EH36

Higher-strength, fine-grain weldable hull structural steel · IACS UR W11 Rev.9, Normal and higher strength hull structural steels · Applicable rules of the vessel's classification society · ASTM A131/A131M-19 when explicitly invoked by the purchase specification

EH36 is the common designation for IACS E36, a class-approved higher-strength hull steel with a minimum yield strength of 355 MPa and mandatory Charpy V-notch toughness at −40 °C. Its identity depends not only on chemistry and tensile properties, but also on approved manufacture, delivery condition, product thickness, impact testing, traceability and certification by the applicable classification society. It should not be purchased or substituted as a generic S355-type structural plate.

355 MPa minimum yield; 490–630 MPa tensile strengthStrength level · IACS UR W11 requirements for E36 products within its applicable thickness range.
Charpy V-notch tested at −40 °CToughness grade · The letter E identifies the impact-test temperature; required energy increases with product thickness.
Plate and wide flat ≤100 mm; sections and bars ≤50 mmStandard thickness scope · Greater thickness requires case-specific class consideration; IACS Recommendation 197 provides guidance for plate and wide flat above 100 mm through 200 mm.
Normalized or TMCPRequired plate condition · For E36 plate and wide flat through 100 mm under UR W11 Rev.9; ordinary as-rolled plate is not the standard delivery route.
Class-approved steelworks and process requiredManufacturing status · A chemistry-and-mechanics match without the required approval, survey and certification is not class-certified EH36.
UR W11 Rev.9 remains current on October 1, 2026Current IACS revision context · UR W11 Rev.10 is scheduled to enter into force on January 1, 2027, principally harmonizing high-heat-input welding provisions.

Overview

Designation system: IACS/classification-society hull structural steel designation
Product forms: Hot-rolled plate, Wide flat, Structural sections, Bars
Condition: Normalized (N), Thermo-mechanically rolled/controlled processed (TM/TMCP), As-rolled or controlled-rolled sections only by special classification-society approval
Density: 7850 kg/m³ (Representative engineering density for carbon-manganese structural steel; not a grade acceptance requirement of IACS UR W11.)

What the designation means

EH36 is normally written with H between the toughness letter and strength number. In the underlying IACS system the unified grade is E36, and IACS permits the H indicating higher strength to be placed before or after the basic grade mark. The number 36 identifies the nominal 355 MPa yield-strength level historically associated with 36 kgf/mm²; it is not a carbon content or plate thickness. The letter E identifies the −40 °C Charpy V-notch test temperature.

EH36 is a certification-based marine grade rather than merely a chemical composition. Compliance includes manufacture at an approved works, an approved process route, specified deoxidation and grain refinement, mechanical testing, product identification, survey and documentation. Individual societies may use marks such as an ABS, DNV, LR, BV, ClassNK or other class prefix while implementing the IACS minimum requirements, and may impose additional project or rule requirements.

Governing framework and applicability

Documents and their roles

Document	Practical role
IACS UR W11	Minimum unified requirements for manufacture, chemistry, delivery condition, mechanical properties, testing, marking and certification of normal- and higher-strength hull steels.
Classification-society rules	The contractual certification basis. They implement UR W11 and may contain additional requirements, approved-manufacturer restrictions, survey arrangements or application rules.
IACS UR W2	Mechanical test specimen and test-method requirements referenced by UR W11.
IACS UR W13	Thickness tolerances for classed steel plates and wide flats.
IACS UR W14	Additional requirements for Z25 or Z35 through-thickness properties when specified.
IACS UR W17 and W28	Approval of welding consumables and qualification of welding procedures for hull structural steels.
ASTM A131/A131M	A parallel ship-structural-steel product specification containing EH36. ASTM compliance alone does not establish approval or certification by the vessel's class society.

IACS Unified Requirements are minimum requirements incorporated into member-society rules. The purchase order, approved drawings and class rules—not the shorthand grade name alone—determine the governing acceptance basis.

Chemical and metallurgical definition

IACS UR W11 Rev.9 ladle-analysis limits for E36

Element	Requirement, mass %	Qualification
C	≤0.18	For A, D and E higher-strength grades; TMCP chemistry may be varied or further restricted with class approval.
Mn	0.90–1.60	Minimum may be reduced to 0.70% at thickness ≤12.5 mm.
Si	≤0.50	Maximum.
P	≤0.035	Maximum.
S	≤0.035	Maximum.
Al, acid soluble	≥0.015	Total Al ≥0.020% may be determined instead.
Nb	0.02–0.05 when used singly	Nb, V and Ti total is limited to 0.12%.
V	0.05–0.10 when used singly	Specified individual minimum does not apply when grain refiners are used in combination.
Ti	≤0.02	Included in the combined Nb+V+Ti limit.
Cu	≤0.35	Maximum.
Cr	≤0.20	Maximum.
Ni	≤0.40	Maximum.
Mo	≤0.08	Maximum.

