Section
3 Higher strength steels for ship and other structural applications
3.1 Scope
3.1.1 Provision is made for material to be supplied in five strength levels, 27S,
32, 36, 40 and 47.
3.1.2 The required
notch toughness is designated by subdividing the strength levels into
Grades AH, DH, EH and FH.
3.1.3 For the designation to fully identify a steel and its properties the
appropriate grade letters should precede the strength level number, e.g. AH32 or FH40
and specify a suffix where applicable.
3.1.4 Provision is made for plates specifically intended for longitudinal
structural members in the upper deck region of container ships (such as hatch side
coaming, upper deck, hatch coaming top and the attached longitudinals etc.). The brittle
crack arrest suffix is to be assigned to grades EH36, EH40 and EH47 in accordance with
Table 3.3.9 Requirement of brittle crack
arrest properties for brittle crack arrest steels (Note 1), when the brittle crack
arrest properties are demonstrated at the time of approval and at batch release .
3.1.5 The requirements of this Section are primarily intended to apply to plates,
wide flats, sections and bars not exceeding the thickness limits given in Table 3.3.1 Thickness limits. Thicknesses
deviating from this table may be specially considered, in which case, variations in the
mechanical properties requirements may be permitted or required for particular
applications but a reduction of the required impact energy is not allowed.
Table 3.3.1 Thickness limits
Steel designation
|
Thickness (t) limit mm
|
Plate
and wide flat
|
Sections and Bars
|
AH27S
|
DH27S
|
EH27S
|
FH27S
|
Maximum 100
|
Maximum 50
|
AH32
|
DH32
|
EH32
|
FH32
|
AH36
|
DH36
|
EH36
|
FH36
|
AH40
|
DH40
|
EH40
|
FH40
|
EH47
|
50
< t ≤ 100
|
Not
applicable
|
Brittle Crack Arrest Steel
|
EH36-BCA1, EH40-BCA1, EH47-BCA1
|
50 <
t ≤ 100
|
Not applicable
|
EH40-BCA2, EH47-BCA2
|
80 <
t ≤ 100
|
3.1.6 It should
be noted that the fatigue strength of weldments in steels of high
strength levels may not be greater than those of steels of lower strength
levels.
3.2 Manufacture
3.2.1 All the grades
of steel are to be in the killed and fine grain treated condition.
3.3 Chemical composition
3.3.1 The chemical compositions of ladle samples for all grades of steel are to
comply with the requirements of the approved manufacturing specification and the limits
given in;
Table 3.3.2 Chemical composition for higher strength steels
Grades
|
AH, DH, EH
|
EH47
|
FH
|
Carbon %
max.
|
0,18
|
0,18
|
0,16
|
Manganese %
|
0,9 – 1,60
(see Note 1)
|
0,9 – 2,0
|
0,9 – 1,60
|
Silicon %
max.
|
0,50
|
0,55
|
0,50
|
Phosphorus %
max.
|
0,035
|
0,020
|
0,025
|
Sulphur %
max.
|
0,035
|
0,020
|
0,025
|
Grain refining
elements
(see Note 2)
|
|
Aluminium (acid
soluble) %
|
0,015 min. (see Note 3)
|
Niobium %
|
0,02 – 0,05
|
Vanadium %
|
0,05 – 0,10
|
Titanium %
|
0,02 max.
|
Total (Nb + V + Ti)
% (see Note 5)
|
0,12 max.
|
Residual
elements
|
|
|
|
Nickel %
max.
|
0,40
|
1,0
|
0,80
|
Copper %
max.
|
0,35
|
0,35
|
0,35
|
Chromium %
max.
|
0,20
|
0,25
|
0,20
|
Molybdenum %
max.
|
0,08
|
0,08
|
0,08
|
Nitrogen %
max.
|
|
|
0,009 (0,012 max.
if Al is present)
|
Note 1. For AH grade steels in all strength levels and thicknesses up to
12,5 mm, the specified minimum manganese content is 0,70%.
Note 2. The steel is to contain aluminium, niobium, vanadium or other
suitable grain refining elements, either singly or in any combination.
When used singly, the steel is to contain the specified minimum content
of the grain refining element. When used in combination, the specified
minimum content of each element is not applicable.
Note 3. The total aluminium content may be determined instead of the acid
soluble content. In such cases the total aluminium content is to be not
less than 0,020%.
Note 4. Alloying elements other than those listed above are to be included
in the approved manufacturing specification.
