Application of lotus-type porous carbon steel to moving body of machine tools

Lotus-type porous carbon steel (lotus carbon steel) plates with a porosity of 50% were fabricated by continuous casting technique. A saddle was built by welding the fabricated lotus carbon steel plates together and was loaded on a machining center. The static stiffness, cutting performance, dynamic characteristics, electrical consumption and thermal displacement of the machining center were evaluated. Although the weight of the saddle was reduced largely by 41% compared with a conventional saddle made of cast iron, the reduction of the static stiffness was only 13 - 27% and the degradation of the cutting performance was not so significant. These results were due to high flexural rigidity and torsional rigidity per unit weight of the lotus carbon steel plate compared with nonporous cast iron parts, since the lotus carbon steel plate had a unique structure with nonporous skin surfaces and porous part inside. The thermal displacements of the saddle made of lotus carbon steel were 17-36% larger than that of cast iron. Furthermore, the reduction of the weight of the saddle resulted in a reduction of the required time for acceleration by half and a reduction of the energy consumption during machining by 15 - 20 %.