Method for producing shaped article of aluminum alloy, shaped aluminum alloy article and production system

1. A method for producing an aluminum-alloy shaped product, comprising the following steps in the order indicated:

(a) continuously casting molten aluminum alloy into a forging material in the form of a rod, wherein the molten aluminum alloy contains Si in an amount of 10.5 to 13.5 mass %, Fe in an amount of 0.15 to 0.65 mass %, Cu in an amount of 2.5 to 5.5 mass %, Mg in an amount of 0.3 to 1.5 mass %, Ni in an amount of 2.4 to 3 mass %, Pin an amount of 0.003 to 0.02 mass %, Zr in an amount of 0.04 to 0.3 mass %, V in an amount of 0.01 to 0.15 mass %, Cr in an amount suppressed to not more than 0.5 mass %, Na in an amount suppressed to not more than 0.015 mass %, Ca in an amount suppressed to not more than 0.02 mass % and the balance comprising aluminum and an inevitable impurity;

(b) subjecting the forging material to a pre-heat treatment by maintaining the forging material at a temperature of at least 370° C. and 480° C. or lower for two to six hours;

(c) upsetting the forging material in an upsetting apparatus;

(d) forging the forging material into a forged product, wherein during the forging, a percent reduction of a portion of the forging material that requires high-temperature fatigue strength resistance is regulated to 90% or less;

(e) subjecting the forged product to a post-heat treatment to obtain the aluminum-alloy shaped product, wherein crystallization products of the aluminum-alloy shaped product comprise eutectic Si, an intermetallic compound and their aggregates in the form of crystallization product networks, acicular crystallization products or crystallization product aggregates, and

the aluminum-alloy shaped product having a eutectic Si area share of 8 to 18%, an average eutectic Si particle diameter of 1.5 to 4 μm, 25% or more of eutectic Si having an acicular eutectic Si ratio of a value of dividing a maximum length of the eutectic Si by a width of the eutectic Si orthogonal to the direction of the maximum length of 1.4 to 3, an intermetallic compound area share of 1.2 to 7.5% and an average intermetallic compound particle diameter of 1.5 to 4 μm; and

(f) obtaining the aluminum-alloy shaped product exhibiting a tensile strength of 65 MPa or more and a fatigue strength of 40 MPa or more at a temperature of 300° C.

2. The method according to claim 1 , wherein the aluminum alloy 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 %.

3. The method according to claim 1 , wherein the aluminum alloy contains the Mg in an amount of 0.5 to 1.3 mass %.

4. The method according to claim 1 , wherein during the forging step, the percent reduction of a portion of the forging material that requires high-temperature fatigue strength resistance is regulated to 70% or less.

5. The method according to claim 1 , wherein in the forging step, the heat treatment step is performed at a temperature of 380 to 480° C.

6. 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.

7. The method according to claim 6 , wherein the continuously cast rod is produced at a casting speed of 300 to 2,000 mm/minute.