subject: Astm A 278 - Standard For Gray Iron Castings for Pressure Containing Parts [print this page] This specification covers gray iron for castings suitable for pressure-containing parts for use at temperatures up to 650F (350C).
Classes of Iron:
1. Castings of all classes are suitable for use up to 450F (230C). For temperatures above 450F and up to 650F, only Class 40, 45, 50, 55, and 60 castings are suitable.
2. Castings of all classes are suitable for use up to 230C. For temperatures above 230C and up to 350C, only Class 275, 300, 325, 350, 380, and 415 castings are suitable.
Heat Treatment:
1. Whether or not heat treatment is required for Class 40, 45, 50, 55, and 60 castings to be used at temperatures at 450F or less.
2. Whether or not heat treatment is required for Class 275, 300, 325, 350, 380, and 415 castings to be used at temperatures at 230C or less.
Tensile Requirements
Class of Iron Tensile Strength, min, MPa
No. 20 20
No. 25 25
No. 30 30
No. 35 35
No. 40 40
No. 45 45
No. 50 50
No. 55 55
No. 60 60
No. 150 150
No. 175 175
No. 200 200
No. 225 225
No. 250 250
No. 275 275
No. 300 300
No. 325 325
No. 350 350
No. 380 380
No. 415 415
Chemical Composition
1. Class 40, 45, 50, 55, and 60 castings intended for service above 450F (230C) 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 230C 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 132 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.
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