LR Grade A and LR Grade B are classifications for hot-rolled, general-strength shipbuilding steel, certified by Lloyd's Register, used in marine construction; Grade B offers better low-temperature toughness than Grade A, with A being the basic grade (Yield 235 MPa, Tensile 400-520 MPa) and B having similar strength but better impact resistance at 0°C, while D and E provide even colder performance (D at -20°C, E at -40°C).
Chemical Composition
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LR A general Strength Chemical Composition |
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Grade |
The Element Max (%) |
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C |
Si |
Mn |
P |
S |
Al |
N |
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LR A |
0.21 |
0.50 |
2.5×C% |
0.035 |
0.035 |
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Nb |
V |
Ti |
Cu |
Cr |
Ni |
Mo |
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LR GRADE B general Strength Chemical Composition |
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Grade |
The Element Max (%) |
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C |
Si |
Mn |
P |
S |
Al |
N |
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LR GRADE B |
0.21 |
0.35 |
0.80 |
0.035 |
0.035 |
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Nb |
V |
Ti |
Cu |
Cr |
Ni |
Mo |
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Mechanical Property
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LR A general strength property |
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Grade |
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Mechanical Property |
Charpy V Impact Test |
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Thickness |
Yield |
Tensile |
Elongation |
Degree |
Energy 1 |
Energy 2 |
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LR A |
mm |
Min Mpa |
Mpa |
Min % |
20 |
J |
J |
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t≤50 |
235 |
400-520 |
22% |
20 |
27 |
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50＜t≤70 |
235 |
400-520 |
22% |
24 |
34 |
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70＜t≤100 |
235 |
400-520 |
22% |
27 |
41 |
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Note: Energy 1 is transverse impact test, Energy 2 is longitudinal |
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LR GRADE B general strength property |
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Grade |
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Mechanical Property |
Charpy V Impact Test |
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Thickness |
Yield |
Tensile |
Elongation |
Degree |
Energy 1 |
Energy 2 |
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LR GRADE B |
mm |
Min Mpa |
Mpa |
Min % |
0 |
J |
J |
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t≤50 |
235 |
400-520 |
22% |
20 |
27 |
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50＜t≤70 |
235 |
400-520 |
22% |
24 |
34 |
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70＜t≤100 |
235 |
400-520 |
22% |
27 |
41 |
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Note: Energy 1 is transverse impact test, Energy 2 is longitudinal |
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Key Characteristics:
LR Grade A: The foundational grade, suitable for general structural parts, with good mechanical properties but lower impact toughness than higher grades.
LR Grade B: Offers improved impact properties over Grade A, tested at 0°C, making it more versatile for colder conditions or critical structures.
Strength: Both typically share a yield strength of around 235 MPa (34 ksi) and tensile strength of 400-520 MPa (58-75.5 ksi).
Application: Primarily for shipbuilding, marine structures, offshore platforms, and ship repair.
The primary distinction lies in the Charpy V-notch impact test, which measures toughness at specific temperatures.
Grade A: Tested at 20°C.
Grade B: Tested at 0°C.
