basics and applications of induction furnaces
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FurnacesTRANSCRIPT
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 1
Technical basics and applications of induction furnaces
Prof. Dr.-Ing. Egbert Baake Institute of Electrotechnology
Leibniz University of Hanover (Germany)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 2
Introduction Fundamentals and application of the induction
crucible furnace Fundamentals and application of the induction
channel furnace Other industrial induction melting applications
Outline
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 3
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, carburization process) Avoiding of erosion and clogging of the ceramic lining Avoiding of melt instabilities, splashing or pinching Intensive stirring for cleaning of the melt (zinc removing)
Optimisation of the heat and mass exchange in the melt
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 4
magnetic field - distribution of power - electromagn. forces geometry of melt
velocity field homogenisation of melt
temperature field
meniscus shape
- overheating - heat flow
skull formation liquid-solid-interface
Physical correlations in induction furnaces
alloy composition melt components
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 5
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
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 6
Construction of induction crucible furnace
melt
steel- construction
concrete-ring
meniscus
melt flow
crucible
induction coil
magnetic yoke
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 7
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
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 8
Example: Induction crucible furnace
melt
steel- construction
concrete-ring
meniscus
melt flow
crucible
induction coil
magnetic yoke
Height of meniscus is proportional to:
Velocity v of the melt is proportional to the inductor current I: v ! I
Velocity v of the melt is proportional to:
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 9
Spec. kinetic energy of turbulence:
k = ½ (v´x12 + v´x2
2 + v´x32)
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
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 10
3D hydrodynamic model of an industrial induction crucible furnace
P = 4540 KW
Hind = 1.33 m
Rcr = 0.49 m
Filling level 90 %
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 11
Calculation of the melt flow velocity in the ICF: (3D transient LES)
symmetric state unsymmetric state
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 12
Calculation of the melt flow velocity in the ICF: Melt surface (3D transient LES)
calculated time: 5 sec calculated time: 40 sec
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 13
Example of medium frequency induction crucible furnace: 12 t/9,3 MW/250 Hz
source: ABB Industrietechnik AG
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 14
MF-ICF-melting installation with two furnaces: 12 t, 9,3 MW/250 Hz
Source: ABB
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 15
Induction crucible furnace installation for melting of grey cast iron
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 16
Induction craucible furnace during pouring
Medium frequency-ICF
Capacity: - 6 t grey cast iron
Power: - 3300 kW/250 Hz
Quelle: ABB Industrietechnik AG, Dortmund
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 17
Induction crucible furnace: capacity 8 t grey cast iron with charging vehicle
Source: ABB Industrietechnik AG
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 18
Back tilt position of an ICF for 8 t grey cast iron during slag cleaning process
Source: ABB Industrietechnik AG
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 19
Induction crucible furnace (ICF): Advantages in comparison with competitive processes
Homogenisation of the melt due to stirring of the melt
Less oxidation losses (dross) because no local overheating
High accurate alloying process
Well defined melt temperature
Simple automatic process control
High quality of the melt even with cheap charge material (scrap)
High throughput because fast melting and fast heating up of the melt
High furnace efficiency
Simple handling of the furnace and the process
Well defined controlling of the power input
Good working conditions for the workers at the furnace
Environmental friendly (small dust emission, no exhaust gas)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 20
Induction crucible furnaces melting material, capacities, power rates, frequencies
Material Capacities [t]
Power rates [MW]
Frequencies [Hz]
LF-furnaces:
Cast iron, steel 1,3 ... 100 0,5 ... 21 50 ... 60
Light metal 0,5 ... 15 0,2 ... 4 50 ... 60
Heavy metal 1,5 ... 40 0,5 ... 7 50 ... 60
MF-furnaces:
Cast iron, steel 0,25 ... 30 0,3 ... 16 150 ... 1000
Light metal 0,1 ... 8 0,2 ... 4 90 ... 1000
Heavy metal 0,3 ... 70 0,3 ... 16 65 ... 1000
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 21
Charging of line-frequency induction crucible furnace
heal starting blocks
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 22
Energy supply of induction crucible furnaces
a) LF-Energy supply via switching transformer b) MF-Energy supply via converter
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 23
Energy flow diagramm of a MF induction crucible
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 24
Parallel operation of two ICF
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 25
Design of a melt processor control system
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 26
Melt processor with operator
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 27
Melt processor main menu
- sintern
- starting with
cold crucible
- melting
- overheating
