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Converter steelmaking efficient utilization of scrap steel technology

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Converter steelmaking is the main steelmaking method for smelting high-quality steel in the world. Its technological progress and development have a huge role in promoting energy conservation, emission reduction, cost reduction and efficiency improvement in the steel industry.

Greening is one of the important development trends in the world today. In the context of “double carbon”, the steel industry with high energy consumption and high pollution emissions faces major energy conservation and emission reduction challenges. Converter steelmaking is the main steelmaking method, and it is also a key process in long-process steel production. Its green and intelligent level plays an important role in the optimization and upgrading of steelmaking structures. This article systematically reviews and summarizes the achievements and progress of several key technologies such as efficient utilization of scrap steel in converters, optimization of molten pool flow characteristics and smelting process systems, and intelligent steelmaking, and looks forward to its future development trends.

The melting behavior of scrap steel was studied from two aspects: theoretical analysis and practical exploration, and the scrap melting mechanism was revealed. The research on the flow characteristics of the converter molten pool such as the injection method and bottom blowing process is analyzed and summarized. The development status and prospects of converter end point control technology are introduced from the aspects of metallurgical mechanism and data model. Finally, from the perspective of overall optimization of the metallurgical process, the progress and existing problems of integrated steelmaking-refining-continuous casting technology are introduced from mathematical modeling to platform simulation. The development of converter intelligence requires the support of more equipment, methods and technologies. Converter intelligent steelmaking is a comprehensive practical application case involving metallurgy, automation, computers and other disciplines.

Converter efficient utilization of scrap steel technology

According to statistics, using 1 ton of scrap steel instead of 1 ton of molten iron in converter smelting can save 500kg of standard coal. Every time the scrap ratio of converter smelting increases by 1%, the blow loss of non-ferrous elements such as manganese and chromium will decrease by about 0.04%. If the scrap ratio in converter steelmaking increases by 10%, the total carbon dioxide emissions can be reduced by 6%. Therefore, the efficient utilization of scrap steel in the converter has become one of the important development directions for optimizing the converter steelmaking process. In industrial practice, steel companies improve converter scrap ratio by developing converter heat efficient utilization technology. On the one hand, to increase the heat income from converter smelting, measures mainly include increasing the temperature of molten iron, preheating scrap steel, slag-retaining operations in the converter, secondary combustion technology, fuel addition technology, and converter bottom powder spraying technology. On the other hand, to reduce the heat expenditure of converter smelting, the heat loss during transportation can be reduced by developing ladle capping and ladle capping technologies and improving the compactness of the production organization and the level of smelting operations. Studies have shown that increasing the temperature of the molten iron by capping the molten iron tank increases the scrap steel ratio. For every 100 C increase in the molten iron temperature, the scrap steel ratio can increase by 4%.

In theoretical research, scholars believe that the melting rate of scrap steel is the key factor limiting the improvement of the scrap ratio in the converter. Some studies have pointed out that the melting of scrap steel in the iron-carbon molten pool is caused by the melt lowering the melting point of the scrap steel by carburizing the surface of the scrap steel, thereby promoting the melting of the carburized layer. As a result, a new surface continuous phase change process appears, as shown in the figure; scrap melting occurs due to the generation of temperature and concentration boundary layers on the surface of molten iron and scrap steel, which is affected by the coupling effect of heat and mass transfer between molten iron and scrap steel. as shown in picture 2.

converter steelmaking efficient utilization of scrap steel technology

In order to study the melting behavior of scrap steel in the iron-carbon molten pool, scholars have carried out laboratory thermal simulation tests, water model tests, numerical simulations and industrial tests. In order to further clarify the melting mechanism of scrap steel, scholars have analyzed the structural changes and carburization phenomena of scrap steel melting under different working conditions. Figure 3 shows the scrap temperature distribution through numerical simulation, the scrap melting behavior simulated by water, the scrap melting morphology simulated by thermal simulation, and the interface carbon concentration distribution during the scrap melting process.

converter steelmaking efficient utilization of scrap steel technology
converter steelmaking efficient utilization of scrap steel technology
converter steelmaking efficient utilization of scrap steel technology

Considering the properties of scrap steel, a large number of researchers believe that the shape, size and carbon content of scrap steel affect its melting time in the converter: increasing the carbon content and specific surface area of scrap steel can promote the melting of scrap steel. Some scholars pointed out that the stacking density of scrap steel also affects the melting state of scrap steel. When the porosity of scrap steel is 0.82, the melting time of multi-grade scrap steel and single scrap steel is the same, as shown in Figure 42. In addition, some scholars pointed out that the silicon content of scrap steel is inversely proportional to its melting rate in the converter.

converter steelmaking efficient utilization of scrap steel technology

Considering the converter molten pool, the composition, temperature and dynamic conditions of the converter molten pool affect the heat and mass transfer rules between scrap steel and the molten pool. Some scholars believe that increasing the carbon content, temperature and stirring intensity of the molten pool can speed up the heat and mass transfer between scrap steel and the molten pool. This can reduce the melting time of scrap steel. An increase of 50 C in molten pool temperature or an increase of 0.6% carbon mass fraction in the molten pool can increase the scrap melting rate by 1mm/min, as shown in Figure 5a. In addition, the distribution pattern of scrap steel and the gas supply flow rate have a direct impact on the mixing time and flow characteristics of the molten transfer pool. The uniform distribution and inclined distribution of scrap steel shorten the mixing time by 20% to 40% compared with the centralized distribution; the bottom blow flow rate increases from 15 L/min to 50 L/min, and the volume ratio of the low speed zone decreases by 89.46%. As shown in Figure 5b and Figure 5c, the distribution pattern of scrap steel when using numerical simulation and physical simulation respectively.

converter steelmaking efficient utilization of scrap steel technology
converter steelmaking efficient utilization of scrap steel technology

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As professional one-stop solution provider, LIAONING MINERAL & METALLURGY GROUP CO., LTD(LMM GROUP) Established in 2007, and focus on engineering research & design, production & delivery, technology transfer, installation & commissioning, construction & building, operation & management for iron, steel & metallurgical industries globally. 

Our product  have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time.

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As professional one-stop solution provider, LIAONING MINERAL & METALLURGY GROUP CO., LTD(LMM GROUP) Established in 2007, and focus on engineering research & design, production & delivery, technology transfer, installation & commissioning, construction & building, operation & management for iron, steel & metallurgical industries globally. 

Our product  have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time.

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