The element S in steel is the main source of sulfide inclusions, which is easy to produce red hot brittleness; element P mainly affects the temper brittleness and hot brittleness of P91 steel pipe. Therefore, the mass fraction of S and P in steel should be low; V, Nb and N It is a strengthening element and can increase the strength of P91 steel pipe.
Elements such as Cr and Si can make the metal oxide film formed during high-temperature operation dense and firm, and improve the oxidation resistance of P91 steel pipe. P91 steel pipe has a low mass fraction of harmful elements, high oxidation resistance, and increased strengthening elements. It is a high temperature and high pressure pipe superior to P22 steel.
On the other hand, the room temperature yield limit of P91 steel pipe is twice that of P22 steel, and its tensile strength is 41% higher than that of P22 steel. The mechanical properties of P91 steel pipe are better.