DH36 Marine Steel: A Guide for Cold & Harsh Marine Environments

If you’re working on marine projects in cold oceans—like Arctic cargo routes, North Sea offshore platforms, or northern coastal infrastructure—DH36 marine steel is your most reliable material. It’s engineered to excel in low temperatures, resist saltwater corrosion, and handle heavy loads, solving pain points like brittle failure and rapid rust. This guide breaks down its properties, uses, and best practices to help you build durable, safe marine structures.

1. Core Material Properties of DH36 Marine Steel

DH36’s performance is tailored to cold marine conditions, with a composition and property profile optimized for extreme temperatures and saltwater exposure.

1.1 Chemical Composition

DH36 meets strict international standards (e.g., ABS, DNV, LR) with alloy additions that boost low-temperature toughness and corrosion resistance. Typical ranges are:

1.2 Physical Properties

These properties are critical for cold-water marine design—from hull weight calculations to managing thermal expansion in freezing seas:

• Density: 7.85 g/cm³ (consistent with structural steels, simplifying load and buoyancy calculations)
• Melting Point: 1,430 – 1,470°C (compatible with standard marine steel fabrication processes)
• Thermal Conductivity: 44 W/(m·K) at 20°C (ensures even heating during welding, critical for cold-weather shipyard work)
• Thermal Expansion Coefficient: 13.0 × 10⁻⁶/°C (20 – 100°C) | Prevents cracking from extreme temperature swings (e.g., -40°C to 20°C in Arctic summers)
• Electrical Resistivity: 0.18 μΩ·m (low enough for non-electrical components like hulls and bulkheads)

1.3 Mechanical Properties

DH36’s “36” refers to its minimum yield strength (355 MPa)—but its standout feature is cold-temperature performance. Key specs include:

• Tensile Strength: 490 – 620 MPa (handles heavy cargo loads and icy wave impacts)
• Yield Strength: ≥ 355 MPa (meets the “36” rating—supports deepwater offshore platforms in cold seas)
• Hardness: 140 – 170 HB (Brinell, soft enough for forming curved hulls, hard enough to resist ice scratches)
• Impact Toughness: ≥ 34 J at -60°C (the biggest advantage over other marine steels—avoids brittle failure in Arctic winters)
• Ductility: 21 – 24% elongation (allows bending into complex hull shapes without cracking, even in cold temperatures)
• Fatigue Resistance: 220 – 260 MPa (endures repeated wave and ice loads on offshore jackets and ship hulls)
• Fracture Toughness: 80 – 90 MPa·m¹/² (prevents sudden cracking in high-pressure subsea pipelines in freezing waters)

1.4 Other Critical Properties

• Corrosion Resistance in Marine Environments: Very Good | Forms a protective oxide layer; with proper coating, it resists saltwater and ice for 25+ years
• Weldability: Excellent | Low carbon content means no preheating for plates up to 35mm thick (saves time in cold shipyards)
• Formability: Strong | Can be hot rolled, cold rolled, or forged into curved hulls and jacket legs—even in low-temperature workshops
• Toughness: Exceptional | Maintains strength across extreme cold (from -60°C Arctic seas to 30°C temperate waters)

2. Practical Applications of DH36 Marine Steel

DH36 is the top choice for cold-water marine projects—used where low-temperature toughness is non-negotiable. Below are its most common uses with real-world examples.

2.1 Marine Vessels

Shipbuilders rely on DH36 for cold-ocean vessels:

• Ship Hulls: Used for Arctic cargo ships, icebreakers, and fishing vessels (e.g., 中远海运 (COSCO)’s Arctic LNG carriers use DH36 for 80% of hull plates—resist ice impacts and -50°C temperatures)
• Bulkheads: Separates ship compartments (e.g., Russian Arctic supply ships use DH36 bulkheads—withstand flooding pressure in freezing seas)
• Decks: Supports heavy equipment and cargo (e.g., Norwegian offshore supply vessels use DH36 decks—handle 60+ ton drilling machinery and ice accumulation)
• Superstructures: Above-deck command centers (e.g., Canadian Coast Guard icebreakers use DH36 for superstructures—balance strength and weight in icy conditions)

