1 A Brief Review of Inclusions in AI Deoxidized Steel 1.1 Classification of Inclusions 1.2 Fatigue Defects Initiated by Inclusions 1.3 Influence of Refining Slag on Steel Cleanliness and Control of Inclusions 1.3.1 Chemical Reactions Among Slag-Steel-Inclusions 1.3.2 Influence of Slag Compositions on Steel Cleanness 1.3.3 Influence of Slag Compositions on the Control of Inclusions 1.4 Control of Calcium Magnesia Aluminate Inclusions in Steel 1.4.1 Influence of Calcium Treatment on the Control of Inclusions 1.4.2 Influence of Slag-Steel Reaction on the Control of Inclusions References 2 Formation of Spinel Inclusions in HSLA Steel Refined by CaO-SiO2-Al203-MgO Slag 2.1 Slag-Steel Reaction Experiments in Lab 2.1.1 Determination of Reaction Time by Pre-equilibrium Experiments 2.1.2 Slag-Steel Reaction Experiments 2.2 Results and Discussion 2.2.1 Determined Reaction Time Between Steel and Slag 2.2.2 Inclusions in Steel Melts 2.2.3 [AI]-[O] Deoxidation Equilibrium 2.2.4 Saturation Behavior of MgO in Slag 2.2.5 Chemical Reaction Equilibrium Among Slag-Steel-Spinel Inclusion 2.2.6 Calculation on Stability Phase Diagram of MgO-MgO·Al203-Al203 2.3 Summary References 3 Formation Thermodynamics of Inclusions in Al Deoxidized Low Alloy Steel 3.1 Fundamental Data Related to Calculation 3.1.1 Chemical Compositions of Steel 3.1.2 Fundamental Thermodynamic Data 3.2 Formation Thermodynamics of Inclusions 3.2.1 Chemical Reaction Equilibrium Between Steel and CaO-SiO2-Al203 System 3.2.2 Chemical Reaction Equilibrium of Steel and CaO-SiO2-Al2O3-MgO System 3.2.3 Formation of Low Melting Point Calcium Magnesia Aluminate Inclusions 3.3 Summary References 4 Slag-Steel Reaction and Control of Low-Melting-Point Inclusions in Al-Deoxidized Steel 4.1 Slag-Steel Reaction Experiments in Lab 4.1.1 Preparation of Steel and Slag Materials 4.1.2 Experimental Procedures 4.2 Determination of Slag-Steel Reaction Time 4.3 Control of Inclusions in Steel Refined by High Basicity High Alumina Slag A 4.3.1 Chemical Compositions of Steel and Slag 4.3.2 Non-metallic Inclusions in Steel 4.4 Control of Inclusions in Steel Refined by High Basicity High Alumina Slag B 4.4.1 Chemical Compositions of Steel Samples and Slag Samples 4.4.2 Non-metallic Inclusions in Steel 4.5 Effects of Al2O3 Contents in High Basicity High Alumina Slag on the Control of Inclusions 4.5.1 Comparison on Chemical Compositions of Refining Slag 4.5.2 Comparion on Steel Cleanness 4.5.3 Comparison on Non-metallic Inclusions 4.6 Summary 5 Formation and Evolution Mechanisms of Inclusions in Steel 5.1 Variations of Inclusions with Reaction Time 5.1.1 Influence of Reaction Time on the Sizes of Inclusions 5.1.2 Influences of Reaction Time on the Chemistry of Inclusions 5.1.3 Characterization on the Features of Inclusions at Different Reaction Time 5.2 Descriptions on the Evolutions of Inclusions 5.3 Evolution Mechanisms of Inclusions 5.3.1 Concentration Gradients of Elements in Inclusions 5.3.2 Model Estabishment on the Evolution of Inclusions 5.4 Summary References 6 Influence of Refractory Material on the Formation Low-Melting-Point Inclusions 6.1 Laboratorial Experiments 6.1.1 Experimental Procedures 6.1.2 Chemical Analysis and Characterization of Inclusions 6.2 Cleanness and Non-metallic Inclusions in Steel 6.2.1 Steel Composition and Slag Composition 6.2.2 Observation of Inclusions 6.2.3 Formation Thermodynamics of CaO-Al2O3-ZlO2 Inclusions 6.2.4 Effects of ZrO2 Crucible on the Formation of Low Melting Point Inclusions 6.3 Summary References 7 Prevention of CaO-Contained Inclusions in Steel During the Basic Slag Refining 7.1 Considerations on Inclusion Forma