Analisa Strukturmikro dan Pengaruhnya terhadap Sifat Mekanis Batangan Rel Tipe R54 [Microstructure Analysis and Its Effect to Mechanical Properties of Rail Track Type R54]

Robby Dwiwandono, Leksono Firmansyah, Satrio Herbirowo, M Yunan Hasbi, Fatayalkadri Citrawati

Abstract

This study was conducted to observe the mechanical properties and microstructures of two rail tracks type R54 used in Indonesia, which produce in Germany (rail steel G) and China (rail steel C). During its application, it is necessary for rail track to have high toughness to bear the dynamic load from wheel movement.  In this study, several examinations and observations have been made, which comprise OES chemical composition analysis, metallography by using OM, tensile test, and micro Vickers hardness test. The OES chemical composition result shows that both rail tracks belong to Fe-C-Mn rail steels, in which, rail steel G has higher Zr micro alloy content than rail steel C. These differences do not significantly affect their tensile strength, which are 1050 MPa and 1044 MPa for rail steel G and rail steel C, respectively. Moreover, both samples were observed to have elongation of 13%. The difference in micro alloys, specifically Zr, may influence the hardness of the samples through precipitate strenghtening. The average hardness in the body part of the tracks show that rail steel G has slightly higher hardness value compare to rail steel C. It is 341 HV for rail steel G and 324 HV for rail steel C. This hardness difference was also found between the head part and the body part of both rail tracks. In the head part, the area near the edge of the rail tracks e has an average hardness of 452 HV for rail steel G and 423 HV for rail steel C. These values are higher than the hardness value of the body part of both rail tracks. The difference in hardness of the body part and the head part might be due to the phases in their microstructure, which observed to be dominated by pearlite.

Abstrak

Penelitian ini dilakukan dengan tujuan untuk mengetahui sifat mekanik dan struktur mikro dari beberapa jenis batangan rel bertipe R-54 yang digunakan di Indonesia, yaitu yang berasal dari Jerman (kode sampel G) dan Cina (kode sampel C). Dalam aplikasinya, ketangguhan tinggi diperlukan agar material batangan rel mampu meredam atau menahan beban roda kereta api saat berjalan. Dalam penelitian ini, beberapa pengujian telah dilakukan, antara lain pengujian komposisi kimia dengan optical emission spectrometer (OES), pengamatan metalografi dengan optical microscope (OM), pengujian keuatan tarik serta uji keras Micro Vickers. Dari hasil pengujian komposisi kimia didapatkan bahwa sampel G memiliki unsur pemadu mikro Zr lebih besar dari sampel C. Perbedaan komposisi kimia ini tidak mempengaruhi besarnya kekuatan tarik pada kedua sampel secara signifikan, dimana dari hasil pengujian tarik didapatkan nilai kekuatan tarik untuk sampel G sebesar 1050 MPa dan sampel C sebesar 1044 MPa dengan nilai elongasi yang sama yaitu sebesar 13%. Pengaruh dari perbedaan kandungan unsur-unsur pemadu, dalam hal ini Zr, dimungkinkan dapat mempengaruhi nilai kekerasan rata-rata dari kedua sampel melalui pembentukan presipitat, dimana dari hasil pengujian kekerasan pada bagian badan rel, secara keseluruhan, sampel G memiliki nilai kekerasan rata-rata lebih tinggi dibandingkan sampel C, yaitu 341 HV (sampel G) dan 324 HV (sampel C). Perbedaan pada nilai kekerasan juga ditunjukkan untuk bagian kepala dan bagian badan rel dari kedua sampel. Pada bagian kepala, terutama diseputaran bagian permukaannya, memiliki nilai kekerasan rata-rata yang lebih tinggi, yaitu 452 HV (sampel G) dan 423 HV (sampel C), dibandingkan dengan kekerasan rata-rata pada bagian badan, baik di area tepi maupun tengah. Perbedaan kekerasan yang terjadi antara bagian kepala dan badan rel pada kedua sampel salah satunya dipengaruhi oleh struktur mikronya, yang didominasi oleh fasa perlit.

Keywords

Baja rel; rel kereta; strukturmikro; sifat mekanis; R54; perlit; jarak lamela; Rail steel; rail track; microstructure; mechanical property; R54; pearlite; lamellar spacing

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