Microstructure and mechanical properties of gas metal arc-welded Fe-Mn-Si seismic damping alloy

A brace-type seismic damper made of an Fe-15Mn-11Cr-7.5Ni-4Si alloy solidified in the ferrite-austenite (FA) mode and SN490B steel, which can be constructed via welding, was proposed. To realize the proposed seismic damper, gas metal arc welding was applied to produce similar FMS/FMS fillet welds and dissimilar FMS/SN490B fillet weld joints. Based on the Schaeffler diagram, similar and dissimilar welding consumables were designed such that the fillet weld metal solidified in the FA mode without solidification cracking. Sound similar fillet welded joints were obtained using two types of welding consumables with different Cr/Ni equivalent ratios although both the similar fillet weld metals had a coarse columnar austenite grain structure. These displayed higher tensile strengths (716–736 MPa) and marginally lower elongations (67–70%) than the FMS alloy. Moreover, a similar fillet weld metal with a chemical composition almost identical to that of the FMS alloy exhibited a remarkable low-cycle fatigue life (5740 cycles). This was shorter than that of the FMS alloy (9351 cycles) owing to the easier formation of α'-martensite. A dissimilar fillet welded joint with a chemical composition within the austenite region was produced without solidification cracking. The dissimilar fillet weld metal showed high tensile strength (867 MPa) and total elongation (61%). These were comparable to those of similar fillet weld metals.