Influence of multiple repairs on the quality of duplex welded joints

Duplex stainless steels (DSSs) find increasing use as a substitution to austenitic stainless steels in oil, gas and petrochemical industries, particularly in aggressive environments. Duplex stainless steels with appropriate controlled ferrite-austenite balance combine the attractive properties of excellent strength, general corrosion performance and adequate weldability. All the welding joints subjected to the regulation must be controlled before commissioning the pipeline and even before hydrostatic tests; all not acceptable defects detected with NDT control methods must be eliminated. In some cases, several successive repairs are often preferred to part replacement in the pipeline due to lack of experience of the welder performing the repairs or lack of expertise of the controller ensuring the application of the welding procedure. The purpose of this work is to study the influence of repairs on the same welding joint on the microstructure and the mechanical properties of the heat-affected zone in duplex stainless steel with ۲۲% chromium welding joints. For this purpose, a cylindrical specimen is prepared, on which the various repairs are carried out. Then, an NDT control and the main mechanical and micrographic tests are conducted. The results obtained after four repairs revealed that the multiple repairs made to the same joint did not affect the quality of the welding joints.

Keywords:

Duplex stainless steel , Pipe , Successive repair , Welding defect