Papers by Keyword: Lotus-Type Porous Carbon Steel

Abstract: Lotus-type porous carbon steel (lotus carbon steel) plates were fabricated by continuous casting technique in a pressurized nitrogen atmosphere. The experiments were done both with adding 0.3wt% of NiO powder in molten carbon steel in a ceramic crucible and without NiO powder. The lotus carbon steel fabricated without NiO powder under nitrogen pressures of 0.1 and 0.5 MPa had single pores which grew independently. On the other hand, the lotus carbon steel fabricated with adding NiO powder had pores which coalesced each other and became in irregular shapes. Under nitrogen pressure of 2.5 MPa, the pores formed with adding NiO powder were smaller than that formed without NiO powder. The porosity increased by adding NiO powder in every pressurized nitrogen atmosphere. From these results, NiO powder in molten carbon steel is considered to act as nucleation sites for pores at the solid-liquid interface and to increase of the pore number.

Abstract: The lotus-type porous carbon steel with cylindrical pores has been fabricated by continuous zone melting technique in pressurized mixture of hydrogen and helium gases. In order to investigate the mechanical properties, the tensile and compression tests were carried out. The ultimate tensile strength of the specimen with cylindrical pores parallel to the solidification direction is lower than the estimated value assuming that the strength is decreased in proportion to decreasing cross section area of the specimen, while the yield strength is higher than that estimated. The compressive yield strength is also higher than that estimated. The increase in yield strength is attributed to the precipitation strengthening. The tensile strength is increased by quenching and tempering, while the elongation decreases. Such mechanical properties are discussed in terms of microstructureal analysis. Furthermore, simulations of the mechanical properties by FEM analysis were carried out.