When you order ship steel plate to ABS classification, five mechanical properties decide whether the material is accepted: yield strength (ReH), tensile strength (Rm), elongation at fracture, Charpy V-notch impact energy, and bend formability. These requirements are defined in the ABS Rules for Building and Classing Steel Vessels, Part 2 (Rule Requirements for Materials and Welding), with test procedures referenced to ASTM A370 / A131.
This guide summarises the typical minimum values for the common grades, points out where thickness changes the number, and explains how to confirm the binding values on the approved class drawings and the Mill Test Certificate (MTC) of each heat. Values below are reference data for pre-selection; the figures that govern acceptance are those on the approved drawings and the MTC.
Key Takeaways
- Governing document: ABS Rules for Building and Classing Steel Vessels, Part 2; test methods per ASTM A370 / A131, elongation per ASTM E8/E8M.
- Grade A: yield ≥235 MPa, tensile 400–520 MPa, elongation ≥22 % (50 mm gauge).
- AH36: yield ≥355 MPa, tensile 490–620 MPa; EH40: yield ≥390 MPa.
- Charpy: Grade D ≥27 J at −20 °C; EH36 ≥34 J at −40 °C; LNG-service 9 % Ni steel ≈60 J at −196 °C (order-specific).
- Bend: 180° bend, mandrel 2×t for Grade A, 3×t for high-strength grades (AH32 and above).
- CEV: graded by plate thickness in the ABS Rules - there is no single universal limit for high-strength grades.
- Binding documents: approved class drawings + Mill Test Certificate (MTC); cross-check the toughness letter (A/D/E/F) before substituting equivalent grades.
1. Yield Strength (ReH)
Yield strength is the stress at which the material starts to deform plastically. ABS sets grade-dependent minimum values (reference values, subject to the thickness tables in ABS Rules Pt.2):
- Grade A: ≥235 MPa - normal-strength grade for general hull plating.
- AH36: ≥355 MPa - high-strength grade for hull structure and deck.
- EH40: ≥390 MPa - high-strength grade specified for ice-class and low-temperature service.
Tensile testing is carried out per ASTM A370 on specimens cut transversely to the rolling direction. Where discontinuous yielding occurs (typical of thermo-mechanically rolled, TMCP, plates), yield is determined by the 0.2 % offset method. For thick high-strength plates (e.g., FH460-class),
ABS may require through-thickness (Z-direction) testing - ordered as Z25/Z35 options - to control lamellar tearing risk in highly restrained joints.
2. Tensile Strength (Rm)
Tensile strength defines the maximum stress the plate withstands before fracture. ABS specifies ranges rather than single minimums, balancing strength against ductility and weldability:
- Grade A: 400–520 MPa.
- EH36 (36-class family): 490–620 MPa.
Weldability is protected by carbon equivalent (CEV) limits that ABS grades by plate thickness for high-strength grades. For the AH36 class, the cap is about ≤0.38 % at t ≤ 50 mm and relaxes toward roughly 0.40–0.43 % at greater thicknesses; the exact figures are the Rules tables for each grade/thickness combination - always verify against the Rules edition and the MTC, not against a single published number. For quenched and tempered (Q&T) grades (e.g., EH47-class), tensile properties must stay uniform across the thickness, which is verified by multi-layer testing.
3. Elongation at Fracture (%)
Elongation measures ductility - the ability to absorb dynamic loads such as wave slamming and collision impacts without cracking.
- Grade A: ≥22 % (50 mm gauge length).
- Higher-strength grades: minimum elongation steps down with grade and thickness per ABS Rules Pt.2 (the 36-class is typically ≥21 % on a 50 mm gauge - reference figure; confirm the exact value against the Rules table for your thickness and on the MTC).
Testing follows ASTM E8/E8M, and results are sensitive to specimen geometry (proportional vs. non-proportional). Fine-grain microalloying (Al-Nb-V) improves both elongation and impact toughness, which is why micro-alloyed TMCP plates are the norm for high-strength hull steel.
4. Charpy V-Notch Impact Toughness
ABS mandates minimum absorbed energy at defined service temperatures to prevent brittle fracture:
- Grade A: Charpy test normally not required (ambient-temperature service; check the Rules for thickness-dependent exceptions).
- Grade D: ≥27 J at −20 °C (typical for thicker plates).
- EH36: ≥34 J at −40 °C - the grade family specified for polar and low-temperature routes.
