DH32 ERW Pipe Steel Material Grade
DH32 ERW Pipe Steel Grade: Shipbuilding and Offshore Structural Steel Pipe
Comprehensive material analysis of DH32 electric resistance welded (ERW) pipe steel, including chemical composition, mechanical properties, physical data, and international equivalents.
Electric Resistance Welding (ERW), Cold Forming, Hot Forming, Welding
- Phone : +8618037372205
- Email : [email protected]
- WhatsApp: Contact via Whtsapp
- WeChat: +8618037372205
DH32 ERW Pipe Steel Grade Introduction
DH32 is a high-strength hull structural steel grade commonly used in shipbuilding and offshore engineering, designated by classification societies under IACS UR W11. The 'D' indicates specified impact toughness at -20°C, while '32' denotes a minimum yield strength of 315 MPa (32 kgf/mm²). DH32 ERW pipe is fabricated from hot-rolled strip/plate into welded pipes by electric resistance welding, offering excellent weldability, low-temperature toughness, and moderate strength for marine and structural applications. The material is typically supplied in normalized or thermo-mechanically rolled condition, meeting stringent requirements for hull and offshore structures.
DH32 ERW Pipe Steel Grade Chemical Composition
The chemical composition complies with IACS UR W11 for DH32 high-strength hull steel. Residual elements and micro-alloying elements (Nb, V, Ti, etc.) may be present to achieve required mechanical properties and grain refinement. Carbon equivalent (CEV) is typically required to ensure weldability.
| Chemical Element | Specified Value (max, unless range) | Remarks |
|---|---|---|
| Carbon, C | ≤ 0.18% (typical 0.14-0.16) | For improved weldability, carbon is tightly controlled. |
| Manganese, Mn | 0.90 - 1.60% | Key strengthening element; higher end improves toughness. |
| Silicon, Si | ≤ 0.50% (typically 0.10-0.50%) | Deoxidizer; in fully killed steel, Al is also used. |
| Phosphorus, P | ≤ 0.035% | Strict limit to avoid brittleness. |
| Sulfur, S | ≤ 0.035% | Strict limit for ductility and weldability. |
| Aluminum, Al (total) | ≥ 0.015% (acid-soluble) | Grain refinement to assure fine grain and toughness. |
| Niobium, Nb | ≤ 0.05% (might be added) | Microalloying for strength; optional. |
| Vanadium, V | ≤ 0.10% (might be added) | Optional grain refiner. |
| Titanium, Ti | ≤ 0.02% (if added) | For grain refinement and toughness. |
| Nitrogen, N | ≤ 0.012% (or as agreed) | Controlled to avoid aging effects. |
| Carbon Equivalent (CEV) | ≤ 0.40% (typical) | Calculated as C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15, typically limited for weldability. |
DH32 ERW Pipe Steel Grade Thermal and Electrical Physical Properties
Physical properties are not part of the DH32 material standard but are provided as typical for carbon-manganese structural steel at ambient temperature unless noted. Values may vary slightly with exact chemical composition and heat treatment.
| Property | Typical Value | Unit | Test Conditions |
|---|---|---|---|
| Density, ρ | 7.85 | g/cm³ | At 20°C |
| Elastic Modulus, E | 205 | GPa | At 20°C, longitudinal |
| Shear Modulus, G | 79 | GPa | Calculated from E and ν |
| Poisson's Ratio, ν | 0.29 | -- | Typical for steel |
| Coefficient of Thermal Expansion, α | 11.7 | 10−⁶ / K | Mean value, 20-100°C |
| Thermal Conductivity, λ | 51.9 | W/(m·K) | At 20°C |
| Specific Heat Capacity, cp | 0.46 | J/(g·K) | At 20°C |
| Electrical Resistivity, ρe | 0.14 | μΩ·m | At 20°C (approximate) |
DH32 ERW Pipe Steel Grade Mechanical Properties
Requirements for DH32 steel plate/strip used for ERW pipe production, based on IACS UR W11. Tensile test is transverse (for pipe, longitudinal may apply). Impact toughness at -20°C is mandatory for grade D. For pipe, properties may be certified on base material and/or weld seam.
