Stainless steel becomeing a magnete

By hogan

Date 05-22-2008 22:40

try a search of the forum

By 357max

Date 05-23-2008 15:58

If it is a ferritic stainless steel it could be magnetic. The 300 series austenitic is non magnetic.
As you travel about; check out the local eateries. A number of them in my travels have magnetic stainless steel cutlery. It provides entertainment for the kiddies when you make a "train" and pull around the table. Excellent way to entertain when the service is slow. I should probably find a higher class of eatery. Or, eat out less.

By Hugh Cunningham (*)

Date 05-24-2008 11:41

A lot of stainless steel cutlery, knives and tools are magnetic because they are either ferritic or martensitic steels (the duplex steels are also magnetic, but not so strongly). Only the 200 and 300 series stainless steels, which are austenitic, are non-magnetic, and even they can be made magnetic locally with sufficient work hardening.

By kendall (*)

Date 05-25-2008 02:27

I know that martensitic and ferritic stainless steels are magnetic, but what is confusing me is that the pliers are causing the magnetic pull. I have not seen this with any other knife or tool that I have.

By DaveBoyer (*****)

Date 05-25-2008 03:20

Have they been magnetised as long as You have had them, or have they recently become magnetised?

By kendall (*)

Date 05-25-2008 03:54

They recently become magnetised. I bought them a few months ago. They are the pliers in a leatherman.

By Hugh Cunningham (*)

Date 05-25-2008 08:19

Have they been subject to any strong magnetic fields recently? If they were used on or near a permanent magnetic, especially if they were drawn across the magnet in one direction, they will become magetised if they are ferritic or martensitic. I suspect they will be martensitic to give the wear resistance. Even moving the pliers through the induced magnetic field surrounding an electric cable (DC) can induce magnetism if the cable has a reasonably high currrent flowing. Its all part of the same principle that electric motors and generators work on.

Try this for an experiment: Take a pair of ordinary scissors (even the cheap ones say "stainless", but they will not be 300 series), a paper clip and a fridge magnet. Try to pick up the paper clip with the scissors by just touching the paper clip. There will be no apparent magnetic attraction. Now stroke the scissors along the length of the blades with the fridge magnetic (one side will do). Always stroke in the same direction, lifting the fridge magnet clear at the end of each stroke and returning to the start. Stroke maybe 50 times. Now touch the paper clip with the tip of the scissors and lift the paper clip. The attraction will not be very strong, but you should be able to lift the paper clip off the table.

The stronger the magnetic field in the magnetising element the greater the induced magnetism in the item you are trying to magnetise. Ever tried welding on a pipe that has had MPI done nearby? The residual magnetism can make the arc jump everywhere but where you intend it to be! This is why demagnetisation should be done after MPI if welding is ongoing.

By kendall (*)

Date 05-25-2008 17:30

Thank you for that response. This problem has been bugging me for a little while, but no one around here seems to know too much about this kind of thing.

By kendall (*)

Date 05-25-2008 22:52

Is there anything I could do to unmagnetize them? It can be a bit of a pain when I am try to set up and hold small pieces.

By DaveBoyer (*****)

Date 05-26-2008 04:18

There is a device called a demagnetizer, it is a coil energised by alternating current [plain old house current] You move the magnetized item through the alternating magnetic field, and the item looses it's magnetism. If You have acess to a machine shop, tool & die shop, etc. or know someone who does, there is a pretty good chance they can demagnetize it for You.

If You want to make a demagnetizer of Your own, take a long length of insulated single conductor wire and wind it into a coil big enough to pass the tool and Your hand through. Put this coil in series with a 100 watt light bulb [otherwise it would be a dead short]. Remove Your watch before You mess arround with this, it might not ruin it, but it won't do it any good. Energise the coil and pass the tool through the coil [keep it moving] several times turning it as You go. You should feel the 60 Hz vibration in the tool. Turn off the power when the tool IS NOT in the field. If You don't fully understand this description and are not somewhat experienced with electricity, You should not try this.