Performance of P91 steel

    P91 steel is to fill the pearlite heat-resistant steel and austenitic heat-resistant steel 600 ~ 650 ℃ between the temperature area of the new soda water pipeline steel, are martensitic heat-resistant steel, the maximum temperature of 650 ℃, the actual On the basis of the original 9Cr-1Mo steel added V, Nb, N and other strengthening elements, the formation of a new type of deterioration of steel.

    P91 welding performance

    P91 steel can be arc welded according to existing methods, including welding by means of argon welding (TIG). The choice of electrodes and flux should be made as close as possible to the chemical composition of the weld and the base metal so that the weld metal has the same or better creep and lasting strength as the base material. As the steel is not sensitive to hot cracking, pre-heating to 150 ~ 200 ℃ before welding will not appear cracks, and with a variety of steel, such as P22 steel (pearlitic heat-resistant steel), X20CrMoV121 (martensite hot steel) and TP304H (austenitic heat-resistant steel) and other steel welding, the following describes the welding of P91 steel:

    A) P91 steel and P91 steel welding, the choice of 9Cr-1Mo (T9) or improved 9Cr-1Mo (T91) electrode, wall thickness greater than 25 mm using the latter, the preheating temperature of 200 ℃, after welding slowly Cooled to room temperature and then tempered at temperatures above 730 °C;

    B) P91 steel and 10CrMo910 welding, the welding material to match with the 10CrMo910, 730 ℃ after the release of stress should be cooled in the air 2 h, because the two parts of the welding parts of a decarburization area, if the use of 10CrMo910 electrode welding, To ensure that the carbon content of welding metal is high enough to meet the requirements of lasting strength;

    C) P91 steel and P22 steel welding, the electrode can be used 2.25Cr-1Mo electrode, preheating temperature of 200 ℃, after welding slowly cooled to room temperature, and then 700 ~ 725 ℃ tempering, but also in the P91 steel side Welding 5Cr1-1Mo electrode, and then welding with the P22 steel;

    D) P91 steel and X20CrMoV121 welding, the use of two matching welding materials, such as P91 steel electrode, preheating temperature of 250 ℃, after welding slowly cooled to 80 ~ 100 ℃, above 750 ℃ temperature tempering;

    E) P91 steel and TP304H welding, with Inconel 182Ni-based alloy electrode, preheating temperature of 200 ℃, after welding to room temperature, at 700 ~ 730 ℃ tempering.

    Above the heat treatment temperature after welding depends on the pipe wall thickness, small diameter pipe treatment 0.5 h, large diameter pipe to the wall thickness every 25 mm treatment 1 h. Because P91 creep strength is high, under the same conditions, the pipe wall thickness is thinner than that of P22 steel, and the amount of metal filled with weld is relatively small, but P91 steel is sensitive to weld type IV crack. Therefore, it is necessary to minimize the P91 steel Of the system stress, the wall thickness of more than 12.5 mm of the pipe, the requirements of the cold after welding to 100 ℃ or more tempering.