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Views: 1 Author: Wang Publish Time: 2024-09-12 Origin: Site
Alloy 254 SMO is a very high end, molybdenum and nitrogen alloyed super austenitic stainless steel with low carbon content. It was originally developed to withstand the corrosion of acids, especially in the presence of halide ions, such as hydrochloric acid, hydrofluoric acid, phosphoric acid, and sulphuric acid contaminated with chlorides. In certain environments it is an alternative to more expensive nickel alloys and titanium alloys. It demonstrates outstanding resistance to pitting, crevice corrosion stress cracking, and corrosion fatigue uniform corrosion.
Alloy 254 SMO is substantially stronger than the common austenitic grades, with strength nearly twice that of 300 series stainless steel. It is also characterized by high ductility and impact strength. With high levels of chromium, molybdenum, and nitrogen, Alloy 254 SMO is frequently used in high chloride environments, such as brackish water, seawater, pulp mill bleach plants, and other chloride process streams. In some applications it has even been found to be a more cost effective substitute for high nickel and titanium alloys.
Stainless steel 254 SMO is a 18% Ni, 20% Cr, 6% Mo super austenitic stainless steel grade with 0.2% nitrogen additions, particularly designed to be cost effective. The 18% nickel and 0.7% copper additions combined with the chromium and molybdenum additions enhance the performance of the steel in many corrosive solutions encountered for example in chemical and petrochemical processes or chloride containing solutions. The alloy is also seawater resistant and has extensively been used in offshore applications (It is not recommended for use in stagnant seawater applications with temperatures higher than 30°C (86°F).
Element | Wrought | Castings |
Carbon | ≤0.020 | ≤0.025 |
Chromium | 19.5-20.5 | 19.5-20.5 |
Nickel | 17.5-18.5 | 17.5-19.5 |
Molybdenum | 6.0-6.5 | 6.0-7.0 |
Nitrogen | 0.18-0.22 | 0.180-0.240 |
Copper | 0.50-1.00 | 0.50-1.00 |
Sulfur | ≤0.010 | ≤0.010 |
Phosphorus | ≤0.030 | ≤0.045 |
Silicon | ≤0.80 | ≤1.00 |
Manganese | ≤1.00 | ≤1.20 |
Iron | Balance | Balance |
254SMO is a kind of super austenitic stainless steel with high corrosion resistance. It is developed for halide and acid environment, and is widely used in high concentration of chloride ion media, seawater and other harsh conditions. In some industrial environment with acidic medium, especially with halogenated acid, 254SMO performs much better than other stainless steels, which can be like Hastelloy alloy and titanium in some circumstance. With low carbon content and high molybdenum, it has good pitting and crevice corrosion resistance as well as excellent intergranular corrosion resistance. It is a kind of cost-effective stainless steel, which is widely used in chemical industry, desulfurization and environmental protection at home and abroad.
Due to the exceptionally high work hardening rate and lack of sulfur content, stainless steel grade 254 SMO is quite difficult to mill; however, sharp tools, powerful machine machines, positive feeds, and a substantial amount of lubrication, and slow speeds tend to offer decent machining results.
Welding stainless steel grade 254 SMO necessitates the use of filler material, which results in inferior tensile qualities. AWS A5.14 ERNiCrMo-3 and alloy 625 are approved as filler metals. The electrodes used in the process must comply with AWS A5.11 ENiCrMo-12.
The annealing temperature for this material should be 1149-1204°C (2100-2200°F), followed by a water quench.
Forging, upsetting and other operations relating to this material can be performed at 982 - 1149°C (1800 - 2100°F). It is recommended that temperatures do not exceed this range as it would result in scaling and reduction in the workability of the material. To re-attain maximum corrosion resistant properties, it is advisable to perform post-process annealing.
Cold working can be carried out using all the traditional methods; however the process would be tough due to its high work hardening rate. The result will provide the material with increased strength and toughness.
Heat treatment does not affect stainless steel grade 254 SMO. Only cold reduction allows for hardening.
Stainless steel 254SMO is a high-performance alloy known for its excellent resistance to pitting and crevice corrosion in chloride environments. It is often used in situations where materials are exposed to harsh conditions that would quickly degrade other types of stainless steel. Here are some common applications of 254SMO:
1. Marine Environments: Due to its resistance to chloride-induced corrosion, 254SMO is frequently used in marine applications, such as in shipbuilding, offshore oil and gas platforms, and coastal structures.
2. Chemical Processing: It is used in chemical processing plants where exposure to corrosive chemicals is common. This includes equipment such as pumps, valves, and heat exchangers.
3. Pulp and Paper Industry: In the pulp and paper industry, 254SMO is employed in applications where high resistance to chlorides and other aggressive substances is required, such as in bleaching systems and digesters.
4. Desalination Plants: Its resistance to seawater makes it suitable for use in desalination plants, where it can be used in components like pumps and heat exchangers.
5. Oil and Gas Industry: 254SMO is used in various parts of the oil and gas industry, including in wellheads, blowout preventers, and other equipment exposed to harsh conditions.
6. Power Generation: It can be found in power generation facilities, particularly in components that are subject to high corrosion rates, such as in flue gas desulfurization systems.
7. Architectural Applications: Occasionally used in architectural applications where both aesthetic and corrosion resistance properties are important, such as in coastal buildings and structures.
254SMO's high molybdenum content gives it superior resistance to chloride-induced pitting and crevice corrosion compared to standard stainless steels, making it a go-to choice for these demanding applications.
