Lightweight cast-iron product

Abstract

Provided is a cast-iron product that satisfies demands for both weight reduction and strength enhancement with good balance. A cast-ion product having an inner honeycomb structure is produced by a process including: a decarburization step, in which a cast-iron product made of a hypoeutectic cast iron is heated to form a decarburized layer on the surface of the cast-iron product; an outflow-hole formation step, in which an outflow hole penetrating through the decarburized layer into an inner region is formed; and a liquation step, in which the cast-iron product is heated to a temperature lower than the melting point of the decarburized layer and higher than the melting point of the hypoeutectic cast iron remaining inside, while being held in such a manner that the outflow hole is located in the lower portion thereof.

1 . A lightweight cast-iron product comprising a shell portion having a melting point increased by surface decarburization and a honeycomb region inside the shell portion. 
     
     
         2 . The cast-iron product according to  claim 1 , wherein a a carbon equivalent of a composition of a cast-iron before the surface decarburization is hypoeutectic. 
     
     
         3 . A method for producing a lightweight cast-iron product, comprising:
 a) a decarburization step, in which a cast-iron product made of a hypoeutectic cast iron is heated to form a decarburized layer on a surface of the cast-iron product;   b) an outflow-hole formation step, in which an outflow hole penetrating through the decarburized layer into an inner region is formed; and   c) a liquation step, in which the cast-iron product is heated to a temperature lower than a melting point of the decarburized layer and higher than a melting point of the hypoeutectic cast iron remaining inside, while being held in such a manner that the outflow hole is located in a lower portion thereof.