Provided is a black heart malleable cast iron and a method for manufacturing the same which can significantly shorten the time required for graphitization, as compared with the prior art. The black heart malleable cast iron includes a matrix of ferrite and lump graphite included in the matrix, and includes at least one selected from the group consisting of (i) 0.0050% by mass or more and 0.15% by mass or less of bismuth and 0.020% by mass or more of manganese, and (ii) 0.0050% by mass or more and 1.0% by mass or less of aluminum and 0.0050% by mass or more of nitrogen. In addition, the grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph of the matrix and a standard grain size chart.

Provided is a black heart malleable cast iron and a method for manufacturing the same which can significantly shorten the time required for graphitization, as compared with the prior art. The black heart malleable cast iron includes a matrix of ferrite and lump graphite included in the matrix, and includes at least one selected from the group consisting of (i) 0.0050% by mass or more and 0.15% by mass or less of bismuth and 0.020% by mass or more of manganese, and (ii) 0.0050% by mass or more and 1.0% by mass or less of aluminum and 0.0050% by mass or more of nitrogen. In addition, the grain size of the matrix is 8.0 or more and 10.0 or less in terms of grain size number, numerically determined by comparison between a metallographic photograph of the matrix and a standard grain size chart.

The present invention refers to a vermicular cast iron alloy specially designed for internal combustion engine blocks and heads having special requirements of mechanical strength and fatigue strength. Vermicular iron alloy with high mechanical strength and high fatigue strength for the production of internal combustion engines blocks and heads characterized by having a microstructure of pearlitic matrix and predominantly vermicular graphite (>70%) and presence of graphite nodules in up to 30%, wherein its graphite microstructure is described by the Microstructure Factor (FM), as defined below, with Microstructure Factor values higher than 0.94.

The present invention refers to a vermicular cast iron alloy specially designed for internal combustion engine blocks and heads having special requirements of mechanical strength and fatigue strength. Vermicular iron alloy with high mechanical strength and high fatigue strength for the production of internal combustion engines blocks and heads characterized by having a microstructure of pearlitic matrix and predominantly vermicular graphite (>70%) and presence of graphite nodules in up to 30%, wherein its graphite microstructure is described by the Microstructure Factor (FM), as defined below, with Microstructure Factor values higher than 0.94.

The invention provides a method for increasing the quality of graphite balls. The method comprises melting molten iron in an electric furnace, increasing the sulfur content in the molten iron during the melting process, and adding rare earth in the electric furnace or in a nodularizing ladle; after the molten iron is completely melted, pouring the molten iron into the nodularizing ladle and nodularizing; and after nodularization, adding ferromanganese to a transfer ladle. In the present invention, sulfur is added to molten iron in advance, and rare earth is added to a nodularizing ladle previously, so that a large number of dispersed rare earth sulfide particles are formed in the molten iron during the nodularization process. Rare earth sulfide particles serve as the nuclei of graphite crystallization to increase the number of graphite balls, and improve the roundness of graphite balls.

The invention provides a method for increasing the quality of graphite balls. The method comprises melting molten iron in an electric furnace, increasing the sulfur content in the molten iron during the melting process, and adding rare earth in the electric furnace or in a nodularizing ladle; after the molten iron is completely melted, pouring the molten iron into the nodularizing ladle and nodularizing; and after nodularization, adding ferromanganese to a transfer ladle. In the present invention, sulfur is added to molten iron in advance, and rare earth is added to a nodularizing ladle previously, so that a large number of dispersed rare earth sulfide particles are formed in the molten iron during the nodularization process. Rare earth sulfide particles serve as the nuclei of graphite crystallization to increase the number of graphite balls, and improve the roundness of graphite balls.

