![]() Non-Magnetic Steels - Definition: Austenitic steels such as the 14% manganese steels and the 303 type 18/8% chromium-nickel stainless steels. You'll have to look deeper into the theory behind para- and dia-magnetic material alloys. These materials are very useful in building experimental apparatus cheaply.īy the way, nickel is also magnetic, so the fact that you have an alloy made of nickel instead of iron is not an adequate explanation. You can pick some up at a surplus store and extract metal parts that have the weight and strength of steel, but cannot be magnetized and don't stick to magnets. A good example is your typical hard-drives, especially larger ones. ![]() They are used in motors, and mechanical devices that require magnetically sensitive parts to be protected from stray magnetizing effects. Yes this is quite true: there is a variety of interesting alloys, especially 'steels' that are deliberately made not to interact with magnetic fields. (I probably don't have the spelling correct, but this audio noise is called "Barkhausen noise" if memory serves me correctly) The slow movement of the magnet to contact the SS will not produce any audio noise, but if a cascade of domains flipping is heard with one magnet and not the other, my speculatons are supported. One could experimentally explore this concept with a high sensitivity audio amplifier and a pick up coil wound around the front face of the magnet so it is essentially in contact with the SS surface. Perhaps this does start with micro feromagnetic crystals near the surface and almost instanteously propigate inward. That is, perhaps the randomly oriented domains in the presence of the weak magnet remain random, but in the presence of the stronger magnet, domains flip and align. (neclecting nuclear spins) Perhaps the domain- domain interaction in the presence of the stronger magnet type is significant but not in the case of the weaker magnet. This does not envolve any motion of the atoms in the SS, only the spin alingments of the unbalanced orbitals. Now we must also consider that there can be an interactions between domains in the SS. The only thing I can think of under this constraint, is that one (the stronger one) may saturate small feromagnetic domains in the SS, especialy those near the face of the magnet (one surface of SS in contact with magnet). If his magnets were of different size and with fields of different shape, there could be explanations in this fact, and I bet it likely they were, but I a looking for some reason for a difference if the two magnets differed only in the strength of the field, but not it their field geometery. Thus lets assume, as a first approximation, that the both types of magnets have the same external field pattern and it is not greatly changed in shape when in contact with the SS. Then placing it up against the magnet face, will not reshape the field distribution greatly, as say placing a strongly feromagnetic material (iron, nickel etc) would. I thought his basic question was why did one type of magnet show different effects from the other?įirst, note tht if the stainess steel is only weakly feromagnetic, perhaps only paramagnetic. I doubt there's much call to distinguish between stainless steel and nickel-copper alloys that don't stick even to neodymium magnets.Ĭlick to expand.I am not sure exactly what you are agreeing to James, but I think I have a slighly different take on this. A neodymium magnet will stick and hold up its own weight, but it is easily removed. Ceramic magnets don't stick at all, as far as I can tell. This also tells me that if you want to use a magnet to test whether a sample is stainless or not, either use a weaker magnet or know what you are doing. I suspect that it's because fairly pure iron exists in small crystals near enough to the surface to be attracted to the magnet. This experiment is one more thing that tells me that experiments should be tried and not just dismissed because theory says something. They stick to every kind of stainless steel I could find at home and at work. These were small neodymium magnets I purchased from All Electronics. Yet, I have seen permanent magnets sticking to stainless steel. I have been told that magnets don't stick to stainless steel.
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