Analisa Pengaruh Waktu Temper terhadap Struktur Mikro, Komposisi Unsur Kimia dan Kekerasan pada Baja VCN 150

Arjendra, Julius Nugrahadi (2024) Analisa Pengaruh Waktu Temper terhadap Struktur Mikro, Komposisi Unsur Kimia dan Kekerasan pada Baja VCN 150. S1 thesis, Universitas Kristen Indonesia.

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Abstract

Baja karbon sedang VCN150, memiliki kekuatan sangat tinggi dan memadukan antara hardenability yang baik, keuletan, ketangguhan, dan ketahanan terhadap fatigue dan creep yang tinggi. Tujuan penelitian ini untuk menganalisis pengaruh temper terhadap struktur mikro, komposisi kimia, kuat tarik, dan kekerasan. Proses perlakuan panas yang dilakukan adalah hardening pada temperatur 850°C kemudian quenching media air, dilanjutkan proses tempering pada temperatur yang sama yaitu 400°C dengan holding time yang berbeda 2 jam, 5 jam, dan 9 jam. Karakterisasi Pengujian meliputi pengujian kekerasan dengan skala Brinell, pengujian struktur mikro dengan mikroskop optic, dan komposisi unsur kimia dengan Optik Emisi Spektrometer . Hasil pengujian kekerasan material as cast 215 Hb, setelah hardening 850°C dan quenching di media air memiliki kekerasan 465 HB. Namun kekerasan berkurang sesudah di tempering 400°C menjadi 401 HB ke 334 HB. Untuk pengujian kuat tarik setelah hardening 850°C dan quenching memiliki kuat tarik 1604,25 MPa. Namun kuat tarik berkurang sesudah di tempering 400°C menjadi 1383,45 MPa ke 1152,30 MPa. Hasil uji komposisi kimia menunjukkan unsur karbon mengalami penurunan yang signitifikan, tetapi unsur lainnya seperti Si, Mn, Ni, Cr yang mengalami kenaikan sekitar 4-6,5%. Hasil pengamatan strukturmikro setelah di temper memperlihatkan mikrograf fasa bainit temper, fasa ferlit, dan martensit sisa. Peningkatan waktu tempering mengakibatkan struktur menjadi kasar dan mengakibatkan perubahan bentuk pada fasa sementit (Fe3C). yang semula berbentuk panjang semakin cenderung menjadi bulat. / VCN150 medium carbon steel, has very high strength and combines good hardenability, ductility, toughness, and high resistance to fatigue and creep. The aim of this research is to analyze the effect of tempering on microstructure, chemical composition, tensile strength and hardness. The heat treatment process carried out is hardening at a temperature of 850°C then quenching in water media, followed by the tempering process at the same temperature, namely 400°C with different holding times of 2 hours, 5 hours and 9 hours. Characterization testing includes hardness testing with the Brinell scale, microstructure testing with an optical microscope, and chemical element composition with an Optical Emission Spectrometer. The hardness test results of the as cast material were 215 Hb, after hardening at 850°C and quenching in water the hardness was 465 HB. However, the hardness decreases after tempering at 400°C to 401 HB to 334 HB. For tensile strength testing after hardening at 850°C and quenching, the tensile strength was 1604.25 MPa. However, the tensile strength decreases after tempering at 400°C to 1383.45 MPa to 1152.30 MPa. The results of the chemical composition test showed that the carbon element experienced a significant decrease, but other elements such as Si, Mn, Ni, Cr experienced an increase of around 4-6.5%. The results of observations of the microstructure after tempering show micrographs of the tempered bainite phase, ferlite phase and residual martensite. Increasing the tempering time causes the structure to become rough and results in changes in the shape of the cementite phase (Fe3C). what was originally long in shape increasingly tends to become round.

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