Welding microstructure analysis and residual stress simulation of P92 steel

The welding experiments of P92 steel plate with four layers and four passes were carried out. The welding residual stress was measured by X-ray diffraction method, the microstructure of the weldments was characterized by optical metallography microscope, and the hardness of the weldments was measured by Vickers hardness tester. At the same time, the welding simulation of P92 steel plate was carried out based on SYSWELD software under the same conditions, and the calculation results of welding stress field and strain field were obtained. The dynamic changes of residual stress after welding of different welds were compared using the life-and-death element technology, and the generation and influencing factors of multi-layer welding residual stress were explored. The metallographic test results show that the microstructure of the weld is quenched martensite, and the maximum hardness is up to 436 HV. The base metal structure is tempered martensite with an average hardness of 236 HV. The hardness of the heat affected zone decreased gradually from the overheated zone to the normalized zone. The finite element calculation results show that the residual stress distribution obtained by simulation is in good agreement with the measured value, which proves the accuracy of the welding model. The maximum values of transverse tensile stress and longitudinal compressive stress appear at the weld, and the maximum values of longitudinal tensile stress and transverse compressive stress appear at the junction of the heat-affected zone and the base metal, but the distribution trend of residual stress is basically unchanged with the change of the weld height. The thermal load of the upper pass has a great influence on the residual stress distribution of the lower pass, and the solid phase transformation effect not only affects the residual stress distribution, but also causes the large angular deformation of the plate during welding.