How to melt Steel with Electricity?

[wj]

How to melt Steel with Electricity?

The question boils down to concentrating heat.

You can force heat into a crucible with heat from resistive coils.

Or you can zap the right material in a microwave and it will heat up. (Examples have found use graphite, magnetite, and silcon carbonate).

Or maybe a sort of induction furnace could work using a resistive crucible.


Are any of these methods more efficent than the others? What are some standard industrial methods?

 

[Njorl]

I believe a spark gap is the most common way to melt steel locally.

Njorl

 

[dlgoff]

Hey Njorl,

I use to work for the power company and I believe you are correct. I think that they use electrodes directly into the steel. When the steel is cold and first powering up, it creates a lot of havoc(transisits, frequency drag, etc) on the system.

Regards

 

[chroot]

Plasma cutters.

- Warren

 

[wj]

So you attach electrodes to the solid steel and use the heat created by resistance to melt the steel? What material do you use to supply the current?

 

[chroot]

http://www.plasma-cutter.com/technical.htm

- Warren

 

[russ_watters]

Originally posted by wj
What material do you use to supply the current?

Are you thinking that if the plasma cutter can cut steel that steel wouldn't work for the wires to supply the current? Not so: the wire just needs to be thicker than the arc. That said, most decent quality wires are made of copper.

 

[wj]

Originally posted by dlgoff


I think that they use electrodes directly into the steel.

And Plasma cutters work by superheating gas which cuts the steel.

Are two methods being discussed? one where electrodes run current through the steel, and one where electrodes run current through gas which melts steel?

Method 1)

Power Source -> Wires -> Direct Contact with Steel

or?

Method 2)

Power Source -> Wires -> Gas(Plasma) -> Direct Contact with Steel

Does it make any difference?
I thought that high quality alloys were melted in vacuum to avoid impurities or do you just use a gas medium that will improve the alloy?

 

[dlgoff]

Are two methods being discussed? one where electrodes run current through the steel, and one where electrodes run current through gas which melts steel?

The plasma cutter at the link chroot provided is for cutting but I'm not sure that this is used for smelting large vats of steel like what I was thinking.

 

[chroot]

Sorry, I didn't realize we were talking about melting large quantities!

- Warren

 

[Averagesupernova]

Originally posted by wj
And Plasma cutters work by superheating gas which cuts the steel.

Are two methods being discussed? one where electrodes run current through the steel, and one where electrodes run current through gas which melts steel?

Method 1)

Power Source -> Wires -> Direct Contact with Steel

or?

Method 2)

Power Source -> Wires -> Gas(Plasma) -> Direct Contact with Steel

Does it make any difference?
I thought that high quality alloys were melted in vacuum to avoid impurities or do you just use a gas medium that will improve the alloy?

Some alloys may be this way, but a lot of steel for castings are just a molten pot of steel. I have toured a foundry and I know someone who worked in the EXACT same foundry. Large carbon electrodes are dropped into a pot of scrap iron. The current is turned on and the steel starts to melt. It is actually an arc in an open pot. I believe there were 2 carbon electrodes dropped in side by side. If I recall correctly, they looked red hot. They called this step in the process "arc melt". I believe more is added as the scrap melts and the level goes down because the air space in between the scrap is filled with molten steel. I imagne they watch what the various levels of certain types of metal are and add accordingly. I once asked my friend what type of things they dumped in. His reply was "Anything that will melt." Of course it is unlikely that you would dump aluminum castings in a pot of steel, but you get the picture. He once told me that they got a shipment of Craftsman tools that were returns. He said everyone filled their pockets and headed for Sears. I wonder how many times some tools go around. LOL

Now for your original concern, a layer of 'slag' is formed on the surface of the molten steel. It keeps the oxygen out of the rest of the steel. The same thing can be seen on a pot of molten solder used for dipping circuit boards. You skim the surface right before you dip the board to get a fresh bunch of solder.

I have a book on metal casting. It actually has many plans and suggestions on how to make your own castings. It is a strange process. So crude in some ways, yet very precise and critical in others.

 

[Michael D. Sewell]

Check out www.steel.org Click on learning center, and how is steel made. Hope this helps. -Mike

 

[wj]

Great information!

Thanks