ASTM A299 Grade B and A302 Grade B are both manganese-silicon carbon steel plates for boilers/pressure vessels, but A299 Gr B is a non-alloy steel with higher C, Mn, Si for general welding, while A302 Gr B is a manganese-molybdenum alloy steel, offering superior strength and toughness, especially at lower temperatures, used in more critical applications like nuclear or high-pressure gas storage. The key difference lies in A302's added Molybdenum (Mo) for enhanced properties, making it a higher-performance material than A299, which relies on carbon, manganese, and silicon.
Chemical Composition
|
A299 Grade B Chemical Composition |
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|
Grade |
The Element Max (%) |
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|
C |
Si |
Mn |
P |
S |
Mo |
|
|
A299 GR.B |
0.28-0.30 |
0.13-0.45 |
0.84 -1.62 |
0.035 |
0.035 |
- |
|
A302 Grade B Chemical Composition |
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|
Grade |
The Element Max (%) |
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|
C |
Si |
Mn |
P |
S |
Mo |
|
|
A302 GR.B |
0.2-0.25 |
0.13-0.45 |
1.07 -1.62 |
0.035 |
0.035 |
- |
Mechanical Property
|
Grade |
A299 Grade B Mechanical Property |
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|
Thickness |
Yield |
Tensile |
Elongation |
|
|
A299 GR.B |
mm |
Min Mpa |
Mpa |
Min % |
|
t≦50 |
310-325 |
550-690 |
19 |
|
|
50<t≦200 |
310-325 |
550-690 |
19 |
|
|
A302 Grade B Mechanical Property |
A302 Grade B |
|
Tensile strength, kis [MPa] |
80-100 [550-690] |
|
Yield strength, min, kis [MPa] |
50 [345] |
|
Elongation in 8 in. [200 mm], min, % |
15 |
|
Elongation in 2 in. [50 mm], min, % |
18 |
ASTM A299 Grade B:
Type: Manganese-Silicon Carbon Steel.
Composition: Higher carbon, manganese, and silicon content.
Applications: Welded boilers, pressure vessels, storage tanks, pipelines, heat exchangers in petrochemicals.
Properties: Good weldability and strength, used where moderate temperature/pressure conditions are met.
ASTM A302 Grade B:
Type: Manganese-Molybdenum Alloy Steel (Low Alloy).
Composition: Contains Molybdenum (Mo), making it stronger than A299.
Applications: More critical pressure vessels, nuclear industry components, storage of toxic/liquefied gases.
Properties: Excellent low-temperature toughness, superior fracture resistance, higher yield/tensile strength than A299.
Key Differences
Alloy vs. Non-Alloy: A302 Gr B is an alloy (molybdenum added), A299 Gr B is primarily a carbon-manganese-silicon steel.
Performance: A302 Gr B offers better mechanical properties, especially at low temperatures, for demanding environments.
Use Case: A299 is for general-purpose vessels; A302 is for critical, high-risk applications.
