Pengaruh normalising terhadap struktur mikro dan sifat mekanis pada poros dan Disc Turbin Crossflow T14 setelah mengalami proses pengelasan

ANTARIKSA, Yudono Cahyo, Ir. Subarmono, MT.PE

2004 | Tesis | S2 Teknik Mesin (Magister Sistem Teknik)

Penelitian ini bertujuan untuk mencari pengaruh normalising terhadap struktur mikro dan sifat mekanis pada poros dan disc turbin Crossflow T.14 setelah mengalami proses pengelasan. Bahan poros dan disc yang terbuat dari baja karbon rendah disambung dengan las busur listrik menggunakan bahan elektroda RB 26, diameter 2,6 mm, arus 90 amper dengan pengelasan satu lapis bolak-balik. Proses normalising dilakukan dengan memanaskan kembali poros dan disc, sesuai kadar karbon baja sebesar 930ºC, dengan percobaan normalising menggunakan holding time 15, 30 dan 45 menit. Kemudian bahan-bahan tersebut dibuat benda uji tarik, geser, kekerasan dan pengamatan struktur mikro. Hasil penelitian menunjukkan uji tarik bahan dasar disc sebesar 34,18 kg/mm², bahan dasar poros 55,3 kg/mm² dan sambungan disc yang di normalising sebesar 28,92 kg/mm². Pengujian geser sambungan poros dan disc 31,57 kg/mm², setelah di normalising menjadi 34,83 kg/mm². Hasil pengujian kekerasan sambungan poros dan disc di normalising pada pusat las 110,13 kg/mm², HAZ disc 117,45 kg/mm², HAZ poros 109,19 kg/mm², bahan dasar disc 98,91 kg/mm² dan bahan dasar poros 112,85 kg/mm². Struktur mikro pada sambungan poros dan disc setelah di normalising didapatkan struktur yang halus dan seragam.

The goal of this research was to find out effects normalizing on the micro structure and mechanical properties on the shaft and disc Crossflow turbine T.14 after a local heating process. The shaft material and disc were made of low carbon steel which were joined with arc welding by using RB 26, electrode with 2.6 mm diameter, 90 ampere electrical current through one layer vice versa welding. The process of normalizing through shaft and disc, has heated at the normalizing temperature 930ºC, by using holding time at 15, 30 and 45 minute. After the previous process of the material was made the tensile strength, shear strength, hardness and observation of micro structure specimens. The result of research shows the tensile strength of the base material of disc is 34.18 kg/mm², base material of shaft is 55.3 kg/mm² and normalizing use joint the disc is 28.92 kg/mm². The result of shear strength on shaft joint and disc is 31.57 kg/mm² and after normalizing becomes 34.83 kg/mm². The result of hardness Vickers on shaft and disc joint after normalizing in the center of welding is 110.13 kg/mm², on the HAZ of the disc is 117.45 kg/mm², HAZ of the shaft is 109.19 kg/mm² and on base material of the disc is 98.91 kg/mm², base material of the shaft is 112.85 kg/mm². The micro structure on the shaft and disc joint after normalizing is found homogen structure of ferrit and pearlit.

Kata Kunci : Mikrohidro,Turbin Cross Flow T14,Pengelasan, Normalizing, Micro Structure and mechanical properties