In this study, effects of stirring time and stirring speed on the microstructure of semisolid rheocast (SSR) aluminum alloy ADC12 were examined. The research method was done by gravity casting using a metal mold. The aluminum ADC12 slurry is stirred by a mechanical stirrer (round rod stirrer) at 610OC with a variation of speed 0, 250, 300, 350 rpm for 0, 20, 40, 60 seconds. Furthermore, the aluminum slurry of ADC12 is poured on a metal mold with temperature 600OC. The microstructure characteristics were examined by direct observation using optical microscopy, secondary -Al phase dendrite arm spacing, shape factor, and Si eutectic phase were identified. The mechanical properties were investigated by hardness test and tensile test. A short period of stirring below the liquidus temperature to form a non-dendritic structure. The final morphology of the primary particles after a short period of stirring time has little impact as the stirring time increases. The optimal mechanical properties (hardness and tensile strength) were obtained at 20 seconds of stirring time and 300 rpm of stirring rate.
Penelitian ini bertujuan untuk mengetahui pengaruh variasi quenching bertingkat dengan menggunakan media pendingin oli dan air pada baja AISI 1045 terhadap sifat mekanik dan struktur mikro. Sifat mekanis yang dianalisa meliputi uji kekerasan, uji impak dan pengamatan struktur mikro. Metode yang digunakan yaitu diawali dengan proses Perlakuan Panas (Heat Treatment) pada temperatur 850º dengan waktu Penahanan (Holding Time) selama 4 jam. Setelah itu dilanjutkan Pendinginan Cepat (Quenching) dengan volume air dan oli yang divariasikan untuk setiap spesimen. Nilai kekerasan tertinggi didapatkan pada media pendingin air saja tanpa campuran oli sebesar 71.74 HRC atau meningkat sebesar 796.75% atau delapan kali lipat dari kekerasan raw material sedangkan kekerasan terendah dari variasi oli dan air tejadi pada variasi 50:50 (%) sebesar 46,38 HRC atau meningkat sebesar 475% atau hampir lima kali lipat. Kekuatan impak baja AISI-1045 cenderung mengalami peningkatan kekuatan pada media pendinginan air + oli diatas 10% dibandingkan raw material, ini menunjukkan bahwa semakin tinggi jumlah volume oli terhadap air sebagai media quenching, maka akan meningkatkan keuletan baja namun menurunkan kekerasan baja. Jenis variable pendinginan yang menghasilkan baja yang tangguh (keras dan ulet) adalah pada variable quenching air 80:20 (%) oli dan air 70:30 (%) oli. Namun, berdasakan pertemuan dua garis linear pada grafik perbandingan nilai kekerasan dan impak, ditemukan perbandingan variasi pendinginan yang paling optimal yakni pada variasi air 68% dan oli 32%.
The industrial sectors in Indonesia is currently growing very rapidly because it is supported by the development of technology in the field of manufacturing. One of the most frequently used machining operations in the manufacturing industry is welding operations. Welding operation is the most efficient and efficient method to combine two or more metal components. The product quality of welding can be obtained by using the production tool (fixture). The purpose of this research is to improve the quality of turbine runner product by using the welding fixture. The method was to design and make welding fixture of turbine runner welding, test the concentricity, straightness of the dish, the stability of the dish to the shaft, and the alignment of the blades to the shaft, and to analyze the deviation of measurement results. Based on the result of welding fixture design of cross-flow turbine runner component, a prototype welding fixture which can facilitate the assembling process of cross-flow turbine runner component was obtained. The conclusions of this research were: 1) The quality of the cross-flow turbine runner product can be increased along with the small geometrical deviation on cross-flow turbine runner using accelerator tool, 2). The maximum deviation of the runner disc placement to the axis of the axis on the 300mm diameter runner is 1.2mm and the runner of 200mm with diameter of 0.68mm, and 3). The assembling time of the turbine runner components is shorter using weld assembly tools with better accuracy.
Penelitian ini bertujuan untuk mengefisienkan waktu dan meningkatkan keakuratan pembuatan produk kontur ukiran pada benda kerja seperti logam lunak, akrilik, dan kayu. Mesin Pemotong Laser Mini CNC keluaran penelitian ini nantinya digunakan sebagai salah satu tugas praktikum mata kuliah Praktik Pemrograman Dasar NC. Metode perancangan yang digunakan adalah penelitian terapan eksperimental berupa rancangan dan gambar untuk laboratorium dengan ukuran 45 x 45 cm. Selanjutnya dilakukan perhitungan dan pemilihan bahan, pembuatan komponen mesin dan penggunaan software Arduino uno sebagai bahasa pemrograman dasar untuk mengubah gerak menjadi alat. Pengujian performa mesin pada mode pergerakan dua sumbu yaitu mode manual, MDI, dan otomatis sumbu kedua X dan Y menggunakan program NC. Hasil yang diperoleh menunjukkan keakuratan dan ketepatan lintasan sumbu X dan Y sesuai nilai toleransi yang diijinkan, yaitu masing-masing 0,01 mm, 0,01 mm dan 0,05 mm. Kesesuaian program yang dibuat dan hasil pemesinan pada kontur ukiran benda kerja tidak menunjukkan penyimpangan yang berarti, masing-masing 0,1 mm untuk sumbu X dan Y.
This study aims to analyze the effect of the stirrer model, stirring rotation (400, 500, 600 rpm), for 20 seconds, and pouring temperature (565, 570, and 5750C) on the microstructure and mechanical properties of the aluminum alloy ADC12. The methods of research are a) preparing material aluminum alloy ADC12, b) making molds, c) casting, d) making specimens for testing, e) micro structure testing and hardness testing, f) analyzing data using Microsoft excel applications. Results of the study show that the smallest grain size occurs in casting parameters: stirrer angle 00, 600 rpm rotation, and pouring temperature 5650C with a value of 27.715 µm. The biggest shape factor occurs in casting parameters: stirrer angle 00, rotation 600 rpm, and pouring temperature 5650C with a value 0.76. The highest hardness occurs in casting parameters: stirrer angle 00, rotation 600 rpm, and pouring temperature 5650C with a value 88.0 HB.
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