Pengaruh Variasi Arus Pengelasan SMAW Posisi 3G terhadap Sifat Mekanik, Struktur Mikro, dan Kualitas Sambungan Baja AISI 1041

Heraldi, Muhammad (2026) Pengaruh Variasi Arus Pengelasan SMAW Posisi 3G terhadap Sifat Mekanik, Struktur Mikro, dan Kualitas Sambungan Baja AISI 1041. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Shielded Metal Arc Welding (SMAW) posisi 3G banyak digunakan pada aplikasi industri dengan struktur vertikal dan sambungan tidak dapat diputar, di mana variasi arus pengelasan berpengaruh langsung terhadap heat input, siklus termal, dan kualitas sambungan. Penelitian ini bertujuan untuk menganalisis pengaruh variasi arus pengelasan terhadap sifat mekanik, mikrostruktur, dan kualitas sambungan las baja karbon sedang AISI 1041 menggunakan elektroda E7018 berdiameter 3,2 mm dengan variasi arus 110 A, 125 A, dan 140 A, tanpa preheat dan menggunakan polaritas Direct Current Electrode Positive (DCEP). Evaluasi kualitas sambungan dilakukan menggunakan penetrant test, sedangkan karakterisasi mekanik meliputi uji tarik dan uji kekerasan Vickers. Analisis mikrostruktur dilakukan pada daerah base metal (BM), heat affected zone (HAZ), dan weld metal (WM) melalui pengamatan metalografi. Hasil penelitian menunjukkan bahwa peningkatan arus pengelasan meningkatkan heat input yang berdampak pada perubahan mikrostruktur dan respons mekanik sambungan las. Nilai kekerasan rata-rata meningkat pada seluruh zona, dengan BM dari 161,1 HV menjadi 201,7 HV dan WM dari 151,1 HV menjadi 184,9 HV, sedangkan HAZ tetap memiliki kekerasan terendah. Mikrostruktur berkembang dari ferrite–pearlite menuju ferit bermorfologi terarah, terutama Widmanstätten ferrite, akibat transformasi difusional tanpa terbentuknya fasa non-difusional. Hasil uji tarik menunjukkan bahwa arus 110 A menghasilkan performa mekanik yang belum stabil, arus 125 A memberikan kekuatan tarik dan keuletan tertinggi dengan kegagalan pada daerah BM, sedangkan arus 140 A menunjukkan penurunan keuletan dan munculnya kegagalan pada daerah HAZ. Berdasarkan keseluruhan hasil pengujian, arus pengelasan 125 A menghasilkan karakteristik sambungan las paling optimal dengan keseimbangan terbaik antara kekuatan tarik, keuletan, kestabilan mikrostruktur, dan kualitas sambungan.

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Shielded Metal Arc Welding (SMAW) in the 3G position is widely applied in industrial structures involving vertical joints that cannot be rotated, where welding current variation directly affects heat input, thermal cycles, and joint quality. This study aims to investigate the effect of welding current variation on the mechanical properties, microstructure, and joint quality of medium-carbon steel AISI 1041 welded using E7018 electrodes with a diameter of 3.2 mm at welding currents of 110 A, 125 A, and 140 A, without preheating and using Direct Current Electrode Positive (DCEP) polarity. Joint quality was evaluated using penetrant testing, while mechanical characterization was conducted through tensile testing and Vickers hardness testing. Microstructural analysis was performed on the base metal (BM), heat affected zone (HAZ), and weld metal (WM) using metallographic observation. The results indicate that increasing welding current increases heat input, leading to significant changes in microstructure and mechanical response of the welded joints. The average hardness values increased in all zones, with BM hardness rising from 161.1 HV to 201.7 HV and WM hardness from 151.1 HV to 184.9 HV, while the HAZ consistently exhibited the lowest hardness. Microstructural evolution was characterized by a transition from ferrite–pearlite to directionally oriented ferrite, predominantly Widmanstätten ferrite, resulting from diffusional transformation without the formation of non-diffusional phases. Tensile test results show that welding at 110 A produced unstable mechanical performance, whereas 125 A resulted in the highest tensile strength and ductility with fracture occurring in the base metal. At 140 A, a reduction in ductility and fracture initiation in the HAZ were observed. Overall, a welding current of 125 A provides the most optimal joint characteristics, offering the best balance between tensile strength, ductility, microstructural stability, and joint quality.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	las SMAW, pengelasan posisi 3G, arus pengelasan, baja AISI 1041, sifat mekanik, struktur mikro, kualitas sambungan las, SMAW welding, 3G welding position, welding current, AISI 1041 steel, mechanical properties, microstructure, weld quality
Subjects:	T Technology > TS Manufactures > TS227 Welding.
Divisions:	Faculty of Vocational > Mechanical Industrial Engineering (D4)
Depositing User:	Muhamad Heraldi
Date Deposited:	03 Feb 2026 08:49
Last Modified:	03 Feb 2026 08:49
URI:	http://repository.its.ac.id/id/eprint/129878

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