Studi metode almunizing untuk mencegah die soldering pada baja h420 j2
F enomena die soldering adalah peristiwa melekatnya logam cair yang telah membeku pada permukaan cetakan baja. Proses ini merupakan reaksi antar muka antara aluminium cair dengan permukaan cetakan. Hal ini mengakibatkan terjadinya kegagalan cetakan sehingga menurunkan tingkat produktivitas, karena cetakan logam harus diperbaiki terlebih dahulu sebelum di pakai lagi. Pada penelitian ini metode almunizing diteliti sebagai upaya mencegah terjadinya die soldering. Baja H420 J2 digunakan sebagai sampel. Proses almunizing sebagai berikut, baja akan direndam selama 3 menit ke dalam paduan Al-55,3%Cu cair (800°C) dan setelah itu sampel didinginkan sampai suhu ruang. Untuk mengetahui ada atau tidaknya efek die soldering, baja yang sudah di almunizing digunakan sebagai cetakan pada proses simulasi die casting. Proses simulasi die casting sebagai berikut, logam Al cair (700°C) dituang ke atas permukaan baja yang telah di almunizing. Cairan dibiarkan membeku diatas permukaan baja tersebut sampai suhu kamar. Proses almunizing pada suhu 800°C dan direndam selama 3 menit menyebakan kekerasan sampel baja meningkat dari sampel awal. Pada sampel A kekerasan meningkat sebesar 32,18% dan 23,10% pada sampel B. Proses simulasi die casting pada sampel yang telah di almunizing menurunkan nilai keras, yang besar penurunannya sebesar 35,34% pada sampel A dan 3,3% pada sampel B. Proses simulasi die casting juga menurunkan kekerasan sampel baja yang tidak di almunizing sebesar 28,84% pada sampel A. Penyebab naiknya nilai keras dikarenakan adanya lapisan intermetalik dan bertambahnya mikrostruktur perlit pada sampel baja yang telah di almunizing. Penyebab penurunannya nilai keras setelah proses
T he phenomenon of die soldering is a phase when the metal liquid that has been frozen sticking to the surface of the steel cast. This process is a face to face reaction between the liquid aluminium and the cast surface. This thing cause the failure of the cast soit decrease the productivity, the cast must be repaired before reuse. On this research the almunizing method was investigated as way to prevent die soldering. H420 J2 steel used as sample. This is the step of almunizing process, the steel will be sinked in 3 minutes inside the Al-55,3%Ou (800°C) liquid blend furthermore, the sample will be chilled until it reach the room temperature. To know it there is a die soldering effect, the steel that has been almunizing is used as the cast for the simulation of die casting process. The simulation process of die casting as follows, the liquid Al (700°C) is poured on the surface of the steel that has been almunizing. The liquid is left to chill on the 'surface of the steel until it reached the room temperature. agip The almunizing process at 800°C and been sinked for 3 minutes causing the hardness of the steel sample raised from the early sample. On sample A, the hardness raised to 32,18% and 23,10% on the sample B. The simulation process of die castinglon the sample that has been through the almunizing process decrease the hardness, the reduction is 35,34% on sample A and 3,3% on sample B. The simulation process of die casting also decrease the hardness of the steel sample that has not been through almunizing process for 28,84% on sample A. The rised of the hardness is occurred by the intermellic layer and the increasing of perlite microstructure on the steel sample that has been through the almunizing process. The drop of the hardness after the almunizing process on the die casting simulation occurred by the increasing of ferrit microstructure and the decreasing of perlite.