For example, let's say that I have a finished blade made from some powdered 'super' steel. (I don't want to get side-tracked in discussing the specifics of the steel--just a high-end powdered steel that is capable of becoming magnetic after it has been hardened and tempered.) Let's say I place my blade against a very strong magnet long enough for the steel in my knife blade to become magnetic itself. What, if anything, has happened to the micro structure (austenitic/martensitic properties) of the steel in the blade? Have these changes affected the hardness or durability of the blade edge?
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What are the affects of magnetic fields on heat treatment and properties of steel?
- Thread starter -=Gill=-
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Richard338
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Most of the articles that came up in a quick search are related to stress or damage inducing changes in magnetization, for example in pipelines.
I did find one article on the magnetic treatment of cutting tools, with the intention of improving mechanical properties. They claim grain refinement and increased hardness in tests on M42 steel. I didn't read beyond the abstract so I didn't form an opinion or have time to look for corroborating studies.
I did find one article on the magnetic treatment of cutting tools, with the intention of improving mechanical properties. They claim grain refinement and increased hardness in tests on M42 steel. I didn't read beyond the abstract so I didn't form an opinion or have time to look for corroborating studies.
JoeBusic
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Changing high magnetic field (several T min. and in low Hz) can be very beneficial but time consuming as aging after the induction is when the magic happens. Normal handheld magnet (no matter the size) does nothing except magnetize.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Joe is pointing out what I recalled.
There are magnets, and then there are MAGNETS.
Even a strong fishing magnet is not strong enough to affect the structure of steel. These magnets are in the 1000-4000 Gauss rating. Rare Earth magnets may reach 15,000 Gauss. An MRI may have a rating of 70,000 Gauss, and research magnets in labs may approach 500,000 Gauss.
The earth's magnetic field has a Gauss rating of only .3 to .5 Gauss.
An interesting sideline to this discussion is that in welding you can't have much of a magnetic field at the joint or it will affect the weld. 5-10 Gauss is all it takes to mess thing up. When using welding magnets to hold things in place, you should make tack welds and then remove the magnets.
There are magnets, and then there are MAGNETS.
Even a strong fishing magnet is not strong enough to affect the structure of steel. These magnets are in the 1000-4000 Gauss rating. Rare Earth magnets may reach 15,000 Gauss. An MRI may have a rating of 70,000 Gauss, and research magnets in labs may approach 500,000 Gauss.
The earth's magnetic field has a Gauss rating of only .3 to .5 Gauss.
An interesting sideline to this discussion is that in welding you can't have much of a magnetic field at the joint or it will affect the weld. 5-10 Gauss is all it takes to mess thing up. When using welding magnets to hold things in place, you should make tack welds and then remove the magnets.
JoeBusic
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Those who play with induction can easily check the disturbance of a magnet field when quenching with a magnet on. Magnetized part is totally weird. Heats slower than the rest and it needs more heat to austenitize. Usage of that steel is questionable.
Btw, to add a thing. Magnetic influence (the beneficial one) is never explained correctly. What they did observe is carbon diffusion. So is it just re-martensitisation? If so, why bother with magnets when one can just treat it to higher hardness and avoid 5 days of magnetic ageing. All benefits are really in the category of a stronger steel.
Although it seems like an attractive idea, practice makes it obsolete.