Dynamic Method & System For Adjusting And Controlling Nodularization & Inoculation Of Ductile Iron

The industrial production of ductile iron can not been carried out stably and efficiently without reliable measurement and control technologies. Due to the restriction of our country′s basic conditions, there are big gaps between China and other powerful casting countries in the development and application of optimizing control system during ductile iron production process, which leads to weakly economic and social benefits from such high-tech material-ductile iron in China. In order to optimize the production technique, reduce the production cost and improve the production quality for ductile iron, in this paper, the research of the dynamic method of adjusting and controlling nodularization and inoculation for ductile iron and establishment work for such an experimental system have been carried out based on the comprehensive evaluation and regulation of base iron metallurgical status. The main research contents involve the dynamic method of evaluating and regulating metallurgy status of base iron melt, the dynamic method of regulating and controlling nodularization and inoculation of ductile iron, the method of fast evaluating nodularizing and inoculating results, the method of regulating and controlling final status of the ductile iron melt, the dynamic experiment system of regulation and control based on the above design methods, and so on.The key technologies of the adjusting and controlling nodularization &inoculation for ductile iron preparation mainly have the base iron metallurgy status evaluation and regulation, the additive amount calculation of nodularizer, the nodularization and inoculation effect evaluation, the dynamic control system establishment, etc. A grey relational comprehensive evaluation model was established with selected seven characteristic parameters, such as T_L、T_EU、R、T_S、O_XF in gray cooling curve, TE in white cooling curve and S content of the base iron.According to the correlation degree γG size, the base iron quality was divided into four classes. By the results of the gradually nodularizing experiments, the mathematical calculation model for nodularizer addition was established containingγG, the influences of RE and nodularization temperature.The overheating temperature and holding time were optimized using boiling temperatue TB of the Si O₂-CO deoxidation metallurgy reaction and thermal analysis related characteristic parameters, which provided the theoretical guidance basis for the base iron smelting process. Then, taking deoxidization balance temperature Teq as the reference point, the accurate method of the adjusting carbon and silicon content using gray and white dual cooling curves was studied by selecting the directly relative characteristic parameters with the equivalent chemical composition. Under the experimental conditions, the mathematical formula CEL from liquidus temperature TL in gray cooling curve and formula Si E from eutectic temperature TE in white cooling curve were derived with the correlation coefficient were all higher than 0.9, the carbon content was back-calculated from CEL and Si E values. Because of the increase of the testing stabilization and precision, the main chemical composition of the base iron could be controlled within a narrow range. The thermal analysis assessment methods of the oxygen and sulfur content, as well as their metallurgical behaviors in base iron were studied by the deoxidizing sample cup with different Al additon. The results shown that the primary temperature TL in the gray cooling curve could half-quantitatively indicate the active oxygen content information, simultaneously, the minimum eutectic temperature T_EU could better indicate the influences of deoxidation and desulfurization products′ status on the eutectic graphite nucleation capability in base iron melt. The metallurgical behavior of sulfur was different with oxygen from the experimental results. The desulfurization reaction was relatively slow in the nodularizing process compared with oxygen, and significantly affected by process factors in experiments. The minimum eutectic temperature T_EU in gray cooling curve was the key parameter for eutectic solidification evaluation, which increased with strengthen of the nucleation capability monotonously. Otherwise, the composite index PN represented the developing extent of the graphite nucleation potential energy.The optimizing experiments were carried out with thermal analysis relatedcharacteristic parameters as the judge criteria for choice of the nodularizer granularity distribution, covering style of the modify agents and the treatment temperature. By above adjustment and control processes, the nodularization treatment processes were improved significantly. A jointing test method of thermal analysis-eutectic expansion dual parameters was studied for solidification characteristics evaluation, the optimal nodularizer choice and its secondary addition of the ductile iron. The accuracy rate of the established nodularizating degree decision model with double thermal-expansion parameters was high above 90%.From the perspective of the thermodynamics, the deoxidization condition of the nodularizing iron melt was analyzed, the obtained conclusion works in concert with the homogeneous nucleation theory, as well as the oxide and sulfide heterogeneous nucleation theories. By the thermal analysis method with increasing inoculant amount in sample cup step by step, the mathematical statistics model of inoculant addition was established using referring characteristic temperature parameters in gray cooling curve. Otherwise, the optimizing choices of the inoculant granularity distribution and the inoculation temperature were also studied by thermal analysis method, respectively. The same as the nodularizing control, the rapid evaluation method of the inoculation effect, inoculant choice and secondary adding method for the nodularized iron melt were also preliminary studied. The thermal analysis evaluation methods for Mg% index and inoculation index were studied for the trimming control of the final metallurgical status of ductile iron melt. Furthermore,the pouring temperature for ductile iron production was optimized using thermal analysis corresponding characteristic temperatures in gray cooling curve. Through experimental examples, it shown that the adjustment and control methods were feasible for the nodularizaiton effect regulation, inoculation effect regulation and final trimming regulation of the pouring melt during ductile iron production.A dynamic experiment system of adjusting and controlling nodularization and inoculation treatment of ductile iron was established based on the design methods in paper. The designed dynamic experiment system has various functions, including the fast evaluation of the base iron metallurgical status, the on-line calculation of the nodularizer addition, the fast evaluation of the nodualrization effect & inoculation effect and providing the plan design of the nodularizer and inoculant for second addition. Through laboratory simulation experiments, it shown that the dynamicadjustment and control system was effective for the on-line measurement and control of the base iron metallurgy status, nodularization effect and inoculation effect during ductile iron preparation.