DISTRIBUTION OF Cu AND ITS EFFECT ON MICROSTRUCTURE OF Cu-BEARING STEEL

In order to investigate the distribution of Cu and its effect on the microstructure of Cu-bearing steel, a series of mild steels containing different contents of Cu are developed by vacuum electric arc furnace. These steels are annealed at 1 260℃, 1 100℃and 1 000℃respectively for one hour and followed by furnace cooling to room temperature to simulate the heat treatment before the rolling process. The results show that Cu did not obviously segregate in annealed steels. The scanning electron microscope (SEM) observation show that the main microstructures in Cu-bearing steel are ferrite and pearlite; The volume fraction of pearlite in steel increase with increasing Cu content. The grain size reduces with the decrease of annealing temperature. The results of energy dispersive X-ray analysis (EDXA) suggest that the Cu content in pearlite is higher than that in ferrite, which means that the microstructure-segregation of Cu exists. However, the cast specimens show that Cu content in MnS and S-rich phase is very high, and Cu changed the distribution of MnS in steel. In addition, the optimal Cu content in steel between 0.2%-0.4% and the optimal annealing temperature between 1 100-1 200℃are determined by the economical and practical principles.