- holding
- crucible wear
detection
Operation modes:
Source: ABB Industrietechnik AG
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 28
Induction channel furnace (one loop design)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 29
Channel inductor (ABP): - single loop - P = 250 kW - symmetrical channel
Design of a single loop induction channel furnace
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 30
Dopple loop induction channel furnace
Source: ABB Industrietechnik GmbH Dortmund
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 31
Melting in the induction channel furnace
Homogenisation of the entire melt
Sufficient overheating of the entire melt
Avoiding of overheating of the melt in the channel
Efficient heat and mass exchange between the channel and the furnace vessel is the key point
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 32
Melt flow in a model single loop induction channel furnace (measurements)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 33
3D-Simulation model for electromagnetic calculation of the channel inductor
(power density and electromagnetic force density)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 34
Channel inductor: distribution of power density in the melt
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 35
Channel inductor: distribution of electromagnetic force density
Parameters:
P = 60 kW I = 850 A
Melt: Wood-metal
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 36
Channel inductor: distribution of elektromagnetic force density
Parameters: P = 60 kW I = 850 A
Measured Melt flow distribution
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 37
Line frequency induction channel furnace used for storing, holding and pouring of cast iron
Quelle: ABB Industrietechnik AG
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 38
CIF used in non-ferrous metal industry (aluminium foundry)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 39
CIF used in non-ferrous metal industry (aluminium foundry)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 40
Source: ABB Industrietechnik AG
CIF installation used in non-ferrous metal industry (aluminium foundry)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 41
Channel inductor for melting of copper and brass
• power: 2400 kW
• frequency50...70 Hz
• mass:15 t
Quelle: ABB Industrietechnik GmbH Dortmund
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 42
Induction channel furnace melting material, capacities, power rates, frequencies
Melting materials Capacities [t]
Power rates [MW]
Frequencies [Hz]
Cast iron 10 ... 135 0,1 ... 3 50 ... 60
Aluminium, Al-alloys 5 ... 70 0,1 ... 6 50 ... 60
Copper, Co-alloys 5 ... 160 0,5 ... 10 50 ... 60
Zinc, Zinc-alloys 10 ... 100 0,2 ... 10 50 ... 60
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 43
Energy flow diagram of an induction channel furnace
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 44
Comparison: induction crucible vs. induction channel furnace
Crucible furnace Channel furnace
application melting, holding, all metal materials
Holding, melting, all metal materials
Melting rate (power) high (MF) medium
Meltíng process heal, scrap pieces Heal
Furnace volume medium big
Lining live time good vessel very good, Channel sufficient
Efficiency sufficient high
Operating frequencies 50 ... 1000 Hz 50 ... 60 Hz (60 ... 120 Hz)
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 45
Design of a pressure controlled pouring installation with induction heating
1 pressure vessel with melt 5 output valve 2 channel inductor 6 melt level controlling 3 input spout 7 main frame with rolls 4 output spout 8 casting mould
Source: RWE-Information Prozesstechnik
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 46
Induction pouring installation 10 t, 500 kW
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 47
Induction pouring installation Presspour®, 2,5 t, 130 kW
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 48
Holding processor for channel furnaces
Quelle: ABB Industrietechnik AG
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 49
Clogging, erosion and infiltration of the ceramic lining of the channel inductor influenced by e.g.:
Heat transfer and temperature distribution in the channel
Mass transfer in the channel and in the vessel
Type of alloy (purity)
Type of ceramic lining
and many others …
Clogging and erosion of a channel inductor used for holding of grey cast iron
Practical problems: induction channel furnace
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 50
Holding processor for channel furnaces Inductor-diagram
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 51
Crucible inductor furnace
Industrial applications: Comparison with induction channel furnace: • holding and casting of grey cast iron + flexible operation,energy saving, easier to clean • melting and holding of non-ferrous metal due to complete emptying • reduction process in steel industry – but: lower efficiency
Experimental furnace Industrial furnace for casting of grey cast iron
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 52
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
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 53
Melting in the Induction Furnace with Cold Crucible
high reactive and high purity materials, e.g. TiAl
melting, alloying, over- heating and casting in one process
no pre-alloys necessary, using of scrap material
good homogenisation of the melt due to intensive electromagnetic stirring
Prof. Dr.-Ing. E. Baake / Institute of Electrotechnology, Leibniz University of Hannover 54
Cold crucible induction skull melting process
inductor
crucible
vacuum chamber
High reactive and high purity materials, e.g. TiAl
Melting, alloying, over- heating and casting in one process