Mangabraze and E-Z Braze are engineered alloys, not generic AR plates
with fancy names. The high levels of Nickel (1 1/2%) and Manganese (2%)
allow special mill processing which increases depth of hardness.
Mangabraze is made in controlled electric furnaces to minimize
impurities, which detract from a material's toughness. The molten metal
is vacuum-degassed to draw off impurities (e.g. sulfides). Any
microscopic impurities that remain are then refined to neutralize their
effects upon the steel. This process is known as "inclusion shape
control," and is the same type of process used in refining impurities in
the most critical applications (e.g. airplane landing gear). This
process also increases the ability of the plate to resists weld cracks.
High levels of Manganese are added to allow the formation of extremely
hard alloy carbides which resist wear similar to the way carbide tool
bits resist wear.
High levels of Nickel are added to promote deeper, more uniform
hardening. Not having such high levels of Nickel, commercial AR plate
products are only able to develop irregular surface levels of hardness.
Note that in recent mill evaluations heavy sections of Mangabraze
actually displayed increased hardness toward the mid-area of thickness.
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Manganese and Nickel
together, present in the levels established for Mangabraze, allow the
employment of a very high-temperature tempering process, which follows
heat treatment. This process removes mill rolling stresses and has the
unique ability to add toughness to the steel. In steels that do not have
the rich chemistry of Mangabraze, a lower temperature tempering process
must be used to remove the thermal stress caused by heat treatment.
Lower temperature in this process results in decreased toughness in the
steel.
In severe service
this combination of Manganese and Nickel also promotes additional
"cold-working" hardness of up to 17% of the as-delivered hardness. This
additional hardening allows the plate to "self-polish," providing the
added benefit of minimizing drag when moving bulk materials.
There are many AR
plate products that are economically produced to what is commonly
referred to as the "Chrome-Manganese-Boron" formula. This formula does
not produce a steel in the class of Mangabraze. Close inspection of
their composition reveals that they are all very similar. The hardening
ability of moderate amounts of Boron to achieve an erratic, not uniform,
low-depth hardness that lacks toughness and is unpredictable in service.
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