Physical and technical basics of induction melting processes
3 likes2,430 views
The document discusses the physical and technical principles of induction melting processes, emphasizing multifunctional applications and industrial requirements such as mixing, homogenization, and efficiency. It provides insights into the operational mechanisms of induction furnaces, various simulation techniques, and the benefits of advanced technologies like induction skull melting and electromagnetic levitation melting. The presentation concludes with a summary highlighting the advantages of induction melting, including high quality, efficiency, and environmentally friendly processes.
![E. Baake: 12-05-2016
23
Time-averaged flow pattern [m/s] (3D-transient LES)
P = 4 540 KW
Hind = 1.33 m
Rcr = 0.49 m
3D hydrodynamic model of an industrial
induction crucible furnace melting cast iron](https://image.slidesharecdn.com/baake-epm16-webinar-presentation-190619064214/85/Physical-and-technical-basics-of-induction-melting-processes-23-320.jpg)
![E. Baake: 12-05-2016
24
Cross-section of the transient
melt flow [m/s]
3D transient simulation of the melt flow of an industrial
induction crucible furnace using LES model
Length-section of the transient
melt flow [m/s]](https://image.slidesharecdn.com/baake-epm16-webinar-presentation-190619064214/85/Physical-and-technical-basics-of-induction-melting-processes-24-320.jpg)
Physical and technical basics of induction melting processes
- 1. E. Baake: 12-05-2016 EPM Academy Webinar May 12, 2016 1 Physical and technical basics of induction melting processes Egbert Baake Institute of Electrotechnology Leibniz University of Hannover Hannover / Germany
- 2. E. Baake: 12-05-2016 2 Outline Introduction Physical principles of induction melting Electromagnetic shaping and stirring Process simulation Power balance and efficiency Classical applications New developments Conclusions
- 3. E. Baake: 12-05-2016 3 Induction Melting: Multifunctional Applications
- 4. E. Baake: 12-05-2016 4 Industrial process requirements for melting in induction furnaces Mixing and homogenisation of the entire melt Homogenisation of the temperature, avoiding of local overheating, but realizing of sufficient superheating of the entire melt Intensive stirring at the melt surface (melting of small-sized scrap) Avoiding of erosion and clogging of the ceramic lining Avoiding of melt instabilities, splashing or pinching Intensive stirring for cleaning or degassing of the melt
- 5. E. Baake: 12-05-2016 5 Why induction technologies for melting processing solutions? Heat can be generated within the material High energy density and fast processing if required High temperature if required Homogeneous temperature distribution in the melt High efficiency Low specific energy consumption High reliability Low thermal inertia Less environmental impact Clean melting in any atmosphere Electromagnetic stirring High level of automation Reproducible process conditions Good integration in the production line Electromagnetic processing High reliability Electromagnetic shaping
- 6. E. Baake: 12-05-2016 electro- magnetic field velocity field temperature field free surface shape liquid-solid interface Physical correlations in induction melting processes processes alloy composition non-linear material properties 6
- 7. E. Baake: 12-05-2016 7 Principle of induction heating Example: Induction heating of a tube Source: RWE-Information Induktive Erwärmung Principle of induction heating Eddy currents
- 8. E. Baake: 12-05-2016 J: Stromdichte J 8 Current density distribution in a cylindrical workpiece (approximation) Electromagnetic penetration depth Source: RWE-Information Induktive Erwärmung Current density distribution and skin effect With: ρ = spec. electrical resistance μ = permeability f = frequency J: current density
- 9. E. Baake: 12-05-2016 melt steel- construction concrete-ring meniscus melt flow crucible induction coil magnetic yoke 9 Induction furnaces for melting Induction crucible furnace Induction channel furnace Used mainly for melting Medium high efficiency Operating frequency: 50 ... 1000 Hz Used mainly for holding and pouring High efficiency Operating frequency: 50 Hz, 60 Hz Source: RWE-Information Prozesstechnik thermal isolation magnetic yoke inductor channel furnace vessel refractory melt induction coil
- 10. E. Baake: 12-05-2016 10 Scheme of an induction crucible furnace melt steel- Construction meniscus melt flow crucible induction coil magnetic yoke
- 11. E. Baake: 12-05-2016 11 Example of medium frequency induction crucible furnace: 12 t/9,3 MW/250 Hz source: ABB Industrietechnik AG
