×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

QC of Magnetic Permeability of StainLess Steel

QC of Magnetic Permeability of StainLess Steel

QC of Magnetic Permeability of StainLess Steel

(OP)
I have a requirement for a Deep Drawn Stainless Steel Component to have a Relative Permeability of less than 1.05. The austenitic annealed material meets this spec. but a high percentage of cold work could raise the value.

Finding a metal fabricator to tool and manufacture the part who also is familiar with the magnetic requirements and has a QC system in place for it has been a problem.

How should the requirement for low permeability be controlled and measured by our component vendor?

RE: QC of Magnetic Permeability of StainLess Steel


Is there a correlation to be had between surface (work) hardening and magnetic permability?

RE: QC of Magnetic Permeability of StainLess Steel


That is very interesting, thank you!

RE: QC of Magnetic Permeability of StainLess Steel

The best way to approach this is probably indirectly. call for the part to be bright annealed after drawing. check by hardness testing. either that or you have to obtain a magnetometer to measure permeability directly. In my past we had a assembly that used stainless screws in a magnetic sensor assembly, cold work from the heading and thread rolling made the sensors erratic. brass screws tended to have thier heads twist off (they were #2-56). we ended up having to use Ti6Al4V screws. (can you say expensive?)

RE: QC of Magnetic Permeability of StainLess Steel

(OP)
This part is for a magnetic sensor assembly also.  I am researching equipment to measure the magnetic characteristics as we would like to avoid post-draw anneal if possible. We are planning to qualify the material and manufacturing process. If OK, we will need a plan and procedure to do magnetic inspection on the finished parts. My concern is that the variation in chemistry of the SS may cause some parts to be out of spec.

Ron

RE: QC of Magnetic Permeability of StainLess Steel

Your concern about chemistry is a valid one. you may want to consider specifying cartech's Custom Flo 302HQ, it has small amounts of copper added to lower it's strain hardening rate. see here:

http://crswnew.cartech.com/wnew/techarticles/TA00009.html

There are other 3xx series that have alloy additions that are intended to suppress strain hardening, but my mind is blank right now. If I think of which ones, I'll repost later.

Monel or Aluminum may also be an option

RE: QC of Magnetic Permeability of StainLess Steel

(OP)
We plan to evaluate a low perm digital meter by Foerster Instruments. It has a handheld probe and direct readout over the permeability range of 1.000 to 2.000. They call it a Magnetoscope.
Are you familiar with it and how does it compare to the Severn Gage?

Ron

RE: QC of Magnetic Permeability of StainLess Steel

No, I have never used the Magnetoscop (http://www.foerstergroup.com/Maintenance/permeability_measure.html), but I have used a Foerster %IACS meter and came away with the impression that it was a quality instrument.  Out of curiosity, I went looking for a price (at www.corvib-int.com) on the Magnetoscop (to compare the $575 for the Severn Gage) and came up with a price of $9,975 (ouch!) for:

Operating Instructions
Magnetoscop 1.069 Measuring Device
Permeability Probe, X1
Calibration Standard MU 1.2
Batteries (5) AA
Carrying Case

The Magnetoscop provides a "value" (as opposed to the "less than / more than" standard comparsion provided by the Severn Gage).  Please let us know how your evaluation goes.

RE: QC of Magnetic Permeability of StainLess Steel

(OP)
I received two Magnetoscops yesterday and started playing with one today.  So far, it looks good.  
The unit is a microprocessor driven digital readout meter that comes with a probe and calibration standard.  The standard we received is 1.223 u. On power up, you place the probe on the standard, enter the perm value (1.223) and the processor self calibrates. When done, the unit reads 1.000 when the probe is in air. When the probe is placed on the test piece (in our case austenitic Stainless Steel)the permeability value is displayed directly.

Next week we will verify correlation in the readings of the two units. Our plan is to consign one unit to our vendor and the other to our incoming inspection. We need to be able to reproduce each others reading.

RE: QC of Magnetic Permeability of StainLess Steel

(OP)
The Magnetoscops are working out well.  The two units are producing compareable results.  The only complication that we found was that the permanent magnetic field that the probe emits will magnetize any ferrous inclusions in the stainless steel. This remnant field will affect any subsequent closeby permeability readings. To solve this, we had to add a demagnetize step between readings to the procedure.

Ron

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

eBook - 10 Reasons to Choose CATIA on the Cloud
To compete in today’s fast-paced and competitive market, smaller and newer firms need a powerful platform that will enable them to compete with bigger players, without the heavy investments needed in computer hardware, software and personnel. Download Now
White Paper - Smart Manufacturing for Electronics
This white paper describes a transformative approach to electronics manufacturing made possible by the addition of Mentor Graphics to the Siemens family. It describes a completely digitalized strategy that supports both printed circuit board (PCB) and mechanical design and manufacturing, uniting the entire product lifecycle – from idea and production to customers and back. 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