Note 5. The grain refining elements are to be in accordance with the
approved specification.
|
3.3.5 Where the
grain refining elements Niobium, Titanium and Vanadium are used either
singly or in combination, the chemical composition is to be specifically
approved for each Grade in combination with the rolling procedure
to be used.
3.3.6 When any
grade is supplied in an approved thermomechanically controlled processed
condition, variations in the specified chemical composition may be
considered, provided that these variations are documented and approved
in advance.
3.3.7 For plate
supplied from coil, the chemical analysis can be transposed from the
certificate of the coil manufacture onto the re-processor's certificate.
Table 3.3.3 Carbon equivalent requirements for higher strength steels up to 100 mm in
thickness when supplied in the TM condition
Grades
|
Carbon Equivalent, max (%)
|
t≤50 (Note
1)
|
50 < t ≤ 100
(Note 1)
|
AH 27S
|
DH 27S
|
EH 27S
|
FH 27S
|
0,36
|
0,38
|
AH 32
|
DH 32
|
EH 32
|
FH 32
|
0,36
|
0,38
|
AH 36
|
DH 36
|
EH 36
|
FH 36
|
0,38
|
0,40
|
AH 40
|
DH 40
|
EH 40
|
FH 40
|
0,40
|
0,42
|
EH47 (Note 2)
|
Not applicable
(see
Table 3.3.1 Thickness limits)
|
0,49
|
Note 1. t = thickness in mm
Note 2. For EH47, the maximum Pcm is 0, 22%
|
Table 3.3.4 Chemical composition for brittle crack arrest steels
Grades
|
EH36-BCA1
|
EH40-BCA1
EH40-BCA2
|
EH47-BCA1
EH47-BCA2
|
Carbon %
max.
|
0,18
|
0,18
|
0,16
|
Manganese %
|
0,90 – 2,00
|
0,90 – 2,00
|
0,90 – 2,00
|
Silicon %
max.
|
0,50
|
0,50
|
0,55
|
Phosphorus %
max.
|
0,020
|
0,020
|
0,020
|
Sulphur %
max.
|
0,020
|
0,020
|
0,020
|
Ni max.
|
2,0
|
2,0
|
2,0
|
Grain
refining elements (Note 1 & Note 2)
|
|
|
|
Aluminium (acid
soluble) % (Note 3)
|
0,015
min
|
0,015
min
|
0,015
min
|
Niobium %
|
0,02 – 0,05
|
0,02 – 0,05
|
0,02 – 0,05
|
Vanadium %
|
0,05 – 0,10
|
0,05 – 0,10
|
0,05 – 0,10
|
Titanium %
|
0,02
max
|
0,02
max
|
0,02
max
|
Total
(Nb + V + Ti) %
|
0,12
max
|
0,12
max
|
0,12
max
|
Residual elements (Note 4)
|
|
|
|
Copper
% max
|
0,50
|
0,50
|
0,50
|
Chromium % max
|
0,25
|
0,25
|
0,50
|
Molybdenum % max
|
0,08
|
0,08
|
0,08
|
Carbon
equivalent Ceq max
|
0,47
|
0,49
|
0,55
|
Cold cracking
susceptibility Pcm max
|
-
|
-
|
0,24
|
Note 1. The steel is to contain aluminium, niobium, vanadium or other
suitable grain refining elements, either singly or in any combination.
When used singly the steel is to contain the specified minimum content of
the grain refining element. When used in combination, the specified
minimum content of a fine graining element is not applicable.
Note 2. The grain refining
elements are to be in accordance with the approved specification.
Note 3. The total aluminium content may be determined instead of the acid
soluble content. In such cases the total aluminium content is to be not
less than 0,020%.
Note 4. Alloying elements other than those listed above are to be included
in the approved manufacturing specification.
|
3.4 Condition of supply
3.4.2 Where normalising
rolling and thermomechanically controlled rolling (T.M.) processes
are used, it is the manufacturer's responsibility to ensure that the
programmed rolling schedules are adhered to. Where deviation from
the programmed rolling schedule occurs, the manufacturer must ensure
that each affected piece is tested and that the local Surveyor is
informed.
3.4.3 The use of
precipitation hardening steels is not acceptable, except where such
hardening is incidental to the use of grain refining elements.
