Special steel materials used in marine oil and gas resource development engineering are generally Cr-Ni-Mo stainless steels, super stainless steels, or Ni-Cr-Mo corrosion-resistant alloy materials. These materials are characterized by high pitting resistance equivalent, high purity, and nitrogen alloying.
Typical Components and Performance Indicators
Components made from these high-alloy materials for marine oil and gas resource development, such as storage and transportation equipment, process pipelines, heat exchangers, desalination units, oil well pipes, drilling equipment, and platform legs, typically exhibit high strength and corrosion resistance to meet their specific service conditions. Normally, corrosion resistance and strength are two key performance indicators for special steel materials used in marine platforms.
Advanced Steel Grades
The advanced, exceptional steel grades for marine platforms primarily include super austenitic stainless steel, super ferritic stainless steel, high-strength austenitic non-magnetic stainless steel, nickel-based alloys, and iron-nickel-based corrosion-resistant alloys. These categories of special steel materials have different alloy compositions, resulting in varying strengths in their properties.
Marine Oil and Gas Port
Classification of Steel for Marine Oil and Gas Resource Development Engineering
High Mo Content Cr-Ni-Mo Super Austenitic Stainless Steel
Super austenitic stainless steels generally have high Cr and Ni content, with a certain Mo content (6% to 7%). They exhibit excellent resistance to localized corrosion and uniform corrosion at elevated temperatures. Their pitting resistance equivalent number (PREN) value, calculated as (Cr + 3.3Mo + 16N), typically exceeds 30, with some materials even reaching above 50. The high PREN value ensures outstanding corrosion resistance for these materials, while reasonable nitrogen alloying provides a balance of high strength and ductility.
Typical Grades and Typical Compositions:
- 254SMO (Cr20-Ni18-Mo6-Cu-N)
- 654SMO (Cr24-Ni22-Mo7-Mn3-Cu-N)
- AL-6XN (Cr20-Ni24-Mo6-N)
- NAS254N (Cr23-Ni25-Mo5.5-N)
- NAS354N (Cr23-Ni35-Mo7.5-N)
Nickel-Based or Iron-Nickel-Based Corrosion-Resistant Alloys
Nickel-based or iron-nickel-based corrosion-resistant alloys have higher contents of Cr, Ni, and Mo. In tropical waters and complex ionic marine environments, they exhibit superior resistance to localized corrosion and stress corrosion compared to super austenitic stainless steels. These materials can be widely applied in oil and gas media, oil-water separation, or other more demanding chemical process pipelines, pumps, valves, and centrifuges in industrial conditions.
Typical Grades and Typical Compositions:
- Incoloy 825 (Cr20-Ni35-Mo3-Cu3-Nb)
- Inconel 625 (Cr22-Ni58-Mo9-Nb3)
- Sanicro 28 (Cr27-Ni31-Mo3-Cu)
- Alloy 20 (Cr20-Ni35-Mo3-Cu3-Nb)
- Alloy 31 (Cr27-Ni31-Mo7-Cu-N)
- Nicrofer 33 (Cr33-Ni31-Mo-Cu-N)
High-Nitrogen Austenitic Stainless Steel
The extremely high nitrogen alloy content significantly enhances the material’s strength characteristics, providing excellent strength performance at both room and elevated temperatures. By using Mn-N to replace Ni as an austenite stabilizing element, these materials achieve superior performance at a lower cost, making them highly cost-effective for meeting field conditions. Recent optimizations in their alloy systems, combined with the addition of specific Mo elements, have also endowed them with excellent localized corrosion resistance. Continuous increases in Cr content and reductions in C content have improved the intergranular corrosion resistance of these materials, presenting significant potential for basic applications.
Typical Grades and Typical Compositions:
- P550 (Cr20-Mn20-Mo-N)
- P650 (Cr19-Mn20-Mo2-Ni4-N)
- Datalloy 2 (Cr15-Mn15-Ni2-Mo2-N)
- 15-15HS (Cr20-Mn18-Ni3-Mo-N)
Marine Oil
Application Fields of Special Steel in Marine Oil and Gas Development Engineering
High-performance austenitic and super austenitic stainless steels, as well as corrosion-resistant alloy products, have been widely used in three main application areas: above marine platforms, underwater transportation pipelines, and downhole drilling. They are currently used extensively in the construction of platforms in hundreds of offshore oil fields, with specific application areas as follows.
Above Marine Platforms
- Seawater Desalination Systems: 254SMO, Alloy 31, Nicrofer 33
- Seawater Pipelines: 254SMO, Incoloy 825
- Cam Devices: 254SMO, 654SMO, AL-6XN (N08367)
- Equipment Casings: 654SMO, AL-6XN (N08367)
- Centrifugal Separators: 654SMO, AL-6XN (N08367)
- Tubular Heat Exchangers: 654SMO, AL-6XN (N08367), NAS354N, Alloy 31, Alloy 20
- Plate Heat Exchangers: 654SMO, AL-6XN (N08367), NAS354N, Alloy 31, Alloy 20
- Gravity Separators: 904L, AL-6XN (N08367)
Deep-Sea Downhole Drilling
- MWD Non-Magnetic Casing, Non-Magnetic Drill Collars, Stabilizers, Rotary Steerable Drilling Units: P550, 15-15HS, Datalloy-2, Inconel 718
Drill Collars
Underwater Transportation Pipelines and Pump Valves
- Oil and Gas Composite Pipelines, Valve Assemblies, Pipeline Hangers, Jumpers, and Splice Cables, Cable Buoyancy Components, Lift Pipes, and Flow Pipes: Inconel 625, 254SMO, AL-6XN (N08367), Sanicro 28, Incoloy 825
- Manifolds: 254SMO, AL-6XN (N08367), NAS800HT
Other Units
- Platform Support Structural Components: NAS254N, AL-6XN (N08367)
- Fire and Explosion Walls: 316L, P530
- Wall Cladding Layers: 316L, P530
- Cable Drums: 316L, P530
- Stairs, Passages, and Elevators: 316L, P530
- Natural Gas Systems: 316L, P530
Special steel materials for marine platforms have been commercially produced abroad for many years, with representative manufacturers including Germany’s VDM, Outokumpu, America’s ATI, SMC, HAYNES, Japan’s Yakin, Nippon Steel & Sumitomo Metal Corporation, Sweden’s Sandvik, and America’s Carpenter. Many of these companies have patented products and grades.
