Pengaruh Penambahan Pb Sebesar 20 % Pada Pengecoran Aluminium Dengan Ukuran Scrap 5x5x1 Cm, 7,5x7,5x1 Cm, 10x10x1 Cm Menggunakan Cetakan Permanen Silinder Tirus Dan Cetakan Permanen Silinder Terhadap Nilai Kekerasan, Komposisi Kimia, Struktur Mikro

This study aims to determine the effect of differences in aluminum and aluminum alloy lead on hardness, chemical composition, and microstructure with dimensions of scrap dimensions 5 x 5 x 1 cm, 7.5 x 7.5 x 1 cm, and 10 x 10 x 1 cm of aluminum. The casting process begins with the preparation of permanent molds with a cylindrical shape and cylindrical shape. Before doing molten aluminum pouring into the mold, the first thing to do is to clean the mold wall, then preheat the mold so that the castings are not sticky to the mold. Then the next stage is the base of the permanent mold coated with red sand. Then liquid aluminum with scrap dimensions 5 x 5 x 1 cm, 7.5 x 7.5 x 1 cm, and 10 x 10 x 1 cm poured into the mold pernanen taper shape. Then the remelting process with a permanent mold of a cylindrical shape with the addition of lead by 20%. When aluminum has cooled and hardened the mold is disassembled to get the results of the castings. The hardness test of aluminum (Al) with the Brineel hardness test obtained a value of 77.733 BHN while in aluminum alloy tin (Pb) of 20% for the material size of 5 x 5 x 1 cm was 98.559 BHN, for 7.5 x 7.5 x 1 cm is 88,832 BHN, and 10 x 10 x 1 cm is 83,63 BHN. When viewed from the table the chemical composition of the largest element content in this study is aluminum alloy silicon (Al-Si). In testing the microstructure with the addition of lead, the grain size of the microstructure is larger and smaller in number, compared to the aluminum castings without mixture having a small grain size and a large number. This is caused by the nature of lead which can protect other metals from porosity. Keywords: Casting, Aluminum Alloy of Black Tin (Al-Pb), Permanent Mol