The kinetics of small-impurity grain-boundary-segregation formation in cold-rolled deep-drawing 08C-Al and if steels during post-deformation annealing

An investigation of small-impurity grain-boundary-segregation (GBS) kinetics in deep-drawing steels (DDSs) allows us to improve the mechanical properties of these steels by optimizing the post-deformation heat-treatment parameters. The kinetics of the GBS formation for C, N, P and S was determined with a series of isothermal expositions of specimens in the spectrometer work chamber at temperatures of 250-650 °C. The surface chemical composition of the samples was measured with Auger electron spectroscopy (AES). Isodose C-curves of the GBS for each detected impurity were plotted. The time - temperature intervals of the preferential GB enrichment with C, N, P, S were determined for the 08C-Al steel with various reduction ratios and for the IF-steels with various concentrations of the micro-alloying elements Nb and Ti. It was found that cold rolling of the 08C-Al steel with a reduction ratio from 48 % to 80 % dramatically increases the preferential carbon GBS temperature from 350 °C to 450 °C due to the necessity of the carbon detachment from Cottrell atmospheres with the annealing of dislocations. The influence of the IF-steel micro-alloying with Nb and Ti on the concurrent multicomponent GBS of interstitial and substitution impurities is also demonstrated in the article.