Simulasi pencampuran bahan-baku skrap aluminium yang berbeda,peramuan dan pemaduan serta peleburan diharapkan akan menghasilkan ingot yangsesuai atau mendekati standar aluminium coran. Pemanfaatan bahan-baku skrapmampu menampung bahan buangan yang menoemari lingkungan menjadi berguna.Telah dibuat ingot standar paduan aluminium coran BS 1490 seri LM4 dan LM13dengan menggunakan bahan-baku skrap. Skrap aluminium yang digunakan diambildari ind ustri kecil menengah pengecoran Iogam bukan besi di daerah Pasuruan JawaTimur, terdiri dari skrap piston, kawat, plat, hanger Iistrik, roda gigi, blok mesin danlain-lain. Pada peneiitian ini, bahan-baku skrap dipisahkan berdasarkan jenisnya,kemudian dianalisa komposisi kimianya dengan menggunakan Spektrometer.Perhitungan peramuan dan pemaduan secara komputerisasi dilakukan sebelumpeleburan. Penambahan unsur-unsur paduan pada saat peleburan dilakukan agarkomposisi target tercapai. Peleburan dilakukan dalam tungku krusibel dengan bahan-bakar kokas sampai temperatur 720°C. Logam cair hasil peleburan dituangkankedalam masing-masing cetakan pasir dan cetakan Iogam yang telah disiapkan.Spesimen hasil peleburan kemudian dilakukan pengujlan mekanis berupa uji tarikdan uji kekerasan, juga dilakukan pengujian metalograti dengan mikroskop optik.Pembuatan ingot standar LM4 dan LM13 dengan bahan baku skrap telah berhasildilakukan sesuai dengan komposisi standar yang dipersyaratkan. Kekuatan mekanisdan struktur mikro ingot dengan cetakan Iogam jauh lebih baik dibandlngkan dengancetakan pasir. Porositas mempengaruhi kekuatan mekanis, ingot cetakan pasirdengan porositas yang tinggi menghasilkan kekuatan yang lebih rendah dari ingotcetakan Iogam dengan porositas rendah. Metode pengecoran dengan cetakan Iogammenghasilkan ingot dengan kekuatan mekanis meningkat rata-rata sebesar 30%dibandingkan metode pengecoran cetakan pasir. Dari struktur mikro ingot standarterbentuk fasa-fasa a (AI) dan eutectic yang telah sesuai dengan diagram fasapaduan biner AlSi. Peleburan ulang pada ingot menyebabkan pengurangankandungan silikon sebanyak 30-40%.
Abstract
Mixing simulation between differences feedstock of aluminium scraps,formulation, combination and then melting process were examined to obtain ingot,which has quality similar to that of aluminium casting standard. The utilization ofscrap as a feedstock can minimize environmental problem and also obtain benefitvalue for waste products. The standard ingot from aluminium alloy BS 1490-LM4 andLM13 have made using scraps feedstock, which derived from waste products.Aluminium scraps, which contained piston scrap, wire, plate, electrical arch, gear,and machine block, were obtained from small size industries of metal non-ironprocessing at Pasuruan, East Java.ln this study, scrap feedstock were separated according to their types. Then, theirchemical composition were analysed using spectrometer. Computerize calculation forformulation and fusion were carried out before melting process. Additional matters offusion were conducted as melting process occurs to obtain a target composition.Melting was carried out in the crucible muffle using cokes as fuels at temperature of72O°C. Liquid metal product was poured onto sand and metal moulds. Afterwards,these product were tested in order to find their mechanic strength and stiffness.Nletalographic analyses on these products were also carried out using opticalmicroscope.The making of ingot standard LM4 and LM13 were successfully obtained in fulfillingthe standard composition. The mechanic strength and micro-structure of ingot,produced from metal mould, has shown good performance than that of producedfrom sand mould. This examination shown that the porosity affected mechanicstrength. ingot sand mould, which has high porosity, gave less strength compared tothat of ingot metal mould, which has small porosity.The casting methode using metal mould produced ingot with increasing in mechanicstrength by 30% compared to that of methode using sand mould. It was also foundthat or (Al) and eutectic phases were formed from micro-structure of standard ingot,which shown similar to that phase diagram binary fusion AlSi. It was also evidencethat ingot remelting caused reduction in silicon concentration by 30-40% |
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