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Pressure vessel plates made of ASTM A204 (identical with ASME SA-204) steels are typical molybdenum-alloy steel plates intended particularly for welded boilers and other pressure vessels. The steel grades covered by ASTM A204/ ASME SA-204 are all carbon-molybdenum alloy steels with nominal composition of C-0.5Mo. Plates under this standard specification are available in three grades having different strength levels as follows:
Grade | Tensile Strength ksi [MPa] |
---|---|
A | 65-85 [450-585] |
B | 70-90 [485-620] |
C | 75-95 [515-655] |
The maximum thickness of ASTM A204 plates is limited only by the capacity of the composition to meet the specified mechanical property requirements; however, current practice normally limits the maximum thicknesses of plates made of Grade A, Grade B and Grade C steel to 6″ [150 mm], 6″ [150 mm], 4″ [100 mm], respectively.
The ASTM A204 plates shall be made from killed steels. Plates 1-1/2″ [40 mm] and under in thickness are normally supplied in the as-rolled condition. The plates may be ordered normalized or stress relieved or both. Plates over 1-1/2″ [40 mm] in thickness shall be normalized.
Element | t | Composition, % | ||
Gr. A | Gr. B | Gr. C | ||
C | t≤1" | ≤0.18 | ≤0.20 | ≤0.23 |
1"≤0.21 | ≤0.23 | ≤0.26 |
| |
2"≤0.23 | ≤0.25 | ≤0.28 |
| |
t>4" | ≤0.25 | ≤0.27 | ≤0.28 | |
Mn | All | ≤0.90 | ≤0.90 | ≤0.90 |
P | All | ≤0.025 | ≤0.025 | ≤0.025 |
S | All | ≤0.025 | ≤0.025 | ≤0.025 |
Si | All | 0.15-0.40 | 0.15-0.40 | 0.15-0.40 |
Mo | All | 0.45-0.60 | 0.45-0.60 | 0.45-0.60 |
ASTM A204 | Gr. A | Gr. B | Gr. C |
---|---|---|---|
T.S. MPa [ksi] | 450-585 [65-85] | 485-620 [70-90] | 515-655 [75-95] |
Y.S. min. MPa [ksi] | 255 [37] | 275 [40] | 295 [43] |
El. in 8" min. % | 19 | 17 | 16 |
El. in 2" min. % | 23 | 21 | 20 |
Additional tension test, Charpy V-Notch test, drop weight test, high-temperature tension test, ultrasonic examination, magnetic particle examination.