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The Aging characteristics of a medium carbon steel with and without copper

Uzer, Osman Emre
For many years, copper bearing steels’ usage in steel industry was limited by copper’s detrimental effect on hot working capability. However with the latest findings that eliminates this negative effect with the addition of nickel, copper has emerged as an alloying element option. In various studies, copper is found to precipitate in ferrite phase after aging and leads to an increase in mechanical properties such as hardness and strength while still having a good amount of ductility-strength balance. In this thesis study, the effect of copper addition and the effect of copper precipitation hardening on medium-carbon steels which is not extensively studied previously will be addressed. To understand the effect, Cu-alloyed 4330M and 4330M medium carbon steels were cast and heat treated to obtain either martensitic or bainitic microstructure. These steels were then aged at various temperatures with different times and mechanical and microstructural properties of Cu-alloyed 4330M and Cufree 4330M steels were compared. Copper was found to be retarding the softening in both martensitic and bainitic steels and Cu-alloyed bainitic steel yielded around 50 HV higher hardness values than that of 4330M when aged at 450°C for 270 minutes.