Heat resistant alloys for security tubes
Carbon Steels: Economical materials with nominal corrosion resistance. It is used in small temperature and stress applications where the measured medium secures it from corrosion, oils, petroleum and tars. Highest temperature about 530oC. Large strength steels utilized in pressure vessels and industrial boiler plant. Prevention of attack in chloroform, cleaning agents, food products and carbon disulfide. Highest service- 600oC.
Stainless steel 304: Economical corrosion resistant material, widely utilized in food, beverage and chemical processing where supreme corrosion resistance is needed. A low carbon grade 304l is suitable when welded without impairing it offers corrosion resistance. Highest service temperature about 900oC.
Stainless steel 321: SS 321 offers similar characteristics to SS 304, excluding this grade is titanium stabilized to avoid intergranular corrosion upon welding.
SS 316: This steel grade offers extreme corrosion resistance due to the inclusion of molybdenum, extensively used in the chemical treatment, provides significant resistance to hydrogen sulfide. As with grade 304, the steel type 316l is used for welded applications. Highest service up to 900oC.
Stainless steel 310: It is a good corrosion resistant material that can be utilized about 1150oC with significant resistance in sulfur bearing conditions. It offers superior corrosion resistant to SS 304 however not as better as SS316. It can be welded with precaution.
Stainless steel 446: It offers good resistance to sulfurous conditions at elevated temperature, although because of its small strength at elevated temperature, thermowells constructred from this material must be mounted vertically. It is used in heat treatment procedure, iron and steel furnaces, gas development plant and it has significant resistance to molten lead. It offers supreme resistance to nitric acid, sulfuric acid and various alkalis, offering it the limited service in chemical plant. Highest service temperature is about 1150oC.
Duplex Stainless Steel: These grades offer supreme strength with outstanding corrosion resistance, particularly to chloride stress corrosion cracking, although a potential to brittleness limits their service to about 300 – 315oC highest, subzero service is also limited to about 50oC as of brittleness due to ferrite concentration. Key services include offshore piping, chemical containers, flue gas scrubbers and chimneys.
Super Duplex Stainless Steel: Equivalent characteristics and drawbacks to duplex grades above. These alloys are commonly used to deal with marine water and other brackish waters, marine pumps, oil and gas development and desalination units are specific applications.
Inconel 600: A commonly used NiCrFe alloy with supreme high temperature strength and oxidation resistance, although, it is susceptible to corrosion in sulfurous atmospheres above 500oC. Outstanding resistance to chloride ion stress corrosion cracking and nitriding conditions. Widely used in chemical plants for good strength and corrosion resistance. High weldability of Inconel 600 is usually used without post weld heat processing. Highest service temperature about 1212oC.
Inconel alloy 625: A NiCr alloy with outstanding resistance to pitting and crevice attack, isolated from the radiation embrittlement, commonly used in the aerospace engineering and in marine industry. Supreme weldability can be utilized in the as-welded form. Highest service temperature about 1093oC.
Incoloy 800– Better performance than Inconel 600 in sulfur, cyanide salts and neutral salts. Widely used in steam and hydrocarbon reforming units for pigtail pipes, manifolds and waste heat boilers and in the internal parts of secondary reformers. Commonly used in the heat processing system and as a heater sheath material. Highest temperature about 1093oC.
Incoloy 825: A NiFeCr alloy with the extreme resistance to diverse corrosive media, it is better than various metallic materials for dealing with sulfuric acid and Incoloy 825 offers supreme resistance to phosphoric acid. It is commonly used in the chemical treatment, oil and gas recovery, acid development, pickling services, nuclear fuel retreatment and dealing with radioactive wastes. Highest service about 540oC.
An FeCrAl alloy developed by mechanical alloying, it includes high strength at elevated temperatures with supreme resistance to oxidation, carburization and warm corrosion. These characteristics make it fit for gas turbine combustion units and various severe conditions of sulfur and chloride salts. Highest service about 1350oC.
Monel 400: A NiCu alloy with supreme corrosion resistance, widely used in handling marine water, hydrofluoric acid, sulfuric acid, hydrochloric acid and various alkalis. Standard applications of Monel 400 include marine components, chemical processing units, gasoline and water containers, process vessels and pipes and boiler feedwater heaters. Highest service temperature is 538oC.
Grade C-276– NiMoCr alloy with supreme corrosion resistance particularly in chlorinated media. Commonly employed in chemical units to handle ferric and cupric chlorides, solvents, chlorine, formic acid, acetic acid, brine, wet chlorine gas and hypochlorite. It can be easily welded and sustains its characteristics in the as-welded form. Highest service temperature about 1093oC.
Hastelloy B3– An enhanced version of grade B2 with better heat stability, fabricability and stress corrosion cracking prevention. It is a supreme choice for dealing with hydrochloric acid in whole contents and temperatures, it also adequately deals with hydrogen chloride, euphoric, acetic, hydrofluoric and phosphoric acids. It has the highest service temperature about 538oC to 816oC in the reducing or vacuum media.
Hastelloy C-22: A NiCrMoW alloy offers great resistance to pitting and crevice attack and stress corrosion cracking. It offers supreme resistance to a diverse range of chemical processing conditions for example ferric and cupric chlorides, hot solutions, formic and acetic acids and marine water or brine solutions. The alloy offers excellent welding properties and maintains its characteristics in the welded form.
Hastelloy X: An alloy that can withstand high temperature in addition of prevents attack in oxidizing, reducing and neutral atmospheric media. It is commonly used in aircraft jet engines. It has outstanding high temperature strength due to which it is fit for furnace applications. It prevents stress corrosion cracking in the petrochemical media and can serve highest up to 1204oC.
Haynes 214: Outstanding high temperature material, offering great resistance to oxidation and carburization superior to any other alloy. It offers the highest service temperature about 950oC and higher and can perform up to 1315oC however at this limit, its strength is widely decreased. Its applications include ceramic firing furnace components, automatic catalytic converter internals and in the industrial heating plants.