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Copyright ©2003 by Consarc Corporation
VVACUUM ACUUM CAPCAP FURNACE FURNACE
VACUUM CAP VACUUM CAP FURNACES FURNACES
PROCESSING METALS PROCESSING METALS UNDER VACUUM IN UNDER VACUUM IN
LIQUID STATELIQUID STATE
P.D.ChaubalInductotherm (India) Pvt. Ltd.
Copyright ©2003 by Consarc Corporation
WHAT IS WHAT IS VVACUUM?ACUUM?
• ATMOSPHERIC PRESSURE 1000 MBAR• TOP OF MOUNT EVEREST 650 MBAR• 50 MILES UP 10-3 MBAR (0.001mbar)• 100 MILES UP 10-6 MBAR• 300 MILES UP 10-8 MBAR • 500 MILES UP 10-10 MBAR
• Exposing liquid metal to a vacuum in the ranges of 10-1 -10-3 mbar (one millionth of an atmosphere) will create a significant removal of dissolved gasses and prevent pick up from atmosphere. The key benefit of vacuum melting.
• Thankfully we don’t have to go 50miles up!! These pressure levels are easily achieved with industrial vacuum pumping systems.
Copyright ©2003 by Consarc Corporation
WHY BOTHER WITH WHY BOTHER WITH VVACUUM?ACUUM?
THE SIMPLISTIC VIEW
• Atmospheric air contains Nitrogen, Oxygen and Water Vapour (a source of Hydrogen)
• Unfortunately all these elements usually have an undesirable effect on metals during melting and casting
• Oxygen and Nitrogen react with metallic elements in the molten metal to differing degrees and give rise to inclusions in our castings
• Hydrogen can have a very negative effect on the mechanical properties of castings – embrittlement
• Trapped gases cause porosity
Exposing liquid metal to a vacuum can remove dissolved gases in the molten state to lessen the effects mentioned above
Copyright ©2003 by Consarc Corporation
VIM & VACUUM CAPVIM & VACUUM CAP
VIMVIM
VACUUM INDUCTION MELTINGVACUUM INDUCTION MELTING
VAC CAPVAC CAP
VACUUM INDUCTION VACUUM INDUCTION DEGASSINGDEGASSING
Copyright ©2003 by Consarc Corporation
VIM & VACUUM CAPVIM & VACUUM CAPVIM PROCESS DEFINITIONVIM PROCESS DEFINITION
Melting , refining and pouring in a high vacuum environment (<20 microns 0.02 mbar), using induction melting.
Pouring into static ingot molds in vacuum or a controlled “backfill” of inert gas.
COMPLETE CYCLE UNDER VACUUM
Ingots produced may be used for direct forging, as electrodes for remelting or as master alloys for investment casting / precision casting.
Melt and mix of selected raw materials / scrap in batch sizes of less than 2kg to 30 Tonnes.
Copyright ©2003 by Consarc Corporation
VIM & VACUUM CAPVIM & VACUUM CAPVIM PROCESS DEFINITIONVIM PROCESS DEFINITION
Remove oxygen to low levels by vacuum carbon de-oxidation.
Reduce levels of low vapor pressure contaminants like lead, bismuth, tin, antimony.
Reduce levels of dissolved gases like hydrogen and (limited) nitrogen.
Reduce sulphur level (limited).
Usually a slag free operation.
Suitable for melting and casting metals with high reactive alloy contents e.g Nickel based super alloys containing Ti
Ideally suited to high quality, clean alloy production
Copyright ©2003 by Consarc Corporation
VIM & VACUUM CAPVIM & VACUUM CAPVACUUM CAP DEFINITIONSVACUUM CAP DEFINITIONS
• Melting normally in air from solid or liquid charge (could be vacuum or controlled atmosphere if required)
• Refining in a moderate vacuum environment 1000 – 100 microns (1-0.1mbar), using induction melting
• Pouring in air (or controlled atmosphere if required as an option)
Reaches a product range between traditional Air melt and VIM
Copyright ©2003 by Consarc Corporation
VACUUM CAP DEFENITIONSVACUUM CAP DEFENITIONS
• Vacuum degassing (hydrogen and nitrogen removal) not as deep degassing as VIM procedure
• Reduction of low vapour pressure tramp elements e.g.Pb, Cd, Bi, Zn
• Deoxidation using combination of vacuum and C-O reaction
• Decarburisation - Intensified C-O reaction at low pressure enabling excellent decarburization for extra low carbon levels.
