Microstructure and impact toughness of high strength steel weld metals deposited by MCAW-RE process using different shielding gases

摘要

The MCAW with rotating electrode process (MCAW-RE) is a variation of the conventional MCAW (metal-cored arc welding) process, where reduced costs and superior productivity are obtained due to narrow gap welding, since the rotational motion of the electrode allows the electric arc to reach peripheral regions of the groove, preventing lack of fusion on the sidewall. Although there is some information about the operational characteristics of this process, the literature studying the mechanical properties is very limited. This work evaluates the mechanical and microstructural properties of high strength steel weld metals obtained by the MCAW-RE using two different mixtures of Ar-CO2 as shielding gas. Multipass welding by MCAW-RE was performed with preheating of 100 degrees C, in 500 x 150 x 10 mm steel plates. Weld metals were obtained by the MCAW-RE process using a consumable of the class 700 MPa and two mixtures of Ar-CO2 (5% CO2 and 25% CO2) as shielding gas. The results obtained from mechanical tests (hardness and impact Charpy-V) and metallographic examination (optical microscopy, scanning electron microscopy, and electron backscattering diffraction) carried out in samples removed transversally to the weld bead showed equivalent results for all weld metals. These results evidenced that the MCAW-RE process can provide weld metals with satisfactory behavior with different shielding gases. This process has a high potential for replacement of the conventional GMAW process because the weld metals achieved the requirements for several industrial applications.