Table 3.3.5 Conditions of supply for plates
and wide flats
Grade
|
Grain refining practice
(see Note 1)
|
Thickness range mm
|
Conditions of supply
(see Note 2)
|
|
Al or Al + Ti
|
≤20
|
AR
|
N
|
NR
|
TM
|
|
AH
27S
|
>20
≤ 100
|
–
|
N
|
NR
|
TM
|
(see Note 3)
|
AH 32
|
Nb or V or Al + (Nb or V) or Al + (Ti) + (Nb or V)
|
≤12,5
|
AR
|
N
|
NR
|
TM
|
|
AH
36
|
>12,5≤100
|
–
|
N
|
NR
|
TM
|
|
|
AH 40
|
Any practice
|
≤12,5
|
AR
|
N
|
NR
|
TM
|
|
>12,5 ≤ 50
|
–
|
N
|
NR
|
TM
|
|
>50
≤ 100
|
–
|
N
|
–
|
TM
|
QT
|
|
Al or Al + Ti
|
≤20
|
AR
|
N
|
NR
|
TM
|
|
DH
27S
|
>20≤100
|
–
|
N
|
NR
|
TM
|
(see Note 4)
|
DH 32
|
Nb or V or Al + (Nb or V) or Al + (Ti) + (Nb or V)
|
≤12,5
|
AR
|
N
|
NR
|
TM
|
|
DH
36
|
>12,5≤100
|
–
|
N
|
NR
|
TM
|
|
|
DH 40
|
Any practice
|
≤50
|
–
|
N
|
NR
|
TM
|
|
> 50
≤ 100
|
–
|
N
|
–
|
TM
|
QT
|
EH 27S
|
Any practice
|
≤100
|
–
|
N
|
–
|
TM
|
|
EH 32
|
EH
36
|
EH
40
|
Any
practice
|
≤100
|
–
|
N
|
–
|
TM
|
QT
|
FH
27S
|
Any practice
|
≤100
|
–
|
N
|
–
|
TM
|
QT
|
FH 32
|
FH 36
|
FH
40
|
|
Any practice
|
≤50
|
Not applicable
|
|
EH
47
|
>50 ≤100
|
—
|
—
|
—
|
TM
|
QT
|
|
EH36-BCA1
|
Any practice
|
≤50
|
Not applicable
|
EH40-BCA1
|
>50 ≤100
|
-
|
-
|
-
|
TM
(Note 5)
|
-
|
EH40-BCA2
|
EH47-BCA1
|
EH47-BCA2
|
Note
1. Grain refining elements used singly or
in any combination, require specific approval from Materials and NDE
Department, Southampton GTC Office.
Note
2. AR = as-rolled N = furnace normalised
NR = normalising rolled TM = thermomechanically controlled-rolled QT =
quenched and tempered.
Note
3. Material up to 35 mm thick may be
supplied in the as-rolled condition provided that prior approval has
been obtained from LR.
Note
4. Material up to 25 mm thick may be
supplied in the as-rolled condition provided that prior approval has
been obtained from LR.
Note 5. Other conditions of supply may be accepted under special
consideration.
|
Table 3.3.6 Conditions of supply for sections
and bars
Grade
|
Grain
refining practice (see Note 1)
|
Thickness range mm
|
Conditions of supply (see Note 2)
|
|
Al or Al + Ti
|
≤20
|
Any
|
|
|
|
AH
27S
|
>20≤50
|
N
|
NR
|
TM
|
(see Note 3)
|
AH 32
|
Nb or V
or Al + Nb or A1+ V or Al + (Ti) + (Nb or V)
|
≤12,5
|
Any
|
|
|
|
AH
36
|
>12,5≤50
|
N
|
NR
|
TM
|
(see Note 3)
|
|
AH
40
|
Any practice
|
≤12,5
|
Any
|
|
|
|
>12,5≤50
|
N
|
NR
|
TM
|
|
DH 27S
|
Al or Al + Ti
|
≤20
|
Any
|
|
|
|
DH 32
|
>20≤50
|
N
|
NR
|
TM
|
(see Note 3)
|
DH
36
|
Nb or V
or Al + Nb or Al + V or Al + (Ti) + (Nb or V)
|
≤12,5
|
Any
|
|
|
|
>12,5≤50
|
N
|
NR
|
TM
|
(see Note 3)
|
|
DH
40
|
Any
practice
|
≤50
|
N
|
NR
|
TM
|
|
EH 27S
|
Any practice
|
≤50
|
N
|
TM
|
|
(see Notes 3 and 4)
|
EH
32
|
EH
36
|
EH
40
|
Any
practice
|
≤50
|
N
|
TM
|
QT
|
|
FH 27S
|
Any practice
|
≤50
|
N
|
TM
|
QT
|
(see Note 4)
|
FH 32
|
FH 36
|
FH
40
|
Note
1. Grain refining elements used singly or
in any combination require specific approval from Materials and NDE
Department, Southampton GTC Office.
