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Magnetic conductive material but thermally non conductive

  1. Sep 4, 2017 #1

    I have application where i need to lift metal plate, 3kg weight, ( 3mmX 15mm), 250degree.C hot, for the period of 1min and put it back. For lifting purpose i am using actuators. As i have no opportunity to make hole in plate i have to use magnet for lifting purpose. I got Electromagnet with capacity 10 times of requirment. But it can not withstand temperature above 80degree.C.

    Now my question: i am looking for the material that can act as insulator between magnet and metal plate at the same time it don't reduce magnetic effect less than half of its capacity.

    Any suggestions?

  2. jcsd
  3. Sep 4, 2017 #2
    Calculate the heat transfer during the lifting action and the resultant temperature rise of the workpiece durign the cycle time.
    Any thing that is heated up by a manufacturing process can also be cooled down by various means: dunking in cooling bath or blowing with cooled air.
    Alternatives: mechanical gripper or a vacuum lifting system with high-temperature suction cups.
  4. Sep 4, 2017 #3


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    Welcome to PF.

    You could make pole extensions for the magnet out of thick-wall iron tube. You could push cool air down the the pole extensions to cool them, block the tube ends and put vent holes near the hot end that direct air away from the sample.

    To cool with circulated water, (or air), put a bridge of non-magnetic tube across the gap between the pole extensions at the hot end. Push coolant down one pole extension and recover the hot fluid from the other.

    Austenitic stainless steel tends to be non-magnetic and poorer thermal conductors. Martensitic stainless steel is magnetic. See if you can find a martensitic stainless steel with a lower thermal conductivity than iron.
  5. Sep 5, 2017 #4


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    Or just put a sheet of asbestos or fiber glass on the magnet poles. This however assumes that the duty cycle is rather low so there is an enough cooling time between lifts.

    There are probably some people on this site that can give an idea of the maximum distance betwee the plate and the magnet. With the magnet being 10 times stronger than needed I expect it can be done.

    I have heard of electromagnets that have coolant (a mix of water and antifreeze) running thru plumbing in the core. Doing the machining could be somewhat difficult.

    Do Google search for Switchable Magnetic

    Here is one example: http://www.engineersupply.com/Seco-5114-052-Switchable-Kelly-Magnet-Mount.aspx
    Last edited: Sep 5, 2017
  6. Sep 6, 2017 #5


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    Will the metal plate be magnetic at a temperature of 523K?
    What is the metal? What is the curie temperature of the metal?

    The dimensions are quite confusing. 3mm is probably the thickness, but what are the surface dimensions?
    There is insufficient information to work out the area and if a vacuum might hold the plate.
  7. Sep 6, 2017 #6

    Thank you for your inputs,

    The plate is 3mm thick x 15mm width x 200mm long,

    The plate is made of Mild steel will heated in oven at 250 degree C. After it get hot the process takes place and that has to be done within minute and put back to the oven. Challenge is the temperature should not be reduced below 200 degreeC. Using hand gloves it is difficult to handle, Clip type mechanism takes time to make it attached with. So Magnet is easiest solution. Rare earth type magnet or strong magnet has problem of detaching from magnet ( need to apply lot of force, hot material ) so electromagnet is used. It has only issue that it can not withstand high temperature so i required such a material that are friendly with magnet and insulating type material.

  8. Sep 18, 2017 #7


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    @Tom.G gave a couple of suggestions

    The obvious other choice would be a ceramic tile attached to the surface of the electro-magnet

    you didn't answer his Q about the lifting duty cycle ... that is how often per unit time the lifting will be done ?
    once a minute, once an hour or ...... ??

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