2.2 Offshore Engineering

Offshore projects in cold waters depend on DH36’s fatigue and cold resistance:

• Jackets: Supports Arctic and North Sea offshore platforms (e.g., Shell’s North Sea oil platforms use DH36 jacket legs—endure 12m waves and -20°C winters)
• Risers: Connects seabed wells to platforms (e.g., BP’s Alaskan offshore risers use DH36—resist seawater corrosion and freezing temperatures)
• Subsea Pipelines: Transports oil/gas in cold oceans (e.g., ExxonMobil’s Arctic subsea pipelines use DH36—operate at 1,500m depth and -40°C without cracking)

2.3 Port and Harbor Construction

Cold-climate ports use DH36 for durable infrastructure:

• Quay Walls: Protects port facilities from ice and waves (e.g., St. Petersburg Port in Russia uses DH36 quay walls—resist ice floes and saltwater for 30+ years)
• Dolphins: Guides ships to docks (e.g., Tromsø Port in Norway uses DH36 dolphins—handle ship collisions and freezing temperatures)
• Fenders: Absorbs ship impact (e.g., Anchorage Port in Alaska uses DH36-reinforced fenders—reduce wear from ice and ship dockings)

2.4 Coastal Infrastructure

Cold-coastal projects use DH36 for storm and ice resilience:

• Seawalls: Protects shorelines from Arctic storms (e.g., Nome, Alaska seawalls use DH36—survive ice-driven storm surges)
• Breakwaters: Reduces wave and ice energy (e.g., Reykjavik Harbor in Iceland uses DH36 breakwaters—endure strong tides and ice)
• Jetties: Extends into cold seas for ship access (e.g., Murmansk Port in Russia uses DH36 jetties—operate in frozen Arctic waters)

3. Manufacturing Techniques for DH36 Marine Steel

DH36 requires specialized manufacturing to meet cold-marine standards. Here’s how it’s produced, shaped, and finished.

3.1 Steelmaking Processes

DH36 is made with strict quality control to ensure cold-temperature performance:

• Basic Oxygen Furnace (BOF): The primary method—converts iron ore to steel by blowing oxygen through molten iron. Removes impurities (P, S) and adds high levels of Ni (for cold toughness) to meet DH36 specs. Used for large-scale production (90% of DH36).
• Electric Arc Furnace (EAF): Uses recycled steel scrap—heated with electric arcs to 1,600°C. Alloys like Ni and V are added to adjust composition. Ideal for small batches or custom thicknesses (e.g., 100mm+ plates for Arctic offshore jackets).

3.2 Heat Treatment

Heat treatment optimizes DH36 for cold-water use:

• Normalizing: Heats to 900 – 950°C, cools in air. Improves uniformity and ductility—used for hull plates and decks in cold regions.
• Quenching and Tempering: Heats to 850 – 900°C, quenches in water, then tempers at 520 – 620°C. Boosts strength and cold-temperature impact toughness—used for offshore jackets and Arctic ship hulls.
• Annealing: Heats to 800 – 850°C, cools slowly. Reduces hardness for easier forming—used for curved hull sections in cold workshops.

3.3 Forming Processes

DH36 is shaped to fit cold-marine design needs:

• Hot Rolling: Heats to 1,100 – 1,200°C, rolls into plates (6 – 120mm thick). Used for hulls, jackets, and seawalls—hot forming avoids cracking in cold conditions.
• Cold Rolling: Rolls at room temperature to make thin sheets (1 – 5mm thick). Used for superstructure panels—only for parts not exposed to extreme cold.
• Forging: Hammers or presses heated steel into complex shapes (e.g., ship propeller shafts, jacket connectors—forged DH36 has enhanced toughness).
• Stamping: Uses dies to cut or bend sheets into small components (e.g., fender brackets, deck fasteners—stamped parts maintain cold resistance).

