PENGARUH PERLAKUAN PANAS HARDENING DENGAN MEDIA PENDINGIN AIR PENDINGIN (WATER COOLANT) DAN OLI PELUMAS YANG DITEMPERING DENGAN VARIASI WAKTU TAHAN TERHADAP SIFAT MEKANIK DAN STRUKTUR MIKRO BAJA KARBON MENENGAH

Dwi Kurniawan, Syahputra (2026) PENGARUH PERLAKUAN PANAS HARDENING DENGAN MEDIA PENDINGIN AIR PENDINGIN (WATER COOLANT) DAN OLI PELUMAS YANG DITEMPERING DENGAN VARIASI WAKTU TAHAN TERHADAP SIFAT MEKANIK DAN STRUKTUR MIKRO BAJA KARBON MENENGAH. S-1 thesis, 021008 Universitas Tridinanti.

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Abstract

Medium carbon steel is widely used as an engineering material for machine components due to its relatively good mechanical properties. However, its mechanical properties can be further improved through heat treatment. This study aims to analyze the effect of hardening treatment using water coolant and lubricating oil as cooling media, followed by tempering with variations in holding time, on the hardness and microstructure of medium carbon steel. The hardening process was carried out at a temperature of 783°C with a holding time of 10 minutes, followed by rapid cooling using water coolant and lubricating oil. The specimens were then tempered at 400°C with holding times of 15 and 25 minutes. Hardness testing was conducted using the Rockwell C method at five different measurement points for each specimen, while microstructural observations were performed to identify the phase transformations resulting from the heat treatment. The results showed that the cooling medium significantly affected the hardness of the steel. The raw material exhibited an average hardness of 19.8 HRC, which increased to 51 HRC after quenching using water coolant and to 35.1 HRC after quenching using lubricating oil. After tempering, the hardness of the water-cooled specimens decreased to 42.5 HRC at a holding time of 15 minutes and 40.9 HRC at 25 minutes. Meanwhile, the specimens cooled using lubricating oil exhibited hardness values of 33.7 HRC at 15 minutes and 25.6 HRC at 25 minutes. Microstructural observations showed that water quenching produced a predominantly martensitic structure, whereas oil quenching resulted in a mixture of martensite and pearlite. After tempering, the martensitic structure gradually decomposed into tempered martensite accompanied by the formation and distribution of more stable carbides. Increasing the tempering holding time from 15 to 25 minutes resulted in a decrease in hardness and a more homogeneous microstructure. Based on the results, the combination of water coolant and tempering for 25 minutes provided the best balance between hardness and microstructural stability, with a hardness value of 40.9 HRC. Therefore, the selection of cooling medium and tempering holding time significantly affects the mechanical properties and microstructure of medium carbon steel and can be adjusted according to the intended application. Keywords: Medium Carbon Steel, Hardening, Water Coolant, Lubricating Oil, Tempering, Holding Time, Hardness, Microstructure

Item Type:	Thesis (S-1)
Subjects:	T Technology > TJ Mechanical engineering and machinery
Divisions:	Fakultas Teknik > S1 Teknik Mesin
Depositing User:	Tn DWI KURNIAWAN SYAHPUTRA
Date Deposited:	26 Oct 2026 01:40
Last Modified:	26 Oct 2026 01:40
URI:	http://repository.univ-tridinanti.ac.id/id/eprint/11545

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