Mechanical Technical. Dept, Northern,Technical, University Tikrit, Iraq.


This article examines the correlation between shape of shear lips and temperature change. Impact toughness properties of Standard Charpy-V samples are evaluated at different temperatures for analysis of the energy of fracture of specimens (080M40 Medium Carbon Steel Z3 & Z7 treatment codes). Shear lips are a characteristic sign of the influence of the meso-level mechanisms on the processes of deformation and failure of the material, which is one of the most important property for extending components service life. Therefore, it is important to know the failure of the materials before choosing these steels for producing different machine parts. The 080M40 Medium Carbon Steel (alike to SAE/AISI 1040) is largely used as a machine component in the heat-treated state (tempered and hardened conditions). It has been used eighteen models of specimens, half of them were Z3 treatment while the other half were treated with (Z7) and then examined. In this study, it had been found impact toughness curves at 26, -12, and -38 °C are not similar. The results showed that lowering the rate of temperatures will decrease relatively impact resistance for the 080M40 Carbon Steel by 42% percentage and causes a decrease in the turning angle of shear lips comparative to the longitudinal axle of the samples. An increase tempering treatment from 300 Co to 680 Co was improved dynamic fracture appearance the metal by 63% because that them lowered distortion of the surface structure specimens had been by blisters on the upper shelf region of shear lip.


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