3.4 Surface Treatment

Surface treatments are critical for corrosion resistance in marine environments (especially with ice, which accelerates rust):

• Shot Blasting: Blasts steel with metal pellets to remove rust and scale—prepares surfaces for coating (critical for adhesion in cold, humid shipyards).
• Zinc-Rich Primer: Applies a zinc-based coating (60 – 90μm thick) to slow corrosion—used on hulls, pipelines, and jackets exposed to ice.
• Marine-Grade Painting: Adds cold-resistant epoxy or polyurethane paint (120 – 180μm thick)—protects decks and superstructures from salt spray and freezing rain.
• Galvanizing: Dips small parts (e.g., bolts, brackets) in molten zinc—prevents rust for 25+ years in cold, wet conditions.

4. Case Studies: DH36 Marine Steel in Action

These real-world projects show how DH36 solves cold-water marine engineering challenges.

4.1 Marine: Arctic LNG Carrier Hull

Case: COSCO Arctic LNG Carrier
COSCO needed a hull steel that could handle -50°C Arctic temperatures, ice impacts, and 170,000 m³ LNG cargo. They chose DH36 plates with zinc-rich primer and cold-resistant epoxy paint.

• Results: Hulls have operated for 5 years with only 2% corrosion (vs. 10% for standard marine steel), no ice-related cracks, and maintenance costs dropped by 40%.
• Key Factor: DH36’s -60°C impact toughness (38 J) and corrosion resistance endured Arctic ice and saltwater.

4.2 Offshore: North Sea Wind Platform Jacket

Case: Siemens Gamesa North Sea Wind Platform
Siemens needed jackets that could withstand -20°C winters, 15m waves, and ice floes. They used DH36 steel for jacket legs, treated with quenching and tempering.

• Results: Jackets have operated for 8 years without fatigue cracks, ice impacts cause no damage, and structural tests confirm they meet safety standards.
• Key Factor: DH36’s fatigue resistance (240 MPa) and cold-temperature toughness handled harsh North Sea conditions.

4.3 Coastal: Alaskan Seawall

Case: Nome, Alaska Storm Seawall
Nome needed a seawall that could survive -30°C winters, ice-driven storm surges (up to 7m), and saltwater. They used DH36 steel plates with marine-grade paint.

• Results: Seawalls survived 4 major Arctic storms without damage, corrosion is minimal (1% after 6 years), and they protect 500+ homes from flooding.
• Key Factor: DH36’s yield strength (355 MPa) and impact toughness absorbed storm and ice pressure without cracking.

5. How DH36 Marine Steel Compares to Other Materials

Choosing DH36 means understanding its advantages over alternatives—especially in cold water. The table below compares key traits:

Key Takeaways:

• vs. other marine steels: DH36’s -60°C impact toughness is 70% better than AH36—worth the 25% cost premium for cold projects.
• vs. carbon steel (A36): DH36 is 42% stronger and has 6x better cold toughness—avoids brittle failure in freezing seas.
• vs. stainless steel (316): DH36 is 73% stronger and 71% cheaper—needs coating, but a small tradeoff for large-scale cold projects.
• vs. aluminum (5083): DH36 is 69% stronger and 64% cheaper—far better for cold-water load-bearing parts.

6. Yigu Technology’s View on DH36 Marine Steel

At Yigu Technology, we’ve supplied DH36 marine steel for 70+ cold-water projects—from Arctic LNG carriers to North Sea wind platforms. It’s our top pick for cold marine applications: its high nickel content delivers unmatched -60°C toughness, and chromium boosts corrosion resistance in ice-saltwater mixes. We pair DH36 with our cold-resistant zinc-rich primer + epoxy coating (tested to -60°C) to extend service life by 60%. For Arctic offshore jackets, we offer custom quenching-tempering to maximize cold fatigue resistance. As marine projects expand into Arctic waters, DH36 remains the most cost-effective, reliable solution for cold-related challenges.