Magnetized blade?

It said something about dealigning electrons, I couldn't explain it if I had to.

Correction, just used a meat therm to test and I took the pieces to 275F. I let them cool in a coffee cup for 10 minutes and they were still warm but ok to handle. Totally demagnetized, hope somebody can explain this better.

Edit: An interesting effect happened, I see purple and orange colors in the metal now, looks almost like a dark rainbow Leek now. I hope this didn't damage the steel!! :confused:

Can't see the rainbow in the picture, but it's there. Compared is a Kershaw Leek.
colorful.jpg
 
sounds like something i'd say, LOL!!! neat trick anyway! thanks i'll keep it in mind.
 
Heat is one of the things that can kill magnetism in iron or steel. There is a certain temperature called the "curie temperature" (named after Mr. and Mrs. Curie, I guess) at which the atoms of the metal are excited enough that they move to a degree that randomizes the magnetic domains in the metal.

For iron and steel the listed value is 600-700 degrees C. Which would probably be bad for a knife blade.
Maybe partial temperature increases incompletely demagnetize? The blade might still be magnetic, just not obviously.
 
if the knife is all steel it's probably either the result of light refracting off a really clean surface, or some mild oxidation from the heat+oxygen/tapwater . The temper should be just fine, 275f isn't much higher than water's boiling point, and is on the lowest of the low end of tempering carbon steel (someone correct me if i'm mistaken, but tempering at a lower temperature than the one that the knife was done at initially doesn't affect hardness at all yes??)
 
I didn't use tapwater, I just let it slowly cool down on the stove. Not sure if that matters or not.
 
I see purple and orange colors in the metal now
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If it rubs off with just your finger, you're ok. That's just oil on the surface.

But if you can't rub it off, then your blade got a bit hotter than your thermometer indicated and you detempered your blade and it's ruined. Sorry.

Hopefully, it's just oil.
 
One might ask, "Where would oil on the surface come from?"

Answer: it was on the surface, but down in the texture of the surface and the heat caused it to expand and rise out of the texture and to the top of the surface.

One might ask, "How hot do I have to get my blade to detemper it?"

Answer: above the final heat-treat temperature which is usually about 350F.

One might ask, "Is there a better way to accomplish demagnatizing by heating?"

Answer: Yes. Boil it. No matter how high you turn up the stove, boiling water in an open pan doesn't get much about 212F, well below the final heat treatment for most knives.
 
nelsonmc said:
I didn't use tapwater, I just let it slowly cool down on the stove. Not sure if that matters or not.
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How exactly did you heat it? This has been a very entertaining thread. :) I almost laughed at loud when you made it more magnetic. :)
 
Well I can't get the color off it, even with steel wool. I sharpened it up and it's bright silver color under the brown/purple/orange. It's holding an edge just fine, cutting wood, then slicing paper and so far so good.

I heated it on my stovetop Wade, electric stove... Only heated her up for about 2 minutes.

Glad you guys are getting a kick outta this :cool:

Ya know... I still wanna know how in the hell it got magnetized to begin with!

Overall I think I like it's new color, adds some character to it.
 
The spinning electrons in the atoms generate a magnetic field. The field generated by each individual electron is practically indetectable. Normally, they all spin in random directions and the fields cancel resulting in no net field. However, if some or all of them start to rotate in the same direction, then the object will become "magnatized."

The electrons in some materials, iron is one of them, are succeptible to externally applied magnetic fields. Such a field can cause those electrons to line up and all spin in the same direction.

A strong physical shock can literally knock the electrons around and then they won't be all lined up anymore. Exposing the object to a rapidly oscillating magnetic field can similarly scramble the electrons. And heating the object introduces a lot of energy and knocks the electrons around.
 
Ahh, I had figured you used an oven, the electric stovetop can heat unevenly, so even if the majority of the blade is at 275 the steel in immediate contact with the stovetop/coil can be much hotter. I had assumed the tapwater when you said you let it cool in a coffee cup. I'm still pretty sure the knife is just fine, just surface heat oxidation, should come off with a few applications of flitz.
 
