Metals Used in the Maritime Industry Engineering Properties, Manufacturing Considerations, and Classification-Society Hull Steels
Academic technical reference • 17 August 2026
Abstract
Marine structures and equipment require materials that combine strength, fracture toughness, weldability, corrosion resistance, manufacturability, and predictable behavior under cyclic loading and temperature change. This document summarizes representative engineering properties of metals and alloys commonly encountered in shipbuilding and marine engineering. Values are typical room-temperature reference values rather than universal design allowables; actual properties depend on alloy designation, temper/heat treatment, product form, thickness, test direction, and applicable standard.
1. Scope and engineering use
The principal metallic families considered are carbon/low-alloy steels, stainless steels, marine aluminium alloys, copper and copper alloys, copper–nickel alloys, nickel-based alloys, and titanium alloys. The first table is intended for material screening and manufacturing studies. It does not replace a material certificate, mill test report, approved welding procedure specification, or the governing classification-society rule.
2. Representative properties of metals and alloys used in marine engineering
| Material / alloy family | Typical marine applications | Density kg/m³ | E GPa | Yield strength MPa* | UTS MPa* | Elongation %* | Thermal conductivity W/m·K | CTE 10⁻⁶/K | Melting / solidus °C | Corrosion / manufacturing notes |
|---|---|---|---|---|---|---|---|---|---|---|
| Carbon / low-alloy shipbuilding steel (e.g., Grade A / AH36 families) | Hull plating, stiffeners, decks, frames, bulkheads | 7,850 | 200–210 | 235–355+ | 400–630+ | 20–22 | 45–60 | 11–13 | ≈1,425–1,535 | Excellent weldability when grade/Ceq and procedure are controlled; requires coating/cathodic protection in seawater. |
| Stainless steel 304/304L | Piping, accommodation, tanks, fittings, equipment | 8,000 | 193 | 170–310† | 485–620† | 40+ | ≈16 | 17.2 | ≈1,400–1,450 | Good general corrosion resistance; susceptible to chloride pitting/crevice corrosion. |
| Stainless steel 316/316L | Seawater-adjacent equipment, piping, fittings | 8,000 | 193 | 170–310† | 485–620† | 40+ | ≈16 | 16.0 | ≈1,370–1,400 | Mo improves pitting resistance versus 304; not immune to seawater corrosion. |
| Marine aluminium 5083-H116 | Superstructures, fast craft, hulls, decks | 2,660 | ≈70 | ≈215 | ≈305 | ≈10–12 | ≈117 | ≈23.8 | ≈570–640 | High strength-to-weight ratio and good seawater resistance; heat-affected zones in welded structures lose temper strength. |
| Marine aluminium 5086-H116 | Hulls, superstructures, tanks, piping | 2,660 | ≈71 | ≈195 | ≈290 | ≈10–12 | ≈118 | ≈23.8 | ≈570–640 | Good weldability and seawater resistance; account for weld-zone softening. |
| Copper | Electrical conductors, heat exchangers, fittings | 8,960 | 117 | ≈70–220† | ≈200–250† | 10–45† | ≈390 | 16.5–17 | 1,085 | Very high thermal/electrical conductivity; galvanic compatibility must be managed. |
| Cu–Ni 90/10 (CuNi10Fe1Mn) | Seawater piping, condensers, heat exchangers | ≈8,900 | ≈130 | ≈100–200† | ≈300–350† | ≈20–40† | ≈46 | ≈17.0 | 1,100–1,145 | Excellent seawater resistance and biofouling tolerance; useful for heat-transfer and piping systems. |
| Cu–Ni 70/30 (CuNi30Fe1Mn) | Seawater piping, condensers, desalination systems | ≈8,940 | ≈145 | ≈100–220† | ≈330–400† | ≈20–40† | ≈29–35 | ≈16 | ≈1,175–1,230 | Very good seawater corrosion/erosion resistance; lower thermal conductivity than copper. |
| Nickel alloy 625 | Exhaust systems, seawater hardware, high-temperature/corrosive service | 8,440 | ≈205 | ≈345+ | ≈760+ | ≈30+ | ≈9.8 | ≈12.8 | ≈1,290 | Excellent chloride and high-temperature corrosion resistance; costly and harder to machine. |
| Titanium Grade 2 | Heat exchangers, seawater piping, marine hardware | 4,510 | 105 | ≈275 | ≈345 | ≈20 | ≈16–17 | 8.6 | 1,660–1,670 | Outstanding seawater resistance and high strength-to-mass ratio; galling and machining require care. |
* Representative ranges/values; not certification values. † Strongly dependent on product form and temper.
