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Technical Discussions
Ishbel Macdonald
Consultant, Engineering Consultant - NDT
Subsea 7, Norway, Joined Nov 1998, 11

Ishbel Macdonald

Consultant, Engineering Consultant - NDT
Subsea 7,
Norway,
Joined Nov 1998
11
00:49 May-10-1999
Magnetic permeabilities

Hello therr

Does anyone out there have any idea where I can find values for the magnetic permeabilities of steels such as duplex and super duplex? I am looking into the possibility of carrying out MPI, and so would like to know how "magnetic" these materials are. I know that there are methods to carry out such evaluations, but unfortunately, I do not have access to the equipment.

Regards

Ishbel




    
 
 Reply 
 
Kåre Johansson
Kåre Johansson
04:23 May-10-1999
Re: Magnetic permeabilities
: Hello therr

: Does anyone out there have any idea where I can find values for the magnetic permeabilities of steels such as duplex and super duplex? I am looking into the possibility of carrying out MPI, and so would like to know how "magnetic" these materials are. I know that there are methods to carry out such evaluations, but unfortunately, I do not have access to the equipment.

: Regards

: Ishbel
We did some MPI of 2205 some years back with good result. We assumed a permeability of 60% of carbon steel and it worked reasonably well. This is not theoretically correct as
the permeability will depend on both the amount of ferrite and the chemical composition of the ferrite. Watch for false indications in the HAZ due to changes in ferrite content. If you want more exact values yu could look into the proceedings of some of the duplex conferences which have been held. Maastricht (1997), Glasgow (1994), Baune (1991).Steel producers like Sandvik and Creusot Loire should also be able to help.
Kåre


    
 
 Reply 
 
LK
NDT Inspector,
Norway, Joined May 2008, 104

LK

NDT Inspector,
Norway,
Joined May 2008
104
19:24 Jan-11-2012
Re: Magnetic permeabilities
In Reply to Kåre Johansson at 04:23 May-10-1999 .

Good afternoon.

Any changes within last 12 years ? :)
Anybody have more information about MPI of duplex bars?
One customer requested both PT and MT on them.
I have some doubts about efficiency of mag particle testing.

Looking forward for your comments.
LK

    
 
 Reply 
 
John H
NDT Inspector,
Norway, Joined Nov 2012, 1

John H

NDT Inspector,
Norway,
Joined Nov 2012
1
20:24 Nov-14-2012
Re: Magnetic permeabilities
In Reply to LK at 19:24 Jan-11-2012 .

I look forward to more information on this subject.

    
 
 Reply 
 
John
John
02:14 Nov-15-2012
Re: Magnetic permeabilities
In Reply to John H at 20:24 Nov-14-2012 .

All u can think of is a lift test of the material

    
 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 836

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
836
01:30 Nov-22-2012
Re: Magnetic permeabilities
In Reply to Ishbel Macdonald at 00:49 May-10-1999 (Opening).

Ishbel,

You're not saying wht type of equipment you have or which MPI method you will be using (yoke or mag bench).

Regardless, what you have to remember is that your magnetic field should be strong enough to magnetise your part and show the indication you are seeking. ASTM E709 talks about two way to ensure your magnetic inspection will be succesful is to use a pie gauge and see the artificial defects in it or with a Gauss meter tha will indicate a field of 30 - 60 gauss in the part.

    
 
 Reply 
 
Jianjun Wu
Engineering,
China, Joined Nov 2012, 20

Jianjun Wu

Engineering,
China,
Joined Nov 2012
20
02:22 Nov-22-2012
Re: Magnetic permeabilities
In Reply to Michel Couture at 01:30 Nov-22-2012 .

Recently, I read a book regarding the permeaility of steel materials.

This book specifies the Magnetic characteristic curve of the material which will help us to determine the proper parameters in MT techinque selection. But this book is written in Chinese. However, the symbols and curves could be easily understood. If any one want this book, please leave your mail. Br, Hc are indicated in the curve.

    
 
 Reply 
 
Jianjun Wu
Engineering,
China, Joined Nov 2012, 20

Jianjun Wu

Engineering,
China,
Joined Nov 2012
20
02:29 Nov-22-2012
Re: Magnetic permeabilities
In Reply to Ishbel Macdonald at 00:49 May-10-1999 (Opening).

zoom image
According to the Curve, if Br>0.8T, Hc>1000A/m or (H*B)max>0.4kJ/m3, residual method would be better for this material; otherwise, continuous method will be applied.

Hope this will do some help to you.
    
 
 Reply 
 

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