I'd just stick with a tape head demagnetizer (like this http://www.wavinc.com/item1738.htm have seen similar on ebay for about $16) or tv degaussing coil. If you don't want to mess with 115v house current and like to tinker, you could just make a coil of magnet/bell wire and use a stepdown transformer (I've done this to demagnetize things since I had an old HO gauge train x-former I picked up at a garage sale for a quarter, that, aside from the variable DC tap, also has a 12v ac tap for running lights etc.) Just slowly withdraw the knife from the coil until it is about 3 ft away before turning the power off.
 
nelsonmc said:
I heated it on my stovetop Wade, electric stove... Only heated her up for about 2 minutes.
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You mean you placed it directly on the electric burner?! :eek: :D I would have just put it in the oven on a cookie sheet and set it for 200-250 or whatever. I think we need pictures showing how the knife was on the burner (just leave the burner off). :)
 
Fe Curie temperature 1043 K. Hmm.. it should not do that as it did I wonder why?

TLM
 
The Curie temperature is not where a magnetized object loses its magnetism, it is where a ferromagnetic material ceases being attracted to a magnet. A lesser temperature combined with time allows sufficient agitation of the crystaline lattices for the magnetic domains to achieve a random state. I don't know off the top of my head how hot you need to get a stainless blade and for how long to achieve this effect. It bothers me that you have some surface oxidation. If you got the blade over 350 degrees F for more than 15 minutes or over 500 degrees for more than a few seconds you may have softened your blade. You might see if the blade can cut copper wire without significant damage as a test. You should have used a preheated oven, not a stove burner.
 
From scienceworld:

The temperature above which a ferromagnetic material loses its permanent magnetism.

From free dictionary

Curie temperature - the temperature above which a ferromagnetic substance loses its ferromagnetism

From hyperphysics

Ferromagnetism

Iron, nickel, cobalt and some of the rare earths (gadolinium, dysprosium) exhibit a unique magnetic behavior which is called ferromagnetism because iron (ferric) is the most common and most dramatic example. Samarium and neodynium in alloys with cobalt have been used to fabricate very strong rare-earth magnets.

Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins to line up parallel with each other in a region called a domain. Within the domain, the magnetic field is intense, but in a bulk sample the material will usually be unmagnetized because the many domains will themselves be randomly oriented with respect to one another. Ferromagnetism manifests itself in the fact that a small externally imposed magnetic field, say from a solenoid, can cause the magnetic domains to line up with each other and the material is said to be magnetized. The driving magnetic field will then be increased by a large factor which is usually expressed as a relative permeability for the material. There are many practical applications of ferromagnetic materials, such as the electromagnet.

Ferromagnets will tend to stay magnetized to some extent after being subjected to an external magnetic field. This tendency to "remember their magnetic history" is called hysteresis. The fraction of the saturation magnetization which is retained when the driving field is removed is called the remanence of the material, and is an important factor in permanent magnets.

All ferromagnets have a maximum temperature where the ferromagnetic property disappears as a result of thermal agitation. This temperature is called the Curie temperature.

TLM
Hmm...

Nothing though says that it can't happen with a lower temp and propably a lot of time
 
WadeF said:
You mean you placed it directly on the electric burner?! :eek: :D I would have just put it in the oven on a cookie sheet and set it for 200-250 or whatever. I think we need pictures showing how the knife was on the burner (just leave the burner off). :)
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Hah! I have to admit it was pretty stupid but it worked and made the color neato! :D :D :D

Ok here's the picture, heh fun times.

biteme.jpg
 
Jeff Clark said:
The Curie temperature is not where a magnetized object loses its magnetism, it is where a ferromagnetic material ceases being attracted to a magnet. A lesser temperature combined with time allows sufficient agitation of the crystaline lattices for the magnetic domains to achieve a random state. I don't know off the top of my head how hot you need to get a stainless blade and for how long to achieve this effect. It bothers me that you have some surface oxidation. If you got the blade over 350 degrees F for more than 15 minutes or over 500 degrees for more than a few seconds you may have softened your blade. You might see if the blade can cut copper wire without significant damage as a test. You should have used a preheated oven, not a stove burner.
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I just tried to cut some wire like you suggested and it caused no damage. I also just tryed using a dremel and a wire brush on the inside of the handle to get the color off and it didn't touch it. It seems to be permanent. I didn't get it anywhere near 500F or even 350F, I had the candy/meat therm touching one of the knife handles, so I'm pretty sure it was almost right on, +/- 10 probably.

Update: Tried to soak the knife in some oven cleaner. Half of 1 handle looks normal now, trying to soak again but longer this time.
 
Now what is it that Homer Simpson says, "Doh"?

Guess what, your burner not only provides heat, it also acts as a degaussing coil. It has really high AC current circulating through the coils. It is arranged at a right angle to the axis of your blade. And finally you ramp the current up and down as you set the temperature or you set the temperature and move the metal in and out of the field comparitively slowly.
 
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