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Pengaruh temperatur terhadap struktur mikro dan sifat mekanik dalam proses fussion brazing Ni-Hard 4 dengan S45C menggunakan CuZn 35 sebagai logam pengisi. Siswanto, Ari; Purwadi, W.
Dinamika Teknik Mesin Vol 10, No 1 (2020): Dinamika Teknik Mesin: Jurnal Keilmuan dan Terapan Teknik Mesin
Publisher : Universitas Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/dtm.v10i1.309

Abstract

This research was conducted on white cast iron (Ni-Hard 4) and medium carbon steel (S45C) cast iron materials using a thin brass plate (CuZn 35) 0.3 mm as filler metal by heating at temperatures of 850 to 1050 0C for 120 minutes with a pressure of 2 Mpa in the muffle furnace. The effect of temperature on the microstructure was observed using an optical microscope and scanning electron microscopy equipped with energy dispersive X-ray system (EDS) to determine the chemical composition that occurred between the three meterial layers. The thickness of the interface layer increases with increasing holding temperature. The highest shear strength (79.86 Mpa) was obtained at a temperature of 950 0C.
Investigation of Failure Mechanisms in the U-Bend Tubes of Shell and Tube Heat Exchangers Achyarsyah, Mochamad; Hanaldi, Kus; Purwadi, Wiwik; Hermana, Gita Novian; Siswanto, Ari; Ruskandi, Cecep; Nadi, Muhammad Rizki Gorbyandi
Metalurgi Vol 39, No 3 (2024): Metalurgi Vol. 39 No. 3 2024
Publisher : National Research and Innovation Agency (BRIN)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/metalurgi.2024.775

Abstract

The U-bend tubes of a shell-and-tube heat exchanger made of SA-234 Grade WPB carbon steel failed prematurely within 14 days after replacement and welding. This study investigates failure mechanisms through an integrated failure analysis that includes visual inspection, dye penetrant testing, chemical composition analysis, hardness measurements, and microstructural characterization. The results reveal that the tube contained 0.324 wt.% C, exceeding the maximum limit specified by the standard, which promoted the formation of Widmanstätten ferrite and reduced toughness. The welded joint exhibited multiple defects, including porosity and lack of fusion, which acted as stress concentration sites. Hardness measurements showed average values of 205 HV in the weld metal, 199 HV in the HAZ (heat-affected zone), and 184 HV in the base metal. Under operating conditions of 275 °C and 58.48 barg, these defects progressively opened, leading to fluid leakage. The escaping high-pressure fluid accelerated erosion-corrosion, as evidenced by oxygen-rich corrosion products detected by EDS analysis. The findings demonstrate that the combined effects of material non-compliance, poor welding quality, and unfavorable microstructural evolution governed the premature failure. This study provides quantitative insights to improve welding practices and material selection, thereby enhancing the reliability of U-bend tubes in shell-and-tube heat exchangers.