耐震用Ｎｉ‐Ｃｒ系オーステナイト鋼の開発

Abstract

Buildings and infrastructure in earthquake-prone areas need to be designed and constructed with enough strength and ductility to absorb a large amount of seismic energy during earthquakes. Effective energy absorption can be achieved by placing hysteretic damper in the structures to meet the damage limitation requirements for those structures. Ultra-low carbon steel having low 0.2% proof stress (σ0.2 : 100MPa) has been used in practice for dampers to improve the damping and inelastic cyclic performance of structures. This investigation aims to obtain more ductile materials for the dampers, with a greater capacity to absorb seismic energy. The development of such ductile materials involves three steps : (1) Set 0.2% proof stress to about 100MPa, tensile stress to 400MPa, and elongation to 30% or greater as target values for the material. (2) Select a crystal lattice type capable of achieving these values. (3) Search for optimal systems based on the result of this selection. Tensile tests were carried out on several tens of Fe-Ni and Fe-Ni-Cr alloys produced for this investigation, and an austenitic system having a face-centered cubic lattice and ultra-low carbon content were found to be favorable for meeting the above requirements. Fe-15Ni-15Cr alloy was selected as a suitable candidate. A semi-production heat of this steel was made. Hot-rolled and annealed steel plate exhibited 0.2% proof stress of 76MPa, tensile strength of 421MPa and elongation of 78%.