Reduction of Oxide Scale with Hydrogen

During hot rolling process metals will inevitably oxidize because of high temperature and air condition. In order to guarantee the surface quality, acid pickling is applied to remove the oxide scale while waste acid will do harm to the environment. Faced with the problem, by means of reduction process of hot-rolled plates, the oxide scale will be reduced to iron, so that acid pickling is unnecessary. One pass cold rolling procedure was applied. The compression ratios of hot-rolled plates with oxide scale were 10%, 18%, 26% and 31%, respectively. After that, samples mentioned above including a sample without deformation were separately reduced under hydrogen atmosphere condition (5% H2+95% Ar in volume percent) at 600–1000 °C. The thermal gravimetric apparatus (TGA) was used to establish accurate experimental condition and obtain complete mass loss data. Field emission electron probe microanalysis (EPMA) was applied to analyze scale morphology change and composition distribution through the oxide scale. It was found that the sample with 26 % compression ratio could be reduced completely at 900 °C which was favorable to galvanization.