- 9 % Ni steel (LNG carriers): markedly stricter low-temperature criteria, on the order of ≥60 J at −196 °C - order-specific, per the Rules.
Testing follows ASTM A370 (V-notch, transverse specimens, typically three specimens per batch). For plates above about 50 mm, ABS may require sub-surface Charpy locations to confirm through-thickness homogeneity. Heat-treatment controls support toughness - for example, normalizing is common for Grade D thick plate - and delivery condition (AR / N / TMCP / QT) must be stated on the order.
5. Bend Test Performance
Bend tests verify formability and surface integrity of the plate:
- Grade A: 180° bend with mandrel diameter = 2× plate thickness (t).
- High-strength grades (AH32 and above): 180° bend with mandrel diameter = 3×t.
Cracks or delamination visible after bending disqualify the plate. ABS also uses guided-bend tests for weld-procedure qualification. For TMCP plates, bendability depends on controlled cooling rates that limit excessive hardness; special grades (e.g., corrosion-resistant CR steels) may be subject to additional bend requirements per the approved specification.
6. Grade-by-Grade Mechanical Property Matrix
The table below consolidates the reference values discussed above. Cells marked "(ref.)" are industry-standard reference figures consistent with the harmonised IACS grade requirements; the binding values are those in ABS Rules Pt.2 for the ordered thickness and on the Mill Test Certificate (MTC).
| Grade | Yield ReH, min (MPa) | Tensile Rm (MPa) | Elongation, min (50 mm gauge) | Charpy V-notch (transverse) | Bend 180° | Typical use / notes |
|---|---|---|---|---|---|---|
| Grade A | ≥235 | 400–520 | ≥22 % | Normally not required (ambient service) | Mandrel 2×t | Normal-strength hull plating |
| Grade D | ≥235 (normal-strength family) | 400–520 (normal-strength family) | ≥22 % (ref.) | ≥27 J at −20 °C | Mandrel 2×t | Normal strength with improved notch toughness |
| AH36 | ≥355 | 490–620 | ≥21 % (ref.) | ≥34 J at 0 °C (ref.) | Mandrel 3×t | High-strength hull / deck |
| DH36 | ≥355 | 490–620 | ≥21 % (ref.) | ≥34 J at −20 °C (ref.) | Mandrel 3×t | High strength, moderate low-temperature service |
| EH36 | ≥355 | 490–620 | ≥21 % (ref.) | ≥34 J at −40 °C | Mandrel 3×t | Polar routes / low-temperature hull structure |
| EH40 | ≥390 | See ABS Rules Pt.2 table for thickness range | See ABS Rules Pt.2 table | See ABS Rules Pt.2 table (toughness grade E = −40 °C) | Mandrel 3×t | Ice-class / very high-strength low-temperature service |
7. Equivalent Grades Across Classification Societies
Hull structural steel designations are harmonised across IACS member class societies, so the letters A/D/E/F and the strength number (32/36/40…) mean the same thing everywhere - provided you compare the same toughness letter.
| Toughness class | ABS | LR | DNV | BV / CCS / KR / RINA | NK (ClassNK) |
|---|---|---|---|---|---|
| 0 °C (Charpy at 0 °C) | AH36 | AH36 | A36 | AH36 | KA36 |
| −20 °C | DH36 | DH36 | D36 | DH36 | KD36 |
| −40 °C | EH36 | EH36 | E36 | EH36 | KE36 |
Watch the toughness letter. A common sourcing shortcut maps "ABS AH36" to "DNV E36" - that is not a like-for-like substitution: E36 is the −40 °C grade and matches ABS EH36, while the 0 °C counterpart of ABS AH36 is DNV A36. Equivalence above is approximate and follows the harmonised IACS grade naming (see IACS Rec. 47); actual substitution on an order requires class approval and confirmation on the MTC. Former GL (Germanischer Lloyd) grades are now issued under DNV designations following the 2013 merger.
8. Test Methods and Standards
- Tension, Charpy, and bend testing: performed per ASTM A370 (Standard Test Methods and Definitions for Mechanical Testing of Steel Products), as referenced by the ABS Rules.
- Elongation measurement: per ASTM E8/E8M (Tension Testing of Metallic Materials); ABS elongations are usually quoted on a 50 mm gauge length (or proportional gauge, 5.65√S₀, as stated in the Rules).
- Plate specification basis: ASTM A131/A131M (Standard Specification for Structural Steel for Ships) or the equivalent approved mill specification; grade letters and energy levels follow IACS Rec. 47.
