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All Journal Logic : Jurnal Rancang Bangun dan Teknologi
Ketut Rimpung
Jurusan Teknik Mesin Politeknik Negeri Bali
Computer Science & IT Education

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Analysis of St. 42 Steel Hardness After Being Heated to 8000c And Quickly Cooled With Fresh Water by Applying Rockwell Method Ketut Rimpung
Logic : Jurnal Rancang Bangun dan Teknologi Vol 18 No 3 (2018): November
Publisher : Pusat Penelitian dan Pengabdian kepada Masyarakat (P3M) Politeknik Negeri Bali

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (243.019 KB) | DOI: 10.31940/logic.v18i3.1133

Abstract

The hardness of machine components which, in operation time, collide and rub against each other and are made of St.42 steel needs to be found out. Therefore, research on the hardness of St.42 steel especially those which are heated needs to be carried out so that it can be chosen as machine component properly. This research tests the change of the surface hardness by applying Rockwell method and is the continuation from a former research. Steel is a technical material which is often used as machine components, so that its strength against external loads is really needed to be known. External loads which are often occurred on machine components are friction load, torsion load, tensile load, bent load and mash load. This research aims to find out how much the change of the hardness of standard St.42 steel surface after being heated at temperature of 8000C and quickly cooled by using fresh water which is carried out in laboratory of material testing, Department of Mechanical Engineering, State Polytechnic of Bali. The result shows that the hardness of the surface of steel which is heated until 8000C and quickly cooled by using fresh water is more lenient than the standard St.42 steel, although it is tested by applying either Rockwell B (HRB) or Rockwell C (HRC) methods. The change of the strength based on Rockwell B method shows the decrease in surface hardness until 19,81%; from 29,93 (Kgf/mm2) to 24,0 (Kgf/mm2). In Rockwell C method there is also decrease in surface hardness which is equal to 20,23%; from 54,7(Kgf/mm2) to 43,63 (Kgf/mm2).
ANALISIS PERUBAHAN KEKERASAN PERMUKAAN BAJA (St. 42) DENGAN PERLAKUAN PANAS 800◦C MENGGUNAKAN METODE VICKERS DI LABORATORIUM UJI BAHAN POLITEKNIK NEGERI BALI. Ketut Rimpung
Logic : Jurnal Rancang Bangun dan Teknologi Vol 17 No 1 (2017): March
Publisher : Pusat Penelitian dan Pengabdian kepada Masyarakat (P3M) Politeknik Negeri Bali

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (425.769 KB)

Abstract

Menurut teori, kekerasan permukaan baja akan naik bila dilakukan pemanasan mencapai batas suhu transformasi lalu didinginkan secara cepat. Demikian juga, kekerasan baja akan turun bila diperlakukan sebaliknya, [2]. Kekerasan baja dapat diketahui melalui pengujian menggunakan mesin uji kekerasan logam yang tersedia di laboratorium pengujian bahan dan metrologi, Jurusan Teknik Mesin, Politeknik Negeri Bali. Proses pengujian kekerasan dilakukan dengan menekan permukaan benda uji menggunakan penetrator tertentu dalam waktu tertentu, sampai permukaan benda uji rusak atau terjadi identasi pada permukaan benda uji. Pengujian ini bertujuan untuk dapat mengetahui perubahan kekerasan baja (St.42 standar) dibandingkan dengan baja jenis yang sama setelah mendapat perlakuan panas untuk dikeraskan maupun yang dilunakkan. Penelitian ini dilakukan bersama mahasiswa programstudi teknik mesin semester IV di laboratorium uji bahan Jurusan Teknik Mesin Politeknik Negeri Bali. Penelitian ini menguji kekerasan baja (St. 42) menggunakan metode Vickers. Hasil pengujian dengan metode Vickes yaitu baja yang dikeraskan melalui pemanasan 800◦C dan didinginkan cepat menggunakan air tawar, ternyata menjadi lebih lunak dibandingkan dengan baja (St.42standar). Fakta hasil penelitian: kekerasan St.42Standar =105,226 Kg/mm2, kekerasan St.42 Hardening = 81,977 Kg/mm2, dan kekerasan St.42 Anaeling =75,264 Kg/mm2. Jadi, ada ketidak sesuaian antara teori dibandingkan fakta hasil pengujian kekerasan dengan metode Vickers, pada baja dengan pendinginan cepat. Sedangkan, fakta hasil pengujian kekerasan baja yang dilunakkan sesuai dengan teori.
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