The metal casting is the most economical manufacturing process. It can make products with complex geometries in one process. Austempered Ductile Iron (ADI) is a cast iron product that has high prospects for application, because ADI has a high strength closed to forged iron. The purpose of this study is to investigate the effect of addition of Cu and Mo on mechanical properties and corrosion resistance of ADI. Cu is added with percentages of 0.5 and 1% by weight, while Mo is added by percentages of 0.3 and 0.6% by weight. The austempering process is conducted on salt bath temperture 350 <sup>o</sup>C for 4 hours. The results of the process were characterized by hardness test, tensile test and corrosion resistance. Hardness and tensile strength of ADI were tested by Brinell hardness test based on ASTM E10 and ASTM E8 repectively. Corrosion resistance of ADI was tested by immersion corrosion testing based on ASTM G31 standard. The results of this study indicate that the addition of Cu element significantly increases the strength of ADI. The addition of Mo element inhibits graphite nodularity and not significantly increases the mechanical properties. Addition of Mo increases corrosion resistance due the amount of retained austenite.
ABSTRAKErupsi gunung berapi selalu mengeluarkan Abu vulkanik yang dikeluarkan dari perut bumi, seperti letusan gunung Kelud pada awal tahun 2014 ini yang mengeluarkan ratusan juta m2 abu Vulkanik. Abu vulkanik salah satu unsur yang terkandung didalamnya adalah lempung/bentonit. Bentonit dalam proses pengecoran logam dimanfaatkan sebagai bahan aditif untuk mengikat antar butiran pasir sehingga pasir bisa dibentuk sebagai bahan cetakan. Kekuatan ikatan antar butiran diuji melalui kuat tekan, mampu bentuk dan kuat geser dari pasir tersebut. Metode penelitian ini dengan cara membuat spesimen dari pasir yang dicampur dengan abu vulkanik 5%, 10 % dan 15%. Kemudian dilihat kekuatan tekan, kekuatan geser dan mampu bentuk serta mampu alir udara atau permeabilitasnya. Pasir cetak dengan tambahan abu vulkanik 15% mempunyai kekuatan tekan sebesar 22,8 kg/mm dan kekuatan geser sebesar 17,7 kg/mm.Kata kunci: Pasir cetak, kadar lempung, pengecoran logam PENDAHULUANIndonesia merupakan negara kepulauan yang mempunyai banyak pulau dengan gunung berapinya, dan berada pada wilayah cincin api, sehingga di Indonesia mempunyai banyak gunung berapi dalam keadaan masih aktif. Salah satu gunung berapi yang masih aktif adalah gunung kelud.Gunung kelud terletak di pulau jawa tepatnya di perbatasan antara tiga kabupaten yaitu Kediri, Blitar dan kabupaten Malang. Gunung kelud baru saja mengalami erupsi dan mengeluarkan ratusan juta meter kubik material dari perut bumi, diantara material yang dikeluarkan adalah abu vulkanik.Abu vulkanik yang dikeluarkan oleh gunung kelud jumlahnya sangat banyak dan tersebar dari wilayah jawa timur, hampir seluruh jawa tengah dan sebagian wilayah jawa barat, bahkan sampai pulau Sumatera.Abu Vulkanik selain menimbulkan bencana, juga membawa manfaat diantaranya adalah dalam jangka panjang akan menyuburkan tanah dan yang tidak kalah penting adalah abu vulkanik dapat dimanfaatkan di Industri Pengecoran.Pengecoran logam di Indonesia sebagian besar menggunakan pasir sebagai bahan cetakannya. Pasir untuk bisa digunakan sebagai bahan cetakan harus mempunyai sifat mampu bentuk, yang dihasilkan dari ikatan antar butirnya. Ikatan antar butir terjadi karena adanya bahan aditif atau bahan penambah yang dinamakan lempung/clay, atau istilah di pengecoran dinamakan Bentonit.Abu Vulkanik mengandung beberapa unsur, salah satunya adalah unsur clay/lempung, sehingga abu vulkanik bisa dimanfaatkan sebagai bahan penambah dalam pembuatan cetakan.Pada penelitian ini dilakukan dengan cara membuat spesimen dari campuran pasir silika ditambah 5%, 10% dan 15% abu vulkanik sebagai bahan pengikatnya, kemudian dilakukan pengujian diantaranya adalah uji Tekan, Uji Permeabilitas/daya salur udara, uji kuat geser dan uji kadar clay/lempungnya. MATERIAL DAN METODOLOGISebagian besar Pengecoran logam di Indonesia menggunakan pasir sebagai bahan utama pembuatan Cetakan. Bahan cetakan Pengecoran logam terdiri dari: 1) Bahan dasar: Pasir dan Non Pasir (Grafit, logam dan Keramik).2) Bahan perekat: Bentonit, Kaolinit, air kaca dan semen.3) Bahan aditif...
The use of cutting fluid is to reduce the friction between tool and workpiece, reduce and dissipate generated heat. The application of cutting fluid is also to improve the surface quality of workpiece and increase the tool life. On the other side, cutting fluid contains chemical carcinogens that causes serious health risks for machine operators and have inherent waste disposal concern on the environment. Due to these problems, some alternative have been sought to minimize or avoid the use of cutting fluid in machining processes. Air cooling techniques were proposed as alternative cooling mediums, i.e air jet cooling (AJC) and cooled-air jet cooling (CAJC), the liquid less method. In this work, air cooling techniques were investigated to be a possible solution of machining problem for cooling medium. This studi was also motivated by economics point of view that the application of AJC and CAJC would be more efficient than liquid method. The purpose of this study is to investigate the effect of AJC and CAJC on turning process of St 60 steel because it is used widely for production of components especially in small and medium enterprises in Indonesia. The tool tip temperatures, surface roughness and tool wear were measured for a range of cutting times. For a comparison purposes, experiments were also carried out with using traditional liquid coolant and without any cooling applied to the tool tip (dry cutting method). Experiments have shown that air cooling technques (AJC, and CAJC) can be used as cooling medium in machining process. Experimental results show that machining with CAJC have shorter tool life compare to machining with AJC and dry cutting, but liquid coolant in this studi is still the best cooling medium for machining of St 60 steel..
A type of flatfoot can be analyzed accurately using the footprint when a human is standing; however, this method cannot be applied when a human is wearing orthotic shoes. This study aims to analyze flatfoot using the rearfoot angle (RFA) measurement. The result is then compared to a footprint measurement known as Cavanagh’s Arch Index (AI). A total of 31 static footprints of the participants consisting of 14 males and 17 females aged 18 to 25 years were collected. According to Cavanagh’s AI as a gold standard, the correlation equation was obtained as RFA = 46.04AI − 6.41 and RFA = 45.32AI − 6.26 for left and right foot, respectively. The correlation coefficient R2 for the left and the right foot is 0.63 and 0.73, respectively. Other statistical analyses using ANOVA and t-tests are presented in this paper. The correlation results obtained from this study are necessary for estimating the reduction in the degree of flatfoot when using orthotic shoes, which is difficult to calculate using the typical AI method from footprint measurements.
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