FORGED SCROLL PART AND PRODUCTION METHOD THEREFOR

摘要

A production method for an aluminum-alloy forged scroll part comprising the steps of casting aluminum alloy containing 8.0-12.5 mass% of Si, 1.0-5.0 mass% of Cu and 0.2-1.3 mass% of Mg to form a round bar up to 130 mm in diameter, cutting the aluminum-alloy round bar into a forging blank, upsetting the above forging blank into a work at an upsetting ratio of 20-70%, pressing by a punch the work at material temperatures of 300-450 DEG C and forming a scroll blade in the punch-pressing direction to complete a forging step, the forging step including the step of applying to the tip end of the scroll blade portion a back pressure that is lower than, and acts in a direction opposite to, the punch-pressing, whereby it is possible to produce a forged scroll part restrained in the occurrence of bulky primary crystal Si, small in variations of blade heights of individual scroll parts, and also small in variations of blade heights among all the produced scroll parts.