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Welding in magnets

  1. Jun 1, 2009 #1
    let me have the honour of posting this dumb question:
    does a magnet lose its property if two like magnetic poles are
    welded together?since like poles are supposed to repel!!
     
  2. jcsd
  3. Jun 1, 2009 #2
    You might better see the result if you simply take two equal bar magnets and force the N ends together with a Gaussmeter placed nearby.

    As to the welding, what temperature will the metal be at when you weld it? What does that temperature do to magnetic properties?
     
  4. Jun 1, 2009 #3

    RonL

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    A knife maker once said, good method of determining the temperature of steel in a tempering process (if you have no controls) is to put a magnet on the steel being tempered, at the magic number the magnet will drop off the steel.
     
  5. Jun 2, 2009 #4
    at a very high temperature do'nt the magnetic properties break,in case of
    welding?and since we weld the like poles together,the object ceases to remain a magnet.
     
  6. Jun 2, 2009 #5

    Lok

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    Welding is local and does not presume that the whole magnet get's heated up. Usually it takes about 730'C to break the magnetic properties. That would mean that the two magnets would glow fiery red.

    What might happen is that the molten welded area after cooling will regain magnetic properties in the form of yet another tiny magnetic area of NSnssnSN ... or similar.
     
  7. Jun 2, 2009 #6
    Even when you manage to keep two magnets together without heating them too much, you won't lose the magnetic properties. It will be simply two magnets stuck together. If you take two magnets and bring them together (like poles together), do you notice that the magnet becomes weaker? Let's say you were strong enough (or the magnets weak enough) to bring them to within a millimeter of each other. Is that fundamentally different from a situation where the magnets are touching? I don't think so...
     
  8. Jun 4, 2009 #7
    when two magnets are kept together with their like poles,they tend to become weak..
    in the same way,two magnets being welded at their like poles,also become weak in course of time...if not entirely losing their magnetic property.. but i do not know
    how a tiny magnetic area of "NSnssnSN" can evolve..
     
  9. Jun 4, 2009 #8

    DaveC426913

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    A bar magnet is magnetic because a large number of its electron spins are aligned in the same direction.

    When you completely demagnetize a bar or iron all that happens is you randomly orient the electron spins.


    So, in answer to your question: "does a magnet lose its property if two like magnetic poles are welded together?"

    The magnetic property is still there, it's just that the magnet ceases to act like a magnet at macro scale because the atomic scale magnetic moments cancel each other out.
     
    Last edited: Jun 4, 2009
  10. Jun 4, 2009 #9

    RonL

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    I think if you browse the net a little under something like " how magnets are made" you will find most high grade magnet (rare earth) production, involves high pressure and temperature.

    Some time in the past I found a web site where a man used black sand from a local river (magnatite I think) mixed this in epoxy, then put the paste in a mold, exposed it to an electromagnetic field, and when the epoxy hardened the mass retained a magnet effect. His purpose was building a three phase alternator. These I'm sure were quite low grade magnets but they did work.

    There are an ongoing studies of earths magnetic fields and how they have changed in the past, the collection of lava cores, which at one time were molten then hardened show the orientation of grains affected by earths mageatic field within minutes.
     
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