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How Ductile Iron Compares to Cast Iron and Cast Steel
 
Chemical Analysis |
Cast Iron ASTM A 126 Class B* |
Ductile Iron ASTM A 395 |
Cast Steel ASTM A 216 WCB |
|
Iron and Residuals% | 94.0 | 94.5 | 98.1 |
Carbon% | 3.3 | 3.0 | 0.3 |
Silicon% | 2.0 | 2.5 | 0.6 |
Manganese% | 0.7 | 1.0 | |
* Typical composition, ASTM Standard does not specify materials to this detail. |
Pressure/Temperature Ratings Comparing Cast Iron, Ductile Iron and Cast Steel |
°F/°C Temperature | ASTM A 126 Cast Iron |
ASTM A 395 *Ductile Iron |
ASTM A 216 WCB Cast Steel |
|
Class 125 | Class 150 | Class 150 | ||
2"-12" | 14"-24" | 2"-24" | 2"-24" | |
-20°F-100°F | 200 psi | 150 psi | **285 psi | 285 psi |
150°F/66°C | 200 psi | 150 psi | 243 psi | |
200°F/93°C | 190 psi | 135 psi | 235 psi | 260 psi |
250°F/121°C | 175 psi | 125 psi | 225 psi | |
300°F/149°C | 165 psi | 110 psi | 215 psi | 230 psi |
350°F/177°C | 150 psi | 100 psi | 210 psi | |
400°F/204°C | 140 psi | 200 psi | 200 psi | |
450°F/232°C | 125 psi | 185 psi | ||
500°F/260°C | 170 psi | 170 psi | ||
550°F/288°C | 155 psi | |||
600°F/316°C | 140 psi | 140 psi | ||
650°F/343°C | 125 psi | 126 psi | ||
* These ratings apply when temperature exceeds 450°F and the valve has 316 SS trim. When ASTM B 584 trim is used, maximum temperature limit is 450°F. ** Engineering Note: Ductile Iron flanges are rated at 250 psi in accordance with ANSI B16.42. |