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gieter (Materials) (OP)
18 Apr 08 8:31
First my apologies for posting a question that has extensively been dealt with in 2007 and 2004
URL:http://www.eng-tips.com/viewthread.cfm?qid=202861
URL:http://www.eng-tips.com/viewthread.cfm?qid=101946
but I think a lot of variables have dramaticaly changed over the last year:

Suppose you would invest at this moment in a 12 ton furnace to make general quality steel (50% unalloyed, 20% low alloyed, 10% high alloyed and 20% high chrome white cast iron) in a jobbing environment, what would be your choice considering:

- Energy consumption ( especialy peak power consumption)
- availability of raw materials
- flexibility
- environmental considerations
- skills needed

Thanks in advance for any contribution,
Helpful Member!  arunmrao (Materials)
18 Apr 08 10:26
gieter,

In these times of increasing raw material,energy and refractory  costs,I think your question is very relevant.

I shall just wait for some others to offer their opinions,before I comment,some of them might be repetetive too!  

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

EdStainless (Materials)
18 Apr 08 13:50
Personally I would do with Induction.  And plan on melting all at night.  Negotiate the rate with your power company.
It is flexible and clean.  No dust and EPA to deal with.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

metengr (Materials)
19 Apr 08 0:08
You better factor in O&M costs related to comparing induction versus EAF, besides power consumption. Also, most power companies don't offer off-peak price breaks anymore because power is now transported from the Midwest to the east coast. Power demand has been steadily increasing with no serious capacity coming on line; there is no need to worry about backing off of load at night to keep units on, they stay on because the demand is there.  
arunmrao (Materials)
19 Apr 08 3:33
EAF offers one of the most flexible routes to manufacture steel castings of different grades. Charge selection is simpler as one can add all sizes and varieties of scarp including machine shop turnings and borings. As refinement is possible, incidences of high carbon,sulphur and phosphorous is not a problem.  Addition of alloys is simpler and winning some of the alloys from the slag is possible. The increasing cost of clean and dense scrap and its shortage,might outweigh all other factors in favor of EAF.

The negatives would be the need of high power transformers, refractory costs and cost of graphite electrode. Also there is a need to have highly skilled operators which is a major problem. Emissions from the EAF need to be controlled with suitable dust and fume extractors, which will increase the capital costs. Maintenance crew required will be large per shift.

Induction furnaces offer a clean and simple method to melt steel. The capital costs are lower due to low investment on electrical and pollution control equipments. There is virtually no smoke emission from induction melting. Low level of skilled operators are needed and maintenance crew rarely needed.

However it is not versatile in changing over from a high carbon heat to low carbon or from high chrome iron heat to carbon steel heat.Also the charge selection and preparation needs to be  carefully done. (The cost of scrap and alloys charged significantly affect the melt  cost). There is no refinement possible.

I am not able to offer any comment on peak demand charges as this depends on the local electricity supplier. I  always watch for the peak demand recorded as we have two cost components power demand charges and energy units consumed. During a  melt campaign if there is a surge in power demand due to bad scrap distribution in arc furnace,the charges are billed for the complete month,but in Induction Furnace the possibilty does not exist.


 

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

gieter (Materials) (OP)
21 Apr 08 3:18
Gentlemen,

Thanks to all for your valuable comments.

On the metallurgical aspects it is my understanding that the advantage of a EAF is it's shallow pool and the large surface area offering a good contact with the slag.

Induction furnaces are deep with a small surface. Is it correct to put that if (and I stress IF) a good metal-slag contact could be established in an induction furnace, one could do the same as in an EAF?

On the charge material, the possibility to work with lower quality scrap is much emphasised, but the cleaning actions need more energy/ton, are more demanding to the personnel (you might need more and better trained), there is more waste (slag) and there is more fume to be dealt with. So one could ask is this all worthwhile?
 
swall (Materials)
21 Apr 08 8:48
Gieter--at this point you've been given a lot good advice. In my opinion, the final decision comes down to the kind of scrap supply you have available in your area and how stringent your local air resources board is.

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