Hard Material with Low Magnetic Permeability

[rbemben]

Hello,

I have some processing equipment that wraps steel wire around our parts and once wrapped, twists the wire to secure it to the part and breaks off any excess wire. We are starting to see that the tooling is becoming magnetized as it twists this steel wire causing the excess wire to stick to the tooling creating other issues.

I am trying to find an alternative material with a low magnetic permeability but hardness comparable to the current tooling. The current tooling is made of SKD11 steel with a hardness of 61-63 HRC.

Currently I have been looking at material with hardness between 45 & 65 HRC.

Any suggestions on alternative materials?

Best Regards,

Ross

 

[CoryPad]

Cemented carbide with low binder concentration will provide hardness of 63 HRC with magnetic permeability lower than tool steels like SKD11. The multiphase material MP35N has very low permeability with hardness around 50 HRC.

 

[dgallup]

Have you considered hardfacing with stellite? It is not extremely hard but it is very wear resistant and almost totally non-magnetic.

Nitronic 60 also remains almost completely non-magnetic in any condition, again not extremely hard.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[Ceramicguy]

Can you remove the tooling and demagnetize it?

Bruce

http://accuratus.com

 

[EdStainless]

You actually need a material with low coercivity, low tendency to retain magnetization.
Considering that high Cr tool steels used to be used as permanent magnets I am not surprized at your issue.
I would suggest that you look at carbide or ceramic. Carbides with high binder content will be ferromagnetic (attracted to a magnet) but they don't retain the field.
If you need toughness look at some of the toughened zirconia ceramics.

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P.E. Metallurgy, Plymouth Tube

 

[rbemben]

EdStainless: I looked up "coercivity", "the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized". Which sounds to me like the ferromagnetic material is magnetized to begin with but resists becoming demagnetized? Please help me understand this.

Ceramicguy: We have been removing the tooling and demagnatizing it, however it becomes remagnatized about 3 weeks to a month later. It is an option for now, it just takes maintenance an hour to change the tooling so it is not convienient for production.

Currently I am getting the tooling quoted. The quote has MP35N (Nickel, Cobalt, Chromium alloy) 65% cold reduction as the material (suggested by CoryPad). This has a very low magnetic permiablity and a comperable hardness to SKD11 steel at about 48 to 52 HRC.

Thanks for the input! Keep'm comin'!!!

 

[1gibson]

Do you really need to remove the tooling to demagnetize it? I've got a hand held 120v video tape eraser, weights about 1.5 lbs. Works on my screwdrivers. Might be worth a shot to hit it with a big electromagnet and see what happens. It's a good Band-Aid if it works.

 

[EdStainless]

Magnetically soft ferromagnetic materials such as the Si-Fe and ferrites used in cores have high perm and saturation, but they are easily demagnetized when the field is removed of reversed. They retain very little magnetism.
Hard magnetic materials are called permanent magnets. They resist demagnetization, and hence are used to create useful magnetic fields.
You could either use a material that is non-ferromagnetic, or one that is magnetically soft (though mechanically hard).

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P.E. Metallurgy, Plymouth Tube