Abstract: Tensile tests, bending tests, impact tests, and intergranular corrosion resistance tests were conducted on welded joints of thick-walled TP347 steel pipes that underwent stabilizing heat treatment and maintained their weld state. The results showed that plasticity, toughness, and corrosion resistance of the welded joints of thick-walled TP347 steel pipes decreased after stabilizing heat treatment, and the weld seam experienced loss of plasticity damage, leading to reheating cracking. Further analysis was conducted using microscopic characterization techniques such as optical microscopy, scanning electron microscopy, and energy spectrum analysis to study the nucleation and propagation of reheating cracks. During the stabilizing heat treatment process of welded joints of thick-walled TP347 steel pipes, significant welding residual stresses were slowly released, and at high temperatures and under the joint action of stresses, carbides, nitrides, and oxides with a larger amount of chromium and niobium precipitated at grain boundaries. Reheating cracks nucleate at the interface between a large number of precipitates and the matrix (voids). Accompanied by the residual stress, these voids merge, causing cracks to propagate along grain boundaries. The experimental results showed that using stabilizing heat treatment to improve the corrosion resistance of welded joints of thick-walled TP347 steel pipes is not optimal because it is easy to cause damage to the joints under large residual stresses and high temperatures.