- 12. E. Baake: 12-05-2016 12 Meniscus shape and melt flow of the crucible induction furnace
- 13. E. Baake: 12-05-2016 13 Meniscus shape and melt flow of the crucible induction furnace Inductor current: J1
- 14. E. Baake: 12-05-2016 14 Meniscus shape and melt flow of the crucible induction furnace Magnetic field: B Inductor current: J1
- 15. E. Baake: 12-05-2016 15 Meniscus shape and melt flow of the crucible induction furnace Magnetic field: B Inductor current: J1 Induced current density in the melt:J2
- 16. E. Baake: 12-05-2016 16 Meniscus shape and melt flow of the crucible induction furnace Magnetic field: B Inductor current: J1 Induced current density in the melt:J2 Electromagnetic force density: F = J2 x B
- 17. E. Baake: 12-05-2016 17 Meniscus shape and melt flow of the crucible induction furnace Magnetic field: B Inductor current: J1 Induced current density in the melt:J2 Electromagnetic force density: F = J2 x B Melt flow pattern
- 18. E. Baake: 12-05-2016 18 Spec. kinetic energy of turbulence: k = ½ (v´x1 2 + v´x2 2 + v´x3 2) local melt flow velocity in dependence on time Shared in: 1. Time averaged flow velocity convective heat and mass transfer 2. Instationary fluctuations and oscillations turbulent heat and mass transfer Characteristics of turbulent flow in induction furnaces Vmax ≈ 20 cm/s
- 19. E. Baake: 12-05-2016 19 Influence of power and frequency on the melt movement melt steel- construction concrete-ring meniscus melt flow crucible induction coil magnetic yoke Velocity v of the melt flow is proportional to the inductor current I: v ~ I for const. frequency f and therefore proportional to the square root of the spec. power in the melt PS: for const. frequency fSPv~ The height of the meniscus: fPKh SÜ ⋅= Melt flow velocity v is proportional to: 0,4 S f1Pv ⋅~
- 20. E. Baake: 12-05-2016 20 Meniscus shape and melt flow in dependence on the filling level filling level 80% filling level 100% filling level 120% filling level: height of the melt when power is switched off relating to the upper end of active coil
- 21. E. Baake: 12-05-2016 Numerical simulation approach r << λEM Harmonic EM field Alloy shape Alloy HD movement Secondary EM field Steady part of EM force is calculated for fixed free surface shape Volume of Fluid numerical technique for calculation of two-phase fluid hydrodynamics. VF = 0 – phase #1 (air); VF = 1 – phase #2 (melt); 0 < VF < 1 – free surface intersects mesh element. Unsteady Reynolds Averaged Navier Stokes equation for incompressible fluid with k – ω SST isotropic turbulence description and 0 ( ) 0 ef ef ROT B B f µ ⋅∇ ⋅ = 2 2 HD v p ρ= 0 0Rem r vσµ= 0 2 EMδ µ σω = 2 0 04 EM B p µ = qvol = 0 FEM – Ansys Classic FVM – FLUENT and CFXReciprocal interaction Rem << ω ˄ 21
- 22. E. Baake: 12-05-2016 RANS (k-ε model) • Whole energy spectrum is modelled • Relatively low mesh resolution requirements • Steady-state simulations Direct Numerical Simulation (DNS) • All scales are resolved directly • Very high requirements for computational resources • Simulations of industrial installations are impossible Large Eddy Simulation (LES) • Large scales are resolved directly while only small scales are modelled • Relatively high mesh resolution requirements • Transient 3D simulations CFD problem Re ≥ 104 Numerical simulation of CFD problems Mesh 22
- 23. E. Baake: 12-05-2016 23 Time-averaged flow pattern [m/s] (3D-transient LES) P = 4 540 KW Hind = 1.33 m Rcr = 0.49 m 3D hydrodynamic model of an industrial induction crucible furnace melting cast iron
- 24. E. Baake: 12-05-2016 24 Cross-section of the transient melt flow [m/s] 3D transient simulation of the melt flow of an industrial induction crucible furnace using LES model Length-section of the transient melt flow [m/s]
- 25. E. Baake: 12-05-2016 25 Inductor efficiency of a cylindrical arrangement of inductor and workpiece as function of workpiece diameter to penetration depth ratio Source: RWE-Information Induktive Erwärmung Electrical efficiency of induction crucible furnace steel 20°C, μr=100, ρ=0.13 steel 400°C, μr=30, ρ=0.45 graphite 200…1000°C, ρ=10 steel 1000°C, μr=1, ρ=1.2 stainless steel 900°C, μr=1, ρ=1.2 stainless steel 20°C, μr=1, ρ=0.8 aluminium 100°C, ρ=0.038 copper 100°C, ρ=0.022 workpiece diameter / penetration depth
- 26. E. Baake: 12-05-2016 26 75% 4700 kW 390 kWh/t 1% 60 kW 15% 940 kW 1,5% 95 kW 3% 190 kW 1,5% 95 kW 100% 6270 kW 520 kWh/t 3% 190 kW Trans- former Converter Capacitor bus bars Induction coil Furnace Construction Heat Losses Energy balance for a medium frequency (MF) induction crucible furnace for melting of grey cast iron (example)
