Study On Production Technology Of Aluminium Killed Low Carbon Steel

The aluminum killed steel with low carbon content is widely used in automobile, electric appliance, chemical industry and building for its good performance such as good press performance and appearance, and this kind of steel is produced much with good benefits presently. The technology process of the third steelmaking factory of AnShan Iron and Steel Work are as follows:LD melting→LF refining→calcium treatment→continuous castingThe phenomenon of casting nozzle clogging, casting breaking and silicon pick-up happened many times, because of the immaturity of top slag controlling in converter and ladle furnace refining, which causes disadvantage for producing.In order to solve these problems mentioned, based on investigating technology process and combining with the producing condition, the thermodynamics of calcium treatment and of silicon recovery in molten steel were discussed, the proper technology parameters were confirmed, the casting process and silicon recovery of molten steel were optimized, as a result, good effect of industry application was obtained.Through the studies above, the main results have been drawn as follow:(1) The component clogging in ASP casting nozzle of low carbon aluminum killed steel casting is Al2O3 inclusion, and the improper technology process of converter and ladle furnace, incorrect calcium treatment or operation parameters, erroneous protect casting are the main reasons for Al2O3 inclusion clogging;(2) Through the theory analyzing of calcium wire feeding, the calcium wire feeding parameters are optimized:the feeding position should be falling position, feeding speed must be more than 3.5 m/s, feeding depth should be from 2350 mm to 2500mm, argon flow flux should be less than 15 m3/h, the sulfur content of the molten steel should be less than 0.008%. As a result of the optimization, the feeding length decreased from 1200-1500 m per furnace to 400-500 m per furnace, and the calcium yield ratio increased from 5%-15% to 19%-28%;(3) Through the optimization of converter tapping, top slag modifying of LF and calcium treating, the nozzle blocking of continuous casting decreased from 25.9% to 0, the dimension of total inclusions less than 30μm, and most of these inclusions are global.(4) According to the silicon recovery thermodynamics and kinetics of the continue casting low carbon aluminum killed steel, in the range of ladle furnace refining temperature, no matter how change of the temperature, the silicon content of the molten steel always increases, and the practicable silicon content is far more than the theoretical silicon content(less than 0.05%), which is balanced with aluminum for low carbon aluminum killed steel(the aluminum contents of low carbon aluminum killed steel are from 0.02%-0.04%). The stronger of bottom argon stirring, the larger of the reaction area of steel and slag, the more serious trend of increasing silicon;(5) With the sulfur content decreasing from 0.005% to 0.002% in the final of LF refining, the silicon content of steel increases from 0.017% to 0.032%, the higher of the desulphurization ratio in the process of LF refining, the longer of the refining time, the more of the sulfur increasing;(6) Through the methods of controlling the falling slag of converter, optimizing the use of ladle furnace, controlling the level of top slag modifying and refining time and so on, the rate of the low carbon aluminum killed steel for which the silicon content less than 0.03% increased from 87% to 97%.