An investigation has been carried out under controlled laboratory conditions designed to approximate the conditions encountered during the early stages of direct chill of Al-4:5 % Cu aluminum alloy ingots to study the formation of micro-shrinkage crack. Also, a couple models have been established at the author's organization to compute convection patterns, thermal fields, interdendritic thermo-metallurgical strain and macrosegregation distributions. Comparisons between the available microstructure taken from the samples and model predictions of convection streams to verify the mechanism of the random sedimentation of free crystals and therefore the micro-shrinkage crack formation were performed where good agreements were obtained. The effects of convection streams of various melt superheats at different locations in the aluminum ingots on the formation micro-shrinkage crack have been studied and analyzed. The mechanism of micro-shrinkage crack formation with different convection streams patterns and superheats were also discussed. 

An investigation has been carried out under controlled laboratory conditions designed to approximate the conditions encountered during the early stages of direct chill of Al-4:5% Cu aluminum alloy ingots to study the formation of micro- shrinkage crack. Also, a couple models have been established at the author's organization to compute convection patterns, thermal fields, interdendritic thermo-metallurgical strain and macrosegregation distributions. Comparisons between the available microstructure taken from the samples and model predictions of convection streams to verify the mechanism of the random sedimentation of free crystals and therefore the micro-shrinkage crack formation were performed where good agreements were obtained. The effects of convection streams of various melt superheats at different locations in the aluminum ingots on the formation micro-shrinkage crack have been studied and analyzed. The mechanism of micro-shrinkage crack formation with different convection streams patterns and superheats were also discussed.

This investigation on the formation of exuded surface segregation layer "ESSL" is intended to provide experimental and simulated comparison to verify the model developed previously by El-Bealy. Preliminary verification and calibration of the previous 2D mathematical model are demonstrated by quantitative errors between the previous measurements and predictions of temperature and macrosegregation. Also, the results from these comparisons reveal that the errors are in the reasonable and within allowable limits. These comparisons lead to the fact that the exuded surface segregation layer mostly forms on the middle slice of broad sheet ingot face and in the early stages of mold zone. The model predictions point out also that the different interdendritic strain hypotheses associated with fluctuations of mold cooling conditions. This affects the interdendritic liquid flow between the equiaxed crystals which influences the severity of ESSL formation and its macrosegregation level. The mechanism of ESSL with heat flow and interdendritic strain generation has been analyzed and discussed. The quantitative comparisons between the pervious experimental results and numerical simulation in this investigation reveal also several solutions to prevent this defect for future work.

Preliminary mathematical analyses of different interdendritic cracks associated with variation of heat transfer and generation of interdendritic strain in horizontal twin-roll strip casting have been investigated. A 1-D transient finite difference model of heat flow, dendritic solidification and interdendritic thermo-metallurgical strain has been developed. The model contains two cracking criteria to predict qualitatively and quantitatively the tendency of interdendritic crack formation during dendritic solidification of pure aluminium and 6022 aluminium alloy. The model predictions are compared to available analytical methods and previous measurements. This is to verify and calibrate the model where good and reasonable agreements are obtained, respectively. The variations of heat transfer modes during different contact cooling zones and their effects on the generation of interdendritic thermo-metallurgical strain at the surface and central strip locations have been analysed. The model predictions point out that the different contact cooling zones of strip surface and surroundings control the stages of interdendritic crack formation in different mushy regions. The mechanism of interdendritic crack formation in twin-roll strip casting process with previous and present cracking criteria have been explained and discussed. These discussions show the importance of selection of mathematical treatment to predict the stages of interdendritic crack formation. 

A comprehensive model of heat transfer and solidification phenomena has been developed including microstructure evolution and fluctuation macrosegregation in continuously cast steel slabs with an objective of evaluation of various mold cooling conditions. The study contains plant trials, metallographic examinations, and formulation of mathematical modeling. The plant trials involved sample collection from three slab casters in use at two different steel plants. The metallographic study combined measurements of dendrite arm spacings and macrosegregation analysis of collected samples. A one-dimensional mathematical model has been developed to characterize the thermal, solidification phases, microstructure evolution, interdendritic strain, and therefore, the macrosegregation distributions. Two cooling approaches were proposed in this study to evaluate the Newtonian heat transfer coefficient in various mold regions. The first approach is a direct estimation approach (DEA), whereas the second one is a coupled approach of the interfacial resistor model and direct estimation approach (CIR/DEA). The model predictions and standard analytical models as well as the previous measurements were compared to verify and to calibrate the model where good agreements were obtained. The comparison between the model predictions and the measurements of dendrite arm spacings and fluctuated carbon concentration profiles were performed to determine the model accuracy level with different cooling approaches. Good agreements were obtained by different accuracy levels with different cooling approaches. The model predictions of thermal parameters and isotherms were analyzed and discussed.

A new design of air-water mist nozzle "AWM" has been developed to improve the thermo-mechanical rigidity of continuously cast steel slabs. This is by maximization of solid shell resistance against thermo-metallurgical and mechanical stresses. The idea behind this design is optimizing the homogeneity degree of cooling pattern between a pair of rolls. The design description of air-water mist nozzle and the effect of nozzle characteristics on its function have been explained. The mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed. Also, the model can be computed the new concept to examine the micro-quality defined as micro thermo-mechanical rigidity "Mic-TMR". The results indicate that the homogeneity degree of cooling conditions is proportional to the increase in Mic-TMR criterion and therefore improve the inner quality of slabs. Model predications of new design of air-water mist nozzle is compared and discussed with other water and traditional designs of AWM nozzles.

