Material classification and main performance
Unlike micro-alloyed structural steel materials for offshore platforms, special steel materials for offshore platforms are generally high-alloy Ni-Cr or Cr-Ni-Mo-based stainless steels, super-stainless steels or corrosion-resistant alloys, which generally have high points. Characteristics of etch equivalent, high purity and N alloying. Typical parts of offshore platforms prepared by using these high-alloy materials, such as storage and transportation, process piping, desalination, heat exchangers, oil well pipes, drilling and pile legs, are generally high-strength and high-resistance to meet their special service conditions. Corrosive or both. In general, corrosion resistance and strength are two key performance indicators for special steel materials for offshore platforms. At present, advanced special steel grades for foreign offshore platforms mainly include super austenitic stainless steel, super ferritic stainless steel, high-strength austenitic non-magnetic stainless steel, nickel-based and iron-nickel-based corrosion-resistant alloys, etc. Performance varies depending on the design of the alloy composition system.
(1) High Mo content Cr-Ni-Mo super austenitic stainless steel. For super austenitic stainless steels, it generally has a high Cr, Ni content, a certain Mo content (6% to 7%), and has excellent resistance to local corrosion and uniform corrosion at higher temperatures, and pitting corrosion. The equivalent PREN value (Cr+3.3Mo+16N) generally reaches 30 or more, and some materials are even higher than 50, which ensures excellent corrosion resistance of such materials. At the same time, reasonable N alloying makes it both high. Strength and plastic toughness.
(2) Nickel-based or iron-nickel based corrosion resistant alloys. For nickel-based or iron-nickel-based corrosion-resistant alloys, the Cr, Ni, and Mo alloys are higher in content, and have more outstanding local corrosion resistance and stress than super austenitic stainless steels in tropical waters and complex ionic media. Corrosion performance. It can be widely used in oil and gas media, oil-water separation or other more demanding chemical process pipelines, pump valves and centrifuges.
(3) High nitrogen austenitic stainless steel. The extremely high N alloy content greatly enhances the strength index of the material, which makes it have excellent strength properties under high temperature conditions in the chamber. Due to the use of Mn-N Ni to become an austenite stabilizing element, it is excellent in performance. Has a lower production cost. Due to the continuous optimization of its alloy system in recent years and the addition of certain Mo elements, it also has excellent local corrosion resistance, continuous improvement of Cr content and further reduction of C element, which improves the intergranular corrosion resistance of the material.