P91 Tee

Performance and Application of P91 Tee Material P91 material is a medium alloy heat-resistant steel, which is developed on the basis of 9Cr-1Mo steel through the following improvements: vanadium and niobium are added, nitrogen content is controlled at the same time, and its creep strength is greatly improved. After that, the content of carbon element is consciously reduced considering the processing performance. Through the comparison of physical properties required by the design requirements, the thermal conductivity and linear expansion coefficient of P91 and P22 as well as austenitic stainless steel TP304H prove once again that P91 is obviously superior to TP304H and P22. The advantages of P91 over stainless steel lie in its good thermal conductivity and low linear average expansion coefficient

The yield of P91 steel at room temperature is twice as good as that of P22 steel, and the tensile strength is 41% higher than that of P22 steel. Its advantages are: the flexibility of the pipeline system is increased, the expansion force is reduced, the load of supports and hangers is reduced, the thrust and torque at the end point are reduced, the unit load is allowed to change rapidly, the starting time is shortened, and the investment cost is reduced. In the thermal power plant, in order to protect the safe operation of the main steam pipeline, each main steam pipeline with medium temperature of 500 ℃ and above shall be subject to creep monitoring. The main factors affecting creep include temperature, stress and steel itself. The higher the temperature is, the greater the stress is, and the faster the creep speed is. According to the manufacturer's test data, the creep strength of P91 steel is almost twice that of P22 steel at 105h and 550 ℃. At 540 ℃, the allowable stress of P91 steel is about 90% higher than that of P22. The allowable stress is about 90% higher, which makes the design wall thickness of the pipeline and the design wall thickness and weight of the corresponding pipe fittings decrease. Due to the weight reduction, the stress level of the pipe system supports and hangers also decreases. In addition, due to the small linear expansion coefficient, the thermal stress of the pipe system also decreases