SMELTING LOW PHOSPHORUS STEEL BY DOUBLE SLAG RETENTION METHOD IN 120 t TOP-BOTTOM DOUBLE-BLOWN CONVERTER
The phosphorus content in steel will limit and reduce the plasticity and toughness of steel,and will also make the weldability of steel deteriorate,seriously affecting the quality of the finished product.With the development of the national economy,the industry's demand for ultra-low phosphorus steel plate has risen sharply,but its production is extremely difficult,and only a few iron and steel enterprises such as Baosteel,Wugang and Nangang have developed successfully.In order to solve the problem of phosphorus removal in the production of low phosphorus steel under the current equipment of Xiangtan company,the smelting process of extremely low phosphorus steel has been formed under the conditions of reasonable scrap ratio,slag formation control,oxygen supply control and bottom blowing control through the continuous optimization and improvement of the 120 t converter top-bottom double-slag retention process.The double slag retention process can ensure the higher basicity and ferrous oxide content of slag in the early stage,and promote the rapid slag formation in the early stage.The average basicity in the early stage of non-slag retention furnace is 1.21,while that in the early stage of slag retention furnace is 1.92.The control temperature is about 1 350 ℃,and the dephosphorization rate can be controlled at about 80％.Through the process optimization of double-slag slag retention,the qualified rate of phosphorus content of low-phosphorus steel in 2023 is maintained at a high level,and the qualified rate of phosphorus content is gradually increased from 80％in 2022 to 90％or even 100％.On the basis of stable composition at the end point,the phosphorus content of the very low phosphorus steel in the converter is controlled by Xiangtan.
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