Fabrication of lotus-type porous stainless steel by continuous zone melting technique

Lotus-type porous stainless steel (SUS304L) rods were fabricated by continuous zone melting technique under pressurised gases of hydrogen and inert gas such as argon or helium. The pores with cylindrical shape, whose growth direction is parallel to the solidification direction, were observed in the rods. The dependence of the porosity and pore diameter on the partial pressure of hydrogen or the total pressure and on the transference velocity of rods was investigated. It was found that the porosity increases with increasing partial pressure of hydrogen under the constant total pressure and the pore diameter decreases with increasing transference velocity. The maximum porosity was about 60% under the experimental conditions in the present work. The observation of the inicrostructure and the measurement of the tensile strength were also carried out.