Magnetic Phenomenon

Are you sure you are not making this somehow?

http://en.wikipedia.org/wiki/Iron(III)_oxide

(This I remembered from the old school days the magnetic ore of Iron)

They are attracted to the fresh cut ends because that is where the "pole" end now is.

SB has given you a link to iron (III) (the red oxide) what you are describing is more likely droplets/ particle shards that did not oxidize and or were produced at early late stages of cut in reducing area of your flame by the reduction of the red rust particles (When You are not squeezing the Oxygen trigger like a mad banshee....)

Just a hunch.

Other end should be similarly magnetic. but will lack the shards to stick take a few of them to the other end and watch what happens.

milo

Interesting. I haven't seen any filings stick to the un-cut ends, but I'll deliberately put some there and see what happens. The Iron III Oxide sounds like a pretty good explanation.

Are you asking why its magnetic or where do the filings come from?

Well...it seems strange that there are filings with a cutting torch...

but I'm really wondering why the pipe and or filings are magnetic after being exposed to such high temperatures. My understanding was that under such high temperatures, the magnetic domains would become randomly aligned and the object would lose it's net magnetism.

Come to think of it...I was cutting underneath a power line... I would think at such a distance, any fields would be negligible...

The ends are where the "poles" are located and this is where magnetic lines of flux are most concentrated (they don't cross). Heating will destroy magnetism, however only a small area is really hot enough to be effected and the overall magnetism of the length of pipe overcomes this.

I have consider this...but then, why would only one end be magnetized...the freshly cut end?

Normally a magnet has two poles, so the other end, if correctly tested (was it?), would have the opposite pole.....

Hello DAG,

Are the 'filings' melted drops or, perhaps part of the inside of the pipe blown off by the heat?

bb

Why is this stuff magnetic in the first place? Has the pipe got a magnetic charge or has the field been induced?

Pieces of iron and steel, that "sit" somewhere for a long time, pick up magnetism from the earth's magnetic field....

Even things like steel ships (that move) get magnetized/pick up magnetism and have to be "degaussed" before moving over magnetic mines, to reduce their magnetic signature.

All steel RN ships have the coils built in....at least when I was in the Navy....

I suspect that the magnetism is the outcome of the years of flow of materials through the pipe in one direction. Just like static builds in pipes that have unidirectional air flow, there would be induced electrical field (and hence magnetic fields) in the pipe materials.

I would be interested if you could check the "Northness" of the pipes in relation to which way the oil had been running through them. (Use a small bar magnet and see which end is attracted to the upstream end of the tube.)

I would be willing to bet dollars to doughnuts that the pipe was laying roughly north - south. The earth's magnetic field will magnetize the pipe given sufficient time. Even though you obviously exceeded the eutectic point of the steel when cutting it, the residual magnetism in the remaining pipe that wasn't heated over 600 degrees will remagnetize the cut end as it cools down.

We experience a similar effect when welding stainless to stainless or to nickel steel. After welding, the joints show some residual magnetism which remains even after degaussing several times. We've been trying to substitute copper nickel alloys but welding those is a real pig of a job. The units we make have to be shielded from the earths magnetic field using Mu metal housings so this is a big problem.

Explanations for the magnetism seem to say that the ferrite in the stainless or nickel steel is clumping during welding leaving magnetic pockets in the joint.