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Laboratory experiments are performed to study the effect of T.Ca content in the molten steel on the composition, size, and quantity of inclusions. Different amounts of SiCa alloys are added into the molten steel to obtain samples with varied T.Ca contents. Samples are taken at 1, 5, 10, 15, and 20 min after the calcium addition to study the transformation of inclusions with time. After the addition of calcium into the molten steel, the size of pure liquid inclusions is small which are more difficult to be removed from the molten steel than solid ones, while partially liquid inclusions are easily removed from the molten steel so that the total oxygen content of the molten steel is lower. The size of solid inclusions is large due to their large coagulation coefficient value. The number density and area fraction of liquid inclusions are larger than solid inclusions due to the higher adhesion work required for the removal of liquid inclusions. The corrosion of MgO crucible easily occurs by the dissolved calcium in the molten steel. Then, the reaction between the reduced magnesium and inclusions in the molten can occur, leading to the generation of MgO–Al2O3 and CaO–MgO–Al2O3 inclusions. [ABSTRACT FROM AUTHOR]

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/Al2O3 ratio and a lower SiO2 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. [ABSTRACT FROM AUTHOR]

Sulfides like MnS are common phases in resulfurized free‐cutting steels, and are required to be controlled during the hot working process due to its influence on machinability, mechanical, and physical properties of final products. This article extensively reviews published researches on sulfides in resulfurized free‐cutting steels. The formation mechanism and modification of MnS during steelmaking, casting, and heat treatment are discussed based on a number of relevant studies. Measures to control the morphology and number of sulfides are supplied, which are beneficial for the production of resulfurized free‐cutting steels with high quality. Thermodynamic calculation proves to be an effective method to predict and control sulfides. [ABSTRACT FROM AUTHOR]

The localized corrosion induced by different kinds of inclusions in low‐nickel stainless steel is studied through immersion tests and first‐principles calculations. The galvanic corrosion between the steel matrix and different kinds of inclusions occurs in the corrosive environment due to the difference in the electron work function of the steel matrix and inclusions. The electron work function of MnS, CeS, and Ce‐O‐S is smaller than that of the steel matrix, thus, these inclusions first dissolve as the anode. However, the electron work function of cerium‐containing oxides is bigger than that of the steel matrix, and the steel matrix dissolves prior to cerium‐containing oxides. The order of the volume expansion rate of pits induced by inclusions is CeS > Si‐Mn(‐Al)‐O > MnS > Ce‐C‐O‐S > Ce‐Si‐Mn(‐Al)‐O > Ce‐O‐S. For cerium‐containing inclusions, the electron work function of inclusions increases with the increase of the O/Ce ratio and the S/Ce ratio of inclusions. The order of the electron work function of cerium‐containing inclusions is cerium oxides > cerium sulfides > cerium oxysulfide. [ABSTRACT FROM AUTHOR]

Coupling fluid flow, heat transfer, solidification, and particle dissolution behavior, the white spot formation in the vacuum arc remelting process is simulated. The effect of particle initial diameter, dropping position, and dropping height on the remelting behavior is investigated. The results show that the particle from the electrode drops through the arc zone with gravity force and the diameter is reduced in the high‐temperature zone. As the diameter is lower than 5 mm, the particle completely dissolves and the white spot formation can be eliminated. The particle dissolution is less affected by the liquid pool depth, but it is mainly affected by the high‐temperature zone distribution, which is closely related to the electric arc generation. Because of the limited high‐temperature zone near the ingot side surface, the particle from the ingot crown is more difficult to remelt, compared with that from the electrode. Moreover, it is found that the dropping height obviously affects the particle remelting behavior. As the dropping height decreases from 25 to 0, the particle critical diameter that can fully dissolve increases from 4.2 to 6.6 mm. [ABSTRACT FROM AUTHOR]

A 3D model is built to simulate the transport behavior in the slab continuous casting with mechanical reduction. More importantly, the reduction amounts and reduction positions on the center segregation evolution are investigated. The model is verified by the measured solute segregation and surface temperature. The results show that liquid steel from the submerged entry nozzle (SEN) impacts the slab narrow surface directly, which reduces the solidified shell thickness in the edge part. In later solidification, the bulging amount of the edge part is larger than that of the middle part, which promotes solute‐enriched liquid to move from middle part to edge part and results in serious segregation. When the reduction zone is set at 13−17 m from the meniscus, the center segregation of the middle part is reduced, but that of the edge part becomes more serious, due to the enriched liquid compressed to the edge part. The slab solidification end should be within the reduction zone, both for the middle part and for the edge part. The optimum reduction zone is from 15.0−17.0 m to 16.0−18.0 m, where center segregation in the edge part begins to decrease and that in the middle part remains at a lower level. [ABSTRACT FROM AUTHOR]

