Property	Grade A	Grade B	Grade D	Grade E
% of Carbon	0.21 max	0.21 max	0.21 max	0.18 max
% of Manganese	2.5 times %C min	0.8 times %C min	0.6 times %C min	0.7 times %C min
% of Silicon	0.5 max	0.35 max	0.1 – 0.35	0.1 – 0.35
% of Phosphorous	0.035 max	0.035 max	0.035 max	0.035 max
% of Sulphur	0.035 max	0.035 max	0.035 max	0.035 max
% of Aluminum	–	–	0.015 min	–
Ultimate Tensile Strength (N/mm2)	400-520
Yield Strength (N/mm2)	235
% Elongation	22
Temperature at which Impact test is done (deg Cel)	NA	0	-20	-40

High Tensile Steels (HTS)

• HTS can be used effectively in highly stressed areas of the ship.
• They have less thickness for same strength compared to normal steel.
• Strength is increased by adding grain refining elements such as (% Al: 0.015 min, % Nb: 0.02 – 0.05, % V: 0.05 – 0.10, % Ti: 0.02)
• High tensile steels are expressed as AH 36, BH 40, etc.
•  AH stands for High tensile steel of Grade A
• The number represents minimum yield strength in N/mm2 (32 means minimum 315 N/mm2, 36 means minimum 355 N/mm2, 40 means minimum 390 N/mm2)
• Ultimate Tensile Strength for the above three numbers are: 32 —-> 440 – 590 N/mm2, 36 —-> 490 – 620 N/mm2 and 40 —-> 510 – 650 N/mm2
• It should be noted that for Grade A steel temperature for impact test is not applicable. At the same time for Grade AH steel impact test to be carried out at zero degree Celsius.

See Also: Heat Treatment in Marine Steels