This specification covers gray iron castings exposed to elevated temperatures for non-pressure containing parts such as grate bars, stoker links, stoker parts, oil still furnace parts, firebox parts, ingot molds, glass molds, caustic pots, and metal melting pots. The three classes of gray iron covered here are: Class I, possessing superior thermal shock resistance; Class II, possessing average thermal shock resistance and moderately good tensile strength; and Class III, possessing a higher tensile strength than either Classes I or II. It is the intention of this specification to classify the irons in accordance with their carbon content equivalent, wherein the equation for its calculation is given herein.

1.1 This specification covers three classes of gray iron suitable for castings exposed to temperatures encountered in such service as grate bars, stoker links, stoker parts, oil still furnace parts, firebox parts, ingot molds, glass molds, caustic pots, and metal melting pots.

Note 1—This specification is general, covering cast irons normally used for the above types of service, at temperatures as high as 1400°F (760°C). It is not intended to imply that all three classes are suitable throughout this entire temperature range without regard to actual service stresses. Some are suitable for long service at the lower temperatures only, unless low stresses are involved.

1.2 The three classes of gray iron covered by this specification are as follows:

1.2.1 Class I, possessing superior resistance to thermal shock,

1.2.2 Class II, possessing average resistance to thermal shock and a moderately good tensile strength (tensile strengths above 30 000 psi (207 MPa) may be expected), and

1.2.3 Class III, possessing a higher tensile strength than either Classes I or II (tensile strengths as high as 40 000 psi (276 MPa) may be expected).

1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.