FATIGUE CRACK GROWTH AND FRACTURE RESISTANCE OF NARROW GAP PIPE WELDS OF TYPE 304LN STAINLESS STEEL

摘要

This paper aims at quantifying the fatigue crack growth rate and fracture resistance behavior of the austenitic stainless steel pipe welds by carrying out full scale pipe weld tests. Superiority of the welds produced by hot wire Gas Tungsten Arc Welding (GTAW) over the existing cold wire GTAW and shielded Metal Arc Welding (SMAW) has also been brought out. Prediction of fatigue crack growth for the cracked pipe using Paris law has also been reported. The fatigue crack growth rate (FCGR) and fracture resistance of stainless steel weld and heat affected zone (HAZ) were evaluated to support the LBB application. Tests were carried out room temperature. FCGR test results showed lower crack growth rate in HAZ and the weld fusion zone compare to the base metal for both types of weld. By analyzing the microstructures in the weld fusion zone and HAZ, their effects on crack growth rate were discussed. Analytical predictions for fatigue crack growth life were made using the Paris constants generated from compact tension specimens. These predictions were made for pipe weld, its heat affected zone and pipe (base). Prediction for fatigue crack growth has been compared with experimental results. Effect of prior fatigue loading on fracture resistance of the pipe was also investigated by carrying out full scale pipe weld tests on hot wire and cold wire GTAW. It has been shown that there is no significant effect.