Tilahun, Daniel (PhD))Alemayehu, Abiyu2018-07-022023-11-182018-07-022023-11-182016-03http://etd.aau.edu.et/handle/12345678/5287This research is concerned to evaluate the influence of tempering temperature and time of ASTM A36 structural steel; it is one of the accessories for the buildings, bridges and off-highway vehicles and equipment. This steel was heat treated using pack carburization method at the temperature of 9000c for 6 hour and cooled in the Furness then hardened at the temperature of 830 0c for 30min then quenched in water , after this, it was tempered at temperature (200,400&600) 0c for 30, 60&90 minutes for each tempering temperature to modify desired properties. The mechanical behavior, particularly, ultimate tensile strength, yield strength and elongation were investigated using universal testing machine; while the hardness measurement was done on Rockwell hardness testing machine, its toughness was done using Izod impact testing machine and the composition of the material were tested by spectrometer and finally the microstructur of the sample has been tested in metallographic microscope. Result that expected is the ultimate tensile strength and the yield strength decrease while the elongation increases with an increase in tempering temperature and tempering time of different tempered specimen. The hardness of quenched/hardened specimen decreases with an increase in tempering temperature and tempering time. Furthermore, increasing temperature and lowering time produces approximately same result as decreasing temperature and increasing time. Key Words: Carburizing, Hardening, Tempering, Quenching, Martensite, Muffle Furnace composition test, Hardness, impact test, tensile testenCarburizing;Hardening;Tempering, Quenching; Martensite,;Muffle Furnace composition test; Hardness; impact test; tensile testThesis