Document Type : Original Article
Authors
1
- Mining and Material Engineering, Faculty of Civil and Earth Resources Engineering, Central Tehran Branch, Islamic Azad Univercity, Tehran, Iran
2
Assistant Prof. Department of Civil and Earth resources, Central Tehran Branch, Islamic Azad Univercity, Tehran, Iran
3
M.Sc. Student, Department of Petroleum, Mining and Material Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran
10.22034/ijme.2024.423695.1876
Abstract
AISI 4130 and 4340 steels are among the most widely used steels in the defense and aerospace industries due to a set of desirable properties such as high strength, suitable impact energy, and desirable weldability. In this research, the effect of tempering temperature and the type of cooling inviroment on the mechanical properties and microstructure of the weld joint of low alloy steel with medium carbon 4340 to 4130 steel was investigated. The weld microstructure consisted of martensite and ferrite phases. The microstructure of martensite with bainite and ferrite was observed in the HAZ of both steels, in the HAZ of 4340 steel, more acicular ferrite replaced martensite, and in the HAZ of 4130 more acicular ferrite and less martensite, in the HAZ of 4130, martensite was observed. The results of the yield and Ultimate strength of the samples showed that with the increase in tempering temperature, the yield and ultimaite strength decreased. Observing the hardness profile in the weld zone and the HAZ of both metals shows that with the increase of the tempering temperature from 250 to 450 ℃, the hardness has decreased due to the decrease in the density of dislocations in the grain boundaries. Microstructural results showed that samples cooled in polymer have higher strength due to the formation of more martensite and less residual austenite. The values of ultimate strength, yield strength and percentage of elongation in the sample tempered at 250 ℃ and cooled in the polymer are 1705 Mpa, 1480 Mpa and 7.4%.
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