• Desulphurisation – use of reducing slags and / or powder injection in air or controlled atmosphere
• Melt and mix of selected raw materials / scrap in batch sizes of typically 80kg to 20T
Several benefits of VIM are retained in VCAP plus added flexibility for desulphurisation etc
Copyright ©2003 by Consarc Corporation
80kg - 20T Steel shell fce adapted for vacuum Connected to vacuum pumping system
Water cooled vacuum lid (cap)
Sight glassesViewing or pyro
Port for small charger , sampling, ITC
Apron section with vacuum sealing flange
Copyright ©2003 by Consarc Corporation
Applications and Materials The VCAP furnaces are available to suit a wide variety of melting application in sizes ranging from 80kg – 20Tonnes (other sizes available on request). Typical applications might include:
•Low and high carbon steels
•Tool and Die Steels
•Stainless Steels
•Nickel based alloys
•Cobalt based alloys
•Non Ferrous alloys
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Induction furnace with Induction furnace with shell prepared and shell prepared and sealed for vacuum sealed for vacuum
operation operation
Melt down Melt down
Lid off in air Lid off in air
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Degas under vacuum Degas under vacuum lid on lid on
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Pour - lid offPour - lid off
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Inductotherm Inductotherm Dual Dual Voltage VIP power Voltage VIP power
supply for optimum air supply for optimum air and vacuum melting and vacuum melting
efficiencyefficiency
In Air its just as efficient In Air its just as efficient as a normal airmelt as a normal airmelt
systemsystem
Lower voltage Lower voltage (vacuum) and (vacuum) and
frequency at holding frequency at holding power for improved power for improved
stirring and degassingstirring and degassing
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
Anticipated gas levels in Alloys … A Rough Guide!
Actual values cannot be guaranteed as they are very much dependant on the raw materials, scrap mixes used and individual melting practice. Gas levels can also be improved with additional time for holding the liquid metal in the molten state under vacuum.
VACUUM CAP METALLURGICALVACUUM CAP METALLURGICAL
Alloy type Reductions in gas content, ppm and %
Hydrogen Nitrogen Oxygen
Group 1C steels also with elevated Si, Mn contents
5 -> 1.570%
150 -> 8045%
120 -> 6050%
Group 2Low to medium alloy steels
3 -> 166%
200 ->12040%
100 ->5050%
Group 3High alloys steels, Stainless, Ni AlloysFe and Ni alloys
4 -> 1.660%
300 -> 17040-45%
80 ->50>35%
Copyright ©2003 by Consarc Corporation
Deoxidation
The application of negative pressure above the melt bath allows the C-O boil to continue to much greater extent than is possible at atmospheric pressure. Both Oxygen and Carbon levels are simultaneous reduced to lower levels. This effect is time related –> longer time = lower gas levels. Deoxidation can also be enhanced by using Argon purging with porous plug.
VACUUM CAP METALLURGICALVACUUM CAP METALLURGICAL
Copyright ©2003 by Consarc Corporation
Hydrogen and Nitrogen removal
Hydrogen removal is the most rapid of degassing effects and can be reduced to very low levels 1-2ppm Nitrogen removal is slower due to the thermodynamics and is very much influenced by alloy type, vacuum level and time for holding in vacuum state.
VACUUM CAP METALLURGICALVACUUM CAP METALLURGICAL
Copyright ©2003 by Consarc Corporation
Decarburisation
The level of decarburisation is also dependant on a number of factors including alloy type, oxygen level within melt and treatment time. Decarburizations of 0.05 to 0.1% C can be considered in a Vac Cap furnace. This is achieved by the intense C-O reaction at reduced pressure. This effect can also be enhanced by adding small quantities of metallic oxide to the base charge or using dilute oxygen / inert gas mixtures with a porous plug in the base of the furnace. Caution must be taken when using oxygen containing gases in any induction furnace.
VACUUM CAP METALLURGICALVACUUM CAP METALLURGICAL
Copyright ©2003 by Consarc Corporation
Technical Benefits of Degassing
•Generally significant improvement of mechanical properties, such as yield strength, ductility impact strength, fatigue and stress rupture elevated temperature properties.•Improvement of technological characteristics, like hot workability, weldability and machinability.•Better microcleanliness due to strong carbon deoxidation and smaller residual inclusions.•Significantly reduced scatter in product properties and characteristics, less rejections.•More exact chemistry control in general
VACUUM CAP METALLURGICALVACUUM CAP METALLURGICAL
Copyright ©2003 by Consarc Corporation
Foundry Benefits
What does it mean to the foundry….? •Opportunity to process a wider range of alloys (including alloys with small reactive element contents e.g. Ti up to 0.6%) – NEW MARKETS NEW OPPORTUNITIES, HIGHER ADDED VALUE•Can use lower cost scrap for expensive alloys COST•Ability to recycle large quantities scrap materials (70-100%) not possible in air melting (runners and risers) and use lower cost raw materials. COST•Fewer blow holes and rejects of castings due to gas related defects YIELD•Can use lower / quality cost (recycled) sand in the face coat of moulds COST•There is reduced loss of alloying elements COST•Less deoxidation additions required CaSi, CaMnSi, Al, etc COST•Better fluidity of melt, less casting misruns, better casting surfaces YIELD
VACUUM CAP METALLURGICALVACUUM CAP METALLURGICAL
Copyright ©2003 by Consarc Corporation
Of course investing in new Vacuum Technology is more expensive than conventional airmelt
Questions to consider
•Are some of your customers already looking for improved quality?
•Can improved quality and new alloy types open new doors?
•Is it time to invest for the future?
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Copyright ©2003 by Consarc Corporation
VACUUM CAPVACUUM CAP
Pour - lid offPour - lid off
Copyright ©2003 by Consarc Corporation
THANK YOU THANK YOU