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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]

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]

• A full 3D numerical model for transient flow field, temperature, solidification, and segregation during slab continuous casting. • An improved capture criterion for inclusion entrapment that including the primary dendrite arm spacing, solute concentration, force analysis, and critical capture speed is proposed. • Prediction on the number, size, and spatial distribution of inclusions on the entire cross section of the CC slab. • Four accumulation zones of inclusions along the thickness of the CC slab are predicted. In the current study, the LES turbulent model, heat transfer, solidification, species transport model, and discrete phase model (DPM) were coupled to investigate the three-dimensional transient flow, temperature, solidification, segregation, and inclusion transport during the slab continuous casting (CC) process. The number, size, and spatial distribution of inclusions on the entire cross section of the CC slab were successfully predicted using the coupled full solidification model, DPM, and capture criteria at the solidification front. The improved capture criteria that considering the primary dendrite arm spacing (PDAS), different forces acting on inclusions, and the critical capture speed, successfully eliminated the banded distribution characteristics of inclusions under the simple capture criterion. The prediction results were in good agreement with the detection results. Four accumulation zones of inclusions along the thickness of the CC slab were predicted, including the 1/4 thickness and 3/4 thickness from the loose side, and the layer beneath the surface of the CC slab. Two accumulation zones near the layer beneath the surface of the CC slab were issued from the double roll flow pattern in the CC strand. The probability of inclusions contacting the solidification front in the upper recirculation zone increased, increasing the entrapment rate. The accumulation zones near the 1/4 thickness and 3/4 thickness from the loose side were corresponded to the peak value of the Marangoni force on inclusions at the 1/4 thickness and 3/4 thickness from the loose side. The Marangoni force increased the probability of inclusions being pushed to the solidification front. In addition, the accumulation near the 1/4 thickness from the loose side became more severe as the diameter of the inclusions increased due to the buoyancy. [Display omitted] [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]

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]

This work focused on the effects of wettability on bulk Si growth from Si–Sn melts during the zone melting directional solidification. The wettability behaviors of Sn/Si, Si–90 wt%Sn/SiO 2 , and Si/SiO 2 were investigated along with the micro-morphology observation. The results showed that the surface roughness of the Si substrate and the growth temperature were essential factors influencing the wettability evolution. The reaction between Si and O formed SiO 2 layer on the Si substrate, which could introduce a gap at relatively low temperatures, and the released SiO gas due to the reaction between Si and SiO 2 caused the instant Si growth. [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]