The spatial distribution of argon bubbles in an 1800 mm × 230 mm continuous casting strand under different casting speeds and argon flow rates are studied through the numerical simulation using the Euler–Euler‐multiple‐size‐group approach. The calculated fluid flow is validated with water modeling and nail board measurements of industrial trials. Argon bubbles with diameter of 2 mm are injected into the submerged entry nozzle (SEN). The speed of the molten steel near the SEN decreased with the casting speed increasing and increased with the argon flow rate increasing. Most of argon bubbles are larger than 4.5 mm inside the mold at the casting speed of 0.6 m min−1 and the argon flow rate of 18 NL min−1. The breakup rate of bubbles inside the mold increased with the increasing of the casting speed and the coalescence rate increased with the increasing of the argon flow rate. The coalescence and breakage of argon bubbles inside the mold mainly occurred during the rising of bubbles to the top surface and the moving of bubbles with the steel jet to the narrow face. The average diameter of bubbles decreased when the casting speed increased and the diameter increased when the argon flow rate increased. [ABSTRACT FROM AUTHOR]

Laboratory experiments are conducted to study the influence of inclusions on the nucleation of acicular ferrite in Ti–Zr‐bearing steels. The ferrite transformation in steels with different Ti–Zr contents is observed using a high‐temperature confocal laser scanning microscope (HT‐CLSM). The average composition and size of inclusions and the information about the nucleation of acicular ferrite (AF) are analyzed using a scanning electron microscope. When the content of titanium in the steel increased from 70 to 370 ppm, the main composition in the inclusion transformed from Al2O3 to Ti2O3, the volume fraction of AF increased from 24.4% to 52.5%. The average content of ZrO2 in inclusions is 0%, 18.51%, and 90.39%, when the Zr content of steel is 0 80, and 140 ppm, the volume fraction of AF is 52.5%, 76.9%, and 56.8%. The relationship between the cosine of the contact angle at the inclusions‐ferrite interface and the diameter of inclusions is established based on experimental results, which is consistent with the results calculated based on the classic nucleation theory. [ABSTRACT FROM AUTHOR]

A 3D vacuum arc remelting model coupling heat transfer, fluid flow, solidification, nucleation, and grain growth is established. The effect of melting rate and current intensity on the solidification structure, depth of the molten pool, and equiaxed crystal rate is investigated by the simulation. Near the baseplate of the mold, the direction of columnar dendrites is vertically upward. Near the mold lateral wall, the columnar dendrites grow aslant upward. From the initial time to the end of the remelting period, the depth of the molten pool increases continuously and reaches the maximum value of 105.5 mm at the end of the remelting period. In the end feeding period, the depth of the molten pool decreases gradually until the molten pool solidifies completely. With the melting rate increasing from 0.8 to 2.4 kg min−1, the maximum depth of the molten pool increases from 84.6 to 130.3 mm and the equiaxed crystal rate is 42.5%, 57.2%, and 62.7%, respectively. With the current intensity increasing from 2 to 6 kA, the maximum depth of the molten pool increases from 63.1 to 92.9 mm and the equiaxed crystal rate decreases from 51.7% to 45.6%. [ABSTRACT FROM AUTHOR]

With the high temperature confocal laser scanning microscope applied, the effect of cooling rate, temperature interval, and cooling mechanism on the solidification microstructure and primary carbide participation in GCr15 steel are investigated. The solute distribution in interdendritic segregation and participation carbide are analyzed by electron probe microanalysis. The results show that solute concentrate is low in the dendrite zone but it increases clearly in the segregation zone. The carbon concentration in the precipitation can reach 6.49%, which means the primary carbide is M3C. In the heating process, the segregation zone and carbide participation melt first before it reaches the solidus temperature. During the solidification stage, the microstructure is refined and the size of primary carbide is reduced with a higher cooling rate, but the number density of primary carbide is increased. Moreover, it is found that the microstructure is formed in the earlier solidification, before the temperature declines to 1673 K. While the primary carbide participates in the later cooling stage and the transition temperature for the primary carbide is 1503 K. In addition, the primary carbide size can be reduced with the cooling rate larger than 300 K min−1 in the subsequent cooling stage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Diffusion couples of 3CaO·Al2O3 and Fe–S–O–(Al) alloys are prepared to investigate the transformation of calcium aluminate reacting with solid sulfur‐containing alloys. Diffusion behaviors and solid reaction between the alloy phase and the slag phase under 1373 K are studied. Product layers of 12CaO·7Al2O3 and CaS are formed at the interface. After heating for 10 h, the average thickness of CaS layer in samples with and without Al in the alloy phase is 2.10 and 0.71 μm, respectively, while it increases to 3.76 and 1.75 μm after 50 h heating. Aluminum in the alloy makes the solid reaction at the interface easier to happen, meanwhile inhibits the formation of CaS layer by promoting the formation of 12CaO·7Al2O3 layer and suppresses the diffusion of sulfur. [ABSTRACT FROM AUTHOR]

