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.

Investigation of Microstructure and Mechanical Properties of MIG Welded Mild Steel Plates

“…The micro hardness decreased in the order Base Metal > HAZ > Welding zone. Rafael Garcia [11] carried out the metallurgical characterization of API x65 steel joint welded by MIG welding process with axial magnetic field. API x65 was heat treated in nonconventional way to improve the resistance produced mechanically.…”

The effect of external magnetic flux field in the QTS weldment on the change of fatigue crack propagation behaviors

“…Electromagnetic stirring in the weld pool can significantly reduce the porosity of the weld bead, promote the growth of columnar grains and is able to withstand the tense cracks caused by sulfide [26]. Enlarging the electromagnetic force by increasing the welding current will increase the weld heat input, which is certainly not the right solution as it will raise the peak temperature of the weld and the cooling rate which can produce large thermal stresses.…”

A study on the stress corrosion mechanism of microstructures in a heat-affected zone of high-strength steel weldment in artificial seawater

“…Based on the result, the radius of the capacitive loop of the ICHAZ was smaller than that of other microstructures, indicating that the corrosion resistance was reduced by the M/A islands which can facilitate galvanic corrosion. Meanwhile, the radius of the capacitive loop of the HAZs were smaller than BM, which is mainly attributed to the welding defects [23,24], suggesting that welding joints are liable to corrosion. The results were consistent with the potentiodynamic polarization analysis.…”