Methods for Reducing Non-Metallic Inclusions in Continuous Casting Billet
Continuous casting billets refer to semifinished products obtained by continuously casting molten steel in a ladle (or steel-making furnace) into a billet mold and cooling them in the mold. Non-metallic inclusions are the main reason that affecting product quality and process performance of continuous casting billet. The comprehensive control of non-metallic inclusions is to reduce their initial contents in steel-making, chemical adjustment and proper control of furnace parameters, and then reduce the entrainment and aggregation of non-metallic inclusions at the refining and casting process. Therefore, in order to obtain high-quality billet, it is necessary to establish a scientific and reasonable method to further reduce the content of non-metallic inclusions in continuous casting billets.
First of all, advanced steel-making equipments and technologies should be adopted during the production of continuous casting billet. Ironmaking techniques such as oxygen blowing desulphurization, basic oxygen furnace and advanced electric smelting etc., Help to reduce the amount of non-metallic oxides that accompany with the scrap. Meanwhile, the process and techniques such as Vacuum degassing, Deferrization, Combined ladle and submerged electric arc furnace refining with neutral or slightly basic slag and all combinations of several processes should be instituted during steel-making process.
Secondly, before all steel-making processes, it is essential to perform laser analysis of chemistries and to use statistical analysis to monitor and ensure that the steel composition that is produced is optimized. And continual review of process conditions should be made, such as operating temperature and electric power, helping to the prevention of re oxidation and entrainment of non-metallic inclusions.
Thirdly, chemical elements such as Cr and Mo should be added to the steel-making process to improve the performance of the steel’s cleanliness. For example, Al can be added to accelerate the capture of free oxygen and oxidation of sulfide and phosphorus contained in the steel, and Si can also be added to help reduce the solubility of oxygen and nonmetallic inclusions.
Furthermore, during continuous casting process, attention should be paid to control the slag and the bath surface level, adjust the simulation casting speed, adjust the temperature of hot steel, the mode of billet wetting, and the amount of steam added during casting.
Last but not least, perfect advanced clean steel billet production techniques should be applied. This includes techniques like ultra low-oxygen steel smelting, bottom-stirring argon protective ladle refining process, metal isolating degassing, filtering before casting and etc. These techniques, when used together, provide a full spectrum of safety measures and, provide impressive synergy in their actions, leading to very clean and low inclusion level steel casting billets.
In the process of continuous casting billets production, controlling non-metallic inclusions requires reformation on both the large scale of smelting, and the careful and precise control of hot steel temperature and casting speed. Applying advanced steel-making technologies, combined with added alloying elements and modified simulator casting speed and temperature can greatly reduce the content of non-metallic inclusions in continuous casting billets. Therefore, only when manufacturers apply these methods together can help them achieve the best effects and improve the casting product quality to a great extent.
