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Description
Hull
steels are mild steels with a tensile strength ranging
from 400 to 520 MPa and are listed in the “Rules and
Regulation for the Construction and Classification of
Steel ships”, published by Lloyd’s Register of
Shipping.
The
tensile requirements are for plates not exceeding 30mm
in thickness: greater thicknesses are subjects to
special consideration.
Four
grades are specified, namely A, B, C and E.
Although
these grades have the same tensile strength, they are
characterized by an increasing degree of toughness.
The
higher strength grades of steel are grades with a
minimum specified yield equal to or in excess of
335MPa.
Three
grades are AH36, DH36, and EH36.
Chemical
Composition (ladle
analysis, percent %) as specified by Lloyd’s rule
|
Grade
|
C
Max
|
Mn
|
P
Max
|
S
Max
|
Si
|
Al¹
|
Nb
|
|
A
|
0,21
|
²
|
0,035
|
0,035
|
0,50
max
|
-
|
-
|
|
B
|
0,21
|
0,80
min
|
0,035
|
0,035
|
0,35
max
|
-
|
-
|
|
D
|
0,21
|
0,60
min
|
0,035
|
0,035
|
0,10-
0,35
|
0,020
min
|
-
|
|
E
|
0,18
|
0,70
min
|
0,035
|
0,035
|
0,10-0,35
|
0,020
min
|
-
|
|
AH
36³
|
0,18
|
0,07-1,60⁴
|
0,035
|
0,035
|
0,50
max
|
0,020
min
|
0,020
-0,050
|
|
DH36³
|
0,18
|
0,90-1,60
|
0,035
|
0,035
|
0,5
max
|
0,020
min
|
0,020-
0,050
|
|
EH36³
|
0,18
|
0,90-1,60
|
0,035
|
0,035
|
0,5
max
|
0,020
min
|
0,020-
0,050
|
Notes:
1.
Total Aluminum
2. %
manganese not less than 2,5 times % carbon
3. Residual
elements are restricted to the following maximum:
copper ≤ 0,35%; chromium ≤ 0,20% nickel
≤ 0,40%; molybdenum ≤ 0,08%
4.
0,9% -1, 60 manganese for t ≥ 12,5mm
Typical
Chemical Composition (ladle analysis, percent %)
|
Grade
|
Deoxidation
Practice
|
Thickness
t (mm)
|
C
|
Mn
|
P
max
|
S
max
|
Si
|
Al
|
Nb
|
|
A
|
Fully
killed
|
4,5≤
t≤30
|
0,14
|
0,90
|
0,020
|
0,020
|
0,25
|
0,035
|
-
|
|
B
|
Fully
killed
|
4,5≤t≤30
|
0,14
|
0.9
|
0,020
|
0,020
|
0,25
|
0,035
|
-
|
|
D
|
Fully
killed
|
6,0≤t≤30
|
0,12
|
0,95
|
0,020
|
0,020
|
0,25
|
0,035
|
-
|
|
E
|
Fully
killed
|
6,0≤t≤30
|
0,12
|
1,00
|
0,020
|
0,010
|
0,25
|
0,035
|
-
|
|
AH36
|
Fully
killed
|
6≤t≤30
|
0,15
|
1,45
|
0,015
|
0,015
|
0,40
|
0,035
|
0,025
|
|
DH36
|
Fully
killed
|
6≤t≤30
|
0,15
|
1,45
|
0,015
|
0,015
|
0,40
|
0,035
|
0,025
|
|
EH36
|
Fully
killed
|
6≤t≤30
|
0,15
|
1,45
|
0,015
|
0,015
|
0,40
|
0,035
|
0,025
|
Mechanical
Property Requiremens as specified by Lloyd’s rules
|
Grade
|
Tensile
Strength
(MPa)
|
Minimum
Yield
stress
(
MPa)
|
Minimum
Elongation
¹ʹ²
(%)
|
Charpy
V –Notch ³
Impact
test in the
Longitudinal
direction
|
|
Test
temperature(°C)
|
Minimum
average
energy
(J)
|
|
A
|
400-520
|
235
|
22
|
-
|
-
|
|
B
|
400-520
|
235
|
22
|
0
|
27
|
|
D
|
400-520
|
235
|
22
|
20
|
27
|
|
E
|
400-520
|
235
|
22
|
-40
|
27
|
|
AH36
|
490-620
|
355
|
21
|
0
|
34
|
|
DH36
|
490-620
|
355
|
21
|
-20
|
34
|
|
EH36
|
490-620
|
355
|
21
|
-40
|
34
|
Notes:
1. Gauge
length 5,65√S₀,
, where S₀
is the original cross section area of the tensile test
specimen
2. Applicable
to round tensile specimens only.
3. Longitudinal,
full size test specimen.
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