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In the continuous casting process, the heat transfer effect of secondary cooling plays an important role in the quality of the slab. The cooling intensity and cooling uniformity of the secondary cooling nozzle need more efficient spray cooling to achieve. Herein, the cold characteristics of different types of nozzles were compared. It is found that the second type of air mist nozzles have more uniform water density and striking force. On this basis, high‐temperature heat transfer experiments for casting billets were carried out to study the heat transfer coefficients of different air mist nozzles in the secondary cooling zone of continuous casting. It is found that the heat transfer coefficient increases as the distance of the temperature measurement point from the nozzle directly below increases. The heat transfer coefficients of the casting billet in both the jet and non‐jet zones are decreasing to varying degrees. When the temperature drops to 600 °C, the second type of air mist nozzle shows a faster temperature drop at the point of measurement, a smaller difference in time taken for temperature drop between jet and non‐jet zones, and faster and more uniform spraying, leading to a more significant trend of increasing heat transfer coefficient. [ABSTRACT FROM AUTHOR]

A 3D gas–slag–metal model for a 120t converter with nozzle‐twisted lance is established, and the gas jet characteristics, slag–metal interface fluctuations, wall erosion, and changes in the molten pool flow field of the nozzle‐twisted lance of the blowing process are studied. The results reveal that, with the increase in the swirl angle, the length of the jet high‐velocity section, maximum velocity, and dynamic pressure decrease, radial distance increases, and wall shear stress first decreases and then increases. With an increase in the blowing time, the fluctuating intensity of the slag surface and the molten steel surface changes significantly, fluctuating slag surface stabilizes after 1.7 s (fluctuating intensity is 1.08–1.12), and fluctuating steel surface stabilizes after 1.3 s (fluctuating intensity is 1.23–1.33). The turbulent kinetic energy of the gas–slag–metal three‐phase interaction area increases and the wall shear stress gradually increases. [ABSTRACT FROM AUTHOR]

In order to explore the metallurgical behavior and mechanism of bottom blowing CO2 in ladle furnace (LF), CO2 was introduced in the LF refining process. The kinetics and thermodynamics of bottom blowing CO2 were investigated and several mathematical models for kinetic study were established. Some exploratory industrial experiments have been conducted with different proportion of CO2 in a 70 ton LF. The results indicated that it could lead to a little oxidation of elements in molten steel with the processing of bottom blowing CO2 compared with Ar stirring. The average oxidation amount of C was in the range of 0.3-0.8 kg. The average oxidation amount of Mn was reduced by 0.0067% and the average oxidation of Al was increased by 0.003%, while the mass fraction of FeO was less than 0.5% in the slag hence it could meet requirements of reductive reaction. Mass transfer of CO in bubble interface or chemical reaction was the possible rate-determining step by comparing calculated results with experimental results. Compared with bottom blowing Ar, types and compositions of inclusions have no big change, plus, the equal yield density of inclusions has decreased and the cleanness of steel was improved. Therefore, it is possible to use CO2 in LF. [ABSTRACT FROM AUTHOR]

Stirring effects and impacting characteristics of conventional and various swirl-type oxygen lances (Swirl angles are 5°, 10°, and 13°, respectively) on the molten pool were studied. The mixing time, impacting depth and impacting diameter were measured by water model experiment. The flow field characteristics of gas-liquid two phase flow were simulated using Fluent software. It is found that 10° swirl-type oxygen lance injection can get the shortest mixing time which is only 47.6 s. The area surrounded by isovelocity is larger in molten pool when injecting by the swirl-type oxygen lance. When injecting by the 10° swirl-type oxygen lance, the area is the largest and the flow velocity of liquid steel is the highest. On this basis, the 10° swirl-type oxygen lance was experimented in 150 t vanadium extraction converter. The experiment shows that the swirl-type oxygen lance can guarantee the normal smelting process. Compared with the conventional oxygen lance, the reduction ratio of vanadium content in semi-steel is 17.8%, vanadium extraction rate is increased by 5.1%, V2O5 grade of vanadium slag is increased by 0.93% and iron loss is reduced. It provides a new technology to improve the recovery of vanadium resources in converter. [ABSTRACT FROM AUTHOR]

Based on the analysis of reaction mechanism between CO2 and molten pool elements at the steelmaking temperature, and on the calculation of materials and heat balance during converter steelmaking process with blowing CO2, a new technology which uses CO2-O2 as top gas and CO2 as bottom gas in a converter was proposed and experimented in a 30 t converter. It is found that the new technology is feasible absolutely, the amounts of smoke dust and T-Fe are reduced by 11.15% and 12.98% on average, the contents of nitrogen and phosphorus are decreased by 50% and 23.33% respectively, iron loss of slag is lowered by 3.10% and oxygen consumption is reduced remarkably. This research will provide a new blowing method for BOF steelmaking process, which can save steelmaking energy consumption and reduce smelting cost. [ABSTRACT FROM AUTHOR]

A new dephosphorization technology with introduction of partial CO2 into O2 is proposed in this paper. Thermodynamic characteristics and dephosphorization mechanism by introduction of CO2 are analyzed and the results show that using CO2 as partial dephosphorization oxidant can change the selective oxidation condition of steelmaking system, control the temperature of bath, strengthen the stirring ability, and finally obtain a high efficiency of dephosphorization. Meanwhile, the relationship between selective oxidation temperature T of C and P, partial pressure of CO gas, slag activity, and compositions of melt is obtained as follows. T=(PCO/P0)0.0401a4CaO·P2O50.0080·exp(−0.0403[%C]−0.0030[%Si]+0.0011[%Mn]+0.3515[%P]+7.3986) Furthermore, dephosphorization trails are carried out in a 30t steelmaking converter and a 300t special dephosphorization converter, respectively. It is concluded that the new technology of injecting CO2–O2 mixture is beneficial to reduce phosphorus content in liquid steel, increase the partition ratio of phosphorus, and reduce iron loss of slag. A new dephosphorization technology with introduction of partial CO2 into O2 is proposed during steelmaking process. Through the an alysis of thermodynamics and kinetics, it is found that CO 2 can participate in dephosphorization, strengthen s tirring ability, and control the bath temperature. Furthermore, industrial experiments are performed in a 30t steelmaking converter and a 300t special dephosphorization converter, respectively, which obtains good dephosphorization results. [ABSTRACT FROM AUTHOR]