A-897
Grade 2
The ASTM A-897 ductile
iron casting specification is based on demonstrated mechanical
properties which depend on the proper cast iron microstructure.
The
austempering heat treatment is the primary factor in determining the
microstructure and
mechanical properties of the A-897 ductile iron casting. |
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The
austempering process
produces a microstructure that is substantially ausferrite (a mix of
high carbon austenite and acicular ferrite).
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Controlled
changes in the austempering process (temperatures and times) are
used to tailor the ratio of austenite and ferrite and to control the
scale of the microstructure (fineness).
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The
different ADI grades reflect differences in microstructure which
produce the defined mechanical properties.
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For a
given cast iron alloy, the chemistry (carbon, silicon, manganese,
copper, nickel, molybdenum) is precisely controlled so
that the austemper process will consistently give the desired
microstructure and
mechanical properties.
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The
Grade 2 casting meets all the mechanical requirements for ultimate tensile
strength, yield strength, ductility/elongation, impact strength, and hardness.
The Grade 2 is the
best choice.
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