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"Ferokrom 45-75 Cr dan 35-50 Fe paduan penting pembuatan baja tahan karat karena sifat kekuatan dan ketahanan korosi yang tinggi. Ferokrom berasal dari endapan kromit di wilayah Indonesia adanya berkadar rendah dengan ratio Cr/Fe < 1.5 sehingga diperlukan benefisiasi. Tahapan benefisiasinya pemisahan magnetik lemah dilanyutkan pemanggangan temperatur, waktu, jenis reduktor dan berat CaCO3 , hasil pemanggangan dilakukan pemisahan magnetik kuat dan diuji xrf dan xrd. Parameter optimal benefisiasi untuk pembuatan briket input peleburan tanur SAF. Peleburan briket kromit diteliti pengaruh basisitas terhadap parameter ratio Cr/Fe, kadar kromium dan besi, konsumsi energi/berat produk . Pengaruh temperatur pemanggangan 800, 1000 dan 1200 oC terhadap ratio Cr/Fe optimum temperaturnya 1000 oC ratio Cr/Fe sebesar 1,53. Pengaruh waktu pemanggangan 30, 60 dan 90 menit terhadap ratio Cr/Fe optimum waktunya 60 menit ratio Cr/Fe sebesar 1,53. Pengaruh reduktor grafit, kokas dan arang batok terhadap ratio Cr/Fe optimum redukror arang batok ratio Cr/Fe sebesar 1,60. Pengaruh wt CaCO3 5 , 10 dan 20 terhadap ratio Cr/Fe optimum wt CaCO3 pada 20 rasio Cr/Fe sebesar 1,60. Basisitas terak = 2 memberikan ratio Cr/Fe optimum =1,06 , kadar Cr = 50,07 . Konsumsi energi/berat logam optimum 5,7 Kwh/Kg pada nilai basisitas 1,2.

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Ferrochrome is an important alloy of stainless steel due to its high strength and corrosion resistance. Ferromchrome is derived chromite in the Indonesia region low grade Cr Fe "

"ABSTRAKTelah dilakukan proses surface treatment Thermal Reactive Deposition (TRD) dalam pembentukan lapisan tipis karbida pada substrat baja SUJ2 . Pada proses ini menggunakan metode pack cementation menggunakan campuran serbuk Ferrovanadium dan Ferrochromium sebagai carbide former . Serbuk carbide former dan susbtrat dicampur bersama NH4Cl dan Al2O3 untuk diproses selama 6 jam dalam furnace. Dilakukan 3 variasi temperatur yaitu 900, 950 dan 1000 C untuk mengetahui pengaruh temperatur terhadap ketebalan, kehomogenan, kekerasan dan laju keausan lapisan karbida yang terbentuk. Hasil pengamatan pada mikroskop optik menunjukkan bahwa semakin tinggi temperatur proses, maka semakin tebal lapisan karbida yang terbentuk pada permukaan substrat disertai membesarnya butir baja pada subtrat. Hasil linescan mikroskop elektron SEM juga menunjukkan bahwa semakin tinggi temperatur ,proses laju difusi dari carbide former Vanadium lebih tinggi dibandingkan Krom pada tiap temperatur. Hasil lapisan dikarakterisasi menggunakan difraksi sinar-X XRD menunjukkan bahwa lapisan terdiri dari karbida vanadium dan juga karbida krom. Pada pengujian keras mikro Vickers, dihasilkan kekerasan rata-rata yaitu sekitar 2100 HV dan menghasilkan laju keausan yang hampir identik pula yaitu sekitar 3 x 10-4 mm3/m, yang artinya campuran serbuk FeCr dan FeV mendekati nilai kekerasan lapisan dengan penggunaan FeV sebagai carbide former tunggal yang memiliki kekerasan rata-rata lapisan sekitar 2400 HV.

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ABSTRAKIn the present study, surface treatment on SUJ2 steel by thermal reactive Deposition TRD method was studied. Two different carbide former powders, ferrovanadium and ferrochromium were used with pack cementation method. The process was carried out on steel substrate at temperatures of 900, 950 dan 1000 C for 6 hours. The effects of temperature on layer thickness, homogenity and hardness were studied. The result showed that the higher temperature the thicker layer that formed on substrate surface and it is followed by enlargement of substrate grains. Scanning Electron Microscope SEM linescan shows that at higher temperature, diffusion rate of vanadium and chromium are increase with the note that vanadium has higher diffusion rate than chromium. XRD results shows that layer that formed with this process consists of vanadium carbide and chromium carbide. The average micro hardness of coatings for 3 temperature variations was about 2100 HV and wear rate was about 3 x 10 4 mm3 m. This hardness was approaching hardness value of FeV as single carbide former with a hardness value of about 2400 HV. "

