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 600-1 000℃.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℃ which was favorable to galvanization.
Xiao-jiang LIUGuang-ming CAOYong-quan HEMing YANGZhen-yu LIU
Because of the effect of silicon on the formation of oxide scale,red scale is the main surface defect of hotrolled Fe-Si plate,making the scale difficult for descaling compared with carbon steel.Thermogravimetric analyzer(TGA)is used to simulate isothermal oxidation process of Fe-1.5Si alloy for 60min under air condition,and the temperature range is from 700to 1 200℃.Electron probe microanalysis(EPMA)is used to observe cross-sectional scale morphology and analyze elemental distribution of the scale.Relational graph of temperature,scale thickness and scale structure is obtained.It is found that scale structure(outer Fe oxide layer+inner FeO/Fe2SiO4layer+internal Si oxide precipitates)is almost unchanged with temperature except at 1 000and 1 200℃.At 1 000℃internal Si oxide precipitates cannot be found at the subsurface of the alloy,and at 1 200℃FeO/Fe2SiO4not only forms a layer as usual but also penetrates into the outer Fe oxide layer deeply.
LIU Xiao-jiangCAO Guang-mingHE Yong-quanJIA TaoLIU Zhen-yu
