Section 3 Higher strength steels for ship and other structural applications

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.

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.

3.2.1 All the grades of steel are to be in the killed and fine grain treated condition.

3.3.2 The carbon equivalent is to be calculated from the ladle analysis using the formula given below and is not to exceed the maximum value agreed between the fabricator and the steelmaker when the steel is ordered.

For TM steels, the agreed carbon equivalent is not to exceed the values given in Table 3.3.3 Carbon equivalent requirements for higher strength steels up to 100 mm in thickness when supplied in the TM condition. For EH47 brittle crack arrest grade steels, the maximum carbon equivariant value is given in Table 3.3.4 Chemical composition for brittle crack arrest steels.

3.3.3 The cold cracking susceptibility, P_cm, may be used instead of the carbon equivalent for evaluating weldability, in which case the following formula is to be used for calculating the P_cm from the ladle analysis:

The maximum allowable P_cm is to be agreed with LR and is to be included in the manufacturing specification and reported on the certificate. For EH47 non brittle crack arrest steel, the maximum P_cm is given in Table 3.3.3 Carbon equivalent requirements for higher strength steels up to 100 mm in thickness when supplied in the TM condition; EH47 brittle crack arrest grade steels, the maximum P_cm value is given in Table 3.3.4 Chemical composition for brittle crack arrest steels.

3.3.4 Small deviations in chemical composition from that given in Table 3.3.2 Chemical composition for higher strength steels for plates exceeding 50 mm in thickness in Grades EH36, EH40, FH36 and FH40 may be approved provided that these deviations are documented and approved in advance.

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.

3.4.1 All materials are to be supplied in a condition complying with the requirements given in Table 3.3.5 Conditions of supply for plates and wide flats or Table 3.3.6 Conditions of supply for sections and bars. Where alternative conditions are permitted, these are at the option of the steelmaker, unless otherwise expressly stated in the order for the material.

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.

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 2. For full thickness tensile test specimens with a width of 25 mm and a gauge length of 200 mm, see Figure 2.2.4 Test specimen dimensions for plates, strip and sections - II in Ch 2 Testing Procedures for Metallic Materials, the minimum elongation is to be:
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 4. See Ch 3, 1.9 Test material and mechanical tests 1.9.11
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 3.3.9 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.

3.5.9 Where standard subsidiary impact specimens are necessary, see Ch 2, 2.3 Procedure for testing at ambient temperature 2.3.4.

3.6.1 The particulars detailed in Ch 3, 1.12 Identification of materials are to be marked on all materials which have been accepted and, for ease of recognition, are to be encircled or otherwise marked with paint. Where a number of light products are bundled, the bundle is to be identified in accordance with Ch 3, 1.12 Identification of materials 1.12.2.

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.

3.7.3 The steelmaker is to provide the Surveyor with a written declaration as detailed in Ch 3, 1.13 Certification of materials 1.13.2.