Metallurgical Characterization of API X65 Steel Joint Welded by MIG Welding Process with Axial Magnetic Field

Abstract

In this work, API X-65 pipeline steel non-conventionally heat treated, to enhance its mechanical resistance, was welded using the Metal Inert Gas (MIG) process with and without the application of low intensity axial magnetic fields (6 mT). Microstructural and mechanical characterization of the welds revealed that the use of the magnetic field during welding improved the toughness of the welds and therefore increased their mechanical strength. Failure of the welds occurred far from the weld beads. The electromagnetic stirring of the weld pool significantly reduced the levels of porosity in the weld beads and favored columnar grain growth due to the ferromagnetic nature of the base metal and filler wire. Impact toughness was also improved from 120 to 266 J. Hardness values measured across the welds indicate that the use of the magnetic field during welding yields welds suitable for withstanding sulphide stress cracking.

Keywords

• API X-65
• MIG
• Magnetic field
• Welding
• Acicular ferrite