Post welding residual stress in P91 alloy steel
The chromium-molybdenum steel pipe P91 is widely used in the power plants construction, because they can withstand higher temperatures and operating pressures, in order to increase operating efficiency and output. This material has a complex microstructure which is extremely vulnerable to convert into Austenite form near the temperature for heat treatment. During the welding procedure should be very carefully, because otherwise the residual stress installed post welding will reach high values. A series of experimental studies was carried out, which has shown the development in the magnitude of transverse and longitudinal residual stresses and the values in both directions were determined. For but welded joints the residual stresses in the three direction were measured and the results are reported here. For measuring was used the hole drilling method through “measuring balls” or electrical strain gauge. Except the experiments the finite element method was used to determinate the value and the distribution of the residual stresses. The experimental and FEM results were compared between them and no discrepancy was found.