Class 40 Gray Iron
G2, CLASS 40 GRAY IRON. It is a pearlitic gray iron containing Type A graphite. Gray Iron bars
made to this specification have optimal strength, wear and hardness when
compared to the other gray iron grades. This material is well suited
for applications requiring high resistance to wear and response to heat
treatment. This specification is similar to ASTM A48 class 40.
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Class 40 Gray Iron Heat Treatment Response:
G2 Gray Iron can be hardened by fast methods, such as flame and induction
hardening, in addition to conventional quench and temper methods.
G2 Gray Iron can be oil quench hardened from 1600° F (885° C) to a minimum
hardness of Rockwell C 50 on the outside of the bar. The inside diameter
hardness will be less than Rockwell C 50. Lower quench hardness on the
inside diameters are a result of larger graphite flakes and not as loss
of matrix hardness. Typical Jominy end quench test data are shown in the
section on Heat Treating.
Class 40 Gray Iron Microstructure:
The microstructure will contain Type VII, A, size 4-6 graphite as defined
in ASTM A247. The matrix is fully pearlitic. The rim will consist of
Type D, size 4-6 graphite in a pearlite matrix with small amounts of
ferrite. Chill carbides will be less than 5% in any field at 100x and
are well dispersed.
Class 40 Gray Iron Specifications: