Magnetic field effect on grain growth/size?

I was wondering if there have ever been any attempt to see if a strong magnetic field applied to a piece of metal during
forging/quench/anneal/etc.. has any effect on grain size or grain growth.
In paticular in the realm of blades, does it in any way produce a better or worse blade?
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I don't know about grain growth, but tree branches grow funny when they are close to big power lines.
Pete Stanaitis --------------------
John Fly wrote:

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spaco wrote:

Yeah ours do too, but this is due to very active pruners working for my local council ;-) Charles
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John Fly wrote:

Well this is a funny topic.
I watched a bladesmithin' (for some reason the "g" went missing from the commentary on my copy) DVD. The gentleman concerned hardened and tempered his blade and then let it cool whilst he pointed the blade south held in a pair of pliers.
Now I haven't used this method (and no it's not that I'm not sure where to point it 'cause I live in Oz, do I point it at the equator or to the Antarctic), as personally I don't think this matters, I can achieve a nice temper without doing it.
I don't think that you would have access to a sufficiently strong enough magnet to effect the grain growth/structure of metal hot or otherwise.
Of course I could be talking out of my fundament, as my responses are purely my opinion, and I would be happy to see any data on the subject.
Regards Charles
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To add my 2 cents FWIW, I have been making stikers (fire starting) for a few years now and learned that the best method (that works for me) is to quench the peice oriented handle down, north and south. This supossedly makes the finished striker hotter. Don't really know if it works that way all the time, but when using that method at the correct heat I have never had a bad stiker...Except for the time I used a..oh nevermind. ;0)
granpaw
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John Fly wrote:

Well, it might magnetize the workpiece, which might be useful in certain applications. A survival knife that is also a compass springs to mind. A lot would depend on what kind of magnetic field, ie AC or DC, and just how strong it is as the work passes through the transformation temperature point. I don't think it would have a significant effect on grain size, unless you used the field as an induction heater and held the work at temperature for a given time. I do know that a DC field will magnetize, and an AC field will demagnetize; having done some magnetic inspection work (Magnaflux (tm)), but the current requirments are bloody high, say in the 1000 to 2000 amp range. The MF machine had cables the size of my thumb, and they jumped when the juice went through them... say hello to Mister Sparky. You'd probably be better off springing for a computer controlled heat treat oven and nailing down the HT, which is where you get the real benefits. Paragon makes several nice units that are real workhorses. I've had one for fifteen years, and the hardness tester backs up their claims; +/- .5 point Rockwell.
Charly
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Don't forget that when you heat the metal it becomes magnetized by the local or remote fields. Since you have powerful field cables they might be the source. But the earth will do it.
If you have trouble welding something and normally don't - rotate the metal 90 degrees and see what happens. If joining two lengths on the ends - flip ends of one. See. if the two lengths are still flaky - flip both to set the N pole the other way... :-)
The earth is a strong source. Leaving stuff lay around might set up a field.
Auto bumpers get magnetized in that way. Typical parking in the same spot/direction at home and at work...
Martin
Martin [ I know - just hit it harder and get more splatter... ] Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Charly the Bastard wrote:

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Hey Wait a minute Martin, I've found (and a lot of other too) that when you heat metal to critical temperatures it loses it's magnetic properties, this is how (apart from sight) we can tell when a piece of metal will reach its hardening temperature, a magnet wont stick to it.
Regards Charles P.S. It's a phenomenon that I still find freaky
Martin H. Eastburn wrote:

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And when it cools it takes on some magnatism because it cools inside the Earth's magnet field.

I agree. :)
Since I'm such a contrary-sucker, might want to write that on the calender? :/

Picturing the fluid they put in loud-speaker-gaps sometimes... It's magnetic so it stays in the gap. If it wasn't, it just run out.
The liquid iron is non-magnetic so figure there would be no difference, because the iron doesn't regain its magnetic properties until its much cooler than liquid.
Hmmm... I think I'm remembering something... (William Sanderson's character in John Candy's "Wagon's East")
Magnatism has to do with electron spin. And that doesn't effect the atomic attraction of the metallic bonding. "no measurable effect from the Earth's magnet field" is something I think;) I remember from class while talking about welding.
"if thinking and remembering didn't take time a master's level chess game would only takes seconds" -alvin
"welding is casting" -"Curly" Hastings (metallurgy teacher)
"metallic bonding is what's attracting the pool of iron to another pool of iron" -"Curly" (started balding in high school)
What do you think? :) Sound right? :/
Alvin in AZ
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Generally speaking the earth won't force the flame on your stick or MIG weld to wonder by itself. When the field is stored in metal it is stronger than that of the field in the air. That is why we don't make air magnets except in Radio frequency circuits.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
snipped-for-privacy@XX.com wrote:

