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The new book “Vacuum Arc Remelting Ingot” by Felix Shved is published. The book is based on author’s experience in formation and advance of VAR process during 50 years. You may order the book. The details and chapter 7 “Defects of vacuum arc remelting ingot” are at page «“Library”. [Rus., captions are dubbed in English]

CONTENTS

Introduction...6
Chapter 1. Methods of steel ingots production (short review)...11
1.1. Evolution of steel melting and pouring modes...11
1.2. Special means of ingot production...14
Chapter 2. Operating principle and equipment of vacuum arc furnaces. Consumable electrodes ...24
2.1. Electric discharge in the rarefied metallic vapor – energy source at VAR ...24
2.1.1. Base peculiarities of direct current vacuum arc...25
2.1.2. Voltage dependence on current and arc length. Current-voltage characteristic analysis...31
2.1.3. Factors influencing the arc stability...50
2.2. Arrangement of vacuum arc furnace...53
2.2.1 Demands to the power supply...55
2.2.2. Demands to the vacuum-pumping system...56
2.2.3. Current circuit construction, its influence on the magnitude of magnetic fields in the melt area...59
2.2.4. Modern systems of VAR process automatic control...65
2.2.5. Some features of separate components of modern VAR furnaces ...71
2.3. Consumable electrode...74
2.3.1. Chemistry peculiarities of primary metal intended for subsequent VAR...75
2.3.2. Modes of electrode production...75
2.3.3. Demands to the form and diameter. Peculiarities of structure of the cast electrode...76
2.3.4. Demands to the electrode surface...81
Chapter 3. Melt process at the vacuum arc remelt...82
3.1. Heating of consumable electrode...82
3.2. Mean and instant values of melt rate...99
3.3. Modes of melt rate measurement...100
3.4. Electrode diameter and current influence on the mean value of the melt rate...106
3.5. Influence of current polarity....110
3.6. Influence of steels and alloys chemistry...112
3.7. Melt rate periodical fluctuations at VAR of the cast electrodes...115
3.8. Influence of arc stability disturbances...124
3.9. Transients at the changes of current, arc length and electrode diameter...126
Chapter 4. Processes in the liquid part of VAR ingot...134
4.1. Liquid pool form. Pool fixation modes...134
4.2. Liquid pool temperature. Measurement technique. Influence of current and ingot diameter...143
4.3. Evaporation of impurities, elimination of gases and inclusions...151
4.3.1. Common relationships...151
4.3.2. Elimination of gases and inclusions...155
4.3.3. Evaporation of components with high vapor pressure...168
Chapter 5. Heat exchange in the mold and heat balance of the VAR process...194
5.1. Investigation of the heat fluxes through the mold wall and the bottom plate...194
5.2. Heat balance of the VAR process...210
5.3. Influence of mold diameter and helium input in the gap on the heat balance of the large VAR ingot...219
5.4. Evaluation of heat transfer coefficient from ingot side surface to the mold ...224
5.5. Liquid-metal cooling – myth or a reality?... 230
5.6. On the possibility of application of the heat balance information at the VAR-process control...232
Chapter 6. Metal solidification at the vacuum arc remelt...236
6.1. Common relationships of solidification...236
6.1.1. Binary system diagram. Possibilities and limits of diagrams application...238
6.1.2. Plane boundary and criterion of its stability...241
6.1.3. Types of crystalline structure of alloys. Is it possible to reveal the plane boundary in real ingots?...245
6.1.4. An axis or a plate? Of which elements consists really dendrite?...253
6.1.5. Mushy zone. Solidification start and end temperature. Measurement of the real (non-equilibrium) solidus temperature...257
6.2. Peculiarities of the ingot formation in the remelt process. Directional solidification...260
6.2.1. Linear rate of solidification. Time of crystallization (local solidification time)...261
6.2.2. Factors influencing the crystalline structure dispersion...266
6.2.3. Dendrite cell. Dendrite chemical ingomogenity. Forming of nonmetallic inclusions at solidification...285
6.2.4. Periodicity of crystallization...289
Chapter 7. Defects of vacuum arc remelting ingots...298
7.1. Segregation defects of VAR ingot...298
7.1.1. Freckles...299
7.1.2. Radial segregation...310
7.1.3. Light-coloured contour and its connection with remelt regime and pool form...322
7.2. Exogenous defects...328
7.2.1. Light spots...328
7.2.2. Crown (“spiral”)...330
7.2.3. White spot...334
7.2.4. Slag crust...349
7.2.5. Gas bubbles...369
Chapter 8. Steel and alloys properties, remelted by VAR process...377
8.1. Strain resistance and deformability of Ni-base superalloys...377
8.1.1. On the strain resistance of superalloys...378
8.1.2. Effect of VAR on deformability of superalloys...381
8.2. Mechanical properties of VAR remelted structural steel...395
8.2.1. Comparison of mechanical properties of steel melted in electric arc furnaces and remelted by VAR process...395
8.2.2. Comparison of special properties of structural steel melted by various processes...403
Conclusion...416
References...421