Analisa Kegagalan Pengecoran pada Proses Pembuatan Pulley Menggunakan Limbah Bekas Aluminium

Aluminium daur ulang banyak dimanfaatkan sebagai bahan baku pengecoran komponen mekanik, namun kualitas hasil coran sangat dipengaruhi oleh komposisi kimia dan pengendalian proses pengecoran. Penelitian ini bertujuan untuk menganalisis kualitas aluminium bekas yang digunakan pada pengecoran pulley aluminium diameter kecil serta mengidentifikasi cacat yang terjadi. Metode penelitian meliputi uji komposisi kimia, uji kekerasan Brinell, dan pengamatan struktur mikro menggunakan mikroskop optik. Hasil pengujian menunjukkan bahwa komposisi aluminium bekas mendekati standar ADC12, namun kandungan silikon mencapai 14,8% dan melebihi batas standar. Nilai kekerasan rata-rata sebesar 66,35 HB juga lebih tinggi dibandingkan standar ADC12. Pengamatan struktur mikro pada pembesaran 100× hingga 500× memperlihatkan struktur dendritik Al–Si yang tidak homogen serta adanya porositas mikro dan inklusi gas. Secara visual, pulley hasil pengecoran memiliki bentuk geometri yang baik, namun keberadaan cacat internal berpotensi menurunkan keandalan material. Hasil penelitian menunjukkan bahwa komposisi kimia, terutama kandungan silikon, serta pengendalian proses peleburan dan penuangan sangat memengaruhi kualitas aluminium hasil pengecoran.

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Recycled aluminum is widely utilized as a raw material for casting mechanical components; however, the quality of cast products is strongly influenced by chemical composition and casting process control. This study aims to analyze the quality of recycled aluminum used in the casting of small- diameter aluminum pulleys and to identify the defects that occur. The research methods include chemical composition testing, Brinell hardness testing, and microstructural observation using an optical microscope. The test results indicate that the composition of the recycled aluminum is close to the ADC12 standard; however, the silicon content reaches 14.8%, exceeding the standard limit. The average hardness value of 66.35 HB is also higher than the ADC12 standard. Microstructural observations at magnifications of 100× to 500× reveal a non-homogeneous Al–Si dendritic structure, as well as the presence of micro-porosity and gas inclusions. Visually, the cast pulley exhibits good geometric shape, but the presence of internal defects has the potential to reduce material reliability. The results indicate that chemical composition, particularly silicon content, and control of the melting and pouring processes significantly influence the quality of the cast aluminum