The steel must be killed and fine-grain treated. Aluminium, niobium, vanadium or another approved grain-refining system may be used singly or in combination. Consequently, a certificate showing chemistry within the broad limits is not sufficient by itself: the actual approved manufacturing recipe, rolling schedule and delivery condition are important to strength, toughness and weldability.

IIW carbon equivalent used by UR W11

Ceq = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

All terms are mass percent. For TMCP E36, Ceq is limited to 0.38% at t ≤50 mm and 0.40% at 50<t≤100 mm unless the classification society accepts Pcm as the weldability control.

Cold-cracking susceptibility parameter

Pcm = C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B

Pcm may be used instead of Ceq at the classification society's discretion. The acceptable value must then be defined by the applicable approval or project requirements.

Delivery condition and product-form limits

Standard UR W11 Rev.9 supply routes for E36

Product or thickness	Permitted condition	Practical significance
Plate and wide flat, t ≤50 mm	Normalized or TMCP	Either route may meet the same grade requirements, but their response to subsequent heating can differ.
Plate and wide flat, 50<t≤100 mm	Normalized or TMCP	Impact-energy requirements rise with thickness; TMCP Ceq limit also changes above 50 mm.
Sections, within the standard ≤50 mm scope	Normally normalized or TMCP	As-rolled or controlled-rolled E36 sections may be accepted only under special class approval with increased impact-test controls.
Products above the UR W11 primary scope	Special consideration	Do not extrapolate standard requirements. Plate and wide flat above 100 mm through 200 mm may be addressed using IACS Recommendation 197 and society-specific approval.

Normalized EH36 and TMCP EH36 are the same strength/toughness grade but are not processing-identical products. The delivery condition must be retained on certificates, material-control records and welding or forming documentation.

Mechanical properties and toughness

Tensile requirements

Property	UR W11 requirement	Test qualification
Yield strength, ReH or Rp0.2	≥355 MPa	The upper yield stress or, when it cannot be determined, 0.2% proof stress is used.
Tensile strength, Rm	490–630 MPa	Applies to the E36 strength level within the UR W11 product scope.
Elongation, A5	≥21%	Proportional specimen with gauge length 5.65√S0.
Elongation on 25 mm × 200 mm full-thickness flat specimen	13–21% minimum	Thickness-dependent alternative values apply from ≤5 mm through 50 mm; this is not interchangeable with the proportional A5 value.

Charpy V-notch requirements for E36 at −40 °C

Nominal thickness t	Longitudinal average minimum	Transverse average minimum
t ≤50 mm	34 J	24 J
50<t≤70 mm	41 J	27 J
70<t≤100 mm	50 J	34 J

Values apply to standard 10 mm × 10 mm specimens. Longitudinal testing is usual; transverse results may be required for special applications and must be guaranteed when specified.

A Charpy result is assessed as the average of three specimens. One individual result may fall below the specified average, but not below 70% of that average. For product thickness above 40 mm, impact specimens are taken at the quarter-thickness position. For plate below 10 mm, the society may permit sub-size specimens or waive the test; impact testing is generally not required below 6 mm nominal thickness.

E36 plate supplied normalized or TMCP is impact-tested by piece rather than merely by a broad heat lot. This relatively intensive test frequency is an important part of the grade's assurance and should be preserved when reviewing certificates or considering substitutions.

Welding and thermal processing

EH36 is intended to be weldable, but the grade name does not prescribe a universal preheat, heat-input or interpass-temperature range. These controls must be established by a class-accepted welding procedure using the actual product thickness, delivery condition, Ceq or Pcm, joint restraint, consumable hydrogen level, welding process, ambient conditions and required weld-metal/HAZ toughness.

Fabrication controls that deserve explicit review

Issue	Why it matters for EH36
Consumables	Use consumables approved for the required higher-strength and toughness category under the applicable class rules; matching tensile strength alone is insufficient.
Hydrogen cracking	Control diffusible hydrogen, joint cleanliness, preheat/interpass temperature and restraint in accordance with the qualified WPS.
Heat input	Excessive heat input can coarsen the HAZ and reduce toughness. Steel intended for welding above 50 kJ/cm requires the applicable class/manufacturer approval route under current UR W11 provisions.
TMCP reheating	The microstructure and properties produced by TMCP cannot necessarily be restored by normalizing. Hot forming, stress relief, PWHT or uncontrolled flame heating may reduce strength or toughness.
Cold forming	Forming limits and any requirement for procedure qualification depend on thickness, bend radius, strain, direction and class/yard rules; certificate elongation is not a complete forming qualification.
Repair welding	Plate repair at the mill and structural repair in the yard are controlled activities requiring approved procedures, inspection and traceability.