Two types of inclusions in the stainless steels are detected: MnO·Cr2O3–MnS dual‐phase ones and pure MnS ones. The increase of sulfur content can inhibit the formation of MnO–Cr2O3–MnS inclusions and reduce the harm of MnO·Cr2O3–MnS inclusions on the pitting corrosion of stainless steels. When the sulfur content increases from 26 to 70 ppm, the average pitting potential increases from 0.34 to 0.4 VSCE due to the decrease in the number density of MnO–Cr2O3–MnS inclusions. A Cr‐depletion zone exists in the steel matrix around MnO–Cr2O3–MnS inclusions. The size of pits induced by MnO·Cr2O3–MnS inclusions is larger, which poses a more serious threat to the pitting resistance of stainless steels. [ABSTRACT FROM AUTHOR]

A 3D discrete phase model (DPM)‐ and volume of fluid–coupled model is developed to investigate the multiphase flow in a 260 ton argon‐stirred ladle. The flow field and interfacial behavior in the argon‐stirred ladle are accurately predicted. Then, the Lagrangian DPM is used to trace the motion of inclusions in the liquid steel. Residence time maps, which provided the residence time required for inclusions travelling from the bulk liquid steel to the steel–slag interface, are proposed and plotted as functions of inclusion diameter and percentage of inclusions. For inclusions smaller than 10 μm, the average residence time is size‐independent but decreases from 175 to 93 s with an increment in the gas flow rate from 50 to 400 NL min−1. With increasing the inclusion size, the average residence time is dependent on both gas flow rate and inclusion diameter. When the inclusion diameter increases to 1000 μm, the average residence time is almost independent of the gas flow rate. The current model overestimates the inclusion removal rate. However, this overestimation indicates that only appropriately considering the behavior of inclusions at the steel–slag interface can accurately predict the removal of inclusions in argon‐stirred ladles. [ABSTRACT FROM AUTHOR]

Industrial trials and theoretical analysis are performed to study the effect of addition sequences of calcium and sulfur on inclusions in a calcium‐treated and resulfurized Al‐killed steel. The evolution path of inclusions at each production step is Al2O3 → Al2O3–CaO–MgO → Al2O3–MgO and Al2O3–CaS–CaO → Al2O3–MgO–CaS with the calcium treatment before sulfur addition. Calcium treatment after the sulfur addition promotes the formation of (Mn, Ca)S complex sulfide inclusions and is beneficial to modify the shape of sulfide inclusions to spherical ones in the rolled steel, where the size of sulfide inclusions is smaller than that of the heat of calcium treatment before sulfur addition. The relative plasticity of (Mn, Ca)S complex inclusions has a linear relationship with the content of CaS. Thermodynamic calculation results show that the critical solute sulfur content corresponding to the formation of CaS in the molten steel decreases sharply with the increase of the calcium content. With the same amount of calcium in the steel, the calcium treatment after sulfur addition promotes the formation of small (Mn, Ca)S complex sulfide inclusions with lower deformability during the hot rolling process, which is helpful for the mechanical property of the calcium‐treated and resulfurized Al‐killed steel. [ABSTRACT FROM AUTHOR]

Roll‐gap deviation (RGD) is commonly observed in the slab continuous caster, which means the thicknesses of the right and left sides are different. The RGD amounts and positions on the solute redistribution are investigated. In the RGD zone, slab thickness decreases from the left to the right side. Dynamic grid technology is used to consider the mesh deformation in the model. When RGD is set before the solidification end of the slab middle part, the center segregation in the right‐edge part decreases but that in the left‐edge part increases. That is because the solute‐enriched liquid moves from the right to the left side with solid compression. When RGD is set after the slab middle part is solidified, the center segregation in the right‐edge part is deteriorated, while that in the left‐edge part is reduced. This is because the slab right‐edge part is fully solidified in the RGD zone, and the segregation cannot be reduced in the later stage. With the RGD position moving from 15.5 to 18.0 m from the meniscus, the center segregation in the right‐edge part decreases first and then increases, while that in the left‐edge part increases slightly and then declines. [ABSTRACT FROM AUTHOR]

In the current study, laboratory experiments of the slag‐steel reaction are performed to investigate the effect of CaF2 contents in the refining slag on the inclusion absorption of the bearing steel. The increase of the CaO/Al2O3 ratio effectively enhances the absorption of inclusions by slag. The increase of the CaO/Al2O3 ratio enhances the driving force of the inclusion dissolution and lowers the slag viscosity. It is noted that the excessive CaO/Al2O3 ratio led to the formation of solid phases in the slag, lowering the absorption effect of slag. The appropriate addition of CaF2 in the slag is helpful to remove inclusions while aggravating the corrosion of MgO crucibles. The addition of CaF2 mainly reduces the viscosity and melting temperature of slag. The inclusion removal factor is proposed to effectively evaluate the inclusion removal rate in steel during slag steel reaction. As a result, the most recommended composition of slags is 7% CaF2; the CaO/Al2O3 ratio is 2.0. [ABSTRACT FROM AUTHOR]

