Comparative Analysis of Flux-Cored Arc Welding and Shielded Metal Arc Welding Processes on Hardox 450 Steel: Microstructural, Mechanical, and Fractographic Investigation

Abstract

This study investigates the microstructural and mechanical properties of Hardox 450 steel joints welded using flux-cored arc welding (FCAW) and shielded metal arc welding (SMAW) techniques. Hardox 450 steel plates with a thickness of 4 mm were welded using AWS A5.20 E71T-1C filler rods for FCAW and AWS A5.1 E7018 filler rods for SMAW. The welded joints were characterized through macrostructural and microstructural examinations using optical microscopy and scanning electron microscopy (SEM), as well as Rockwell hardness tests and tensile property evaluations. The results showed that both FCAW and SMAW produced defect-free welds with acceptable reinforcement heights and well-defined fusion zones, heat-affected zones (HAZ), and weld zones (WZ). The hardness measurements revealed lower hardness values in the WZ compared to the HAZ and base metal for both welding processes, with FCAW joints exhibiting higher WZ hardness than SMAW joints. Tensile tests demonstrated that the FCAW joints had superior tensile strength of 903.8 MPa compared to the SMAW joints of 755.6 MPa, representing joint efficiencies of 65% and 55%, respectively, relative to the base material of 1385.5 MPa). However, the SMAW joints displayed higher fracture strain of 17.1% than the FCAW joints of 13.6%, indicating greater ductility. Fracture surface analysis using SEM revealed distinct failure mechanisms, with the FCAW joints exhibiting more pronounced cleavage facets and brittle fracture characteristics compared to the SMAW joints. The findings highlight the influence of welding processes and filler materials on the microstructure and mechanical properties of Hardox 450 steel weldments.