A335 P91 high pressure seamless boiler pipes

A335/SA335 P91 is a ferritic alloy steel that has very high strength properties, which do not deteriorate with time, and are creep resistant. It is also called 9 Cr 1 Mo steel, or chrome moly pipe, based on its composition.Compared to its predecessors, the T22 or P22 grade, grade P91 exhibits high strength, enduring temperatures up to 600 °C. The oxidation temperature limits are also higher allowing gineered with less thickness. This contributes to an almost 10 times higher thermal fatigue life and allows engineers to increase the operating temperature to a higher level, increasing efficiency.P91 typically allows a wall thickness reduction by at least a 2-to-1 ratio. A wall that is thinner creates lighter hanger loads, less welding time and uses less filler metal.These advantages are enabled by this steel’s high amount of chromium. Grade 91 contains 9% chromium and 1% molybdenum compared to 2.5% chromium in the next best P22 grade