ASTM A302 is a specification for manganese-molybdenum and manganese-molybdenum-nickel alloy steel plates intended for use in welded boilers and pressure vessels . Both Grade A and Grade C fall under this specification, with the key distinction being that Grade A is a straight manganese-molybdenum steel, while Grade C includes a nickel addition to enhance its properties.
ASTM A302 Grade A is a manganese-molybdenum alloy steel plate. It has a tensile strength range of 75-95 ksi (515-655 MPa) , making it the lowest strength grade within the A302 family . This grade relies on manganese and molybdenum as the primary alloying elements to achieve its mechanical properties. The steel is manufactured using killed steel practices and must conform to fine grain size requirements . It is suitable for general pressure vessel construction where moderate strength levels are adequate.
ASTM A302 Grade C is a manganese-molybdenum-nickel alloy steel plate. It offers a higher tensile strength range of 80-100 ksi (550-690 MPa) , placing it in the higher strength tier of the specification alongside Grades B and D . The addition of nickel to the manganese-molybdenum base provides enhanced hardenability and toughness compared to Grade A. Like all grades under this specification, it is produced as killed steel with fine grain structure
Chemical Composition
ASTM A302 Grade CChemical Composition | |||||||
Grade | The Element Max (%) | ||||||
C | Si | Mn | P | S | Al | N | |
A302 Grade C | 0.20-0.25 | 0.13–0.45 | 1.07-1.62 | 0,035 | 0,035 |
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Nb | V | Ti | Cu | Cr | Ni | Mo | |
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| 0.37-0.73 | 0.41–0.64 | |
ASTM A302 Grade AChemical Composition | |||||||
Grade | The Element Max (%) | ||||||
C | Si | Mn | P | S | Al | N | |
A302 Grade C | 0.20-0.25 | 0.15–0.45 | 0.95-1.41 | 0,035 | 0,035 |
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Nb | V | Ti | Cu | Cr | Ni | Mo | |
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| 0.37-0.73 | 0.45–0.64 | |
Mechanical Property
Grade |
| ASTM A302 Grade CMechanical Property | ||
Thickness | Yield | Tensile | Elongation | |
A302 Grade C | mm | Min Mpa | Mpa | Min % |
6-50 | 345 | 550-690 | 20% | |
50-200 | 345 | 550-690 | 17% | |
Mechanical Property of A302 Grade A steel plate | A302 Grade A |
Tensile strength, kis [MPa] | 75-95 [515-655] |
Yield strength, min, kis [MPa] | 45 [310] |
Elongation in 8 in. [200 mm], min, % | 15 |
Elongation in 2 in. [50 mm], min, % | 19 |
