A discussion on the best tool for melting iron, comparing weaknesses and strengths of induction, cupola and electric arc furnaces from various points of view

1. ALTERNATIVESFORHOTMETALPRODUCTION:CUPOLA,INDUCTIONANDARCFURNACE
Jorge Madias
COLFUN, Buenos Aires, Argentina, October28 –30, 2010

2. metallon
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jorge.madias@metallon.com.ar
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3. metallon
Nextfoundry-relatedopen courses
2nd International CourseonElectric ArcFurnaces, Rosario, Argentina, March29-30, 2011
CourseonAppliedMetallography, Rosario, Argentina, June 28-29, 2011
CourseonMetallurgyof DuctileIron, Rosario, Argentina, November22-23, 2011
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4. Alternativesforhotmetal production
Content:
Introduction
Cupola
InductionFurnace
ArcFurnace
Influencingfactors
Trends
Conclusions
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5. Introduction
Toobtainliquidferrousmetal departingfromcoldcharge, severaltechnologicalalternativesare available
Fora greenfieldnew foundryorbrownfieldcapacityincrease, thesealternativesmustbeevaluated
Theadvantagesand drawbacksare discussedof
Cupola
Inductionfurnace
Arcfurnace
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6. Cupola
Moderncupolafeatures:
Fume takeoff belowcharge
Hot blast
Off gas treatment
Lininglesslargerfurnaces
Highautomationlevel
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7. Cupola7

8. Cupola
Fortresses
Thermalefficiency, in largerunits
Acceptationof widerangeof metallics
Lesssensitivitytoscrapoxidation
Designvariantsforspecificaims(plasma, cokeless, oxycup)
Hot blast: lowmeltingcostforlargertonnages
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9. Cupola
Weaknesses
Big off-gas generation
Tohavegoodenvironmentalperformance, heavy investmentisnecessary
Forductileironproduction, downstreamequipmentisconvenient
Temperatureand chemistrycontrol ismore complex
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10. Inductionfurnace
Fortresses
Cokeorelectrodesnotrequired
Possibilityof producinganamplerangeof materials
Easyand fastcontrol of liquidmetal temperature
Easytemperatureadjustment
Fastchangeof meltingrate
Goodenvironmentalperformance, withlowinvestment
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11. Inductionfurnace
Weaknesses
Limitationsin metallicstobecharged(turningsand borings, dirtyscrap, scrpapsize)
Limitationsformetallurgicaltasksrequiringslag-metal interaction
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12. Inductionfurnace
Highpower
Automation
Becomingusual:
Fume extraction
Pushoutsystem
Backslagging
Robot forsamplingand otherfurnaceoperations
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13. Arcfurnace
Fortresses
Capacitytomelteverything, includingturningsand borings
Abilitytoreachhightemperatures(advantageforcaststeelproduction)
Withbasiclining, possibilitytodecreasesulphurorphosphorusviaslag-metal interaction
Simple and reliableequipment
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14. Arcfurnace
Weaknesses
Noise
Off gas generation(whenoxygeninjectionisused)
Needtocontrol emissions
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15. Arcfurnace
Featuresof modernarcfurnaces
Highpower
Watercooledpanels
Slagfoaming
Excentricbottomtapping
Oxygen, coal, gas and lime throughinjectors
Electroconductivearms
Digital systemforelectroderegulation
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16. Arcfurnace16

17. Arcfurnace
Off gas treatment
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18. Influencingfactors
Availabilityand costof rawmaterialsand consumables
Grades tobeproduced
Investmentcost
Operatingcost
Environmentalrestrictions
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19. Rawmaterialsand consumables
Typesof scrapavailableand cost
Needof recyclingturningsand borings
Availabilityand costof electricpower, cokeand electrodes
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20. Influencingfactors
Grades tobeproduced
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Gray iron(%)
Ductileiron(%)
Caststeel(%)
Aluminum(%)
USA
36
32
9
16
Germany
49
28
4
14
Japan
40
32
4
21
China
60
20
10
7
India
70
9
11
8
Brazil
86
7
7
Argentina
49
34
6
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21. Operatingcost
Item
Cupola(USD/t)
Induction(USD/t)
Metallics
135.4
151.7
Additives
9.3
13.0
Melting
23.4
29.6
Labour
4.0
4.5
Refractories
1.8
3.1
Wastedisposal
1.5
0.5
Maintenance
6.4
4.4
Buildingand others
10.0
10.0
Total
191.8
216.8
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Greenfield; 40 t/h; 16 h /day; 4000 h/year. Hot-blastcupola; mediumfrequency
corelessinductionfurnace. US costs. Kuttnerstudy, 2001

22. Operatingcost
Item
Savingswhenreplacingarcfurnacemeltingbyinductionmelting(USD/t)
Meltingenergy
2.7
Energydemand
-3.3
Electrodes
33.4
Metalliccharge
-20,2
Labour(production)
5,4
Refractories
1,0
Maintenance(materialsand labour)
18,0
Polutioncontrol
4,8
Wastedisposal
0,9
Total
42,8
22John Deere, year2000, whenanalyzinga modernizationwithCapacityincrease. Cupolain intermediateposition

23. Operatingcost
France
1997 cold-blastcupolathecheapest(236 €/t); inductionfurnacethemostexpensive(265 €/t)
2003 Inductionfurnacethecheapest(252 €/t), followedcloselybyhot-blastcupola(253 €/t)
2005 hot-blastcupolathecheapest(295 €/t)
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24. Trends
France –quantityof furnacesforductileiron, castion and malleableiron(1999 162 units; 2002 140 units)
241999Cold-blast cupolaHot-blast cupola
InductionArcRotating2002Cold-blast cupolaHot-blast cupolaInduction
Arc
Rotating

25. Trends
France –tonnageductile, gray and malleableiron(1999, 1,530,000 t; 2002 1,400,000 t)
251999Cold-blast cupola
Hot-blast cupolaInductionArcRotating2002Cold-blast cupola
Hot-blast cupolaInduction
Arc
Rotating

26. Trends
Argentina (Ricardo Velazquez, Foundryindustryin Argentina, COLFUN 2010)
1980 80% cupola, 20% induction
2010 20% cupola, 80% induction
Brazil(Roberto de Deus, privatecommunication)
2010 30% cupola, 70% induction
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27. Conclusions
Worlwidetrendtoreplacemeltingcapacityof cold-blastcupolasbyinductionfurnaces
Forbigproduction, usinghot-blastcupolaas primarymeltingunitisstillcompetitive
Tomaketherightdecision, itisalwaysconvenienttoevaluatethefurnacealternatives, comparingCAPEX, OPEX and otherfactors
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