Thread: Is aluminum magnetic?

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 ?

It isn’t, is it? No, it isn’t.

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.

Perhaps he confused a magnetic field with an inductive field. If you wave a powerful magnet along a piece of aluminum, you will feel resistance.

Originally Posted by Spruewell

Perhaps he confused a magnetic field with an inductive field. If you wave a powerful magnet along a piece of aluminum, you will feel resistance.

Did something similar the other day. Wave one of those super duper magnets past a piece of thick Aluminium ,or even that foreign muck aluminum, and it really feels like there something magnet in there .

Originally Posted by Billtodd

Did something similar the other day. Wave one of those super duper magnets past a piece of thick Aluminium ,or even that foreign muck aluminum, and it really feels like there something magnet in there .

Isn`t that how they seperate aluminium(cans mostly) from the trash

Peter

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

IIRC Eriez magnetics will sell you a system to separate aluminum using that method.

He must have one of them "aluminum magnets" that the new guys are sent to fetch the first day.........

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.

Originally Posted by FlatBeltBob

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.

Originally Posted by ChipSplitter

He must have one of them "aluminum magnets" that the new guys are sent to fetch the first day.........

A stick with double sided tape on the end of it?

Suppose you could run the chips through a magnet grid hopper thing like they use for plastic granules?
Mark

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

Originally Posted by ChipSplitter

He must have one of them "aluminum magnets" that the new guys are sent to fetch the first day.........

Originally Posted by Mtndew

A stick with double sided tape on the end of it?

and it is being stored next to a flashlight duct taped to a knife, which is filed under - cutting torch

I seem to recall a similar thread which was bumped back up a couple years ago. Consensus was more or less than coolant was contaminating the chips.

Oh my gosh, we just discovered magnetic aluminum

At 5 cent a pound its not worth the time or gas, I toss mine...Phil

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.

Originally Posted by ChipSplitter

He must have one of them "aluminum magnets" that the new guys are sent to fetch the first day.........

You mean like Alnico? Alnico - Wikipedia