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Yea but that is experimenting with it. Now start welding with it and have the weld pop and spew all over and watch the flame dance. Ugly.
I got the information from a known good Pipeline welder who was (years ago) on a his first pipeline job and got there - saw the master welders had two sections 90 degrees from the pipeline route welding up. He got the down hole in the slot job of welding and soon was able to climb out to nice welding - another rookie took over the pit.
Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Chilla wrote:

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Yes, I have a degree in Physics to say the least.
However when hot the dipoles start flipping in all sorts of directions - If at that special temp - tougher to determine on alloys than 'pure metal' - but once cooling starts - the dipoles (the magnets of atoms) begin to loose the energy and start setting in the last state they were in. If an AC field is present - you may have a reasonable change of having a neutral field. Without the AC switching field, the local field - earth, wire carrying current, whatever - will determine the final resting state. The faster the 'freeze' from the time of the field and high temp - the stronger the magnet. Therefore a pipe will freeze itself rapidly so if you flame warmed it - the field of the full length would just re-program the region of heating. The stick weld is re-programmed...
Now for the good news - perhaps the pipe was in a stack that was hit by lightening. Perhaps it picked up the field at the furnace - inductive arc types... So when you locally heat - once hot - it behaves better and will always be a little better than at first.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Chilla wrote:

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Hi Martin, Cool I can chuck some physics questions at you if the need arises :-) Do you do classical mechanics also? I'm so unfamiliar with the subject that I don't even recognise the symbols used in the formulas :-(
The magnet trick works with all metals to determine the right temperature for hardening, and I still find it freaky.
I also broke a magnet by heating it, I was testing to see if the magnetic properties of a knife blade were gone and the magnet became too hot, and it no longer worked as a magnet, and for some reason I couldn't seem to magnetise it again, so I binned it :-(
I think forge welding is more to getting it just right as opposed to your magnetic orientation, but a lot of things in the natural world defy logic, and a lot of things that should logically work just plain don't... toast buttered side down anyone?
Regards Charles
Martin H. Eastburn wrote:

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I'll have to look up some of it - some out of this dusty brain. For ME work - Mechanical Engineering - I bought books. I trained and served as a EE and a Sr. Scientist. But Physics is the basis of Engineering and Science.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Chilla wrote:

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Thank you I'll keep you in mind :-) Charles
Martin H. Eastburn wrote:

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"Martin H. Eastburn" wrote:

Strong is a relative term. The Earth's magnetic field has an 'absolute' field strength of one gauss average. An MRI machine has a field strength of tens of thousands gauss. ( It will yank the watch off your wrist from across the room.) Magnaflux uses DC current to magnetize the part, usually a lot of amperage for a very short pulse, then a flourescing slurry is pumped over it to detect external and internal flaws. I magged a splined coupler that was soooo magnetized that you could see the splines inside from the outside in the slurry. It was almost like X-ray. The working principle is that flaws or discontinuities create pole areas where the field is concentrated and detcted by the application of the slurry under the UV light. After inspection, the part is demagged by subjecting it to an AC field, like bulk erasing a tape, and checked for residual magentism with a meter. More than you want to know. eh?
Charly
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I have seen and used some magnets larger than houses. So that isn't an issue.
The Earth has a variable force - it is different all over the world. But the average...
Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Charly the Bastard wrote:

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"Martin H. Eastburn" wrote:

Right, I'll crawl back into my cave now...
Charly
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Charly the Bastard wrote:

Have you guys seen the magnet that picks up grass hoppers and strawberries?
I saw one on a science program, a monster magnet that has a field strength that is really incredible. They float organic items in the magnetic field... antigravity of sorts. Looks weird :-)
Regards Charles
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Doggonit. I just now realized I forgot to ask my metallurgy teacher about that. :/
I had a list! ;) Somehow that wasn't on it. (thought it but didn't write it down)
Oh well, I just about drove the guy plumb-crazy, as it was. :)
Alvin in AZ
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