Note
2. N = furnace normalised NR =
normalising rolled TM = thermomechanically controlled-rolled QT =
quenched and tempered
Note
3. Subject to the special approval of LR,
sections may be supplied in the as-rolled condition provided
satisfactory results are consistently obtained from Charpy V-notch
impact tests.
Note
4. Subject to the special approval of LR,
sections may be supplied in the NR condition.
|
3.5 Mechanical tests and brittle crack arrest
property tests
3.5.1 The results of all tensile tests and the average energy value from each set
of three Charpy V-notch impact tests are to comply with the appropriate requirements
given in the following tables:
3.5.2 For steels
in the as-rolled, normalised, normalising rolled or T.M. conditions,
one tensile test is to be made for each batch of 50 tonnes or fraction
thereof. Additional tests are to be made for every variation of 10
mm in the thickness or diameter of products from the same cast.
3.5.3 Where plate
is supplied from coil, both the tensile tests and the Charpy V-notch
tests are to be taken from the de-coiled plate in accordance with
the frequency specified for the Grade as required by this Section.
3.5.4 For steels
in the quenched and tempered condition a tensile test is to be made
on each plate as heat treated. For continuously heat treated plates,
one tensile test is to be made for each 50 tonnes or fraction thereof
from a single cast. Additional tests are to be made for every variation
of 10 mm in the thickness of the products from a single cast. The
tensile test specimens are to be taken with their axes transverse
to the main direction of rolling.
3.5.5 For products
in the AH and DH grades, at least one set of three impact tests is
to be made on the thickest piece in each batch of 50 tonnes when supplied
in either the normalised or thermomechanically controlled condition.
When the products are supplied in the as-rolled or normalising rolled
conditions a set of impact test specimens is to be taken from a different
piece from each 25 tonnes or fraction thereof. When supplied in the
quenched and tempered condition, a set of impact tests is to be made
on each length as heat treated. Test specimens from the quenched and
tempered plates are to have their axes transverse to the main rolling
direction.
3.5.6 For plates
and wide flats in the EH and FH grades supplied in the normalised
or thermomechanically controlled conditions, one set of impact tests
is to be made on each piece. For plates supplied in the quenched and
tempered condition a set of impact tests is to be made on each length
as heat treated. Test specimens from the quenched and tempered plates
are to have their axes transverse to the main rolling direction.
3.5.7 The brittle crack arrest properties specified in Ch 3, 3.5 Mechanical tests and brittle crack arrest property tests 3.5.8 are to be evaluated for the products in
accordance with the procedure approved by LR during the works approval stage. Test
specimens are to be taken from each piece (the rolled product from a single slab or
ingot if this is rolled directly into plates).
3.5.8 For sections
and bars in the EH and FH grades supplied in the normalised or thermomechanically
controlled conditions, one set of impact tests is to be made on the
thickest piece in a batch not exceeding 25 tonnes. For sections supplied
in the as-rolled or normalising rolled conditions the batch size is
not to exceed 15 tonnes.
Table 3.3.7 Mechanical properties for
acceptance of higher strength steel (see Note 1)
Grades
(see Note 3)
|
Yield Stress
N/mm2 min.
|
Tensile Strength
N/mm2
|
Elongation on
(see Note 2)
|
Charpy V-notch impact tests (see Notes 3, 4,
5 and 6)
|
Average energy
J minimum
|
t ≤ 50 mm
|
50 < t ≤ 70 mm
|
70 < t ≤ 100 mm
|
Longitudinal
|
Transverse
|
Longitudinal
|
Transverse
|
Longitudinal
|
Transverse
|
AH27S
DH 27S
EH 27S
FH
27S
|
265
|
400 -
530
|
22
|
27
|
20
|
34
|
24
|
41
|
27
|
AH32
DH32
EH32
FH32
|
315
|
440 -
570
|
22
|
31
|
22
|
38
|
26
|
46
|
31
|
AH36
DH36
EH36
FH36
|
355
|
490 -
630
|
21
|
34
|
24
|
41
|
27
|
50
|
34
|
AH40
DH40
EH40
FH40
|
390
|
510 -
650
|
20
|
39
|
26
|
46
|
31
|
55
|
37
|
EH47
|
460
|
570 -
720
|
17
|
(Note 6)
|
Impact tests are to be made on the various grades at
the following temperatures:
- AH grades 0°C
- DH grades -20°C
- EH grades -40°C
- FH grades -60°C
|
Note 1. The
requirements for products thicker than those detailed in the table are
subject to agreement, see
Ch 3, 3.1 Scope 3.1.5.
