Method for producing aluminum-alloy shaped product, aluminum-alloy shaped product and production system

Abstract

The present invention are to provide a method for producing an aluminum-alloy shaped product that exhibits high-temperature mechanical strength superior to that of a conventional aluminum-alloy forged product. The present invention provides a method for producing an aluminum-alloy shaped product, comprising a step of forging a continuously cast rod of aluminum-alloy serving as a forging material, in which the aluminum-alloy contains Si in an amount of 10.5 to 13.5 mass %, Cu in an amount of 2.5 to 6 mass %, Mg in an amount of 0.3 to 1.5 mass % and Ni in an amount of 0.8 to 4%, and satisfies a relational expression of “Ni(% bymass)≧(−0.68×Cu(% by mass)+4.2(% by mass)),and heat treatment and heating steps including a step of subjecting the forging material to pre-heat treatment ( 82 ), a step ( 87 ) of heating the forging material during a course of forging of the forging material and a step of subjecting an aluminum-alloy shaped product to post-heat treatment ( 89 ), said pre-heat treatment ( 82 ) including treatment of maintaining the forging material at a temperature of −10 to 480° C. for two to six hours.

1 . A method for producing an aluminum-alloy shaped product, comprising:
 a step of forging a continuously cast rod of aluminum-alloy serving as a forging material, in which the aluminum-alloy contains Si in an amount of 10.5 to 13.5 mass %, Cu in an amount of 2.5 to 6 mass %, Mg in an amount of 0.3 to 1.5 mass % and Ni in an amount of 0.8 to 4%, and satisfies a relational expression of “Ni(% by mass)≧(−0.68×Cu(% by mass)+4.2(% by mass)), and   heat treatment and heating steps including a step of subjecting the forging material to pre-heat treatment, a step of preliminary heating the forging material before a course of forging of the forging material and a step of subjecting a shaped product to post-heat treatment,   said pre-heat treatment including treatment of maintaining the forging material at a temperature of −10 to 480° C. for two to six hours.   
   
   
       2 . The method according to  claim 1 , wherein the pre-heat treatment is performed at a temperature of at least 200° C. and 370° C. or lower. 
   
   
       3 . The method according to  claim 1 , wherein the pre-heat treatment is performed at a temperature of at least −10° C. and less than 200° C. 
   
   
       4 . The method according to  claim 1 , wherein the pre-heat treatment is performed at a temperature of at least 370° C. and 480° C. or lower. 
   
   
       5 . The method according to  claim 1 , wherein the post-heat treatment is performed at 170 to 230° C. for one to 10 hours without performing solid solution treatment. 
   
   
       6 . The method according to  claim 1 , wherein, the aluminum-alloy further contains Fe in an amount of 0.15 to 0.65 mass %. 
   
   
       7 . The method according to  claim 1 , wherein the aluminum-alloy further contains P in an amount of 0.003 to 0.02 mass %. 
   
   
       8 . The method according to  claim 1 ,
 wherein the aluminum-alloy further contains at least one species selected from among Sr in an amount of 0.003 to 0.03 mass %, Sb in an amount of 0.1 to 0.35 mass %, Na in an amount of 0.0005 to 0.015 mass % and Ca in an amount of 0.001 to 0.02 mass %.   
   
   
       9 . The method according to  claim 1 ,
 wherein the aluminum-alloy further contains at least one species selected from among Mn in an amount of 0.1 to 1.0 mass %, Cr in an amount of 0.05 to 0.5 mass %, Zr in an amount of 0.04 to 0.3 mass %, V in an amount of 0.01 to 0.15 mass % and Ti in an amount of 0.01 to 0.2 mass %.   
   
   
       10 . The method according to  claim 1 ,
 wherein during the forging step, a percent reduction of a portion of the forging material that requires high-temperature fatigue strength resistance is regulated to 90% or less.   
   
   
       11 . The method according to  claim 1 , wherein in the forging step, the preliminary heating step is performed at a temperature of 380 to 480° C. 
   
   
       12 . The method according to  claim 1 ,
 wherein the continuously cast rod is produced through continuous casting of a molten aluminum-alloy having an average temperature which falls within a range of a liquidus temperature +40° C. to the liquidus temperature +230° C. at a casting speed of 80 to 2,000 mm/minute.   
   
   
       13 . An aluminum-alloy shaped product produced through the method according to  claim 1  and having a metallographic structure in which crystallization product networks, acicular crystallization products or crystallization product aggregates that have been formed during a course of continuous casting remain partially even after forging and heat treatment steps. 
   
   
       14 . An aluminum-alloy shaped product produced through the method according to  claim 1  and having a eutectic Si area share of 8% or more, an average eutectic Si particle diameter of 5 μm or less, 25% or more of eutectic Si having an acicular eutectic Si ratio of 1.4 or more, an intermetallic compound area share of 1.2% or more, an average intermetallic compound particle diameter of 1.5 μm or more and 30% or more of intermetallic compounds or intermetallic compound aggregates having an intermetallic compound length or intermetallic compound aggregate length of 3 μm or more. 
   
   
       15 . An aluminum-alloy shaped product produced through the method according to  claim 13 ,
 wherein an engine piston is made of the aluminum-alloy and includes a top surface portion and a skirt portion and the high-temperature fatigue strength of the top surface portion is 50 MPa or more.   
   
   
       16 . A production system comprising a continuous line for performing a series of steps for producing an aluminum-alloy shaped product from a molten aluminum-alloy, wherein the series of steps includes at least the steps of the method of  claim 1 .