Method for producing light-alloy casting

Abstract

A light-alloy casting producing method is provided in which a T6 treatment can be given to a light-alloy casting without any heat treatment furnace (or aging furnace), so that its mechanical properties such as tensile strength can be adequately heightened. This method includes: a mold preparing process of preparing a mold which includes a sand mold part which is provided with a riser section, and a metal mold part which is disposed apart from the riser section, the sand mold part and the metal mold part forming a cavity section; a casting process of pouring a molten light-alloy into the cavity section of the mold; a metal mold part removing process of separating the metal mold part from a casting which is formed by pouring; a quenching process of bringing a cooling medium into contact with the surface of the casting from which the metal mold part is removed, and thereby, cooling the casting rapidly; an aging process of covering the metal mold part-removed section of the casting with a heat keeper, and keeping the whole casting which is surrounded with the sand mold part and the heat keeper at an aging temperature for a predetermined period of time, using the heat which is kept by a riser portion.

1 . A method for producing a light-alloy casting, comprising steps of: 
 preparing a casting mold including a sand mold part provided with a riser section, and a metal mold part disposed apart from the riser section, the sand mold part and the metal mold part forming a cavity section;    pouring a molten light-alloy into the cavity section of the casting mold;    removing the metal mold part from a casting made of the light-alloy;    allowing a mold-removed surface of the casting to come into contact with a cooling medium to thereby quench the mold-removed surface; and    aging the casting by heat retained by a solidified light-alloy in the riser section for a predetermined period of time.    
     
     
         2 . A method according to  claim 1 , wherein in the step of aging the casting, the mold-removed surface of the casting is covered with a heat keeper to hold the casting subjected to aging by the retained heat of the solidified light-alloy in the riser section.  
     
     
         3 . A method according to  claim 2 , wherein the cooling medium is blown to the mold-removed surface.  
     
     
         4 . A method according to  claim 3 , wherein the cooling medium is a medium for rapid cooling, further comprising, after the step of blowing the medium for rapid cooling, a step of blowing another cooling medium for slow cooling to the mold-removed surface of the casting for a predetermined period of time.  
     
     
         5 . A method according to  claim 4 , wherein: 
 the cooling medium for rapid cooling is water; and    the cooling medium for slow cooling is atomized water or air.    
     
     
         6 . A method according to  claim 3 , wherein the sand mold part includes a water soluble binder, further comprising, after the step of blowing the cooling medium to the mold-removed surface, a step of immersing the casting in water with the sand mold part attached thereto to thereby cool the casting and break up the sand mold part.  
     
     
         7 . A method according to  claim 6 , wherein in the step of aging the casting, the casting is placed outside the water, and is entirely covered with an insulator to hold the casting subjected to aging by the retained heat of the solidified light-alloy in the riser section.  
     
     
         8 . A method according to  claim 1 , wherein the sand mold part includes a water insoluble binder, and in the step of quenching the mold-removed surface, the casting attached with the sand mold part is immersed in water to allow the mold-removed surface of the casting to come into contact with the water to thereby quench the mold-removed surface, and in the step of aging the casting, the mold-removed surface of the casting is covered with a heat keeper to hold the casting subjected to aging by the retained heat of the solidified light-alloy in the riser section.  
     
     
         9 . A method according to  claim 8 , wherein the water insoluble binder includes a gas-hardening binder having phenol resin as a main material and polyisocyanate as a hardener material.  
     
     
         10 . A method according to  claim 9 , wherein the sand mold part is hardened by an amine gas.  
     
     
         11 . A method according to  claim 2 , wherein the heat keeper is a heat insulating member.  
     
     
         12 . A method according to  claim 1 , wherein the light-alloy casting is made of an aluminum alloy.  
     
     
         13 . A method according to  claim 12 , wherein the quenching temperature is from 480° C. to 530° C.  
     
     
         14 . A method according to  claim 12 , wherein in the step of aging, the casting is kept for 1 to 2 hours within a temperature of 160 to 240° C.  
     
     
         15 . A method according to  claim 1 , wherein the casting is a cylinder head of an engine, the surface of the casting that comes into contact with the metal mold part defines a combustion chamber of the engine.  
     
     
         16 . A method according to  claim 1 , wherein the cooling medium is water.