, whereas underheated steel has not had its grain structure
refined sufficiently, and so will not be at its best. On the other
hand, overheated steel will have a coarser structure, depending
on the extent of overheating.

To determine the proper quenching temperature of any particular
grade of steel it is only necessary to heat pieces to various
temperatures not more than 20 deg.C. (36 deg.F.) apart, quench in water,
break them, and examine the fractures. The temperature producing
the finest grain should be used for annealing and hardening.

Similarly, to determine tempering temperatures, several pieces
should be hardened, then tempered to various degrees, and cooled
in air. Samples, say six, reheated to temperatures varying by 100 deg.
from 300 to 800 deg.C. will show a considerable range of properties,
and the drawing temperature of the piece giving the desired results
can be used.

For drawing tempers up to 500 deg.F. oil baths of fresh cotton seed
oil can be safely and satisfactorily used. For higher temperature
a bath of some kind of fused salt is recommended.





Next: Hints For Tool Steel Users

Previous: Temperatures To Use



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