PENGARUH PENAMBAHAN KROM DAN FORGING TERHADAP KEKERASAN, KEAUSAN, IMPAK DAN STRUKTUR MIKRO BALL MILL

SUMPENA, Dr. Ir. Subarmono, M.T., PE

2013 | Tesis | S2 Teknik Mesin

Finish mill merupakan proses akhir dalam pembuatan semen. Proses penggilingan menggunakan ball mill untuk mendapatkan serbuk halus (±100-300 µm). Saat ini, pabrik semen di Indonesia masih mengimpor ball mill. Kualitas ball mill dapat ditingkatkan dengan krom dalam proses pengecoran kemudian penempaan. Efek dari krom dan penempaan pada sifat mekanik perlu diteliti pada penelitian ini. Komposisi krom ball mill adalah 6,67%; 8,38% dan 14,68%. Ball mill dipanaskan dalam oven pada temperatur 1200oC selama 120 menit. Penempaanball mill denganmesin presshidrolikkapasitas 20 ton, penempaandilakukan untuk membuatbentukelipsmenjadibentuk bola.Ball milldibelah menjadidua bagiandan diujikekerasan, keausan, impakdanstruktur mikro. Kekerasanball milldengan6,67%;8,38%dan14,68% kromadalahberturut-turut 520,11kg/mm2VHN;523,56kg/mm2VHNdan560,03kg/mm2VHN. Sementaralaju keausanmengalami pengurangan berturut-turut yaitu29,49%, 22,15% dan9,62%. Komposisikromtinggidapatmengurangiimpakball milltetapipenempaanball millmeningkatkanimpak. Impak meningkatsetelahditempa pada ball mill6,67%, 8,38% dan14,68% kromberturut-turut adalah27,93%;14,05% dan10,19%. Struktur mikroball mill adalahferit, perlitdankarbida krom.

Finish mill is the last process in making manufacturing of cement.The milling process uses a ball mill in order to obtain a fine powder (±100-300 µm). Currently, the cement plants in Indonesia still import the ball mill. The ball mill qualitycan be improved by chrome in casting process then forging. The effect of the chrome and forging on mechanical properties has to be investigated in this research. The chrome composition in the ball mill was 6.67%; 8.38% and 14.68%. The ball mill was heated in an oven on 1200oCfor 120 minutes. The forging of the ball mill with 20 tons capacity of hydraulic forging press machine was done tomake ellipse shape become ball shape.The ball mill was cleaved into two parts and tested on hardness, wear, toughness and microstructure. The ball mill hardness with 6.67%; 8.38% and 14.68% of chrome is 520.11kg/mm2 VHN; 523.56 kg/mm2 VHN and560.03 kg/mm2 VHN respectively. While the wear rate reduces on 29.49%; 22.15% and 9.62% respectively. The higher chrome composition is reduce the ball mill toughness but the forging of the ball mill increases its toughness. The toughness increasing after forging in 6.67%; 8,38% and 14,68% of chrome is 27.93%; 14.05% and 10.19% respectively.The microstructure of the ball mill is ferrite, pearlite andchrome carbide.

Kata Kunci : ball mill, tempa, pengecoran, krom