A spheroidal graphite cast iron having a chemical composition of: C: 3.0% to 4.0%, Si: 2.0% to 2.4%, Cu: 0.20% to 0.50%, Mn: 0.15% to 0.35%, S: 0.005% to 0.030%, Mg: 0.03% to 0.06%, each by mass, and the balance being Fe and inevitable impurities, where Mn and Cu are contained at 0.45% to 0.75% in total; and a structure in which a ferrite layer encloses spheroidal graphite crystallized out in a matrix of pearlite. Part of the pearlite is extended from the matrix side to the spheroidal graphite side to divide the ferrite layer at one or more areas.

The present invention provides a casting method and cast product of spherical graphite cast iron, in which, even with a small modulus, there is no chill, the spherical graphite in the tissue is further made ultrafine, the dispersion of the particle diameter is small, and the number of the particles is several times that of the conventional one in the as cast state where heat treatment is not carried out.

A casting method of a spherical graphite cast iron comprised from, a melting process, a spheroidizing treatment process, an inoculation process, and a casting process, in which the original molten metal after the inoculation process is poured and filled up to a product space through a gate of a metal mold; wherein the original molten metal before being filled up to the product space is controlled to a semi-solidification temperature range. An amount of nitrogen at the time of melting of the (cast iron?) is controlled to 0.9 ppm (mass) or less. The casting process is carried out by controlling the pouring temperature and the heat removal amount from the molten metal so that the temperature of the raw material when passing through the gate becomes a substantially constant temperature between an eutectic temperature and a liquidus temperature.

The present invention provides a casting method and cast product of spherical graphite cast iron, in which, even with a small modulus, there is no chill, the spherical graphite in the tissue is further made ultrafine, the dispersion of the particle diameter is small, and the number of the particles is several times that of the conventional one in the as cast state where heat treatment is not carried out.

A casting method of a spherical graphite cast iron comprised from, a melting process, a spheroidizing treatment process, an inoculation process, and a casting process, in which the original molten metal after the inoculation process is poured and filled up to a product space through a gate of a metal mold; wherein the original molten metal before being filled up to the product space is controlled to a semi-solidification temperature range. An amount of nitrogen at the time of melting of the (cast iron?) is controlled to 0.9 ppm (mass) or less. The casting process is carried out by controlling the pouring temperature and the heat removal amount from the molten metal so that the temperature of the raw material when passing through the gate becomes a substantially constant temperature between an eutectic temperature and a liquidus temperature.

The present invention provides a die-cast product producing method and a spheroidizing agent of a spherical graphite cast iron with ultrafine spherical graphite by simple method and good reproducibility.

The present invention provides a sand mold producing method and a spheroidizing agent capable of producing an ultrafine spherical graphite cast iron with good reproducibility even in a sand mold thin walled spherical graphite cast iron, which has solidification cooling conditions equivalent to those of a metal mold.

The present invention provides a producing method of a die-cast product of a spherical graphite cast iron using a spheroidizing agent, in which a C amount is 0.5 mass % or more, a total nitrogen amount N is 150 ppm (by mass) or less, and a nitrogen amount generated during melting is 15 ppm (by mass) or less, in a producing method of a sand mold cast product of a thin walled spherical graphite cast iron having a melting process, a spheroidizing process, an inoculation process, and a casting process.

The present invention provides a die-cast product producing method and a spheroidizing agent of a spherical graphite cast iron with ultrafine spherical graphite by simple method and good reproducibility.

The present invention provides a sand mold producing method and a spheroidizing agent capable of producing an ultrafine spherical graphite cast iron with good reproducibility even in a sand mold thin walled spherical graphite cast iron, which has solidification cooling conditions equivalent to those of a metal mold.

The present invention provides a producing method of a die-cast product of a spherical graphite cast iron using a spheroidizing agent, in which a C amount is 0.5 mass % or more, a total nitrogen amount N is 150 ppm (by mass) or less, and a nitrogen amount generated during melting is 15 ppm (by mass) or less, in a producing method of a sand mold cast product of a thin walled spherical graphite cast iron having a melting process, a spheroidizing process, an inoculation process, and a casting process.

The present invention refers to a vermicular cast iron alloy specially designed for blocks and heads of internal combustion engines that have special requirements for mechanical strength and machinability; said vermicular alloy has a microstructure that results in high values of mechanical properties, such as a minimum strength limit of 500 Mpa, a minimum yield limit of 350 MPa, along with good machinability; also, wherein the ferritization factor must be such that it is between 3.88 and 5.48. This set of properties makes it possible to design new engine blocks and heads with complex geometry, high mechanical properties, without compromising machinability, making it attractive both from a technical and economic point of view.

A spheroidal graphite cast iron meeting N.sub.(5-)≥250, N.sub.(5-20)/N.sub.(5-)≥0.6, and N.sub.(30-)/N.sub.(5-)≤0.2, wherein N.sub.(5-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more, N.sub.(5-20) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more and less than 20 μm, and N.sub.(30-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 30 μm or more, among graphite particles observed in an arbitrary cross section of at least 1 mm.sup.2.

A spheroidal graphite cast iron meeting N.sub.(5-)≥250, N.sub.(5-20)/N.sub.(5-)≥0.6, and N.sub.(30-)/N.sub.(5-)≤0.2, wherein N.sub.(5-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more, N.sub.(5-20) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 μm or more and less than 20 μm, and N.sub.(30-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 30 μm or more, among graphite particles observed in an arbitrary cross section of at least 1 mm.sup.2.

An inoculant for the manufacture of cast iron with lamellar, compacted or spheroidal graphite is disclosed. The inoculant has a particulate ferrosilicon alloy having about 40 to 80 wt % silicon, about 0.1 to 10 wt % calcium, 0 and 10% by weight of rare earths, for example cerium and/or lanthanum, and up to 5 wt % aluminium the balance being iron and incidental impurities in the ordinary amount, wherein the inoculant additionally has 0.1 to 10 wt %, based on the total weight of inoculant, antimony oxide where said antimony oxide is in particulate form and is mixed or blended with the ferrosilicon alloy particles, or is simultaneously added to cast iron together with the particulate ferrosilicon alloy particles.

A casting solidification analysis method, which can analyze positions of shrinkage cavities more accurately than in the past, a casting method using the above method, and an electronic program are provided.

A following casting solidification analysis method is provided. An amount of expansion/shrinkage for each solidification step length separated by inflection points in a cooling curve is determined, by setting a solid phase ratio at a completion of pouring to 0, setting a solid phase ratio at an end of solidification to 1.0, and determining the expansion/shrinkage amount for the each solidification step length by proportionally distributing the each solidification step length to the total solid phase ratio length.