Demagnetization threshold
Demagnetization threshold
(OP)
Could anyone help me to give a physical (idealy quantitative) basis on the evaluation of a demagnetization threshold? We need that the magnetization is low enough not to attract ferrous shavings or filings. Our practical upper limit is 8 Gauss (640 a/m) of residual magnetization.
An other question concerns the best mean of measurement. Indeed, we notice big differences of results depending on the mean of control.
An other question concerns the best mean of measurement. Indeed, we notice big differences of results depending on the mean of control.
RE: Demagnetization threshold
The International Magnetics Association has a standard specification for (among other things) demagnetization level, but it is based on the number of particles a magnet picks up. They basically state a magnet is considered demagnetized when it picks up 3 or less particles of soft iron particles within size -5, +10 mesh.
It is sometimes difficult to use a magnetic reading to determine demagnetization. When demagnetizing a magnet via magnetic fields, the face of the magnet has regions that are still magnetized. Sometimes those regions alternate polarity, making it more difficult.
The "best means of measurement" depends on the application. What is the purpose of demagnetizing the magnet?
RE: Demagnetization threshold
In long product (bar and tube) often direct readings are used. In other geometery attraction of particles may be the only meaningful test.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Demagnetization threshold
The IMA specification is very interesting. Could we associate the emperical test with a residual magnetization value?
EdStainless : Today, we measure macroscopic residual magnetization in the air (<8 Gauss) but we have also transveral magnetic induction measurement device. Could we link these 2 measurements?
RE: Demagnetization threshold
If you are looking for an "official" definition of demagnetization level, the IMA spec is a close as you're going to find. It may not be practical in every application. You might need to work with your end customer on a mutually agreeable level or test methodology.
You'll probably find that a part that holds more than 3 particles can still be machined without any problems. The same could be true for the other situations you mentioned.
RE: Demagnetization threshold
Could you give me the reference of the IMA specification concerning the demagnetization level?I do not find it on the web.
RE: Demagnetization threshold
http://www.intl-magnetics.org/pdfs/0100-00.pdf
The demagnetization level is discussed on page 3.
RE: Demagnetization threshold
For example, heavy walled tubing, measured individually with reading 3-6G taken at the ends of 20' long pieces.
When these are in a bundle of 36 pcs the reading is 20G.
When a single piece is cut into 12' lengths the readings range from 1G to 10G.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Demagnetization threshold
The geometries of the different parts are rarely symetric.