×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Demagnetization threshold

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.

RE: Demagnetization threshold

I don't understand what you are looking for.  Are you trying to find a method to demagnetize a magnet or are you looking for a standard (or regulation) for determining when something is demagnetized?

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

What kind of item are you measuring?
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

(OP)
MagMike : Concerning our research, we'd like to know when our parts made of bearing steels are "correctly" demagnetized and how measure them (pb of local magnetization in complex geometry despite global demagnetization). The demagnetization is important for us for machining, non destructive controls and in service reasons.

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

Regarding the IMA specification: It is not possible to associate it with a residual magnetization value.  A number of factors are involved in determining how many particles a magnetic material will pick up.  Residual magnetization is only one of those factors.

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

(OP)
Many thanks for your information.

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

The reason that I asked about geometery is that it has a major impact.
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

(OP)
We have principally flat products made of bearing steels from 6 to 12 mm thick. The parts are fine blanked and heat treated to obtained a hardness of 700-800 HV.

The geometries of the different parts are rarely symetric.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close