Study On The Control Technology Of Oxide Scale Of Hot Rolled Strip

Based on the oxide scales of hot-rolled steel strip as the research object, through combing experimental study and theoretical analysis, the evolution of the oxide scales of hot-rolled steel strip in hot strip rolling process was studied. Through oxidation kinetic experimental, the oxidation dynamic parameters was determination. The effect of hot rolling process parameters on the structure and thickness of oxide was researched by designing simulation experiment. Combined with the experimental simulation results, the black surface steel of510L was produted on commercial strip line and good results have been achieved. The main research contents are as follows:(1) The oxidation curve for the SPHC steel and510L steel was determination. In terms of time, from oxidation starting stage (oxidizing time<30min), oxidation weight gain per unit area with time present a major linear relation. When entering slow oxidation phase (oxidizing time>30min), oxidation weight gain per unit area with time appear parabolic relation. From the oxidation temperature setted by the experiment, oxidation weight gain per unit area with time appears parabolic relation. On the basis of expermentakl data, by the curvilinear method, we got that activation energy of SPHC steel was127.416kJ/mol and activation energy of510Lsteel was164.631kJ/mol. According to the oxidation kinetic model, we can test the evolution of oxide scales thickness with off-line simulation and obtain oxide scales thickness with time.(2) Through simulated experiment of different initial rolling temperature, finishing temperature and coiling temperature and observation of microstructure of oxide scales, the effect of temperature on the thickness and structure of oxide scale was judged. For the original oxide scales structure, with the initial temperature, the original magnetite layer decreased. The effect of finishing temperature for each layer structure of original oxide scale was not very obvious. The precipitation of magnetite and elemental iron from wustite was found along with the changes of coiling temperature. Isothermal-transformation diagram kor the wustite scale layer was drawn out.(3) Aiming at steel of510L, using the control strategy of high speed rolling, coiling temperature reasonable controlled, the corresponding law was summed up on the field production craft and the change of oxide scales. Meanwhile, mechanical properties of the trial coil were detected. The feasibility of process was proved from the experimental point on black surface steel.