Mahros Darsin
(Staf Pengajar Jurusan Teknik Mesin, Fakultas Teknik, Universitas Jember)
Ahmad Effan
(Guru SMK Berdikari Jember, Dosen Luar Biasa Jurusan Teknik Mesin Universitas Muhammadiyah Jember)
Agus Setiawan
(Alumni Jurusan Teknik Mesin Universitas Muhammadiyah Jember)
ABSTRACT: Double hardening is the process of hardening after carburizing process, which ended with the process of tempering. The purpose of the double-hardening process is to improve the structure of the skin together at the core. In this study expected to provide information about changes in the strength of steel resulting from the hardening of steel in a double process of hardening. Materials used in this study is low carbon steel ST 37. Solid cylindrical material with a diameter of 25 mm and a length of 20 mm. Media carburizing using wood charcoal plus ± 40% barium carbonate is carried out at 900 oC with holding time for 4 hours, followed by a double-hardening process at 900 oC and 750 oC with the media water coolers, and then ends the process of tempering with the variation of temperature 180 oC, 250 oC, 300 oC. Vickers hardness test method with weights 50 kg. The value of raw material hardness after carburizing process VHN 547.44. The results were subjected to a double process of carburizing hardening with tempering 180°C has a hardness value 542.54 VHN decreased 0.9%. to the control specimens. While the tempering 250 °C produces violence VHN 442.62, down 23.68% against the control specimens. In the tempering temperature 300 oC has the lowest hardness value 385.15 VHN, declining 42.13% of the control specimens. In the double-hardening process, the resulting structure is cementite, pearlite and ferrite. However, the cementite structure tends to decrease, because it ended with tempers. From this research can be concluded that the control specimen hardness value higher than the double-hardening process, because the control specimen just given carburizing process. The process ends with a double hardening tempering process so as not brittle or fragile. The greater the temperature of tempering steel, the hardness will decrease.
Keywords: carburizing, double hardening, tempering, kekerasan.
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