"The 56Fe16.6Cr25Ni0.9Si0.5Mn austenitic superalloy has been produced in an induction furnace; it was made from granular ferro-scrap, ferrochrome, ferrosilicon, and ferromanganese materials. Originally, this alloy had been proposed for use in high mechanical loads and high temperature conditions (such as in nuclear and fossil fuel power plant facilities). Tensile strength tests showed that the alloy has an average yield strength of about 430.56 MPa, which is higher than Incoloy A-286 (a commercially available alloy). A combination of microscopy techniques by means of an optical microscope, X-ray diffraction [XRD], scanning electron microscopy [SEM], and transmission electron microscopy [TEM] techniques were applied in order to get detailed information about the fine structure of the alloy. XRD confirmed that the alloy matrix exhibits an FCC crystal structure with a lattice parameter of about 3.60 Å and grain sizes ranging from 50 to 100 µm. The results of the TEM analysis revealed the new type of precipitations that formed at the grain boundaries. These needle-like precipitations, probably Fe/Cr-rich precipitations of the (Fe,Cr)xCy type, acted as the source of intergranular corrosion (IGC). Small coherent plate-like and much smaller granular precipitations were found distributed homogenously along grain boundaries and inside the grains. Combining the tensile strength test and microstructure analysis suggested that these precipitations play significant roles in the hardness of the investigated sample."

"ABSTRAKSekitar 95 dari seluruh bijih kromit yang ditambang di dunia digunakan sebagai bahan baku pembuatan ferrochromium FeCr . Pada penelitian sebelumnya, peleburan pasir kromit kadar rendah tidak dapat menghasilkan ferrochromium dengan kadar Cr ge; 60 sehingga pasir kromit kadar rendah harus dilakukan proses benefisiasi untuk meningkatkan kadar Cr dan rasio Cr/Fe sebelum proses peleburan menjadi ferrochromium. Penelitian ini menggunakan pasir kromit kadar rendah asal Kabupaten Konawe, Sulawesi Selatan. Proses benefisiasi yang dilakukan adalah magnetic separation menggunakan medan magnet 800 Gauss dan reduction roasting selama 60 menit pada temperatur 1000 C dengan variabel jumlah reduktor, yaitu 5 lean carbon, stokiometri, 5 excess carbon dan 10 excess carbon serta jumlah aditif CaSO4, yaitu 5 , 10 , 15 , dan 20 . Rasio Cr/Fe dan kadar Cr pada bahan baku pasir kromit adalah 0,9 dan 19,27 . Kromium dalam pasir kromit kadar rendah berada dalam mineral magnesiochromite, aluminian, yang terasosiasi dengan unsur besi dalam struktur spinel. Magnetic separation yang dilakukan pada bahan baku pasir kromit menghasilkan kenaikan rasio Cr/Fe dan kadar Cr menjadi sebesar 1,31 dan 21,33 akibat adanya pemisahan antara kromit yang bersifat paramagnetik dan pengotornya yang bersifat magnetik. Selanjutnya, hasil terbaik dari reduction roasting yang dilanjutkan dengan magnetic separation diperoleh pada proses reduction roasting dengan menggunakan 10 excess carbon dan 20 CaSO4, yaitu menghasilkan rasio Cr/Fe dan kadar Cr sebesar 1,19 dan 20,48 atau setara dengan FeCr yang mengandung 54,5 Cr.

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ABSTRACTAround 95 of mined chromite ore in the world is utilized as raw material for ferrochromium making process. According to the previous research, the melting of low grade chromite sand could not produce ferrochromium with Cr ge 60 so that low grade chromite sand has to be beneficiated to enhance the chromium grade and Cr Fe ratio before the melting process to produce ferrochromium. This research utilized low grade chromite sand from Konawe District, South Sulawesi. The beneficiation processes that was conducted were magnetic separation, which used magnetic field of 800 Gauss and reduction roasting for 60 minutes at 1000 C with various reductant dosage, 5 lean carbon, stoichiometry, 5 excess carbon and 10 excess carbon along with various dosage of CaSO4 as additive, 5 , 10 , 15 , and 20 . Cr Fe ratio and chromium content in low grade chromite sand are 0.9 and 19.27 . Chromium, in low grade schromite sand, was existed as magnesiochromite, aluminian, which associated with iron in spinel structure. Magnetic sseparation process that was conducted to the raw material, resulted in enhancement of Cr Fe ratio and chromium content to 1.31 and 21.33 due to separation of the paramagnetic chromite from the magnetic gangue. Furthermore, the best result from reduction roasting followed by magnetic separation was obtained when reduction roasting used 10 excess carbon and 20 CaSO4, which resulted at 1.19 of Cr Fe ratio and 20.48 of chromium content or equivalent to FeCr with 54.5 Cr."