Numerical Simulation of in-Service Welding Residual Strength Size Effect Based on Sysweld

Abstract: The X70 pipeline steel high temperature tensile test and simulation that based on the welding software of SYSWELD were used to study the in service welding residual strength size effect. The results of tensile test shows that, when the temperature is 700°C, the strength of X70 pipeline steel is 250MPa, when the temperature rise from 800°C to 1300°C, the strength reduce nonlinearly from 102MPa to 19MPa The equivalent method of defect, the numerical simulation results and the high temperature mechanical properties research data were combined to establish residual strength burn through criterion of in service welding, and the influence of the pool size effect to the criterion was also be studied, and the results shows that, when the area of the equivalent defect increased to 1.1 times the bearing capacity decreased from 3.38MPa to 0.5MPa, which showed that the bearing capacity was decreased significantly with a slightly increase of molten pool area, the pool length had little effect on the residual strength, the pool depth and pool width have significant effect on the residual strength, and the change of penetration has a greater affected on the strength distribution of the high temperature area, the pool size effect is obvious.

Key words: in-service welding; gas pipeline; residual strength; size effect; numerical simulation