YUAN Tianxiang, LIU Yanqiang, AN Zeqiu, YANG Chunzheng
Guided by the principles of metallurgical process engineering, Shougang Jingtang United Iron and Steel Co., Ltd. established a differentiated production process system for steelmaking, comprising a "2-1-2" configuration in phase I and a "1-1-2+1" configuration in phase Ⅱ. At the ironmaking-steelmaking interface, following the concept of "laminar flow" control, a hot metal distribution principle is implemented with laminar flow control, specifying that No. 1 and No. 2 blast furnaces supply phase I steelmaking while No. 3 blast furnace supplies phase Ⅱ steelmaking. Within the steelmaking process, a laminar flow dedicated production model has been formed for multiple product categories, including high-end cold-rolled products such as automotive sheets and tinplates, hot-rolled strips such as wheel steel and pipeline steel, medium and heavy plates such as 9Ni steel, and products from the thin slab casting and rolling （MCCR） line. This paper systematically analyzed the current state of the process flow within this production model and proposed a series of optimization measures to address issues such as complex order structures and poor cycle matching. At the ironmaking-steelmaking interface, the laminar flow of materials and efficient collaborative operation are achieved, with the turnover rates of 200 t and 300 t hot metal ladles increasing to 7 times per day and 5.2 times per day respectively, and the hot metal temperature drop decreasing to 78 ℃, reaching historically optimal levels. In the Kambara reactor（KR） process, automatic control for desulfurization and slag skimming is implemented, shortening the desulfurization cycle by 5 minutes. In the converter process, optimization measures such as increasing oxygen supply intensity, enlarging tap hole size, shortening slag splashing time, and optimizing sintering time for the slag splashing layer reduced the smelting cycle from 41 min to 35 min. In the molten steel refining process, phase I steelmaking developed a rapid deep vacuum technology for RH and a carbon content precise prediction control model, which reduced the Ruhrstahl Heraeus（RH） vacuum treatment time for ultra-low carbon steel from 29 min to 20 min. phase Ⅱ steelmaking adopted measures including optimizing the soft blowing time in the ladle furnace（LF） furnace, establishing a dynamic alloy addition model, conducting calcium treatment using ferrosilicon alloy, and developing a sulfur load distribution desulfurization technology, which shortened the refining cycle by 5 min. In the continuous casting process, through process optimization, enhanced equipment functional precision, and improved automation, the throughput per caster in phase I steelmaking reached 7.01 t/min, and the average casting cycle is reduced to 43 min. In phase Ⅱ steelmaking, the maximum throughput per strand for the medium and heavy plate caster increased to 4.7 t/min, and the maximum casting speed for the thin slab casting and rolling caster reached 6.0 m/min. Through practical application, significant improvements in production efficiency and product quality, along with continuous reductions in energy consumption and cost, are achieved. The laminar flow ratio in phase I steelmaking exceeded 60%, reaching a maximum of 73.8%. In phase Ⅱ steelmaking, the laminar flow ratio for the medium and heavy plate production line surpassed 55%, with a maximum of 59.1%, while that for the thin slab casting and rolling production line exceeded 98%. The tapping temperatures for converters in phase I and phase Ⅱ steelmaking decreased from 1 676 ℃ to 1 649 ℃ and from 1 658 ℃ to 1 619 ℃, respectively. The stability of process control is enhanced, with the qualified rate for mold level fluctuation within -3-3 mm （for slabs） increasing from 47.8% to over 75%, the slab qualification rate for O5 grade sheets improving by 20%, and the flaw detection qualification rate for medium and heavy plates rising to 99.7%. The laminar flow operation contributed to a gradual reduction in steelmaking process costs, with costs for phase I steelmaking, phase Ⅱ steelmaking medium and heavy plate line, and phase Ⅱ steelmaking thin slab casting and rolling line decreasing by 26%, 27%, and 46% respectively compared to 2019 （when phase Ⅱ steelmaking commenced）. Furthermore, addressing issues such as increasing order complexity, fluctuations in hot metal temperature, and poor furnace-caster matching, future optimization directions are proposed from the perspectives of whole-process intelligent coordination and refined interface control. This provides a practical reference for implementing a laminar flow dedicated production mechanism in steel manufacturing processes.
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