The aim of the current article is to elucidate the significant effects of macrosegregation distribution and its level on the different stages of interdendritic crack formation during dendritic solidification in continuously cast steel slabs. Couple formations of macrosegregation and interdendritic crack phenomena during dendritic solidification of peritectic carbon steels have been investigated by metallographic study of collected slab samples and by performing a set of mathematical analyses. The metallographic study involved plant trails to measure slab surface temperature of different secondary spray cooling conditions. Also, macro-microexaminations, measurements of dendrite arm spacing, macrosegregation analysis, and interdendritic distance between the dendrites of collected samples from plant trials have been performed. The experimental results show a fluctuation of carbon segregation with respect to distance from slab surface. These results also reveal that the interdendritic cracks vary with this fluctuation in various nano, macro, and microscales based on the cooling conditions. A mathematical model of heat transfer, solidification, structure evolution, interdendritic strain, macrosegregation, and elementary interdendritic area "EIA" has been developed. This model takes also into account the calculating of interdendritic distance between the dendrites "IDD" to evaluate the interdendritic crack width. The model predictions of different thermal and solidification phenomena show a good agreement with measurements. The results pointed out also that the coupled effect of interdendritic strain and macrosegregation phenomena and their distributions can be considered as the most important tools to evaluate the surface and internal interdendritic cracks in continuously cast steel slabs. The formation mechanisms of different types of interdendritic crack with interdendritic strain patterns and fluctuation of macrosegregation levels during various cooling zones have been explained, and the possible solutions to these problems have been discussed.

In order to study the central quality of continuously cast tool steel slabs, the mathematical model has been developed to simulate the quality criteria. The model calculates different quality criteria such as average macrosegregation level criterion "ASL", its average fluctuation level "FSV and its average segregation quality number "SQN" of different segregated elements. These criteria were calculated based on the previous measurements in central areas of lower and upper slab sides. These measurements of carbon and sulfur concentrations were performed by chemical analysis technique. The effect of mechanical soft reduction technique "MSR" on the central quality of slab was also examined and studied. The model predications illustrated that this technique affects the centerline quality significantly by different ways based on the casting speed. These predications pointed out also that the macro-segregation quality criteria and their distributions can be considered as the most simple and important tools of steel industries men to explain preventive techniques and formation mechanisms of different defects in slab central area.

The macrosegregation formed in dendritic equiaxed structure during early stages of solidification of Al-4.5%Cu alloy has been studied by experimental work and by metallurgical study of cast samples taken from the experimental work. An experimental work was conducted to study the coupled effect of natural convection streams, interdendritic strain and mushy permeability of Al-4.5%Cu aluminum alloy solidified in horizontal rectangular parallelepiped cavity at different superheats. The metallurgical study includes macro-microstructure evaluation, measurements of grain size of equiaxed crystals and macrosegregation analysis. This study shows that the level of surface segregation exhibiting as positive segregation varies with superheat whereas the rest of inner ingot areas show the light fluctuation in segregation values. In addition to experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid. This derivation includes also the effects of interdendritic strain and mushy permeability on the local solute redistribution distribution. Owing to the length of the study, it is presented in two parts. The first part describes the experimental work and its results as well as a detail derivation of solute conservation equations. This part also involves comparison and discussion between existing and proposed solute conservation equations. The second part contains the mathematical analyses of a two dimensional mathematical model of fluid flow, heat flow, solidification, interdendritic strain and macrosegregation. Also, this part also contains the numerical simulations by using finite difference technique "FDT" to create convection patterns, heat transfer, interdendritic strain, and macrosegregation distributions. This part also includes comparisons between the available measurements and model predications as well as full discussion of different model simulations. The mechanism of interdendritic strain generation and macrosegregation formation during solidification of dendritic equiaxed structure under different diffusion mechanisms in dendritic solid has also been explained and discussed. Macrosegregation in dendritic equiaxed structure during the early stages of solidification of Al-4.5%Cu alloy has been studied experimentally. The metallurgical study includes macro-microstructure evaluation, measurements of grain size of equiaxed crystals, and macrosegregation analysis. In addition to the experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid.

The mathematical model of derived solute equations in part I for equiaxed dendritic solidification with melt convection streams and interdendritic thermo-metallurgical strain is applied numerically to predict macrosegregation distributions with different diffusing mechanisms in dendritic solid. Numerical and experimental results are present for solidification of a Al-4.5% Cu alloy inside horizontal rectangular cavity at different superheats. The numerical simulations were performed by using simpler method developed by Patanker. The experiments were conducted to measure the cooling curves via thermocouples and the metallurgical examinations to measure the grain size and macrosegregation distributions in Part I. Preliminary validity of the model is demonstrated by the qualitative and quantitative agreements between the measurements and predications of cooling curves and predicted macrosegregation distributions including mushy permeability and interdendritic strain. In addition, several important features of macrosegregation in equiaxed dendritic solidification are identified through this combined experimental and numerical study. Also, quantitative agreements between the numerical simulations and experiments reveal several areas for future research work. The differences and errors between predicted macrosegregation results under different diffusing mechanisms have been discussed. The mathematical model of derived solute equations in Part I for equiaxed dendritic solidification with melt convection streams and thermal is applied numerically to predict macrosegregation distributions with different diffusing mechanisms in dendritic solid. Numerical and experimental results are present for solidification of a Al-4.5% Cu alloy inside horizontal rectangular cavity at different superheats.