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Annealing Of High-speed Steel
For annealing high-speed steel, some makers recommend using g...

Preventing Decarbonization Of Tool Steel
It is especially important to prevent decarbonization in such...

Liberty Motor Connecting Rods
The requirements for materials for the Liberty motor connecti...

Temperature Recording And Regulation
Each furnace is equipped with pyrometers, but the reading an...

Flange Shields For Furnaces
Such portable flame shields as the one illustrated in Fig. 1...

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

Hints For Tool Steel Users
Do not hesitate to ask for information from the maker as to t...

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

Gears
The material used for all gears on the Liberty engine was sel...

The Quenching Tank
The quenching tank is an important feature of apparatus in c...

Testing And Inspection Of Heat Treatment
The hard parts of the gear must be so hard that a new mill f...

Critical Points
One of the most important means of investigating the properti...

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

Open Hearth Process
The open hearth furnace consists of a big brick room with a l...

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

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

Vanadium
Vanadium has a very marked effect upon alloy steels rich in c...

Preventing Cracks In Hardening
The blacksmith in the small shop, where equipment is usually ...

The Leeds And Northrup Potentiometer System
The potentiometer pyrometer system is both flexible and subst...

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



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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