IACS specifically cautions that the fatigue strength of a welded joint in higher-strength steel may not exceed that of the corresponding joint in normal-strength steel. EH36 can reduce scantling where rules permit, but it does not automatically improve welded-joint fatigue life.

Certification, testing and traceability

For class use, the steel must come from a works approved for the relevant grade, product form, thickness range and delivery condition. Acceptance documentation identifies the purchaser's order, hull number where known, cast and piece, steelworks, grade, ladle analysis and delivery condition. TM material may also carry a TM suffix when required by the society.

Minimum certificate review points

Check	What should agree with the order and approved drawings
Certification authority	The specified classification society and required survey endorsement.
Grade identity	EH36/E36, including any TM, Z-quality, corrosion-resistant, BCA or high-heat-input notation.
Manufacturer approval	Steelworks, rolling mill, product form, maximum thickness and delivery condition within the society's approval scope.
Piece traceability	Heat/cast and piece numbers matching product markings and material-control records.
Chemistry	Required ladle analysis, declared grain-refining additions and Ceq/Pcm where applicable.
Mechanical tests	Tensile properties and −40 °C Charpy results with thickness, specimen orientation and any sub-size qualification.
Dimensions and tolerances	Ordered thickness and applicable UR W13 or agreed dimensional standard.
Additional inspection	Specified ultrasonic testing, through-thickness properties, surface class and repair status.

Specifying and purchasing EH36

A technically complete order should identify the governing classification society and rule edition, grade, product form, dimensions, delivery condition, certification level and approved drawing or hull reference. It should also state any requirements not inherent in ordinary EH36: transverse Charpy testing, Z25/Z35 properties, ultrasonic acceptance level, surface condition, dimensional tolerances, corrosion-resistant designation, brittle-crack-arrest properties, high-heat-input welding approval, maximum Ceq/Pcm, special forming requirements or restrictions on weld repair.

“EH36 plate with certificate” is not a complete procurement description. Confirm that the certificate is from the required class society, the mill approval covers the actual thickness and condition, and every piece remains traceable after cutting and fabrication.

Use and substitution boundaries

EH36 is commonly used in highly stressed hull members and marine structures where the design requires the 355 MPa strength level together with E-grade low-temperature toughness. The structural application and required material grade are determined by the vessel's class rules, design temperature, member category, thickness and approved drawings; the −40 °C Charpy test temperature is not by itself a universal minimum service-temperature rating.

Substitution must compare the complete specification, not only yield strength. Relevant differences include toughness temperature and energy, product thickness, delivery condition, chemistry and weldability controls, impact-test orientation and frequency, manufacturer approval, certification, through-thickness properties and any project-specific supplementary requirements. General structural grades such as S355 variants are therefore not automatically interchangeable with class-certified EH36.

Sources

IACS UR W11 Rev.9 — Normal and higher strength hull structural steelsInternational Association of Classification Societies
IACS UR W11 current and future revision statusInternational Association of Classification Societies
IACS Unified Requirements — explanation and implementation frameworkInternational Association of Classification Societies
IACS UR W13 Rev.7 — Thickness tolerances of steel plates and wide flatsInternational Association of Classification Societies
IACS UR W17 Rev.6 — Approval of consumables for welding normal and higher strength hull structural steelsInternational Association of Classification Societies
IACS UR W28 — Welding procedure qualification tests of steels for hull construction and marine structuresInternational Association of Classification Societies
IACS UR W31 Rev.3 — YP47 steels and brittle crack arrest steelsInternational Association of Classification Societies
IACS Recommendation 197 — Hull structural steels above 100 mm and up to 200 mmInternational Association of Classification Societies
ASTM A131/A131M-19 — Standard Specification for Structural Steel for ShipsASTM International

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E36	Underlying IACS unified grade mark	EH36 is the common higher-strength notation; IACS permits H before or after the basic grade mark.
AH36	Same 355 MPa strength level, lower toughness grade	Charpy test temperature is 0 °C rather than −40 °C.
DH36	Same 355 MPa strength level, intermediate toughness grade	Charpy test temperature is −20 °C.
FH36	Same 355 MPa strength level, higher toughness grade	Charpy test temperature is −60 °C and chemistry/delivery requirements are more restrictive.
ASTM A131/A131M Grade EH36	Corresponding ASTM ship-structural-steel designation	Often technically aligned, but ASTM compliance does not replace classification-society approval and certification where class material is required.
EH36Z25 / EH36Z35	EH36 with specified through-thickness ductility	Additional IACS UR W14 requirements apply; ordinary EH36 does not guarantee resistance to lamellar tearing.
EH36-BCA	EH36 with approved brittle-crack-arrest properties	A distinct enhanced designation governed by IACS UR W31; it must not be inferred from ordinary EH36 Charpy compliance.