Pengaruh Variasi Suhu Post-Weld Heat Treatment terhadap Struktur Mikro, Sifat Mekanik, dan Tegangan Sisa pada Sambungan Las Baja SS400

Kamilah, Imada Millatul (2026) Pengaruh Variasi Suhu Post-Weld Heat Treatment terhadap Struktur Mikro, Sifat Mekanik, dan Tegangan Sisa pada Sambungan Las Baja SS400. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Bogie frame merupakan komponen utama pada sistem bogie kereta api yang berfungsi menopang beban statis dan dinamis serta menjaga kestabilan pergerakan kereta. Baja SS400 banyak digunakan untuk komponen bogie frame, namun dalam fabrikasi bogie frame membutuhkan proses pengelasan yang dapat menimbulkan perubahan struktur mikro, tegangan sisa, dan ketidakstabilan sifat mekanik. Oleh karena itu, penelitian ini dilakukan untuk menganalisis pengaruh variasi suhu Post-Weld Heat Treatment (PWHT) terhadap struktur mikro, tegangan sisa, dan sifat mekanik sambungan las baja SS400. Pengelasan dilakukan menggunakan metode Gas Metal Arc Welding (GMAW) dengan single V butt joint dan multipass welding. Setelah proses pengelasan, dilakukan proses PWHT pada suhu 580˚C, 635˚C, serta 650˚C dengan holding time selama 1 jam menggunakan furnace. Untuk mengetahui pengaruh PWHT, dilakukan pengujian metalografi, pengukuran tegangan sisa metode hole drilling, serta pengujian kekerasan microvickers dan uji tarik. Hasil penelitian menunjukkan bahwa PWHT tidak mengubah jenis fasa karena dilakukan di bawah suhu kritis A1. Dimana fasa pada weld metal dan Coarse Grain Heat Affected Zone (CGHAZ) adalah ferrite dan bainite, sedangkan pada Fine Grain Heat Affected Zone (FGHAZ) dan base metal adalah ferrite dan pearlite. PWHT memberikan pengaruh nyata terhadap karakteristik struktur mikro dan sifat mekanik. Penerapan PWHT hingga 650˚C menyebabkan ukuran butir menjadi lebih halus dan homogen dibandingkan kondisi tanpa PWHT, yang menunjukkan tercapainya struktur mikro yang lebih stabil. Selain itu, PWHT 650˚C mampu menurunkan tegangan sisa tarik pada arah longitudinal dan transversal secara signifikan hingga hampir seluruhnya terelaksasi. Kekerasan pada weld metal dan HAZ mengalami penurunan serta menunjukkan distribusi yang lebih seragam, sementara sifat tarik menunjukkan kombinasi kekuatan yang tetap terjaga dengan peningkatan keuletan yang paling tinggi. Secara keseluruhan, PWHT pada 650˚C memberikan kondisi paling optimal, ditinjau dari stabilitas struktur mikro, relaksasi tegangan sisa, homogenitas kekerasan, serta keseimbangan antara kekuatan dan keuletan material.
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The bogie frame is the main component of the railway bogie system that functions to support static and dynamic loads and maintain the stability of the movement of the train. SS400 steel is widely used for bogie frame components, but in bogie frame fabrication it requires a welding process that can give rise to changes in microstructure, residual stress, and instability of mechanical properties. Therefore, this study was conducted to analyze the effect of temperature variations of Post-Weld Heat Treatment (PWHT) on the microstructure, residual stress, and mechanical properties of SS400 steel weld joints. Welding is carried out using the Gas Metal Arc Welding (GMAW) method with a single V butt joint and multipass welding. After the welding process, the PWHT process is carried out at temperatures of 580°C, 635°C, and 650°C with a holding time of 1 hour using a furnace. To determine the influence of PWHT, metallographic tests, residual stress measurements of the hole drilling method, as well as micro Vickers hardness testing and tensile tests were carried out. The results showed that PWHT did not change the type of phase because it was carried out below the critical temperature of A1. Where the phases in weld metal and Coarse Grain Heat Affected Zone (CGHAZ) are ferrite and bainite, while in Fine Grain Heat Affected Zone (FGHAZ) and base metals are ferrite and pearlite. PWHT exerts a noticeable influence on the characteristics of microstructures and mechanical properties. The application of PWHT up to 650°C causes the grain size to be smoother and more homogeneous than without PWHT, which indicates the achievement of a more stable microstructure. In addition, PWHT 650°C can significantly reduce the residual tensile stress in the longitudinal and transverse directions until it is almost completely relaxed. The hardness of weld metal and HAZ decreases and shows a more uniform distribution, while tensile properties show a combination of maintained strength with the highest increase in ductility. Overall, PWHT at 650°C provides the most optimal conditions, judging from the stability of the microstructure, the relaxation of residual stress, the homogeneity of hardness, and the balance between strength and ductility of the material.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	GMAW, PWHT, Sifat Mekanik, Struktur Mikro, Tegangan Sisa, GMAW, PWHT, Mechanical Properties, Microstructure, Residual Stress
Subjects:	T Technology > TS Manufactures > TS227 Welding.
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Material & Metallurgical Engineering > 28201-(S1) Undergraduate Thesis
Depositing User:	Imada Millatul Kamilah
Date Deposited:	21 Jan 2026 00:49
Last Modified:	21 Jan 2026 00:49
URI:	http://repository.its.ac.id/id/eprint/129872

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