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

Quenching The Work
In some operations case-hardened work is quenched from the bo...

Furnace Data
In order to give definite information concerning furnaces, fu...

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

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

Heat Treatment Of Steel
Heat treatment consists in heating and cooling metal at defin...

Fatigue Tests
It has been known for fifty years that a beam or rod would fa...

Tensile Properties
Strength of a metal is usually expressed in the number of pou...

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

Hardening Operation
Hardening a gear is accomplished as follows: The gear is tak...

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

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

Pyrometers
Armor plate makers sometimes use the copper ball or Siemens' ...

Care In Annealing
Not only will benefits in machining be found by careful anne...

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

Phosphorus
Phosphorus is one of the impurities in steel, and it has been...

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

Silicon
Silicon prevents, to a large extent, defects such as gas bubb...

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

Annealing Method
Forgings which are too hard to machine are put in pots with ...



Nickel






Category: ALLOYS AND THEIR EFFECT UPON STEEL

Nickel may be considered as the toughest among the non-rare alloys
now used in steel manufacture. Originally nickel was added to give
increased strength and toughness over that obtained with the ordinary
rolled structural steel and little attempt was made to utilize its
great possibilities so far as heat treatment was concerned.

The difficulties experienced have been a tendency towards laminated
structure during manufacture and great liability to seam, both
arising from improper melting practice. When extra care is exercised
in the manufacture, particularly in the melting and rolling, many
of these difficulties can be overcome.

The electric steel furnace, of modern construction, is a very important
step forward in the melting of nickel steel; neither the crucible
process nor basic or acid open-hearth furnaces give such good results.

Great care must be exercised in reheating the billet for rolling
so that the steel is correctly soaked. The rolling must not be
forced; too big reduction per pass should not be indulged in, as
this sets up a tendency towards seams.

Nickel steel has remarkably good mechanical qualities when suitably
heat-treated, and it is preeminently adapted for case-hardening. It
is not difficult to machine low-nickel steel, consequently it is
in great favor where easy machining properties are of importance.

Nickel influences the strength and ductility of steel by being
dissolved directly in the iron or ferrite; in this respect differing
from chromium, tungsten and vanadium. The addition of each 1 per
cent nickel up to 5 per cent will cause an approximate increase of
from 4,000 to 6,000 lb. per square inch in the tensile strength and
elastic limit over the corresponding steel and without any decrease
in ductility. The static strength of nickel steel is affected to
some degree by the percentage of carbon; for instance, steel with
0.25 per cent carbon and 3.5 per cent nickel has a tensile strength,
in its normal state, equal to a straight carbon steel of 0.5 per
cent with a proportionately greater elastic limit and retaining
all the advantages of the ductility of the lower carbon.

To bring out the full qualities of nickel it must be heat-treated,
otherwise there is no object in using nickel as an alloy with carbon
steel as the additional cost is not justified by increased strength.

Nickel has a peculiar effect upon the critical ranges of steel,
the critical range being lowered by the percentage of nickel; in
this respect it is similar to manganese.

Nickel can be alloyed with steel in various percentages, each percentage
having a very definite effect on the microstructure. For instance, a
steel with 0.2 per cent carbon and 2 per cent nickel has a pearlitic
structure but the grain is much finer than if the straight carbon
were used. With the same carbon content and say 5 per cent nickel,
the structure would still be pearlitic, but much finer and denser,
therefore capable of withstanding shock, and having greater dynamic
strength. With about 0.2 per cent carbon and 8 per cent nickel, the
steel is nearing the stage between pearlite and martensite, and
the structure is extremely fine, the ferrite and pearlite having
a very pronounced tendency to mimic a purely martensite structure.
Steel with 0.2 per cent carbon and 15 per cent nickel is entirely
martensite. Higher percentages of nickel change the martensitic
structure to austenite, the steel then being non-magnetic. The
higher percentages, that is 30 to 35 per cent nickel, are used
for valve seats, valve heads, and valve stems, as the alloy is a
poor conductor of heat and is particularly free from any tendency
towards corrosion or pitting from the action of waste gases of
the internal-combustion engine.

Nickel steels having 3-1/2 per cent nickel and 0.15 to 0.20 per
cent carbon are excellent for case-hardening purposes, giving hard
surfaces and tough interiors.

To obtain the full effect of nickel as an alloy, it is essential
that the correct percentage of carbon be used. High nickel and
low carbon will not be more efficient than lower nickel and higher
carbon, but the cost will be much greater. Generally speaking,
heat-treated nickel alloy steels are about two to three times stronger
than the same steel annealed. This point is very important as many
instances have been found where nickel steel is incorrectly used,
being employed when in the annealed or normal state.





Next: Chromium

Previous: Hardness Testing



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