Spherical graphite cast iron semi-solid casting method and semi-solid cast product

Abstract

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.

1 . A semi-solid casting method of a spherical graphite cast iron comprised from;
 a melting process, in which raw material composed of cast iron is melted and original molten metal is obtained;   a spheroidizing treatment process, in which the original molten metal is spheroidized;   an inoculation process, in which an inoculant is added to the spheroidized original molten metal; 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;   the pouring temperature is controlled to (melting point+40° C.) or less; and a temperature of the raw material when passing through the gate is set to 1140-1170° C.   
     
     
         2 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein an amount of nitrogen at the time of melting of the cast iron is controlled to 0.9 ppm (mass) or less. 
     
     
         3 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein the semi-solidification temperature range is set before the gate by controlling the amount of heat released from the molten metal. 
     
     
         4 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein a temperature of the raw material when passing through the gate is controlled to a constant temperature in the semi-solidification temperature range. 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein a cooling rate of the molten metal from the pouring temperature to a liquidus line passing temperature is controlled to 20° C./sec. or faster. 
     
     
         8 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein a pressurization is carried out after the filling up. 
     
     
         9 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein the raw material composed of the cast iron is melted and the original molten metal is obtained; oxygen is removed from the original molten metal by heating the original molten metal to a predetermined temperature of 1500° C. or more, stopping the heating, and maintaining the stopped temperature for a certain period of time; nitrogen in the original molten metal is reduced by gradually cooling the original molten metal; the spheroidizing treatment is carried out; the inoculation is carried out; and the casting is carried out. 
     
     
         10 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein the spheroidizing treatment is carried out with an oxygen content being 20 ppm (mass) or less. 
     
     
         11 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein a heat insulating coating is applied to a surface of the metal mold. 
     
     
         12 . The semi-solid casting method of the spherical graphite cast iron according to  claim 11 , wherein a thickness of the heat insulating coating is 0.2 mm or more. 
     
     
         13 . The semi-solid casting method of the spherical graphite cast iron according to  claim 1 , wherein the heat insulating coating, whose thermal conductivity is 0.42 W/mk or less, is applied to the surface of the metal mold. 
     
     
         14 . (canceled) 
     
     
         15 . (canceled) 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . A semi-solid metal mold cast product of a spherical graphite cast iron, having a part of tissue, in which a number of the spherical graphite is 3000 particles/mm 2  or more, and the spherical graphite having a particle size of 4-7 μm is 80% (number proportion) or more, in as cast state. 
     
     
         19 . A semi-solid metal mold cast product of a spherical graphite cast iron, having a tissue not including chill; and having a part of tissue, in which a number of the spherical graphite is 3000 particles/mm 2  or more, and the spherical graphite having a particle size of 4-7 μm is 80% (number proportion) or more, in as cast state. 
     
     
         20 . The semi-solid metal mold cast product of a spherical graphite cast iron according to  claim 18 , wherein the modulus of the cast is 2.0 cm or less. 
     
     
         21 . The semi-solid metal mold cast product of a spherical graphite cast iron according to  claim 18 , wherein the modulus of the cast is 0.25 cm or less.