A-897
Grade 1
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 matrix 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
mechanical properties.
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The
Grade 1 casting has more than sufficient ductility/elongation and impact strength, but doesn't meet
the
minimum requirements for ultimate tensile
strength, yield strength, or hardness. The
Grade 1 is not the best choice.
Go Back for Another Choice! |
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