The effect of calcium addition on inclusions (oxides and sulfides) in heavy steel ingot is investigated via lab experiments and thermodynamic calculation. The characteristics (chemistry, size, morphology, and number) of inclusions in the steel samples are investigated by scanning electron microscope with an energy‐dispersive spectrometer. The three‐dimensional morphology of inclusions is investigated by the nonaqueous solution electrolysis method. Inclusions in the fast‐quenched steel are changed from Al2O3 to Al2O3–CaO, Al2O3–CaO–CaS, and CaS after Ca addition. After slow cooling, inclusions in the solid steels are changed from Al2O3, single MnS, and Al2O3–MnS complex inclusions to Al2O3–CaO–CaS–MnS and CaS–MnS. The evolution trajectory of inclusions is Al2O3→Al2O3–CaO→Al2O3–CaO–CaS→Al2O3–CaO–CaS–MnS. With increasing Ca content in the steel, the number density and proportion of single MnS inclusions decrease. The formation mechanism of inclusions after Ca addition is explained by thermodynamic calculation. [ABSTRACT FROM AUTHOR]

A 3D mathematical model combining the large eddy simulation turbulent model and discrete phase model is developed to investigate the influence of the stopper rod location on transient flow characteristics and the deposition of inclusions in a bifurcated submerged entry nozzle (SEN). Transient flow characteristics, including the instantaneous flow pattern, jet speed, vertical and horizontal jet angle, and the backflow zone speed and fraction, are quantitatively compared. Transient jet flow characteristics of the left and right SEN port are almost consistent when the stopper rod is ideally centered. When the stopper rod is offset 10 mm, the discrepancy of the jet speed, vertical jet angle, and backflow zone fraction is 0.12 m s−1, 4°, and 4%, respectively. The horizontal angle and backflow speed are primarily affected by the vortex swirling direction at the bottom region of the SEN well. A positive horizontal jet angle is observed under the counterclockwise vortex, resulting in a higher backflow speed. Conversely, a negative horizontal jet angle and a lower backflow speed are observed when the vortex swirling direction is clockwise. The deposition rate of inclusions on the upper SEN wall is much higher when stopper rod is offset. [ABSTRACT FROM AUTHOR]

Herein, the effect of total sulfur (T.S) on the transformation of inclusions in Al‐killed steels is investigated through lab experiments and kinetic calculations. During the heating process, CaS content in inclusions obviously rises up, while the CaO content reduces. The CaO content in inclusions with 11 ppm S in steel is higher than 15%, while it is less 5% for the steel with 25 ppm S. The initial CaO–Al2O3 inclusions before heating change to CaS–MgO–Al2O3 at 1200 °C. The higher T.S promotes the transformation of inclusions in low sulfur Al‐killed steels, leading to the higher CaS content in inclusions after the heat treatment. A kinetic model is developed to predict the transformation of inclusions in low sulfur Al‐killed steels during the heat treatment. The transformation fraction of inclusions decreases with the larger size of inclusions and increases with the higher T.S content in steel at the heating temperature. [ABSTRACT FROM AUTHOR]

The existence of the dissolved aluminum and other impurity elements in alloys would inevitably lead to the formation of the Al2O3 component of inclusions in Si–Mn killed steels. Herein, the effect of dissolved oxygen at the endpoint of basic oxygen furnace (BOF) on the control of inclusions in a Si–Mn killed steel is investigated. With the increase in the dissolved oxygen at the BOF endpoint, the (FeO + MnO) content in the refining slag increases and the dissolved aluminum in the steel decreases as a whole. Meanwhile, the proper increase in the dissolved oxygen hardly deteriorated the cleanliness of the steel. As the equilibrium dissolved oxygen at the BOF endpoint increased from 148 to 402 ppm, the Al2O3 content of inclusions could be lowered to <4 wt%. Both industrial trials and the thermodynamic consideration indicate that increasing the dissolved oxygen at the endpoint of BOF can be an efficient approach to achieve the ultralow Al2O3 content of inclusions in the Si–Mn killed steel due to the oxidation of the dissolved aluminum by the oxygen both in the molten steel and in the refining slag. [ABSTRACT FROM AUTHOR]

Herein, multiphase flow patterns in a continuous casting slab strand are studied using a 3D numerical model and nail board measurement. The motion and turbulence of the argon gas and molten steel are simulated using the Euler–Euler approach and the realizable κ–ϵ turbulence model, respectively. Casting parameters for a 1435 mm × 200 mm mold are optimized by both the simulation and the capillary number. The capillary number is calculated by the measured velocity and used to evaluate the capability of the slag entrainment by the turbulent flow. The optimized values of the casting speed and the gas flow under the current specific continuous casting condition are 1.4 m min−1 and 8 NL min−1, respectively. Slag entrainment might occur near the narrow face under a casting speed of 1.6 m min−1 and near the SEN under a gas flow rate of 15 NL min−1. Meanwhile, effects of casting speed and argon flow rate on the transformation of flow patterns inside the mold with different dimensions are analyzed. A software incorporated by a Graphical User Interface is developed to predict the flow pattern inside the mold for a given steel grade and casting parameters. [ABSTRACT FROM AUTHOR]

