SUMMARY
253MAa) is an austenitic 21Cr/11Ni high-temperature steel alloyed with silicon, nitrogen and rare earth metals. The rare earth metals combined with silicon give this steel excellent resistance to oxidation and carburisation at temperatures of up to about 1150°C, and nitrogen together with carbon contribute towards a high creep-rupture strength. The steel displays a high degree of structural stability and therefore has little tendency to precipitate embrittling phases during service at elevated temperatures.
Its combination of good corrosion resistance and high creep strength makes 253MA a very suitable material for purposes where 18Cr/8Ni steels are insufficiently resistant to oxidation and carburisation and where stainless chromium steels lack the necessary creep strength. Because of its good structural stability, 253MA can very well be substituted for steels of the 25Cr/20Ni type. Moreover where certain applications are concerned, 253MA is a good alternative to more high-alloy materials such as Alloy 800H and Alloy 601.
253MA has come to be extensively used above all in metallurgical and petrochemical industry, but it is also used in the power industry. Applications include tubes for waste heat recovery systems in metallurgical industry, tubes for heat treatment furnaces and radiant tubes for furnaces in petrochemical industry.
