PENGEMBANGAN METODE PROSES PEMBUATAN PISTON DENGAN SEMI SOLID FORMING

Abstract

Needs on metal forming which can produce parts with high tolerance and inexpensive cost, promote the development in Semisolid Forming that can give those advantages. In Semisolid Fonning, metals are heated until semisolid condition then mechanical or electromagnetic stirring is given to the metals. The purpose is to obtain spherical structure or nondendritic structure in the metals. The variables that affect the formation of nondendritic structure are : cooling time, shape of rotating rod, speed of rotating rod, and the number of solid fraction. In this Research only the effect of cooling time on the formation of nendendritic structure produced by mechanical stirring which is marked by the changes in shape factor value. The stirred A1-18Si are tested by hardness test, metallography, and dilatometry. The results then compared with the nonagitated Al-18Si. The hardness numbers of agitated Al-18Si are lower then the nonagitated one and reach the optimum at t=12 minutes. Shape factors of agitated specimen at the middle part tend to decrease, but the shape factors for the bottom part tend to increase. For the coefficient of linear expansions are constant for both agitated and non agitated Al-18Si.