Résumé:
This thesis investigates the behavior of a low-alloy steel grade API X70 used in the production of spiral welded pipes for hydrocarbon transport. The objective is to assess the influence of forming and welding processes (SAW, SMAW) on the mechanical, chemical, and microstructural properties of the material. The industrial unit ALFAPIPE (Annaba), certified under API 5L standards, served as the application site. The experimental methodology involved tensile tests, Charpy impact testing at -10 °C, Vickers hardness measurements, and metallographic analysis on both the base metal and heat-affected zones. Results confirm the conformity of X70 steel to international standards in terms of strength, ductility, and microstructural homogeneity, highlighting the critical role of precise welding control in ensuring the long-term reliability of pipeline infrastructure.
