ASTM A302 Grade D and Grade B are both manganese-molybdenum alloy steels for pressure vessels, but Grade D typically contains Nickel (Ni), offering enhanced properties, whereas Grade B is standard Mn-Mo; the main difference lies in their chemical composition, with Grade D's Nickel addition improving toughness and performance, while Grade B focuses on base strength and ductility, both serving for high-temperature/pressure applications like boilers.
Chemical Composition
|
A302 GrD Chemical Composition |
|||||||
|
Carbon, max |
% |
Manganese, max |
% |
Silicon, max |
% |
Sulfur max |
% |
|
25mm or under |
0.2 |
Heat Analysis |
1.15-1.50 |
Heat Analysis |
0.15-0.40 |
All thick |
0.035 |
|
25-50mm |
0.23 |
Product Analysis |
1.07-1.62 |
Product Analysis |
0.13-0.45 |
||
|
over 50mm |
0.25 |
|
|
|
|
||
|
|
|
Molybdenum max |
% |
Nickel max |
% |
Phosphorus |
% |
|
|
|
Heat Analysis |
0.45-0.60 |
Heat Analysis |
0.70-1.00 |
All thick |
0.035 |
|
|
|
Product Analysis |
0.41-0.64 |
Product Analysis |
0.67-1.03 |
||
|
A302 Grade B Chemical Composition |
|||||||
|
Carbon, max |
% |
Manganese, max |
% |
Silicon, max |
% |
Sulfur max |
% |
|
25mm or under |
0.2 |
Heat Analysis |
1.15-1.50 |
Heat Analysis |
0.15-0.40 |
All thick |
0.035 |
|
25-50mm |
0.23 |
Product Analysis |
1.07-1.62 |
Product Analysis |
0.13-0.45 |
||
|
over 50mm |
0.25 |
|
|
|
|
||
|
|
|
Molybdenum max |
% |
Nickel max |
% |
Phosphorus |
% |
|
|
|
Heat Analysis |
0.45-0.60 |
Heat Analysis |
… |
All thick |
0.035 |
|
|
|
Product Analysis |
0.41-0.64 |
Product Analysis |
… |
||
Mechanical Property
|
Mechanical Property of A302GrD steel plate |
A302GrD |
|
Tensile strength, kis [MPa] |
80-100 [550-690] |
|
Yield strength, min, kis [MPa] |
50 [345] |
|
Elongation in 8 in. [200 mm], min, % |
17 |
|
Elongation in 2 in. [50 mm], min, % |
20 |
|
Mechanical Property of A302 Grade B steel plate |
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 A302 Specification: Covers low-alloy steel plates for welded boilers and pressure vessels, with grades A, B, C, and D.
Grade B: A standard Mn-Mo (Manganese-Molybdenum) alloy steel, providing good strength and ductility for general pressure vessel use.
Grade D: A Mn-Mo-Ni (Manganese-Molybdenum-Nickel) alloy steel, meaning it adds Nickel to the base composition, which enhances its toughness and suitability for more demanding conditions, often compared to other nickel alloy steels like ASTM A203 Grade D (3.5% Ni) for improved properties.
Key Difference: The primary distinction is the addition of Nickel in Grade D, making it a higher-performance alloy compared to Grade B for specific high-stress or cryogenic applications requiring superior toughness.