Herein, effects of the water temperature and a multichannel stopper rod with various gas hole diameters on the size and distribution of bubbles are investigated using a 0.5‐scale water model of a steel slab continuous casting mold. The breakage ratio of bubbles increases with the increasing of the water temperature. The mean diameter of bubbles decreases from 2.11 to 1.32 mm with the water temperature increasing from 25 to 34 °C. The smaller dynamic viscosity and surface tension of the water at a higher temperature result in large turbulence velocity fluctuation at the bottom of the submerged entry nozzle. The effect of water temperature on the bubble size and distribution can hardly be ignored in the water model experiment. With the increase of the hole diameter of the gas channel (Dh) of the stopper rod, the number of bubbles first decreases to the minimum value at Dh = 1.5 mm and then increases, and bubble mean diameters increase, and the horizontal dispersion and penetration depth increase when the bubble diameter is larger than 1 mm. The multichannel stopper rod with the gas hole diameter of 1.5 mm is recommended under the current specific continuous casting condition. [ABSTRACT FROM AUTHOR]

Herein, laboratory experiments are conducted to evaluate the effect of sulfur and lanthanum content in the steel on the modification of inclusions. The amount, composition, morphology, and size of nonmetallic inclusions in the steel are observed using an automatic scanning electron microscope. Results show that as the lanthanum content in the steel increased from 0 to 72 ppm, the inclusions in the steel with 12 ppm sulfur are modified in the following order: Al2O3–CaO–MgO → LaAlO3 → LaAlO3–La2O2S → La2O2S. Similarly, when the sulfur content is 27 ppm, inclusions transformed in the order of Al2O3–CaO–MgO → LaAlO3 → LaAlO3–La2O2S → La2O2S → La2O2S–LaxS → LaxS as the lanthanum content increases from 0 to 150 ppm. Thermodynamic analysis using FactSage based on a private database is employed to reveal the mechanism for the modification of inclusions. Additionally, a kinetic model is established to study the transformation rate of inclusions in the steel after the addition of lanthanum and sulfur. Liquid Al2O3–CaO–MgO inclusions disappear after 800 s when the steel contains 12 ppm sulfur and 12 ppm lanthanum. The composition of inclusions is 53%LaAlO3–47%La2O2S at 1800 s, while it is 100%La2O2S and 80%La2O2S–18%LaxS–2%CaS when the lanthanum content is 33 and 72 ppm, respectively. [ABSTRACT FROM AUTHOR]

In this study, the viscometer is used to evaluate the viscosity of slag containing 10% SiO2 with varying CaO/Al2O3 ratios. When CaO/Al2O3 ratio increases in the 3.00–4.00 range, the viscosity exhibits a non‐monotonic behavior characterized by an initial decrease followed by an increase, with a minimum value of 0.046 Pa·s observed at 1673 K. The slag with a CaO/Al2O3 ratio above 3.00 has relatively low and stable viscosity within the range of 1373–1673 K, which is beneficial for slab quality of high‐aluminum steel. X‐ray diffraction and Raman spectroscopy are used to better understand the viscosity evolution of slag containing 10% SiO2. A higher CaO/Al2O3 ratio depolymerizes network structures due to the breaking effect of free oxygen O2−. Upon surpassing a CaO/Al2O3 ratio of 3.50, the transformation of the crystallization phase occurs from CaO·SiO2 to 2CaO·SiO2. Additionally, a higher CaO/Al2O3 ratio promotes the precipitation of the 11CaO·7Al2O3·CaF2 crystal in the slag. [ABSTRACT FROM AUTHOR]

Herein, the cerium treatment is used to modify large MnS inclusions in a 303‐ton carbon manganese steel ingot. When the cerium content in steel in the tundish is 90 ppm, the inclusions are CeAlO3 with a small amount of Ce2O2S. The precipitation sequence of inclusions during the solidification and cooling process in the ingot is MgO·Al2O3 + CeAlO3→Ce2S3→MnS→MgS. Due to the inevitable macrosegregation, a small amount of elongated MnS inclusions is precipitated at the radial center. The maximum diameter is 257.80 μm, and the average aspect ratio is 3.28. For heterogeneously nucleated sulfide, the average diameter is less than 13.39 μm, and the average aspect ratio is less than 1.88. The morphology of MnS inclusion is well controlled when the mass ratio of Ce/S in steel is in the range of 0.7–2.8. The average aspect ratio of homogeneously nucleated MnS is less than 1.9. In addition, the formation of CeAlO3 clusters is avoided. According to the atomic mismatch obtained by the edge‐to‐edge matching model, the possibility of heterogeneous nucleation of MnS on the oxide core is CeAlO3 > Ce2O2S > MgO·Al2O3. The Ce2S3 inclusions are mainly precipitated with the core of MgO·Al2O3. [ABSTRACT FROM AUTHOR]

