In tire-cord steel, the deformation behavior of oxide inclusions is primarily influenced by their inherent properties, and fundamentally, it is decided by their structural characteristics. The deformation of oxide inclusions during a four-pass industrial hot-rolling process was investigated using an automatic scanning electron microscope. Subsequently, the corresponding properties and structures of the oxide inclusions in the rolled rods were analyzed using FactSage software and an analytical model. During the hot-rolling process, different types of inclusions exhibited varying deformation behaviors. Specifically, CaO–MnO–Al2O3–SiO2-type inclusions demonstrated the highest deformation index across multiple rolling passes. When the content of SiO2 reached 70 wt.

A kinetic model for the Ruhrstahl–Heraeus (RH) desulfurization process is established based on the FactSage Macro Processing. The desulfurizer addition, the desulfurization reaction, the steel mixing, the flow circulation, and the desulfurizer floating during the RH refining process are considered in the model. Simulated results agree well measured results, indicating that the current model can be used to predict the desulfurization reactions during the RH refining process. The CaO activity increases with a higher CaO/Al 2 O 3 ratio and a lower SiO 2 content, which exhibits a similar tendency with the desulfurization ratio. It is indicated that it is necessary to increase the CaO activity in the desulfurizer to improve the desulfurization ratio. The S content in the molten steel decreases with time and a higher ratio of the powder blowing. The cost increases with time due to the refractory erosion and the steam consumption. The cost of the desulfurizer added by the powder blowing is lower than that of the gravity sinking.

The initial size distribution of inclusions in the molten steel during the Ruhrstahl–Heraeus (RH) refining was investigated through an industrial trial. A three-dimensional numerical model for the steel-argon multiphase fluid flow and the collision, transport, and removal of inclusions in the steel was established to simulate the evolution of inclusions during the RH refining. The particle-size-grouping (PSG) method was applied to evaluate the collision of inclusions, which divided inclusions into sixteen groups with a volume ratio of 2.5 between adjacent groups. Detected inclusions were mostly Al 2 O 3 in aggregations or clusters. The initial number density of inclusions with diameter less than 1 μ m was closed to 1 × 10 15 #/m 3 , while that with diameter greater than 10 μ m was less than 1 × 10 10 #/m 3 . The calculated total oxygen content in the steel dropped from 251 to 93 ppm in approximately 10 minutes and was 14 ppm after refining for 1800 seconds which agreed well with measured ones. The removal fraction of inclusions increased with the refining time, while the removal rate showed a decrease. The removal fraction was larger than 90 pct at 1800 seconds, indicating a high efficiency of the RH refining in removing inclusions. After 300 seconds of collision, the number density of small inclusions with diameter less than 2.5 μ m declined apparently from 10 13 to 10 15 #/m 3 to 10 12 #/m 3 . The distribution of inclusions and the total oxygen content in the steel was position-dependent. Due to the removal condition at the steel surface in the ladle, the number density of inclusions and the total oxygen in the steel near the steel surface and near the zone between two snorkels in the ladle had a minimum value, while that near the side wall of the ladle showed a relatively higher value. The gradient of the T.O content in the cross section near the free surface of the ladle was relatively large, around 15 ppm on the side and less than 2 ppm in the center.

A kinetic model of the RH desulfurization process was established based on the two-film theory, considering the desulfurizer addition in the RH vacuum chamber and the slag desulfurization in the ladle. The kinetic model was used to predict the variation of the sulfur content in the molten steel during the RH desulfurization process, which was in good agreement with industrial trials. Effects of the slag composition and powder blowing parameters were investigated, indicating that the powder blowing method of the desulfurization addition exhibited a higher desulfurization rate than the gravity sinking method due to its better kinetic conditions. The desulfurization fraction was mainly related to the composition and quantity of added desulfurizers. The desulfurization rate increased with a higher CaO/Al 2 O 3 ratio and a lower SiO 2 content in the desulfurizer. Compared with multiple additions, the one-time addition of desulfurizers by the gravity sinking method was suggested to improve the desulfurization rate.

