Analytical-Numerical Methods of Predicting the Mechanical Properties of Welded Joints Made of Steel

The work concerns an analysis of phase transformations in the solid state and the prediction of the structure and mechanical properties of steel using analytical models and numerical methods. The analytical models involve building simplified continuous cooling transformation diagrams for welding, predicting the microstructure based on the chemical composition of steel, as well as assessing the mechanical properties of the welded joint made of S1100QL steel. The kinetics of phase transformations and prediction of mechanical properties distribution in the cross-section of the joint are carried out based on analytical methods. The analytical models presented in this work replace the classic mathematical models of phase transformation kinetics and interpolated experimental continuous cooling transformation diagrams (time-temperature transformation). The analytical relationships presented in the work are determined by the chemical composition of the steel and the cooling time t(8/5). Based on the chemical composition of the steel, the continuous cooling transformation diagrams and the specific volume fractions of phases as a function of the cooling time t(8/5) of the steel are determined. The numerical simulation of the welding process of sheets made of S1100QL steel is carried out in Abaqus software using DFLUX and HEATVAL numerical subroutines. The calculations use the mathematical model of Goldak's volumetric welding source power distribution. Thermal cycles and temperature field are numerically determined. The research results obtained in this work are compared with the experimental results.