A three‐dimensional mathematical model on fluid flow, ferrochrome dissolution, and mixing phenomena in a nitrogen‐stirred gas‐oxygen refining furnace is established. The multiphase fluid flow is simulated using the standard k–ε model, the volume of fluid (VOF) model, and the Lagrangian discrete phase model. Interfaces between fluids are tracked by the VOF model, and nitrogen bubbles are treated as discrete phase particles. The melt time of ferrochrome particles and the local mixing time are calculated using the user‐defined function. Effects of gas flow rate and bottom tuyere configuration on the fluid flow and the melting and mixing of ferrochrome are investigated. The results show that the average turbulent kinetic energy and its dissipation rate first increase and then decrease with the increasing gas flow rate, while the melting time and mixing time first decrease and then increase. The shortest melting and mixing time with the condition of seven bottom tuyeres are reached when the gas flow rate is 6.5 Nm3 min−1, which are 40.5 and 94.6 s, respectively. The mixing time decreases from 190.0 to 104.5 s when the three bottom tuyeres configuration changes to the seven bottom tuyeres configuration with the gas flow rate of 3.9 Nm3 min−1. [ABSTRACT FROM AUTHOR]

The effect of cerium on inclusions and solidification structure of a low‐nickel Si–Mn‐killed stainless steel is studied using laboratory experiments. When the cerium content in steel increased from 0 to 250 ppm, modification sequence of inclusions is Si–Mn(–Al)–O and MnS → Ce–Si–Mn–O–S → Ce(–Si)–O–S → CeS and CeC2. The number density and area fraction of inclusion first decrease with the increase in the cerium content and then increase due to the formation of CeC2 inclusions when the cerium content is bigger than 150 ppm, which is precipitated in solid steel during solidification. When the cerium content increases from 0 to 250 ppm, the fraction of equiaxed grain zones of steel ingot first increases and reaches a maximum value when the cerium content is 54 ppm; then the fraction of equiaxed grain zones decreases with the increase of the cerium content. 2D lattice misfit calculations are performed and it is found that there are no heterogeneous nucleation cores in the steel without cerium during solidification. For the steel with cerium, Ce4.67Si3O13, Ce2O2S, and CeS inclusions act as heterogeneous nucleation cores, increasing the fraction of the equiaxed grain zone. Bigger effective heterogeneous nucleation cores number density leads to a larger fraction of the equiaxed grain zone. [ABSTRACT FROM AUTHOR]

According to the variation in the average composition, the average size, the number density, and the area fraction of large‐size inclusions during Ruhrstahl Heraeus (RH) refining process, large‐size inclusions in the high‐carbon chromium‐bearing steel reach the lowest level when the vacuum cycle time is 25 min. When the soft blowing time reaches over 25 min, the number density and area fraction of large‐size inclusions increase. The rolling contact fatigue (RCF) life of the forged steel samples is measured using a thrust RCF tester, indicating that the fatigue life of no. 1 steel (vacuum cycle 40 min, soft blowing 20 min) is 12% higher than that of no. 2 steel (vacuum cycle 20 min, soft blowing 40 min). Based on the estimation of the characteristic size of inclusions in the forged steel by the statistics of extreme values (SEV) method, it is concluded that when the characteristic size and the chemical composition of inclusions in steels are similar, the RCF life is increased by 12% when the number density of large‐size inclusions decreases from 0.63 to 0.44 mm−2. [ABSTRACT FROM AUTHOR]

Based on the principle of minimum Gibbs free energy, a thermodynamic model is established to predict the composition of inclusions in the Al‐killed steel during the calcium treatment process. The Wagner model combined with coexistence theory is applied to calculate the Gibbs free energy of the steel‐inclusion system. The composition evolution of inclusions is accurately predicted through the current thermodynamic model which is widely applied to predict the modification of inclusions by the calcium treatment process with different contents of total oxygen (T.O), total sulfur (T.S), and total calcium (T.Ca) in the molten steel. Alumina inclusions can be modified to liquid calcium aluminate inclusions with appropriate T.Ca contents. Solid CaS or CaO inclusions can be formed as a result of the excessive calcium addition to molten steel, while the insufficient calcium addition can hardly modify alumina inclusions to liquid ones. The effect of the T.O and T.S contents on the liquid window is also discussed. The relationship between the value of T.S/T.O in the molten steel and the composition of inclusions is also studied. Based on the established thermodynamic model, a software for the precise control of inclusions is also developed to guide the calcium treatment operation timely in the accrual refining process. [ABSTRACT FROM AUTHOR]

Herein, a mathematical model combined with the k–ε turbulence model, volume of fluid multiphase model, and heat transfer and solidification model is established to investigate the steel–air two‐phase flow and solidification during the filling process of a 303 ton heavy steel ingot. The measured temperatures at different times are employed to validate the current mathematical model. The results show that the predicted results are in good agreement with the measured results. At the initial stage of the filling process, a double‐roll flow pattern is formed near the junction between the liquid surfaces due to the high speed of the jet flow. The maximum impinging depth of the jet flow is 1.8 m and the maximum splash height of the molten steel is 0.3 m. An empirical formula for the variation of the entrained air volume with time is proposed. The maximum growth rate in the horizontal direction is 0.08 mm s−1. In the vertical direction, the maximum growth rate of the solidified shell on the central axis is 0.12 mm s−1. The distribution of primary dendrite arm spacing and secondary dendrite arm spacing is obtained by combining the predicted cooling rate. [ABSTRACT FROM AUTHOR]

