690 MPa급 고장력강의 용접성 및 내식성에 미치는 예열의 영향

This study is an evaluation on the effects of pre-heating on the weldability and corrosion resistance of 690 MPa grade, quenched and tempered steel. Micro-structural examination on pre-heated specimen confirmed that pre-heating affects coarse grain microstructures in comparison to the none pre-heated specimen. The tensile strength of welded specimen without pre-heating is higher than the tensile strength of welded specimen with pre-heating. The weld of pre-heated specimen, however, exhibits higher impact absorbed energy capability. The weld fracture morphology reveals both quasi-cleavage and ductile fractures. Corrosion test results on both welds showed increasing current density with increasing concentrations of NaCl solution. The pre-heated specimen exhibited higher corrosion current. Image Quality Mapping analysis in EBSD after impact testing determined less deformation on the pre-heated specimen.