A Dissertation Submitted to Shanghai Jiao Tong University for the Masters Degree

摘要

Ohno连续铸造(OCC)过程中富集于凝固界面前沿的溶质的再分配形式是决定铸锭杂质含量的一个关键因素。因此，要获得高纯铸锭，有必要对OCC连铸过程中的质量传输进行控制。本文研究的目的就是确定OCC连铸时不同铸造速度情况下对熔体进行机械搅拌的方法和搅拌的强度。研究比较了在凸起的凝固界面前沿引入轴向和横向机械搅拌对溶质传输的影响，发现轴向搅拌可以有效地将凝固界面处富集的溶质输送到熔体深处；通过数值模拟确定了不同铸造速度下所需的轴向搅拌的强度；利用ANSYS Fluent12.1软件模拟计算了插入凝固界面前沿熔体中的碳化硅叶片产生的熔体流动对溶质传输的影响，发现，在OCC连铸中通过足够的机械搅拌可以在常规铸造速度下获得高纯铸锭。

目录

封面

声明

DECLARATION

中文摘要

英文摘要

目录

CHAPTER 1 INTRODUCTION

1.1 Background

1.2 Recent Advancements in Metal Purification during Solidification

1.3 Purpose/Scope

1.4 Problem Statement

1.5 Organization of Thesis

CHAPTER 2 LITERATURE SURVEY

2.1 A Brief Review of OCC Process

2.2 The Principle of OCC

2.3 The Separation Theory and OCC Process

2.4 OCC Process Variables and Their Effect

2.5 Local Scale Solute Transport \(Microsegregation Models\)

2.6 Melt Convection

2.7 Interface morphology and Stability

CHAPTER 3 NUMERICAL MODEL

3.1 Introduction

3.2 Phase Change Modeling

3.3 Governing Equations

CHAPTER 4 NUMERICAL SOLUTION SCHEME

4.1 Numerical Procedure

4.2 User Defined Functions:Overview

4.3 Modeling of Melt Stirring \(MRF model\)

4.4 Solution Algorithm

4.5 Implementation in Fluent

CHAPTER 5 DETERMINATION OF THE BEST STIRRING METHOD

5.1 Solution Procedure

5.2 Model and Solution

CHAPTER 6 DETERMINATION OF CRITICAL STIRRING INTENSITIES

6.1 Introduction

6.2 Solution Procedure

6.3 Experimental Results

6.4 Validation of Simulation Results with Literature

6.5 Case1:Numerical Simulation Results in Absence of Melt Convection

6.6 Solute Redistribution Behavior in Absence of Melt Convection

6.7 Computer Simulation Results in Presence of External Melt Stirring

CHAPTER 7 CONCLUSIONS

7.1 Summary of Contributions

7.2 Recommendations for Further Research/Scopes for Future Work

参考文献

Notations and Abbreviations

LIST OF TABLES

LIST OF FIGURES

致谢

APPENDICES