ASTM A278 Standard for Gray Iron Casting for Pressure Parts

ASTM A278 covers gray iron for castings suitable for pressure-containing parts for use at temperature up to 650°F (350°C).

Classes of Iron:
Castings of all classes are suitable for use up to 450°F (230°C). For temperature above 450°F and up to 650°F, only Class 40, 45, 50, 55, and 60 casting are suitable. Casting of all classes are suitable for use up to 230°C. For temperature above 230°C and up to 350°C, only Class 275, 300, 325, 350, 380, and 415 casting are suitable.

Heat Treatment:
Whether or not heat treatment is required for Class 40, 45, 50, 55, and 60 castings to be used at temperatures at 450°F or less. Whether or not heat treatment is required for Class 275, 300, 325, 350, 380, and 415 castings to be used at temperatures at 230°C or less.

Chemical Composition
1. Class 40, 45, 50, 55, and 60 castings intended for service above 450°F (230°C) shall have a maximum carbon equivalent of 3.8 % as calculated from the equation CE = %C + 0.3 (%Si + %P). The maximum phosphorus and sulfur contents shall be 0.25 % and 0.12 %, respectively. 

2. Class 275, 300, 325, 350, 380, and 415 castings intended for service above 230°C shall have a maximum carbon equivalent of 3.8 % as calculated from the equation CE = %C + 0.3 (%Si + %P). The maximum phosphorus and sulfur contents shall be 0.25 % and 0.12 %, respectively.

3. The chemical analysis for total carbon shall be made on either chilled cast pencil-type specimens or thin wafers approximately 1⁄32 in. thick cut from test coupons. Drillings shall not be used because of attendant loss of graphite.

Workmanship, Finish, and Appearance

1. All castings shall be made in a workmanlike manner and shall conform to the dimensions on drawings furnished by the purchaser. If the pattern is supplied by the purchaser without drawings, the dimensions of the casting shall be as predicted by the pattern.

2. The surface of the casting shall be free of adhering sand, scale, cracks, and hot tears as determined by visual examination. Other surface discontinuities shall meet the visual acceptance standards specified in the order.