Effect of reheating on the properties of weld metals obtained by the spin arc process in a narrow gap joint

This work compares the mechanical properties of the surface and root regions of high-strength weld metals deposited by the spin arc process using a metal-cored wire as filler metal under various gaseous atmospheres using a narrow gap joint. Weld metals were deposited using two welding passes in the flat position over carbon steel plates with a thickness of 10 mm, a preheat temperature of 100 °C, a rotation frequency of 1,500 rpm, a rotation diameter of 3 mm, and an average heat input of 2 kJ/mm. Mixtures of Argon containing 5, 10, and 25% CO2 were used as shielding gas. After welding, metallographic examination by electron microscopy and electron backscattering diffraction at the weld metal centerline was conducted. Vickers microhardness tests and Charpy-V impact tests were performed at the positions examined by metallography. The results revealed that the weld metals obtained by the GMAW-RE process with different shielding gases present equivalent microstructure and mechanical properties both at the root and surface regions studied, thus indicating that the root pass is not significantly affected by dilution due to the joint geometry. In addition, the reheated region exerts a strong effect on the impact toughness of weld metal.