Studi Pengaruh Heat Input Dan Holding Time PWHT Terhadap Sifat Mekanik Sambungan Dissimilar Metal Antara SS 347H Dan T91

Purnamasari, Risca Awalia (2022) Studi Pengaruh Heat Input Dan Holding Time PWHT Terhadap Sifat Mekanik Sambungan Dissimilar Metal Antara SS 347H Dan T91. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Dissimilar welding mengacu pada gabungan dua logam atau paduan yang berbeda seperti low alloy steel, baja tahan karat stainless steel dan paduan nickel-base. Kelemahan pengelasan dissimilar metal yang mendasar adalah perbedaan koefisien termal ekspansi masing-masing material menyebabkan degradasi sifat mekanik di zona fusi yang rentan terhadap crack. Untuk mencegahnya dapat dilakukan dengan cara memprediksi komposisi kimia pada weld metal, mengontrol heat input pengelasan, pelapisan (buttering) pada logam induk, dan juga melakukan post weld heat treatment (PWHT) untuk memperkecil tegangan sisa pada pengelasan. Material yang bersifat ductile lebih direkomendasikan untuk menghindari crack. Penelitian ini mempelajari pengaruh parameter pengelasan dan perlakuan panas pada sifat mekanik logam yang berbeda antara sambungan las T91 dan 347H. Sambungan las dibuat menggunakan proses Gas Tungsten Arc welding (GTAW) dengan filler berbahan dasar Ni (ERNiCr-3). Heat input menggunakan arus pengelasan berada pada 60A dan 100A, kemudian dilakukan perlakuan PWHT pada suhu 760 oC dengan holding time 1 jam 3 jam pada kedua sisi material SS 347H dan T91. Pada penelitian ini dilakukan uji struktur mikro, sifat mekanik, dan SEM-EDS. Hasil pengamatan struktur mikro menunjukkan bahwa ada pelebaran ukuran grain size yang dihasilkan dari spesimen heat input dengan arus las 100 A dan holding time PWHT 3 jam di interface T91. Hasil uji kekerasan tertinggi terdapat pada spesimen heat input dengan arus las 60 A dan holding time 1 jam, sedangkan hasil uji kekerasan terendah terdapat pada pada spesimen heat input dengan arus las 100 A dan holding time 3 jam. Nilai kekerasan naik karena adanya martensit yang terbentuk, hal tersebut dibuktikan dengan uji EDS dimana unsur Fe yang naik pada spesimen heat input dengan arus las 60 A dan holding time 1 jam. Pembentukan martensit diindikasi sebagai penyebab timbulnya crack pada garis fusi. Variasi spesimen heat input dengan arus las memberikan dampak seiring dengan meningkatnya heat input dan holding time PWHT nilai kekerasan material semakin menurun sehingga material tersebut bersifat ductile.
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Dissimilar welding refers to joining two dissimilar metals or alloys such as low alloy steel, stainless steel, and nickel-based alloys. The main disadvantage of dissimilar metal welding is that the difference in each material's thermal coefficient of expansion causes degradation of mechanical properties in the fusion zone, which is prone to cracking. To prevent this, it can be done by predicting the chemical composition of the weld metal, controlling the welding heat input , coating (buttering) the parent metal, and doing post weld heat treatment (PWHT) to reduce the residual stress in the welding. Ductile materials are recommended to avoid cracks. This study studied the effect of welding and heat treatment parameters on the mechanical properties of different metals between T91 and 347H welded joints. Welded joints are made using the Gas Tungsten Arc welding (GTAW) process with Ni-based filler (ERNiCr-3). Heat input using welding current is at 60A and 100A, then PWHT treatment is carried out at a temperature of 760 oC with a holding time of 1 hour 3 hours on both sides of the SS 347H and T91 materials. This research conducted microstructure, mechanical properties, and SEM-EDS tests. The microstructure observation results show a grain size widening resulting from the heat input specimen with a welding current of 100 A and a PWHT holding time of 3 hours at the T91 interface. The highest hardness test results are found in the heat input specimen with a welding current of 60 A and a holding time of 1 hour, while the lowest hardness test results are found in a heat input specimen with a welding current of 100 A and a holding time of 3 hours. The hardness value increased due to the presence of martensite formed. This was proven by the EDS test where the Fe element increased in the heat input specimen with a welding current of 60 A and a holding time of 1 hour. The formation of martensite is the cause of the crack in the fusion line. The variation of the heat input specimen with the welding current has an impact as the heat input and holding time PWHT decreases, and the hardness value of the material decreases so that the material is ductile.

Item Type:	Thesis (Masters)
Additional Information:	RTM 671.52 Pur s-1 2022
Uncontrolled Keywords:	Dissimilar welding, T91, 347H, Heat input , Holding time, PWHT
Subjects:	T Technology > TN Mining engineering. Metallurgy > TN879.6 Welding
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis
Depositing User:	Mr. Marsudiyana -
Date Deposited:	12 Feb 2025 02:03
Last Modified:	12 Feb 2025 02:03
URI:	http://repository.its.ac.id/id/eprint/118669

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