Abstract: An additive for use in producing spheroidal graphite cast iron of the present invention contains a fine particle of magnesium oxide having a purity of 90 weight % or more and at least one selected from the group consisting of a graphite-spheroidizing material, an inoculant and a graphite-spheroidizing inoculant. The fine particle of highly pure magnesium oxide increases the number of nuclei in a melt, and as a result thereof, increases the graphite spheroid count of a spheroidal graphite cast iron being produced. Another additive for use in producing spheroidal graphite cast iron of the present invention contains at least one selected from the group consisting of a graphite-spheroidizing material, an inoculant and a graphite-spheroidizing inoculant, and an oxide of a metal which has, at a temperature of a melt at a time when subjected to a graphite-spheroidizing treatment, an affinity for oxygen smaller than that of a graphite-spheroidizing element being used in the graphite-spheroidizing treatment.

Abstract: A method of continuously melting a material comprises the steps of depositing carbon in a crucible furnace provided with a melt outlet and an inlet in an upper portion thereof, heating the carbon by electromagnetic induction heating by an electromagnetic coil provided around the outer periphery of the furnace, continuously supplying the material to be melted onto the heated carbon through the inlet and melting the material to be melted by electromagnetic induction heating so as to cause a melt to continuously flow out of the furnace through the melt outlet. The temperature of the melt flowing out of the furnace is adjusted by controlling the ratio between the quantities of heat supplied by the electromagnetic induction heating to the carbon and to the material to be melted.

Abstract: A tapered mould consisting essentially of a rigid outer frame formed of a set of radially arranged longitudinally extending guide members and a set of axially spaced encircling rings, and a gapped frustoconical tubular casing of resilient sheet material having a set of longitudinal stiffening members arranged thereon for sliding engagement with the respective guide members. The gap in the wall of the tubular casing, extending along a longitudinal line on the periphery of the casing, is opened and closed automatically as the tubular casing inserted in the outer frame is moved axially in opposite directions. Labor - consuming bolt - clamping and releasing operation is completely eliminated and the mould operation can be mechanized with ease, as desired. Packing means interposed between a pair of stiffening members arranged on the opposite sides of the gap further ensures leak - proof gap closing.

Abstract: Labor-consuming bolting operation as required with conventional forms of the gapped or split type has been ingeniously expelled by the provision of a form structure comprised essentially of a rigid tubular frame, a resilient gapped tubular casing arranged therein as a form in which concrete is to be placed, and camming means arranged on the inside of the rigid frame and on the outside of the resilient casing and cooperable to act upon the resilient tubular casing radially and circumferentially thereof with axial movement of such resilient casing relative to the rigid frame so as to close the gap in the resilient casing while holding the latter in coaxial relation to the rigid frame, any loss of moisture content of concrete during centrifugal forming operation can be effectively prevented by arranging an appropriate packing element on the resilient casing along the gap therein.

Abstract: A nitrogen containing additive for strengthening cast iron which contains silicon, calcium, nitrogen, at least one of chromium and manganese and the balance being iron and incidental impurities. Addition of said additive to flake graphite cast iron melt results in increase in tensile strength by 7 - 15 kg/mm.sup.2 and hardness by 20 - 60 in Brinell hardness and reduction in depth of chill due to synergistic effect of the alloying elements contained in the additive.