To better control the multiphase vacuum refining process, a 3D (three-dimensional) comprehensive numerical model was established to study the melting behaviors of two alloy particles. Two melting mechanisms were proposed to represent the melting behaviors of two alloy particles in high-temperature molten steel. A species transport model was then developed to demonstrate the mixing of the alloy element based on the stable flow pattern. The results indicate that the melted alloy particle would be gradually mixed after 3-4 cycles of the recirculation of the molten steel during the refining process which takes approximately 200 seconds. The maximum mixing time increases from 181.8 to 220.4 seconds with the 70 pct Ti–Fe alloy particle diameter changing from 0.01 to 0.05 m. This computational framework could be used to understand the solid particle melting and composition distribution in the high-temperature melt.

A mathematical model for the decarburization coupling with the fluid flow in the RH refining process was established. The decarburization reaction at three sites was considered, including the surface of injection lifting gas bubbles, the gas–liquid interface in the vacuum chamber and the interior of the molten steel bath. The effect of the flow pattern on the transfer of carbon and oxygen in the molten steel was obtained. The decarburization inside the molten steel bath in the vacuum chamber contributed the most, accounting for 55.9 pct of the total decarburization. The gas–liquid interface in the vacuum chamber and the surface of bubbles injected from the up-leg snorkel contributed approximately 32.5 and 11.6 pct, respectively. The oxygen blowing through the top of the vacuum chamber promoted the decarburization of RH refining whenever the oxygen was injected. When the oxygen was injected at the beginning of the decarburization process, the contribution of the decarburization at the top surface of the molten steel in the vacuum chamber to the total decarburization increased from 11.6 to 28.3 pct.

In the current study, the multiphase flow of the molten steel, the dispersion of the desulfurizer, and the desulfurization kinetics were combined to study the desulfurizer injection desulfurization during the RH process using a coupled k–ε model, Volume of Fraction model, Discrete-Phase Model, and unreacted core model. The effect of the desulfurizer diameter on the desulfurization was investigated. The measured sulfur content during the actual RH desulfurization process was employed to validate the mathematical model. Results indicate that the particles accumulated on the steel surface of the ladle beside the down-leg snorkel. Very few of the desulfurizer flowed back to the vacuum from the up-leg snorkel. The desulfurization rate increased with the injection of the desulfurizer particles. The desulfurization rate increased gradually with the continuous addition of the desulfurizer. The maximum desulfurization rate of the 1 mm desulfurizers was twice that of the 2 mm desulfurizers. The sulfur content of the molten steel in the vacuum and the ladle on the side of the down-leg snorkel was much lower than other areas. The sulfur content in molten steel variated with desulfurizer diameter and reaction time was proposed as ln([pct S]/[pct S]0) = − 7.91 × 10–3·dp−2·t.

The deformation of inclusions in the steel was affected by the thermal history during the physical simulation of steel processing. After plain strain compression with a reduction of 30 pct, the average aspect ratio of inclusions in the steel sample cooled down to 1673 K from semi-solid state was 1.89, which was significantly higher than 1.29 in the steel sample heated persistently up to the same temperature. The mechanism was revealed by inclusion transformation.