In situ observation, scanning electron microscope/energy‐dispersive spectrometer detection, and lattice disregistry calculation are combined to investigate the evolution mechanism of inclusions in heavy rail steels with varied aluminum contents from SiO2–Al2O3–MnO to SiO2–Al2O3–MnO–MnS at 1323 K and 1393 K. The precipitation of MnS inclusions on SiO2–Al2O3–MnO inclusions in the steel occurs when the Al2O3 content in identical oxide inclusions is 30% at 1393 K and 30%, 40%, and 59% at 1323 K. The MnS outer layer shows visible precipitation from 3 min after heating at experimental temperature. The area fraction of MnS phase in SiO2–Al2O3–MnO–MnS inclusions with varied Al2O3 content at 1323 K decreases in the following order: SiO2–Al2O3 (30%)–MnO > SiO2–Al2O3 (40%) –MnO > SiO2–Al2O3 (59%)–MnO. The precipitation of MnS is prone to occur on the Al2O3‐less region of the SiO2–Al2O3–MnO inclusion. The solubility of Mn and S decreases with decreasing temperature. Lower heating temperature and lower Al2O3 content in SiO2–Al2O3–MnO oxide cores are profitable to the heterogeneous nucleation of MnS due to lower disregistry between MnS with the SiO2–Al2O3–MnO inclusion. [ABSTRACT FROM AUTHOR]

The modification mechanism of lanthanum on alumina inclusions in a nonoriented electrical steel at 1600 °C is investigated using laboratory experiments. Inclusions are analyzed using an automatic scanning electron microscope equipped with energy‐dispersive spectrum at 1, 5, 10, and 30 min after lanthanum treatment. The contents of total oxygen (TO), total sulfur (TS), and total lanthanum (TLa) in steel are analyzed. Results show that Al2O3 inclusions are modified by lanthanum in two ways. One is that the dissolved lanthanum directly reduces the aluminum in Al2O3 inclusions and forms LaAl11O18 or LaAlO3 ones. The other is that a new La2O2S or LaSx shell is preferentially generated at the outside of Al2O3 and forms multiphase inclusions. With time increasing, the La2O2S or LaSx shell gradually reacts with the Al2O3 core and generates stable lanthanum‐containing inclusions. At the initial stage of lanthanum treatment, many transient inclusions including LaSx, La2O2S, and La–P(–As) are formed due to the high concentration of lanthanum, while gradually redissolving with time increasing. With the increase in TLa content in steel, the formation sequence of stable inclusions is Al2O3 → LaAl11O18 → LaAlO3 → La2O2S → LaSx, which is consistent with thermodynamic analysis. [ABSTRACT FROM AUTHOR]

Herein, the contact angle between a Si–Mn‐killed steel and MgO‐based refractory is measured in a reduction atmosphere at 1853 K using the sessile drop method. As the cerium content in the steel increases from 0 to 0.0450 wt%, the initial contact angle between the steel and the refractory slightly increases from 136° to 138°, the equilibrium contact angle decreases from 131° to 124°, and the steel surface tension reduces from 1.756 to 1.624 N m−1. Cerium in the steel retards the formation of Mg–Si–O oxide on the steel drop surface. A higher cerium content promotes the chemical reaction, resulting in a decrease in the contact angle. The cerium addition leads to an increase in the steel–refractory reaction depth. With an increase in cerium in the steel, the meniscus contact angle between the steel and the micropore in the refractory increases. Consequently, the lower driving force of steel penetrating into the refractory causes the reduction of steel penetration into the refractory. [ABSTRACT FROM AUTHOR]

Calcium treatment experiments with equal calcium amounts using different calcium‐containing cored wires are carried out in the laboratory to investigate the effect of calcium wire types on the modification of inclusions. Inclusions change from Al2O3(–MgO) to calcium aluminates with the feeding of calcium wires; however, the modification degrees are different. The CaO content in inclusions increases to 25.8, 34.5, and 31.0 wt%, respectively, at 1 min after the addition of pure Ca, SiCa, and AlCa. The calcium yield is the highest when using SiCa wire and is the lowest under the use of pure Ca wire. The difference in calcium yield is attributed to the increasing effect of Si or Al on the solubility of calcium in molten steel. When calcium treatment is performed using SiCa and AlCa wires, the local Si and Al content around calcium bubbles would be large, which can promote the dissolution of calcium into steel and increase the yield of calcium. From the perspective of improving calcium yield, calcium treatment with SiCa or AlCa wires is better than that with pure Ca wires. However, steel grade, ladle capacity, and calcium treatment parameters should be further considered in the actual selection of calcium‐containing cored wires. [ABSTRACT FROM AUTHOR]

