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Is aluminum magnetic?

FlatBeltBob

Stainless
Joined
Jul 22, 2007
Location
central WI
I took about 60# of what I thought was clean aluminum chips to the recycler the other day.
I always take great care to clean out my chip pans when changing from steel to alum. wipe up all fines , magnet sweep , paper towels.
I even run the lathe chips through a chip compactor .
The guy runs a strong magnet wand and finds lots of places the wand will stick to . So he offers to pay me $ zero for the lot.
What the hell ! I hate to just throw chips in the trash .
Is it possible that metal fines in the coolant are sticking to the chips
in such an amount to be detectable ?
 
Alum is definitely not magnetic. Maybe your scrap guy is pulling a fast one?
 
Al is not magnetic and wand magnets are not that powerful. so either you have significant iron contamination or else the scrap guy is trying to get you to give him the Al chips. Did you observe "chips" sticking to his magnet while he was checking your scrap? Sounds a lot like a divining rod that only the possessor knows how to use and feel.

You did mention running the lathe chips through a chip compactor. Is there any chance that you had significant contamination in the compactor?

Outside of that, I would be looking to sell scrap to someone else. Most reputable yards run their Aluminum across a trap iron magnetic separator and pull out the offending material.
 
There is a magnetic effect known as Lenz's Law. "The direction of the electric current which is induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field." There are many videos on the internet that show this effect by dropping a magnet through a (nonmagnetic) copper tube. The first one below is very simple. .02 seconds for the steel ball, 4 seconds for the magnet.

Lenz's Law with Copper Pipe - YouTube

This one is Veritasium. He goes into a longer explanation

World's First Electric Generator - YouTube
 
I once had a similar issue with austenitic stainless. I used to give the scrap yard the benefit of the doubt and think they were shysters'. I explained to the owner how stainless can work harden and become magnetic and showed him how heating and cooling it will return its non mag properties. I genuinely believe he didn't know this. So point being, they weren't crooks, they were just stupid!

You would think an owner of a scrap yard would have some basic metallurgical knowledge and I'm sure there are some that do, but it has been my experience that most of them don't know jack shit about metal.
 
I took about 60# of what I thought was clean aluminum chips to the recycler the other day.
I always take great care to clean out my chip pans when changing from steel to alum. wipe up all fines , magnet sweep , paper towels.
I even run the lathe chips through a chip compactor .
The guy runs a strong magnet wand and finds lots of places the wand will stick to . So he offers to pay me $ zero for the lot.
What the hell ! I hate to just throw chips in the trash .
Is it possible that metal fines in the coolant are sticking to the chips
in such an amount to be detectable ?

no, unless its a dedicated machine, you will always get steel chips mixed in to the aluminum. just ones left over in the machine unless you detail every nook and cranny. my local guy says I can have a tiny bit, but if not its called "dirty aluminum" and I get half of what clean is.
 
I have seen aluminum chips in a brand new hopper that came out of a brand new CNC stick to a magnet. I've never been able to understand what was going on and never brought it up to someone because I didn't want to look like an idiot
 
I was working on a brass magnet but finally gave up and started shooting steel case 9mm. With this new info I may switch to aluminum cases.
 








 
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