AH36 vs DH36 vs EH36: Which Grade Is Best for Your Shipbuilding Project?

Grade	Yield Strength	Tensile Strength	Impact Test Temp	Typical Use
AH36	≥ 355 MPa	490 to 620 MPa	0°C	Mild and moderate climates
DH36	≥ 355 MPa	490 to 620 MPa	-20°C	Cold regions and heavy-duty structures
EH36	≥ 355 MPa	490 to 620 MPa	-40°C	Arctic regions, ice-class vessels

Although all three grades deliver similar strength, EH36 offers the highest toughness performance, followed by DH36, then AH36.

Chemical Composition Similarities and Differences

Chemical composition influences weldability, corrosion resistance, and toughness. All three grades generally include:

• Controlled carbon content

• Manganese for strength

• Silicon for stability

• Micro-alloy elements such as Nb, Ti, or V for grain refinement

However, EH36 and DH36 tend to have tighter controls and may use additional alloying to meet low-temperature impact standards.

Why Impact Toughness Matters in Marine Construction

Ships and offshore structures experience:

• Wave impact

• Temperature fluctuations

• Hull deformation

• Vibration

• Dynamic loading

Toughness at low temperatures ensures the steel does not become brittle. This is part of why classification societies strictly regulate AH36, DH36, and EH36 requirements in key structural zones.

Applications of AH36, DH36, and EH36 Steel Plates

AH36 Applications

AH36 is widely used in:

• Deck structures

• Superstructures

• Light to moderate climate vessels

• Cargo holds

• Ship sections above waterline

It provides excellent weldability and strength, making it suitable for general shipbuilding.

DH36 Applications

DH36 is ideal for:

• Vessels operating in colder regions

• Structural components requiring high toughness

• Upper decks and bulkheads in mid-latitude climates

• Offshore support vessels

• Heavily loaded foundations

DH36 is often specified in classification society drawings for critical zones.

EH36 Applications

EH36 is chosen for the most demanding marine environments:

• Icebreakers

• Arctic and polar class ships

• Offshore platforms in freezing climates

• Dynamic positioning vessels

• FPSO and subsea systems

• High-impact structural areas near the bow

EH36 provides superior performance under extreme cold and high stress.

AH36 vs DH36 vs EH36: Which Is Best for Your Project

The best steel grade depends on operating environment, structural requirements, and classification society rules.

Choose AH36 if

• The vessel operates in mild or warm waters

• Structural parts are not exposed to extreme cold

• Project focuses on cost-effective construction

• The application is non-critical in terms of low-temperature toughness

Choose DH36 if

• The vessel may operate in moderately cold climates

• Components require higher toughness than AH36

• You are constructing mid-latitude or mixed-environment vessels

• Structural loads are higher or located in sensitive areas

Choose EH36 if

• The vessel will operate in Arctic waters

• The project requires extreme low-temperature performance

• You are building ice-class, offshore, or deep-sea vessels

• Classification society drawings specify E-grade material

EH36 provides the maximum safety margin in cold-weather marine engineering.

Classification Society Requirements

All grades must be certified by societies such as:

• ABS

• LR

• DNV

• BV

• CCS

Typical requirements include:

• Chemical analysis

• Tensile tests

• Charpy impact tests

• Ultrasonic testing

• Heat treatment verification

• Traceability and stamping

EH36 receives the most scrutiny because of its demanding low-temperature performance.

Heat Treatment and Processing

Marine-grade plates may be supplied as:

• As-rolled

• Normalized

• Controlled-rolled

• TMCP thermo-mechanically controlled processed

TMCP is widely used for DH36 and EH36 because it enhances strength and toughness while maintaining weldability and reducing the need for thick sections.

Weldability Comparison

All three grades offer good weldability, but EH36 requires more careful control of:

• Heat input

• Preheat conditions

• Interpass temperatures

This is due to tighter alloy composition and higher toughness requirements.

Cost Considerations

In general:

• AH36 is most economical

• DH36 is moderately priced

• EH36 is the most expensive due to enhanced toughness requirements And stricter certification demands

Selecting the correct grade can help optimize project cost without compromising safety.

Common Challenges in Grade Selection

1. Misalignment Between Drawing Requirements and Purchasing

Some drawings require E-grade, but shipyards mistakenly purchase A-grade materials.
Solution: Double-check classification society rules before ordering.

2. Incorrect Substitution

Replacing EH36 with AH36 is not allowed in cold regions.
Solution: Follow toughness classification strictly.

3. Incomplete Documentation

Missing MTC or testing records leads to rejection.
Solution: Purchase from reliable suppliers like sakysteel with full traceability and certification.

4. Lack of Low-Temperature Testing

Some mills skip -20°C or -40°C tests unless specified.
Solution: Ensure impact temperature requirements are clearly stated.

Summary Comparison Table