The present invention pertains to a non-magnesium process to produce Compacted Graphite Iron (CGI) by placing a treatment alloy into a treatment ladle, and then placing an inoculant over the treatment alloy in the treatment ladle and pouring a molten base metal there over. The treatment alloy comprises iron, silicon and lanthanum, wherein lanthanum is 3-30% by weight of the treatment alloy, silicon is 40-50% by weight of the treatment alloy, and the remaining is Iron. Lanthanum in the treatment alloy makes the graphite precipitate as vermiculite (compacted form) instead of flake or spheroids. With extended process window offered by this new process (0.03-0.1% residual lanthanum in the metal) required to make CGI, this new process removes the stringent process control (0.01-0.02% residual magnesium in the metal) dictated by the magnesium process of making CGI.

The present invention pertains to a non-magnesium process to produce Compacted Graphite Iron (CGI) by placing a treatment alloy into a treatment ladle, and then placing an inoculant over the treatment alloy in the treatment ladle and pouring a molten base metal there over. The treatment alloy comprises iron, silicon and lanthanum, wherein lanthanum is 3-30% by weight of the treatment alloy, silicon is 40-50% by weight of the treatment alloy, and the remaining is Iron. Lanthanum in the treatment alloy makes the graphite precipitate as vermiculite (compacted form) instead of flake or spheroids. With extended process window offered by this new process (0.03-0.1% residual lanthanum in the metal) required to make CGI, this new process removes the stringent process control (0.01-0.02% residual magnesium in the metal) dictated by the magnesium process of making CGI.

An inoculant for the manufacture of cast iron with spheroidal graphite is disclosed, the inoculant has a particulate ferrosilicon alloy having between 40 and 80% by weight of Si; 0.02-8% by weight of Ca; 0-5% by weight of Sr; 0-12% by weight of Ba; 0-15% by weight of rare earth metal; 0-5% by weight of Mg; 0.05-5% by weight of Al; 0-10% by weight of Mn; 0-10% by weight of Ti; 0-10 by weight of Zr; the balance being Fe and incidental impurities in the ordinary amount, wherein the inoculant additionally contains, by weight, based on the total weight of inoculant: 0.1 to 15% of particulate Bi.sub.2S.sub.3, and optionally between 0.1 and 15% of particulate Bi.sub.2O.sub.3, and/or between 0.1 and 15% of particulate Sb.sub.2O.sub.3, and/or between 0.1 and 15% of particulate Sb.sub.2S.sub.3, and/or between 0.1 and 5% of particulate Fe.sub.3O.sub.4, Fe.sub.2O.sub.3, FeO, or a mixture thereof, and/or between 0.1 and 5% of one or more of particulate FeS, FeS.sub.2, Fe.sub.3S.sub.4, or a mixture thereof, a method for producing such inoculant and use of such inoculant.

An inoculant for the manufacture of cast iron with spheroidal graphite is disclosed, the inoculant has a particulate ferrosilicon alloy having between 40 and 80% by weight of Si; 0.02-8% by weight of Ca; 0-5% by weight of Sr; 0-12% by weight of Ba; 0-15% by weight of rare earth metal; 0-5% by weight of Mg; 0.05-5% by weight of Al; 0-10% by weight of Mn; 0-10% by weight of Ti; 0-10 by weight of Zr; the balance being Fe and incidental impurities in the ordinary amount, wherein the inoculant additionally contains, by weight, based on the total weight of inoculant: 0.1 to 15% of particulate Bi.sub.2S.sub.3, and optionally between 0.1 and 15% of particulate Bi.sub.2O.sub.3, and/or between 0.1 and 15% of particulate Sb.sub.2O.sub.3, and/or between 0.1 and 15% of particulate Sb.sub.2S.sub.3, and/or between 0.1 and 5% of particulate Fe.sub.3O.sub.4, Fe.sub.2O.sub.3, FeO, or a mixture thereof, and/or between 0.1 and 5% of one or more of particulate FeS, FeS.sub.2, Fe.sub.3S.sub.4, or a mixture thereof, a method for producing such inoculant and use of such inoculant.