ANALISIS POROSITAS DAN KEKERASAN PADUAN Al-12,6%Si DENGAN VARIASI WAKTU TUNGGU DALAM CETAKAN DAN MEDIA PENDINGIN MENGGUNAKAN CETAKAN PASIR BASAH

Abstract

The purpose of this research is to know the influence of waiting time in mold and cooling media to porosity and hardness value of foundry product. The foundry method uses gravity casting. The mold used is wet sand mold. Material used from Al alloy (scrap) of piston. The melting furnace uses a crucible furnace. Al alloy (scrap) is heated in the furnace until it is melted and then poured into the mold at the pouring temperature of 600 0 C. Then cooled in a mold with time variations of 10 and 15 minutes. subsequently cast out of the mold then cooled with a variation of cooling medium; air, water and brine. Then the result of casting made specimen and done by porosity and hardness test. The results showed that the type of cooling medium and the waiting time in the mold had an effect on porosity and hardness of castings. The longer the waiting time in the porosity mold is higher while the hardness decreases. The smallest porosity (0.6%) occurs at waiting time in a 10 minute mold with a median cooler from the air, while the largest porosity (4.4%) occurred at waiting time in a 15 minute mold with cooling medium from air. The smallest hardness value (93.49 HV) occurred at waiting time in a 15 minute mold with a cooling medium of brine, while the greatest hardness value (128.68 HV) occurred at waiting time in a 10 minute mold with a cooling medium of brine.