TY - BOOK

T1 - A study on macrosegregation in continuous casting of bronze

AU - Grasser, Monika

N1 - no embargo

PY - 2008

Y1 - 2008

N2 - Technical bronzes tend to form both macrosegregations and microsegregations during DC-casting, therefore a heterogeneous cast microstructure forms. The intensity of macrosegregation in DC-casting can effectively be influenced by casting parameters like casting velocity, primary cooling or inlet geometry which in fact change the relative flow between the melt and the forming solid. The aim of the presented work was to apply an already developed solidification model on continuous casting of technical bronze alloys. Since the thermodynamics of Cu-Sn-P is necessary as an input for the simulation of solidification, the ternary system has been studied by computational thermodynamics and experimental work. For the thermodynamic data input it was necessary to validate already published data. Therefore, DSC -measurements and diffusion experiments have been performed for the binary, Cu-Sn and Cu-P, and the ternary, Cu-Sn-P, systems. For the binary systems the performed DSC measurements confirm the already published phase diagrams. In the ternary system it is of special interest to define and confirm the ternary eutectic point which is thought to be responsible for specific rigidity changes in technical bronze alloys. The presented experimental work shows generally good agreement with already published phase diagrams and published numerical assessment work. In order to understand influence and interaction of the related flow phenomena during solidification, simulation methods are applied to 2D and 3D geometries. The first step was to apply, adapt, and further improve an already developed multiphase solidification model for continuous casting of bronze. For this the CFD software FLUENT was used in combination with UDFs. The solidification of the strand as well as the formation of macrosegregation are simulated with a two phase volume averaging model. Correspondingly, the velocity field of the melt flow is explicitly calculated by solving the momentum conservation equations. within the mushy zone. Based on the recent study, it was shown that strong flow locally in the mushy zone induces strong macrosegregation. In addition, an increase of mush premeability leads to a higher interaction of the flow with the mush and causes therefore changes in the solute distribution. It can be stated that microsegregation in combination with relative velocity between liquid and solid phase induces macrosegregation.

AB - Technical bronzes tend to form both macrosegregations and microsegregations during DC-casting, therefore a heterogeneous cast microstructure forms. The intensity of macrosegregation in DC-casting can effectively be influenced by casting parameters like casting velocity, primary cooling or inlet geometry which in fact change the relative flow between the melt and the forming solid. The aim of the presented work was to apply an already developed solidification model on continuous casting of technical bronze alloys. Since the thermodynamics of Cu-Sn-P is necessary as an input for the simulation of solidification, the ternary system has been studied by computational thermodynamics and experimental work. For the thermodynamic data input it was necessary to validate already published data. Therefore, DSC -measurements and diffusion experiments have been performed for the binary, Cu-Sn and Cu-P, and the ternary, Cu-Sn-P, systems. For the binary systems the performed DSC measurements confirm the already published phase diagrams. In the ternary system it is of special interest to define and confirm the ternary eutectic point which is thought to be responsible for specific rigidity changes in technical bronze alloys. The presented experimental work shows generally good agreement with already published phase diagrams and published numerical assessment work. In order to understand influence and interaction of the related flow phenomena during solidification, simulation methods are applied to 2D and 3D geometries. The first step was to apply, adapt, and further improve an already developed multiphase solidification model for continuous casting of bronze. For this the CFD software FLUENT was used in combination with UDFs. The solidification of the strand as well as the formation of macrosegregation are simulated with a two phase volume averaging model. Correspondingly, the velocity field of the melt flow is explicitly calculated by solving the momentum conservation equations. within the mushy zone. Based on the recent study, it was shown that strong flow locally in the mushy zone induces strong macrosegregation. In addition, an increase of mush premeability leads to a higher interaction of the flow with the mush and causes therefore changes in the solute distribution. It can be stated that microsegregation in combination with relative velocity between liquid and solid phase induces macrosegregation.

KW - Macrosegregation

KW - continuous casting

KW - bronze

KW - copper

KW - solidification

KW - thermodynamics

KW - diffusion experiments

KW - Thermodynamik von Bronze

KW - Kupfer

KW - Bronze

KW - Strangguss

KW - Modellierung von Erstarrung

KW - Erstarrungssimulation

KW - Diffusionsexperimente

M3 - Doctoral Thesis

ER -