Abstract: According to the invention, by setting the linear thermal expansion amount when a mold made of a molding sand is heated from a room temperature to 1000° C. to be not more than 0.9%, and the ratio (D/d) between the diameter of a slump (D) and the diameter of a slump cone (d) in a slump test of the molding sand having a hardening agent kneaded to be not less than 1.65, a molding sand preferable for use in a mold produced using the self-hardening type of three dimensional laminate molding sand mold, having low thermal expansibility preventing occurrence of a veining defect, and capable of forming a large and complicated shape can be obtained.

Abstract: According to the invention, by setting the linear thermal expansion amount when a mold made of a molding sand is heated from a room temperature to 1000° C. to be not more than 0.9%, and the ratio (D/d) between the diameter of a slump (D) and the diameter of a slump cone (d) in a slump test of the molding sand having a hardening agent kneaded to be not less than 1.65, a molding sand preferable for use in a mold produced using the self-hardening type of three dimensional laminate molding sand mold, having low thermal expansibility preventing occurrence of a veining defect, and capable of forming a large and complicated shape can be obtained.

Abstract: There is provided a method for obtaining a pure melt in which the impurities Mn, Al, Ti, Pb, Zn, and B are removed from molten cast iron and depletion of useful C and Si is suppressed, the method wherein an excess oxygen flame having a theoretical combustion ratio of fuel and oxygen (amount of oxygen (volume)×5/amount of fuel (volume)) of 1 to 1.5 is directly exposed to the surface of pre-melted molten cast iron, the temperature of the molten cast iron is held at 1250° C. or more and less than 1500° C. while the melt surface is superheated and an acidic slag is brought into contact with the melt, and an oxygen-containing gas is injected into the interior of the molten cast iron.

Abstract: A method for predicting and preventing occurrence of shrinkage cavity in an iron casting of any of various shapes or in each part of an iron casting precisely prior to casting. The shape of an iron casting is approximated entirely or partially to a rectangular parallelepiped or a cube, to the sum of the two long sides is divided by the short side to determine a shape coefficient, and occurrence of shrinkage cavity is predicted by determining whether the value exceeds a predetermined value (determination coefficient) or not.

Abstract: A method of metal surface hardening treatment inducing transformation, in which transformation is induced in a surface interior of material as hardening treatment object by simple, rapid treatment utilizing a frictional heat under pressure without the occurrence of melt loss, quench crack, soft spot, deformation, etc. to thereby reform the structure of surface interior of material as hardening treatment object into a miniaturized martensitic structure.

Abstract: A combined roll is provided which offers excellent resistance to thermal shock. In this combined roll, an external ring portion is formed of a cemented carbide, and an internal ring portion is formed of a ductile iron metallurgically bonded to the external ring portion by means of casting. The external ring portion is formed of a cemented carbide containing, as binder phase-defining components, Co: 5-27%, Ni: 2-12% and Cr: 0.3-3% and WC as substantially all of the balance and as a hard phase-defining component. The internal ring portion is formed of a ductile iron composed of C: 3 4.5%, Si: 1.5-4.5%, Mn: 0.1-2% and Mg: 0.02-0.2% and, as the balance, Fe and incidental impurities. The internal ring portion may also contain 0.1-5% of one or more of Mo, Cu, Cr, V, W, Sn and Sb. The internal ring portion contains a cored spheroidal graphite structure dispersed in a mixed phase of either perlite, beinite and martensite phases with a ferrite phase.

Abstract: The present invention aims to provide a method of regenerating foundry sand whereby the carbon component adhering to the surface of spent foundry sand and similar substances is combusted efficiently, allowing the foundry sand to be regenerated at low cost. In the present invention, in order to achieve this aim the spent foundry sand with the carbon component adhering to it is placed in a combustion furnace which is connected on one side to a pressure-reducing pump and is open on the other, the pressure-reducing pump is operated to draw air from within the foundry sand and introduce air into it, and the accretion is ignited upwind of the current of air which is being introduced, allowing combustion of the accretion to proceed successively on the downwind side. Foundry sand can thus be recycled at very low cost, simply and reliably because it is allowed to self-combust continuously without any heating or agitation from elsewhere, and because the resin is combusted entirely.