The Influence Of Silicon And The Hot Rolling Process Parameters On The Microstructure And Properties Of Oxide Scale

The influence of silicon and hot rolling process parameters on the microstructure and properties of hot-rolled steel oxide scale were studied in this paper. Firstly, the oxidation kinetics performance of the two kinds of experimental steel were preliminary understood and studied at different temperature and in same oxidation atmosphere conditions with TGA(Thermogravimetric Analysis). Oxidation kinetics curves and oxidation activation energy were obtained. The effect of silicon on the oxidation capacity of hot rolled steel was analyzed. Secondly, the effect of silicon on the two kinds of experimental steel oxide scale was researched. While the optimal process for forming silicon-rich layer was analyzed, through a tube furnace heating experiments to simulate the oxidation behavior of two experimental steels in the case of different heating temperature and heating time. With the several times site rolling test, the spotted, bubble, color difference and other issues were successfully resolved by laboratory research and process improvement. Through theoretical experimental and actual production for some time, it obtained the following conclusions:(1) The oxidation kinetics analysis showed that with the raise of temperature, the degree of oxidation of steel become more severe from 300℃ to 1200℃,which is a turning point at 800℃. Oxide scale is thinner when it below 800℃.When it is above 800℃, oxidation increased significantly, the average thickness of the oxide scale is increased rapidly. On the other hand, with the increase of the content of Si in hot-rolled steel, oxidation resistance of the carbon steel can be improved.(2) Two experimental steels were heated at different temperatures,which is at high temperature section(1100℃-1200℃), for different holding time in the tube furnace. The results show that oxide scale organization at 1100℃ were similar with that at 1150℃ and 1200℃, both Fe O and Fe3O4. But it did not observe significant silicon-rich layer at 1100℃. In addition, it formed a liquid-rich silicon layer at 1150℃ and 1200℃ for 5min to 60 min with a sign of spreading to oxide scale layer. Oxide scale has even been destroyed for a longer holding time. It is more complete and uniform of the oxide scale layer and the siliconrich layer at 1150℃ for 10 min.(3) Combined with on-site production, defects of spots and fold were eliminated by improving the rolling process. 1) The tapping temperature of billet steel is reduced to less than 1150℃. 2) rough rolling temperature is controlled, and the temperature and time before finish rolling is reduced. 3) Descaling process is reasonably adjusted. Thereby eliminated defects of spotted and fold, verified the reliability and stability of the optimization process.