3. Manufacturing-relevant properties
For shipbuilding and marine equipment, material selection should consider more than tensile strength. Elastic modulus controls elastic deflection and buckling; density affects displacement and weight; thermal conductivity and the coefficient of thermal expansion influence welding, thermal gradients and heat-exchanger design; toughness and impact energy control fracture resistance; corrosion resistance controls coating, cathodic-protection and corrosion-allowance requirements; and weldability governs joint design, preheat/interpass control, consumable selection and post-weld treatment.
- Welding: carbon equivalent, hardenability, hydrogen control, heat input and heat-affected-zone toughness are critical for steels. Aluminium alloys generally experience strength loss in the welded heat-affected zone.
- Forming: ductility, anisotropy, strain hardening and thickness strongly influence cold bending, flanging and roll forming.
- Machining: hardness, thermal conductivity, work hardening and chip formation affect tool life and cutting parameters.
- Joining: galvanic compatibility is particularly important where aluminium, steel, copper alloys and stainless steels are connected in seawater service.
- Thermal design: conductivity and CTE should be considered for heat exchangers, exhaust components, cryogenic systems and welded assemblies.
4. Marine-grade carbon/manganese hull structural steels certified under classification rules
The following grades are conventional classification-society hull structural steel designations. The A/B/D/E suffixes primarily distinguish toughness/impact-test temperature requirements, while the 32/36 strength numbers identify higher yield-strength groups. The table gives the common strength groups requested. Classification requirements can vary with thickness, product form and society rule edition.
| Grade family | Common grades | Classification strength group | Minimum yield MPa | Tensile strength MPa | Minimum elongation % | Charpy impact test temperature* | Typical use / note |
|---|---|---|---|---|---|---|---|
| Ordinary strength | A, B, D, E | Normal strength | 235 | 400–520 | 22 | A +20 °C; B 0 °C; D −20 °C; E −40 °C | General hull plating, decks, frames, bulkheads and stiffeners. |
| High strength | AH32, DH32, EH32 | 32 group | 315 | 440–570 | 22 | AH +0 °C; DH −20 °C; EH −40 °C | Higher-strength hull structure where weight reduction is useful. |
| High strength | AH36, DH36, EH36 | 36 group | 355 | 490–630 | 21 | AH +0 °C; DH −20 °C; EH −40 °C | Very common high-strength shipbuilding grades for hull structures. |
* Impact requirements are simplified summaries; the applicable classification rule specifies specimen orientation, thickness-dependent energy requirements, testing procedure and acceptance criteria.
5. Classification-society context
IACS guidance identifies A, B, D and E as normal-strength hull grades and AH/DH/EH as higher-strength grades, with minimum yield strengths of 235 MPa for ordinary strength, 315 MPa for the 32 group and 355 MPa for the 36 group. ABS rules provide corresponding tensile-property tables; Bureau Veritas and DNV rules use the same fundamental strength groups, subject to their individual requirements. Therefore, a steel should be specified by its complete certified grade, product form, thickness and applicable society rules—not only by a generic designation such as “AH36”.
6. Design and certification cautions
- Do not use the representative property table as a substitute for certified material data.
- For hull structures, verify the current rules of the selected classification society and the vessel's notation.
- Check thickness-dependent yield/tensile requirements and any special requirements for through-thickness properties.
- Verify Charpy impact energy, test temperature, specimen orientation and sampling requirements.
- For welding, use the approved welding procedure and classification-approved consumables; assess carbon equivalent and preheat requirements.
- For aluminium and non-ferrous alloys, verify the exact alloy-temper designation and welded-condition properties.
7. References
- IACS Recommendation No. 47, Shipbuilding and Repair Quality Standard, Rev. 10 (2021), especially Table 4.2 on normal- and higher-strength hull structural steels.
- ABS, Rules for Materials and Welding, Part 2, Materials for Hull Construction, current/recent editions; tensile-property tables for ordinary- and higher-strength hull structural steel.
- Bureau Veritas, Rules for the Classification of Steel Ships / IACS Common Structural Rules; hull steel mechanical-property tables.
- DNV, Rules for Ships, Pt.3 Ch.1, Hull structural design principles; material designations and strength groups.
- Copper Development Association, Copper-Nickel Alloys: Properties, Processing, Applications; physical-property tables for Cu–Ni alloys.
- ASTM A131/A131M, Standard Specification for Structural Steel for Ships (consult the current edition when specifying material).
Source notes
Classification values in Section 4 are supported by IACS Recommendation 47 and published ABS, DNV and Bureau Veritas rule material tables. The Cu–Ni physical-property values are based on Copper Development Association reference data. Representative properties for other material families are engineering reference values and should be checked against the specific alloy standard before design or procurement.
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