- 27. E. Baake: 12-05-2016 27 Induction channel furnace: main features Joule heat and Lorentz forces are generated in the melt of the inductor channel heat transport from the inductor channel to the furnace vessel is important thermal isolation magnetic yoke inductor channel furnace vessel refractory melt induction coil Primary and secondary current
- 28. E. Baake: 12-05-2016 28 3D electromagnetic and fluid-dynamic model for ICF (examples) ~ 0.8 m throat Iron yoke induction coil channel cooling shield electromagnetic model fluiddynamic model channel vessel inductor throat
- 29. E. Baake: 12-05-2016 Distribution of the electromagnetic force density and melt flow in the cross section of the channel 29 EM-force density Time averaged melt flow distribution
- 30. E. Baake: 12-05-2016 30 Kraftdichteverteilung Melt flow (Simulation)Melt flow (Measurement) Distribution of the electromagnetic force density and melt flow in the cross section of the channel
- 31. E. Baake: 12-05-2016 31 3D-simulation of the melt flow velocity in the induction channel furnace
- 32. E. Baake: 12-05-2016 Channel of a double loop induction channel furnace for melting of copper after solidification of the melt 32 „Solidified“ flow eddies structure Complete channel Part of the channel
- 33. E. Baake: 12-05-2016 3D transient result of the temperature distribution 33 Original design with symmetrical channel: power: 240 kW Overheating ΔT: 50 K
- 34. E. Baake: 12-05-2016 34 melt with meniscus shape crucible segment inductor bottom slit skull current melt flow EM-forces heat conduction radiation (water cooled) (water cooled) (water cooled) Features of the Induction Furnace with Cold Crucible slitted crucible to realize efficient electromagnetic transparency free melt surface and intensive melt stirring, based on electromagnetic forces water cooled bottom and crucible segments leads to solid layer (skull) heat losses by radiation and conduction depending on the meniscus shape
- 35. E. Baake: 12-05-2016 35 Melting in the Induction Furnace with Cold Crucible (IFCC) High reactive and high purity materials, e.g. TiAl Melting, alloying, over- heating and casting in one process Good homogenization of the melt caused by electromagnetic stirring Overheating temperature is the key-parameter of the process
- 36. E. Baake: 12-05-2016 36 Principle of induction skull melting technology Intensive cooling of inductor and bottom formation of a skull skull protects against impurities layer of initial material water-cooled inductor skull melt water-cooled bottom magnetic field Advantages of induction skull melting High process temperatures High power density High purity of the melt and the final product High efficiency Process can be realized in different gas atmospheres or in vacuum Compact melting equipment
- 37. E. Baake: 12-05-2016 37 Electromagnetic levitation melting (ELM) Features: • contactless melting process • no reaction with crucible • high purity of the molten material • high temperature of the melt • high efficiency • mixing and homogenization of the melt • defined fast solidification due to maximal under cooling of the melt is possible Applications: • precision casting of special alloys • medicine and dental applications, e.g. implantats • aeronautics, e.g. precision casting components • investigation of new material compositions • determination of material properties • investigations of under-cooled melts
- 38. E. Baake: 12-05-2016 New setup for EM-levitation melting Ief = 1.1 kA, f1 = 30 kHz, f2 = 40 kHz Yoke: μr = 5000, Bef < 250 mT Horizontal magnetic fields generated by two pairs of induction coils with different frequencies Magnetic flux guiding system 500 g 38
- 39. E. Baake: 12-05-2016 39 Time-averaged flow v, m/s Supporting Lorentz force forms a single torroidal vortex with an upward directed flow on the z-axis
- 40. E. Baake: 12-05-2016 EM levitation melting of aluminum sample m = 500 g 40
- 41. E. Baake: 12-05-2016 41 Induction melting processes – Summary melt homogenisation due to melt stirring small material losses because no local overheating exact adjustment of the alloy composition exact temperature control easy automatic process control high quality of the melt high throughput due to fast heating up speed high furnaces efficiency relatively simple handling good energy control friendly working conditions environmental friendly (small emission of dust, no exhaustion gas) new future oriented technologies, like skull melting and levitation melting
- 42. E. Baake: 12-05-2016 42 Thank you very much for your attention!