Plain strain deformation trials were carried out on samples of pipeline steels at 1473 K, 1673 K and 1723 K, respectively. The deformation of inclusions in the solid steel at different temperatures and in the semi-solid steel was studied. The composition of inclusions changed from 60.62%Al2O3–16.10%CaO–10.27%MgO–13.01%CaS before deformation to 60.59%Al2O3–13.03%CaO–12.74%MgO–13.63%CaS, 59.69%Al2O3–7.04%CaO–11.51%MgO–21.76%CaS, and 68.26%Al2O3–22.56%CaO–6.68%MgO–2.5%CaS with corresponding deforming temperatures of 1473 K, 1673 K and 1723 K. While the average aspect ratio of inclusions increased from 1.28 to 2.23, 1.32, and 1.35, respectively. Thermodynamic calculations performed by FactSage 7.0 verified the composition transformation from CaO to CaS during the solidification and cooling process of the steel. A kinetic model was used to calculate the dynamic transformation of the inclusion composition at compression temperatures. The inclusion transformation ratio from CaO to CaS increased from 38.28% at 1473 K to 50.50% at 1673 K. For the deformation in the solid steel at the temperature below 1673 K, the thickness of the hard phase CaS increased with the soaking temperature, while the hardness of the steel matrix decreased. The larger hardness difference between inclusions and the steel matrix led to a higher aspect ratio of inclusions after deformation. For the deformation in the semi-solid steel, the small difference of hardness between the soft inclusion phase and the soft steel matrix resulted in a low aspect ratio of inclusions in the semi-solid steel after deformation.

A physical water model based on the similarity principle is established to investigate the fluid flow and mixing phenomena during the Ruhrstahl–Heraeus (RH) steel refining process. The velocity distribution and the turbulent features on the center section are obtained using particle image velocimetry (PIV) measurement. Two vortexes between the down‐leg snorkel and the ladle sidewall are observed. The effects of the number of gas‐injection nozzles and the liquid levels in the vacuum chamber on the fluid phenomena are performed. More injected nozzles and a higher liquid level in the vacuum chamber generate larger velocity in the ladle. Twenty monitors in the ladle are used to monitor the variation of the conductivity to obtain the mixing time, indicating that the mixing time varies much with locations. The distribution of the mixing time on the vertical center section of the ladle is obtained. Moreover, the relationship between the circulation rate and the mixing time is obtained, indicating that the mixing time decreases with increasing circulation rate, and the slope of their relationship is −0.35.

Experiments were carried out to investigate the deformation and fracture of non-metallic inclusions in steel at different temperatures. The deformation of inclusions at high temperature could be characterized by viscosity. Meanwhile, the apparent deformation of inclusions at high temperature was also related to the difference of viscosity between inclusions and the steel matrix. Lower inclusion viscosity leads to better deformability when the viscosity of inclusions was smaller than that of steel matrix, otherwise, the inclusion deformation would be limited. The Young's modulus of inclusions could be used to characterize the deformation of inclusions at low temperature. Generally, the deformation of inclusions at low temperature increased with the decrease of Young's modulus. The intrinsic reason for the different characterization parameters of inclusion deformation at different temperatures was supposed to be the brittle to ductile transition phenomenon of inclusions in the process of temperature change. The work provided new ways to control the deformation of inclusions, for instance, by adjusting the temperature and strain rate during the processing of steel.

The effect of continuous air absorption on inclusions in molten steel during calcium treatment was investi-gated using the induction furnace .Before reoxidation occurred ,the vaporization of calcium significantly influence the composition of inclusions .After reoxidation ,the reaction between aluminum ,calcium ,silicon and oxygen occurred . The evolution of inclusions was CaO-CaS-Al2O3 →CaO-(CaS)-Al2O3 → (CaO)-Al2O3 →Al2O3 →SiO2 .The number density of inclusion increased from 10 to 210/mm2 ,and finally increased to 300/mm2 .Based on the measured re-sults of composition of steels ,the process was divided to three stages ,i .e .,the vaporization of calcium ,the reoxi-dation of aluminum and the reoxidation of silicon .The composition of inclusions was predicted accurately via ther-modynamic calculation in different stages during the process .

介绍了首钢迁钢210 t 钢包外装式透气砖的发展概况，重点对外装式透气砖在210 t 钢包上应用实践过程中的安全使用及其底吹效果的改善进行了归纳总结，形成了首钢迁钢自有的210 t 钢包外装式透气砖应用的管理模式。

According to the production practice of RH,the flow rate and volume trend of exhaust gas,steam consumption,cooling water parameter,leaking out ratio and pump capacity testing,the problems of vacuum system can be found and treated.

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