A335 P91 alloy pipe steel is equivalent to the national standard 10Cr9Mo1VNb. T91/P91 (10Cr9Mo1VNb) P91 alloy pipe features: not only has high oxidation resistance and high temperature steam corrosion resistance, but also has good impact toughness and high and stable durable plasticity and thermal strength. When the service temperature is lower than 620℃, its allowable stress is higher than that of austenitic stainless steel. Above 550℃, the recommended design allowable stress is about twice that of T9 and 2.25Cr-1Mo steel.

A335 P91 alloy tube application

It can be used as high temperature superheater and reheater steel pipe for subcritical and supercritical boiler wall temperature ≤625℃, high temperature header and steam pipeline with wall temperature ≤600℃, as well as nuclear power heat exchanger and furnace tube of petroleum cracking unit.

A335 P91 seamless steel pipes

• Standard: ASTM　A213　ASTM　A335
• Tensile strength: ≥585 (MPa)
• Yield strength: ≥415 (MPa)
• Elongation rate: ≥20 (%)

P91 steel is a new type of martensitic heat-resistant steel jointly developed by the National Xiangshuling Laboratory and the Metallurgical Materials Laboratory of the American Combustion Engineering Company. It reduces the carbon content on the basis of 9Cr1MoV steel, strictly limits the content of sulfur and phosphorus, and adds a small amount of vanadium and niobium for alloying. According to ASTM213/A213M-85C, the chemical composition of P91 steel is shown in Table 1.

The German steel number corresponding to P91 steel is X10CrMoVNNb91, the Japanese steel number is HCM95, and France is TUZ10CDVNb0901.

A335 P91 alloy tube heat treatment process

The final heat treatment of P91 is normalizing + high temperature tempering, the normalizing temperature is 1040℃, the holding time is not less than 10 min, the tempering temperature is 730～780℃, and the holding time is not less than 1h. The final structure after heat treatment is tempering. Fire martensite.

Mechanical properties of A335 P91 alloy pipe

The tensile strength of P91 steel at room temperature is ≥585 MPa, the yield strength at room temperature is ≥415 MPa, the hardness is ≤250 HB, the elongation (standard circular specimen with a gauge length of 50 mm) is ≥20%, and the allowable stress value is [σ]650 ℃=30 MPa.

According to the carbon equivalent formula recommended by the International Welding Society, the carbon equivalent of P91 is 1.631, and the weldability of P91 is poor.