|
|
Note 3. Subject to
special approval by LR, the minimum tensile strength may be reduced to
470 N/mm2 , for grades AH36, DH36, EH36 and FH36, in the TM
condition when micro-alloying elements Nb, Ti or V are used singly and
not in combination and provided the yield to tensile strength ratio does
not exceed 0,89. For plates with a thickness ≤12 mm, the yield to tensile
strength ratio is to be specially considered.
|
|
Note 5. For steel of
H47 strength grade, the yield to tensile strength ratio is not to exceed
0,94.
|
Note 6. The Charpy
V-notch impact energy for EH47 in the longitudinal direction are as the
following:
50 < t ≤ 70 mm 53J
70 < t ≤ 85 mm 64J
85 < t ≤ 100 mm 75J
|
Table 3.3.8 Mechanical properties for acceptance of brittle crack arrest steel
Grade
|
Yield
Strength
(N/mm2)
min.
|
Tensile
Strength
(N/mm2)
|
Elongation
(%) min.
|
Impact test (J) min.
(Longitudinal)
|
Test
Temp
(oC)
|
50 < t ≤ 70
mm
|
70 < t ≤
85
mm
|
85 < t ≤
100
mm
|
EH36-BCA1
|
355
|
490-630
|
21
|
-40
|
41
|
50
|
50
|
EH40-BCA1
EH40-BCA2
|
390
|
510-650
|
20
|
46
|
55
|
55
|
EH47-BCA1
EH47-BCA2(Note 1)
|
460
|
570-720
|
17
|
53
|
64
|
75
|
Note 1: For EH47-BCA1 and BCA2 grades, the yield to tensile strength ratio
is not to exceed 0,94.
|
Table 3.3.9 Requirement of brittle crack
arrest properties for brittle crack arrest steels (Note 1)
Grade
|
Thickness (mm)
|
Crack Arrest Temperature
CAT (oC) (See Note 2)
|
EH36-BCA1
EH40-BCA1
EH47-BCA1
(See
Note 1)
|
50 < t ≤ 100
|
-10 or below
|
EH40-BCA2
EH47-BCA2
|
80 < t ≤ 100
|
CAT corresponding to
Kca=8,000 N/mm3/2 to be validated and
approved by LR during manufacturer approval stage
|
1. Brittle crack arrest
steels are defined as steel plate with tested brittle crack arrest
properties expressed as Crack Arrest Temperature (CAT) or crack arrest
toughness Kca. The crack arrest properties of the
material are to be measured during the works approval stage and during
the production test for batch release purpose.
To
demonstrate the crack arrest properties for batch release purpose,
validated small scale tests can be used. E.g. manufacturer can
validate the relationship between CAT and the Nil Ductility
Temperature or other properties by tests during the works approval
stage to establish the correlation formula similar to the one below,
or a version specified by the manufacturer which is validated by
testing:
where
CAT |
= |
crack arrest temperature in oC |
NDTT |
= |
nil ductility test temperature in
oC |
σ |
= |
2/3 of the minimum specified yield strength in
N/mm2 |
B |
= |
thickness of the plate in mm |
The crack arrest test specimens are to be
taken from each piece (the rolled product from a single slab or ingot
if this is rolled directly into plates.
Note 2. As an alternative to
crack arrest temperature (CAT), crack arrest properties may be
demonstrated by large scale ESSO tests for BCA1 grades
Kca≥6000 N/mm3/2 at -10°C and BCA2 grade
Kca ≥ 8000 N/mm3/2 at -10°C.
|
3.6 Identification of materials
3.7 Certification of materials
3.7.1 At least two copies of each test certificate are to be provided. They are to
be of the type and give the information detailed in Ch 3, 1.13 Certification of materials and,
additionally, are to state the specified maximum carbon equivalent. As a minimum, the
chemical composition is to include the contents of any grain refining elements used and
of the residual elements.
3.7.2 For steels
which have been specially approved, the agreed identification mark,
the specified minimum yield stress and, if applicable, the contents
of alloying elements are additionally to be stated on the test certificate
or shipping statement.
|