Casting green sand mold for forming cast steel article and its production method, and method for producing cast steel article using such green sand mold

Abstract

A green sand mold for producing a cast steel article, which is formed by casting sand comprising sand, a binder, and 3 parts or less by mass of a carbonaceous component per 100 parts by mass of sand, and provided with a coating layer of a thermosetting resin formed at least on a recess including a cavity for forming the cast steel article, the coating layer having average hardness (measured by a self-hardening hardness meter) of 50-95 and a thickness of 0.5-2.5 mm.

1 . A green sand mold for producing a cast steel article, which is formed by casting sand comprising sand, a binder, and 3 parts or less by mass of a carbonaceous component per 100 parts by mass of sand;
 at least a recess including a cavity for forming said cast steel article being provided with a coating layer of a thermosetting resin; and   said coating layer having average hardness (measured by a self-hardening hardness meter) of 50-95 and a thickness of 0.5-2.5 mm.   
     
     
         2 . The green sand mold according to  claim 1 , wherein the amount of the thermosetting resin forming said coating layer is 100-500 g/m 2  on a solid basis. 
     
     
         3 . The green sand mold according to  claim 1 , wherein the amount of carbon remaining in a unit volume of said coating layer is 20-200 mg/cm 3  after heated to 800° C. at a speed of 10° C./minute in the air. 
     
     
         4 . A method for producing the green sand mold recited in  claim 1 , comprising
 forming casting sand comprising sand, a binder, and 3 parts or less by mass of a carbonaceous component per 100 parts by mass of sand, into at least a pair of green sand mold parts comprising a recess including a cavity for forming said cast steel article;   coating at least said recess with a coating solution comprising a thermosetting resin and an organic solvent; and   thermally curing said thermosetting resin coated on said recess to form a coating layer having average hardness (measured by a self-hardening hardness meter) of 50-95.   
     
     
         5 . The method for producing a green sand mold according to  claim 4 , wherein said thermosetting resin is thermally cured before and/or after combining said mold parts. 
     
     
         6 . The method for producing a green sand mold according to  claim 5 , wherein at least a pair of green sand mold parts are combined after thermally curing said thermosetting resin. 
     
     
         7 . The method for producing a green sand mold according to  claim 5 , wherein the hardening of a coating layer obtained by drying the applied coating solution is carried out by a first hardening step of heating to obtain average hardness (measured by a self-hardening hardness meter) of 30-45, and a second hardening step of further heating the primarily hardened coating layer to average hardness (measured by a self-hardening hardness meter) of 50-95. 
     
     
         8 . The method for producing a green sand mold according to  claim 4 , wherein said coating solution has a viscosity of 15-100 mPa·s. 
     
     
         9 . A method for producing a cast steel article using the green sand mold recited in  claim 1 .