Forged scroll parts and production process thereof

Abstract

A process for producing an aluminum alloy-made forged scroll part includes a step of casting an aluminum alloy material into a round bar having a diameter of 130 mm or less, the aluminum alloy material comprising 8.0-12.5 mass % of Si, 1.0-5.0 mass % of Cu and 0.2-1.3 mass % of Mg; a step of cutting the aluminum alloy round bar into a stock material for forging; a step of subjecting the stock material to upsetting at an upsetting ratio of 20-70% to form a pre-shaped product that is a workpiece; and a forging step of applying pressure onto the workpiece with a punch at a temperature of 300-450° C. to form a scroll wrap in a direction of the punch pressure, and wherein the forging step includes a single step in which a forged scroll part is press-formed while a back pressure smaller than the punch pressure is applied to an end of the scroll wrap in a direction opposite to the punch pressure direction. With this method, it is possible to produce a forged scroll part capable of suppressing occurrence of coarse primary Si crystals and reducing a variation in height of a wrap in a scroll part and in every scroll part being forged.

1 . A forged scroll part produced from an aluminum alloy material comprising 8.0-12.5 mass % of Si, 1.0-5.0 mass % of Cu and 0.2-1.3 mass % of Mg, characterized in that the scroll part contains Si particles having a size of less than 15 μm and a mean Si particle size of 3 μm or less.  
     
     
         2 . The forged scroll part produced from an aluminum alloy material according to  claim 1 , wherein the aluminum alloy further comprises 2.0 mass % or less of Ni and/or 0.5 mass % or less of one or more species selected from among Sr, Ca, Na and Sb.  
     
     
         3 . The forged scroll part produced from an aluminum alloy material according to  claim 2 , wherein it is subjected to solution heat treatment and aging treatment.  
     
     
         4 . The forged scroll part produced from an aluminum alloy material according to  claim 1 , wherein it is subjected to solution heat treatment and aging treatment.