Study On The Structure Transformation,Acid-pickling Behavior And Atmospheric Corrosion Resistance Of The Oxide Scale On Hot-rolled Carbon Steel Plates

SEM and TG/DTA meter were used to explore the law of transformation of the scale structure when the plate under continuous coiling. The acid-pickling behaviors of the oxide scale at different positions in plate width are different. The effect of the difference in oxygen supply in the width direction on the scale structure and acid-pickling behavior of hot-rolled strip were analyzed. The effect of different structures of scale on the atmospheric corrosion resistance of hot-rolled strips was studied by wet/dry cyclic corrosion test. Based on these theory researches, practical problems are solved. The main research contents are as follows:1. It was found that when the oxide scale under continuous cooling conditions, high cooling speed will stop the eutectoid reaction in the scale, the structure of the scale in the room temperature is mainly Fe3O4and FeO. When the scale cooling form450℃, rate is1℃/min, the structures of the scale are mainly the eutectoid reaction products in the room temperature. The law of the scale transformation also followed a similar C-curve trend. The nose temperature of the C-curve is appearance at about450℃. Due to the atom diffusion capacity is feeble in the low temperature, when the scale cooling start from350℃, the eutectoid reaction was absolutely stopped.2. At the edge regions, the scale continued to grow after coiling because oxygen was available as a result of airline ingress to there regions during coil cooling. Higher oxides as the products will improve the difficult to pickling. At the strip-center regions, because of the absence of oxygen, further oxidation of the steel substrate tool place at the expense of the higher oxides. A lot of FeO was remained to the room temperature. Because of the remained FeO, the scales can be pickled easily. The thickness of the scale directly affects the pickling efficiency. The thinner the scale is, the shorter pickling time will be.3. The weight gain of corrosion at the scale with no proeutectoid and eutectoid reactions is the least. The result of the electrochemistry proved this kind of scale has the best corrosion resistance. The corrosion products of this kind of scale are smooth and compact. The scale can protect the steel availably.4. The scale that has a compact structure can protect the steel well. If there are many crackle in the scale, which will led to crevice corrosion. If the scale is covered by higher oxides, due to the unity and compact structure, this kind of scale can slow down the corrosion reaction.