- Sampling: typically one tension specimen and one bend specimen per heat/batch, plus a set of three Charpy specimens where impact testing applies; sub-surface Charpy locations for thick plates; Z-direction testing as a separate order option (Z25/Z35) for thick high-strength plates.
9. Procurement Checklist - How to Specify ABS Plate
- State grade + toughness letter + thickness. The letter (A/D/E/F) sets the Charpy test temperature; the number sets the yield class. "ABS AH36 × 25 mm" is not the same requirement as "ABS EH36 × 25 mm".
- Request the MTC with every offer. The Mill Test Certificate must show the chemical composition (including CEV) and the mechanical results for each heat, with the ABS-approved values for the ordered thickness.
- Fix the delivery condition. AR (as-rolled), N (normalized), TMCP, or QT - the condition drives impact toughness and bend behaviour, and it must match the approved drawing.
- Confirm class survey. ABS surveyor witnessing and class certificates are usually mandatory for hull steel; third-party inspection (e.g., SGS, Bureau Veritas) can be added if your contract requires it.
- For t > 50 mm high-strength plates, ask whether sub-surface Charpy locations and through-thickness (Z25/Z35) properties apply to your design - both affect price and lead time.
- Check CEV against the Rules table for your thickness, not against a single number quoted from memory.
- Confirm the bend requirement on the order (2×t for Grade A, 3×t for high-strength) and the Charpy sampling frequency (typically three specimens per batch).
10. FAQ
Q1. Which ABS rule document governs the mechanical properties of ship steel plates?
The ABS Rules for Building and Classing Steel Vessels, Part 2 (Rule Requirements for Materials and Welding), sets the mechanical property requirements for hull structural steel. Test procedures are referenced to ASTM A370 / A131. Always confirm grade- and thickness-specific values against the current Rules edition and the approved class drawings.
Q2. Does ABS require a Charpy V-notch impact test for every ship plate grade?
No. Grade A is normally supplied without a Charpy requirement for ambient service (subject to thickness limits in the Rules). Notch-toughness grades carry defined energy/temperature requirements: Grade D ≥27 J at −20 °C, EH36 ≥34 J at −40 °C, and LNG-service 9 % Ni steel on the order of ≥60 J at −196 °C (order-specific).
Q3. What is the ABS carbon equivalent (CEV) limit for high-strength grades like AH36?
There is no single universal number. ABS sets CEV limits by plate thickness: for the AH36 class the cap is about ≤0.38 % at t ≤ 50 mm and relaxes toward roughly 0.40–0.43 % as thickness increases. The binding values are the Rules tables and the MTC for each heat.
Q4. Is ABS AH36 the same grade as DNV E36?
No. The toughness letter matters: ABS AH36 is a 0 °C grade and matches DNV A36, not E36. DNV E36 is the −40 °C grade and corresponds to ABS EH36. Grade names are harmonised under IACS recommendations, but never substitute across toughness letters without class approval and MTC confirmation.
Q5. What documents prove that a plate meets ABS mechanical requirements?
The binding documents are the approved class drawings and the Mill Test Certificate (MTC), which states the chemical composition (including CEV) and mechanical test results for each heat. ABS surveyor certificates and optional third-party inspection reports provide additional assurance.
Request a Quote for ABS-Certified Ship Steel Plate
Send us your specification and we will reply with the grade recommendation, thickness/width options, delivery condition, and MTC documentation:
Grade and toughness letter (e.g., ABS AH36 / DH36 / EH36, or EH40), thickness × width × length, quantity.
Classification requirement (ABS surveyor witnessing, class certificate), delivery condition (AR / N / TMCP / QT), destination port.
Optional: through-thickness (Z25/Z35) or third-party inspection request.
Email: alloy@gneesteelgroup.com
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This guide was prepared by the technical team of Gnee Steel (Tianjin) Co., Ltd, a supplier of shipbuilding and alloy steel plates (chinaalloyplates.com).
Contact: alloy@gneesteelgroup.com · WhatsApp/WeChat: +86-15824687445
Address: No.4-1114, Beichen Building, Beicang Town, Beichen District, Tianjin, China
Disclaimer: mechanical values in this article are reference data for pre-selection. The figures that govern acceptance of an order are those on the approved class drawings and the Mill Test Certificate (MTC) of each heat. Always verify against the current edition of the ABS Rules and the applicable standard. No fabrication of case data, inventory, or lead times is implied; delivery lead time is typically 30–45 days subject to mill schedule - confirm at quotation.
