Residual Stress Induced by Phase Transformation and its Role in the Delayed Cracking Performance of 22MnB5 Hot Roll Bending Pipes

Residual stress plays an important role in the delayed cracking performance of the 22MnB5 hot roll bending pipe. In the present study, the residual stress distribution of the 22MnB5 hot roll bending pipes with different pipe thicknesses is compared. The results show that both the tensile and compressive residual stresses can be traced in the bending zone for the pipe with plate thickness around 1.5 mm. On the contrary, only tensile residual stress obtains in the residual stress measurement positions for the thicker one (~ 2.3 mm). In addition, the thicker 22MnB5 pipe exhibits poor delayed cracking behavior in the solution of 0.1 mol/L HCl for 300 h. Compared with thinner 22MnB5 pipe, high tensile residual stress occurs in the thicker one induced by phase transformation and deformation during the hot roll bending process, deteriorating its delayed cracking performance.