P91 steel
P91 steel description:P91 is a ferritic alloy steel. This material has been in use successfully in power plant service. It is also called 9 Cr 1 Mo steel based on its composition.
Compared with the T22 or P22 grade, grade 91 exhibits high strength up to temperatures in the range of 600 °C. Also the oxidation temperature limits are higher. This allows the power plant designers to engineer components, superheater coils, headers and steam piping, with less thickness. This contributes to a higher thermal fatigue life of almost ten times. This allows them to increase the operating temperature to a higher level, increasing the efficiency of the power plant.
Grade 91 contains 9 % Chromium and 1 % Molybdenum compared to 2.5 % Chromium in the next best P22 grade. Chromium improves high temperature strength and increases oxidation resistance. Molybdenum increases the creep resistance. Also present are smaller quantities of Nickel and Manganese which increase the hardenability of the steel.
More important than the alloying elements is the formation of this alloy steel. The steel is formed by normalizing at 1050 °C, air cooling down to 200 °C. It is then tempered by heating to 760 °C. The temperatures and the cooling rates are very important. This produces the microstructure that results in the high creep strength properties.
This steel is not tolerant to variations in its microstructure, unlike P22 grade or other grades.
P91 steel Application:ideally suitable for plants that operate on a cyclic basis like combined cycle plants. Also the reduction in thickness suits HRSG designers since in an HRSG the temperature head is limited and locating the coils in the heat transfer path is very critical.
BEBON STEEL can provide P91 steel immediately, if you need P91 steel, please be free to contact us.
Thanks for your attention in advance.
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