Herein, the transformation process of the martensitic stainless steel under different austenite temperatures, holding times, and cooling rates were in situ observed using the confocal laser scanning microscope. The grain boundary migration energy of the austenite grain was 241.51 kJ mol−1. The grain size at different temperatures and holding times was predicted, agreeing well with measured values. The relationship between the martensite start temperature and the grain size is proposed. The martensitic start temperature was significantly influenced by the cooling rate. With the increase of the cooling rate, the martensitic start temperature first decreased then rose up due to the quenching vacancy and internal stress, respectively. [ABSTRACT FROM AUTHOR]

Laboratory experiments are performed to study the transient evolution of inclusions in Si–Mn‐killed stainless steels with additions of 40, 100, and 400 ppm cerium. With the increase of the cerium content in the molten steel, the evolution path of inclusions is Al2O3–SiO2–MnO–CaO → Ce2O3–Al2O3–SiO2–MnO–CaO → Ce2O3 → Ce2O3–CeS. The addition of 40 ppm cerium gradually increases the Ce2O3 content in liquid oxide inclusions. After the addition of 100 ppm cerium, inclusions first evolve to Ce2O3–Al2O3–SiO2–CaO–CeS, then to Ce2O3. The CeS is generated as a transient product then disappears. After the addition of 400 ppm cerium, liquid Al2O3–SiO2–MnO–CaO inclusions are modified to solid Ce2O3–CeS ones. The addition of 40 ppm cerium into the steel lowers the size from 1.74 to 1.53 μm. After the addition of 100 and 400 ppm cerium into the steel, the size of inclusions immediately decreases due to the formation of small Ce2O3–CeS inclusions and then increases owing to the collision of solid inclusions. A higher cerium content in the steel promotes the collision of Ce‐rich inclusions. [ABSTRACT FROM AUTHOR]

Herein, contact angles between the Si–Mn‐killed steel with and without cerium and the MgO–SiO2 refractory are measured in a reducing atmosphere. With the increase of the SiO2 in the refractory from 3 to 10 wt%, the initial contact angle for the steel without cerium decreases from 140.2° to 131.4°, and the equilibrium contact angle decreases from 136.8° to 127.8°. For the cerium‐containing steel, the initial contact angle and equilibrium contact angle decrease from 140.9° and 120.6° to 131.6° and 107.4°, respectively. With the increase of SiO2 content in the MgO‐based refractory, the increase of the Mg2SiO4 in the refractory causes the reduction of the initial contact angle between the Si–Mn‐killed steel and the refractory. The interfacial reaction between the steel and the refractory decreases the contact angle. The addition of cerium in the steel promotes the interfacial reaction, obviously decreasing the contact angle. [ABSTRACT FROM AUTHOR]

Effect of iron carbon agglomerates (ICA) on the reduction of iron‐bearing burden (pellet and sinter) is greatly important for blast furnace (BF) smelting. Herein, the effect of addition amount and reactivity of ICA on the reduction of pellets with different reducibility is studied, and coupling mechanism between reduction reaction of pellet and gasification reaction of ICA is revealed. The results show that as the addition amount of ICA‐1 increases from 0 to 25 mass%, the reduction degrees of pellet A (PA) with a lower reducibility and pellet B (PB) with a higher reducibility are improved from 40.09% and 46.57% to 46.37% and 52.66%, respectively. With the increase in the reactivity of ICA from 52.81% (ICA‐1) to 66.20% (ICA‐2), the reduction degrees of PA and PB are increased from 46.37% and 52.66% to 50.06% and 58.11%, respectively. Regardless of additional amount and reactivity of ICA, the promotion effect of ICA on the reduction of PB with a higher reducibility is more significant. The coupling mechanism is that the products of reduction reaction of pellet and the gasification reaction of ICA are reactants of each other, and the mutual coupling process between the two reactions occurs in a continuous cycle. [ABSTRACT FROM AUTHOR]

steel research int. 2024, 2300084 https://doi.org/10.1002/srin.202300084 The above article, published online as accepted article, prior to the version of record, on 13 April 2023 in Wiley Online Library (https://doi.org/10.1002/srin.202300084) has been withdrawn by agreement between the authors, the journal's Editor in Chief, Sandra Kalveram, and Wiley‐VCH GmbH. [ABSTRACT FROM AUTHOR]

Herein, a 3D mathematical model is established to investigate the initial solidification and heat transfer at different locations of the mold through considering the steel–slag–air three‐phase fluid flow, the heat transfer, the solidification, and the mold oscillation. The meniscus solidification on different sections is revealed, and the heat flux on hot face of the mold is compared. Through the simulation, the meniscus solidification on longitudinal sections parallel to narrow face is the largest at the center and the edge of wide face, and is the lowest at a quarter of wide face. The thickness of the total slag on the cross section is larger at the corner than that far from the corner. In the current simulation, the largest heat flux along the vertical direction is 2.6–3.5 MW m−2 at approximately 14 mm below initial meniscus. With the increase in thickness of the slag rim on different longitudinal sections, the thickness of the slag increases, resulting in the decrease in the heat flux on the hot face. Therefore, the initial solidification and heat transfer are significantly affected by the thickness of the slag as well as the heat supplement from the upper backflow. [ABSTRACT FROM AUTHOR]