EFFECTS OF AUSTEMPERING TIME ON MECHANICAL PROPERTIES AND MICROSTUCTURES OF AISI 4340 STEEL: A CRITICAL REVIEW

• Main Author: Akhmad, Fandi
• Format: Final Project
• Language: Indonesia
• Subjects: Metalurgi
• Online Access: https://digilib.itb.ac.id/gdl/view/51663
• Institution: Institut Teknologi Bandung

The demand for high strength steel in the advanced technology era becomes more increasing. In 2013, Balai Besar Logam dan Mesin Indonesia doing an improvement to the cast steel for track link usage on a tank as a substituted product from the imported track link. This works revealed that there was a significant improvement in the toughness of austempered steel than imported products. For getting a better understanding of the effect of austempering on AISI 4340 steel, a critical review was done from four researchers from 2011 to 2020 about the effect of the austempering process to the change of hardness, toughness, and microstructure of medium carbon steel AISI 4340 (0.38-0.43% C). A Critical review was done by comparing the results from each researcher and fit the relevancy theory than have been trusted. AISI 4340 steel was chosen on this topic because of the wide range usage in an industrial company and the special performance that exists in it. This critical review concluded that (1) An austempering process can reduce hardness as the holding time increases, but there is a slight increase in initial holding due to the influence of ?-carbide. (2) The toughness increases until the holding time of 60 minutes then decreases, except at temperatures above 350oC the toughness decreases since the initial austempering containment due to the temper embrittlement mechanism. (3) The increasing of the austempering time, the bainite structure will be completely formed at a certain point of time then it will experience the deformation of the bainite structure at a longer holding time, the microstructure observation by SEM shows the presence of bainite, martensite, and residual austenite phases.