Influence of welding gap on microstructure and mechanical performance of AH36 steel SAW joints

Abstract

The present investigation explored how welding gap sizes (5, 8, and 11 mm) influence the microstructural evolution and mechanical performance of AH36 steel joints produced by submerged arc welding (SAW). Macroscopic and microscopic analyses showed sound weld formation without major defects. The heat-affected zone (HAZ) width increased with larger gaps. The deposited weld metal was primarily composed of fine ferrite, pearlite, and minor granular bainite, with fine oxide inclusions providing pinning effects. All joints exhibited good bending performance, maximum hardness of 193 HV, and Charpy impact energy above 50 J (up to 208 J). The 5 mm gap joint achieved the highest tensile strength of 629 MPa with 28% elongation. These results offer valuable guidance for optimizing SAW parameters in shipbuilding.