| Property | Specified Value | Unit | Test Conditions |
|---|---|---|---|
| Yield Strength, ReH (min) | 315 | MPa | Tensile test transverse; thickness ≤ 100 mm; for t > 100 mm consult class. |
| Tensile Strength, Rm | 440 - 590 | MPa | Typical range; guaranteed. |
| Elongation, A5 (min) | 22 | % | Gauge length L0=5.65√S0 (50 mm); thickness ≤ 50 mm. |
| Elongation, A5 (min) | 21 | % | Thickness 50-70 mm. |
| Elongation, A5 (min) | 20 | % | Thickness 70-100 mm. |
| Charpy V-notch Impact Energy, KV2 (longitudinal) | ≥ 31 (min avg) / 22 (min single) | J | At -20°C; full-size 10x10 mm specimen. |
| Charpy V-notch Impact Energy, KV2 (transverse) | ≥ 22 (min avg) / 16 (min single) | J | At -20°C; may be required for certain products. |
| Bend Test (mandrel diameter) | 3t (t=thickness) | no crack | 180° bend test; specimen width 40 mm. |
DH32 ERW Pipe Steel Grade Exact Equivalent Standards and Grades
| Country/Region | Standard/Specification | Grade/Designation | Remarks |
|---|---|---|---|
| International (IACS) | IACS UR W11 | DH32 | High-strength hull structural steel; basis for class rules. |
| China | GB/T 712 | DH32 | Chinese classification society CCS also accepts this. |
| USA | ABS Rules | DH32 | American Bureau of Shipping; identical properties. |
| France | BV Rules | DH32 | Bureau Veritas; same as IACS. |
| Germany | DNV Rules (now DNV GL) | DH32 | Det Norske Veritas; may also be marked as NV D32. |
| UK | LR Rules | DH32 | Lloyd's Register. |
| Italy | RINA Rules | DH32 | Registro Italiano Navale. |
| Japan | NK Rules | DH32 | ClassNK. |
| Korea | KR Rules | DH32 | Korean Register. |
| EU | EN 10025-3/N? Not directly equivalent but similar grade S315NC? Not exact. | -- | No direct EN standard for shipbuilding steel; EN 10025 grades for structural steels are different. |
DH32 ERW Pipe Steel Grade Application Introduction
DH32 ERW pipe is tailored for marine and offshore structural piping systems where high strength, good weldability, and notch toughness at low temperatures are required. Its use covers shipboard piping, ballast systems, cargo oil lines, risers, and structural hollow sections. ERW process allows cost-effective production of straight-seam pipes with consistent wall thickness.
Product Applications: Straight seam ERW pipes for marine piping systems, Tubular structural members for ship hulls, Riser pipes for offshore drilling and production, Conductor pipes and casings, Ballast water and bilge system pipes
Processed into products: Pipe spools and elbows for ship engine rooms, Deck piping for fuel and lube oil transfer, Firefighting water mist piping headers, Structural pillars and columns on vessels, Offshore platform cooling water intake pipes
Application industries: Shipbuilding and Ship Repair, Offshore Oil & Gas Platforms, Marine Engineering, Port and Harbour Construction, Pressure Piping Systems (subject to code approval)
DH32 ERW Pipe Steel Grade Similar/Comparable Steel Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | IACS UR W11 | EH32 | Same strength, better low-temperature toughness (-40°C). |
| International | IACS UR W11 | DH36 | Higher yield (355 MPa) and tensile strength; similar toughness (-20°C). |
| EU | EN 10025-2 | S355J2 | Min. yield 355 MPa; impact at -20°C 27J; structural steel, not ship-specific, may substitute for non-marine use. |
| USA | ASTM A 572 / A 709 | Grade 50 [345] | Min. yield 345 MPa; general structural, not -20°C impact guaranteed unless supplementary requirement. |
| Japan | JIS G 3106 | SM490B | Min. yield 325 MPa; impact at 0°C; not directly equivalent. |
Notes:
DH32 ERW pipe may require additional testing such as weld seam toughness, NDE (ultrasonic/radiography), and hydrostatic test per applicable pipe standard (e.g., API 5L for line pipe or ASME B31.3 for process piping). The material can be normalized or stress relieved after welding to improve weld zone properties. For sour service (H2S), DH32 may not normally be suitable without special testing for SSC/HIC resistance; DH32 modified grades with controlled chemistry (DH32Mod) are available for such environments. Always consult the specific classification society's rules for precise requirements of pipe applications.
- Share
