高けい素鋳鉄の急冷組織について

抄録

  The solidification behavior on casting iron in metal mold is characterized by fast solidification rate, large supercooling and steep temperature gradient. Metal mold casting structure, which is susceptible to solidification according to the metastable iron-iron carbide system, is ordinarily improved by heat treatment. It is reasonable to make an attempt to minimize or eliminate this treatment process by taking advantage of the self-annealing effect which is obtained by recalescense after supercooling of molten iron in metal mold. A very interesting as-cast structure resulted by obtaining a prominent self-annealing effect during solidification and cooling of molten iron in metal mold selecting carbon and silicon contents as well as the cooling rate. Most effective composition of iron was about 2.9%C and 5.2%Si and cast into water-cooled copper mold 15mm in diameter. The spheroidal graphite structure of this iron without spheroidization treatment was such that the graphite was smaller in size and the nodule number was higher than those of normal ductile cast iron. And moreover, the transition structure of graphite form was observed proceeding from the edge to the center of the specimens.