Effect Of Cr On Sheet Metal Forming Of Hot Rolled Steel

This paper is focused on the influences of chromium on the scale formation of hot rolled steel belt,in which the excitements performed with the 5% chromium content of Fe-5Cr and 10% chromium of Fe-10 Cr steels as the experimental materials are mainly discussed.On conditions of different flows of mixed gases(air and 95% relative humidity vapor)and 1000? temperature,the TGA instrument has been applied to perform oxidation dynamics excitements.the oxidation rate constant of the steels calculated as well as curves of oxidation weight increment plotted out.Meanwhile a tube-type furnace for high temperature heating has been also used.At temperatures of800?,900?,1000? and 1100?,and with 60 minutes oxidation period the research on the temperature influence on thickness and structure of these two steels has been studied.Finally,through the use of OM and SEM instruments the surface macro-appearance and internal organization of the oxidation scale generated are observed and analyzed.The conclusion of the experiments is shown as follows:It has been known through oxidation dynamics experiments that,the weight increment per unit area of the steel with relatively low chromium content is higher than that of the steel with relatively high chromium content.Within the same kind of steel,the greater the flow of mixed gases from experience start-time,the higher the oxidation weight increment per unit area.Calculations show that,with the same flow of mixed gases the higher the chromium content is,the smaller the oxidation rate constant will be.The sectional scan also shows that,the rich accumulation of both silicon and chromium exist when the chromium has 1% content,and also the degree of the centeration for silicon and chromium is similar.When the chromium reached up to 5% content,the chromium has its rich centeration along one side of the base,which impacts on the diffusion of silicon.When chromium reached its content up to 10%,rich accumulation of chromium happens,whereas rich concentration of silicon disappears basically.After 60 minutes oxidation at different temperature conditions,neither Fe-5Cr nor Fe-10 Cr steel generates any obvious oxidation materials if the temperature for oxidationis below 900?.with the oxidation temperature being higher than 900?,Fe-5Cr and Fe-10 Cr steel specimens start to generate oxidation materials and the obvious layering phenomenon of these oxidation materials can be seen,among which Fe oxidation is manly on the upper layer with lower layer of Si and Cr respectively.