Process for production of roughly shaped material for engine piston

Abstract

A production method of a roughly shaped material for an engine piston includes a continuous casting step for obtaining a cast rod ( 31 ) having a diameter of 85 mm or less by continuously casting a molten aluminum alloy ( 30 ) at a molten alloy temperature of 720° C. or higher, and a forging step for obtaining a roughly shaped material ( 11 ) for an engine piston by forging a forging material ( 32 ) obtained by homogenizing the cast bar ( 31 ) at 370 to 500° C. A composition of the molten alloy ( 30 ) includes Si: 11.0 to 13.0 mass %, Fe: 0.6 to 1.0 mass %, Cu: 3.5 to 4.5 mass %, Mn: 0.25 mass % or less; Mg: 0.4 to 0.6 mass %, Cr: 0.15 mass % or less, Zr: 0.07 to 0.15 mass %, P: 0.005 to 0.010 mass %, Ca: 0.002 mass % or less, and the balance being Aluminum and inevitable impurities.

1 . A production method of a roughly shaped material for an engine piston, comprising:
 a continuous casting step for obtaining a cast rod having a diameter of 85 mm or less by continuously casting a molten metal consisting of Si: 11.0 to 13.0 mass %, Fe: 0.6 to 1.0 mass %, Cu: 3.5 to 4.5 mass %, Mn: 0.25 mass % or less; Mg: 0.4 to 0.6 mass %, Cr: 0.15 mass % or less, Zr: 0.07 to 0.15 mass %, P: 0.005 to 0.010 mass %, Ca: 0.002 mass % or less, and the balance being Aluminum and inevitable impurities with a temperature of the molten metal before pouring into a continuous casting mold set to 720° C. or higher; and   a forging step for obtaining a roughly shaped material for an engine piston by forging a forging material obtained by subjecting the cast rod to a homogenization treatment at a temperature of 370 to 500° C.   
     
     
         2 . The production method of a roughly shaped material for an engine piston as recited in  claim 1 , wherein an additive amount of P in a composition of the molten metal satisfies the following formula:
   0.0025×additive amount of Si−0.025≦additive amount of P≦0.0025×additive amount of Si−0.02  (1),
   
       where a unit of the additive amount of P and that of Si are “mass %”, respectively. 
     
     
         3 . A roughly shaped material for an engine piston produced by the production method of a roughly shaped material for an engine piston as recited in  claim 1 ,
 wherein, at least in a skirt portion corresponding portion and a piston ring groove portion corresponding portion in the roughly shaped material, primary Si exists, and   wherein, in an entirety of the roughly shaped material, no primary Si having a maximum grain diameter of 50 μm or larger exists and no Al—Fe—Cr—Mn series giant crystal having a maximum grain diameter of 50 μm or larger exists.   
     
     
         4 . A roughly shaped material for an engine piston produced by forging, wherein a composition of the material consists of Si: 11.0 to 13.0 mass %, Fe: 0.6 to 1.0 mass %, Cu: 3.5 to 4.5 mass %, Mn: 0.25 mass % or less; Mg: 0.4 to 0.6 mass %, Cr: 0.15 mass % or less, Zr: 0.07 to 0.15 mass %, P: 0.005 to 0.010 mass %, Ca: 0.002 mass % or less, and the balance being Aluminum and inevitable impurities. 
     
     
         5 . The roughly shaped material for an engine piston as recited in  claim 4 , wherein an additive amount of P in the composition of the roughly shaped material satisfies the following formula:
   0.0025×additive amount of Si−0.025≦additive amount of P≦0.0025×additive amount of Si−0.02  (1),
   
       where a unit of the additive amount of P and that of Si are “mass %”, respectively. 
     
     
         6 . The roughly shaped material for an engine piston as recited in  claim 4 ,
 wherein, at least in a skirt portion corresponding portion and a piston ring groove portion corresponding portion in the roughly shaped material, primary Si exists, and   wherein, in an entirety of the roughly shaped material, no primary Si having a maximum grain diameter of 50 μm or larger exists, and no Al—Fe—Cr—Mn series giant crystal having a maximum grain diameter of 50 μm or larger exists.   
     
     
         7 . A roughly shaped material for an engine piston produced by the production method of a roughly shaped material for an engine piston as recited in  claim 2 ,
 wherein, at least in a skirt portion corresponding portion and a piston ring groove portion corresponding portion in the roughly shaped material, primary Si exists, and   wherein, in an entirety of the roughly shaped material, no primary Si having a maximum grain diameter of 50 μm or larger exists and no Al—Fe—Cr—Mn series giant crystal having a maximum grain diameter of 50 μm or larger exists.   
     
     
         8 . The roughly shaped material for an engine piston as recited in  claim 5 ,
 wherein, at least in a skirt portion corresponding portion and a piston ring groove portion corresponding portion in the roughly shaped material, primary Si exists, and   wherein, in an entirety of the roughly shaped material, no primary Si having a maximum grain diameter of 50 μm or larger exists, and no Al—Fe—Cr—Mn series giant crystal having a maximum grain diameter of 50 μm or larger exists.