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Material properties for annealing cage

  1. Sep 11, 2014 #1
    When looking at the cage or structure used to carry materials into an oven for the annealing process, what material properties are most important?

    Lets saying during full annealing of aluminum, the oven is heated to 540 degrees Celsius. A cage is used to carry the aluminum into the oven. After the cage with aluminum is finished heating it is dropped into water and cooled to below 35 degrees Celsius. What material properties are most important to reduce the amount the cage deforms?

    I understand that the design of the cage will help reduce deformation also, but I was just curious about the material itself. I'm assuming the thermal expansion coefficient of the material is important. Are there other properties (hardness, tensile strength, etc?) that are also important to take into consideration?
  2. jcsd
  3. Sep 15, 2014 #2
    I'm sorry you are not finding help at the moment. Is there any additional information you can share with us?
  4. Sep 16, 2014 #3
    What other information would be useful?
  5. Sep 16, 2014 #4


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    What other material or mechanical properties are affected by temperature or rapid temperature change (i.e. rapid quenching)?

    What is the mass of Al being annealed?

    Also, one wouldn't want the Al or Al alloy to chemically react with the cage material.
  6. Sep 16, 2014 #5
    Yes, the cage holding the aluminum plates is heated to 540 degrees C, then lowered (quickly) into water at ~22 degrees C. The water temperature does not exceed 35 degrees C, because it is pumped and cooled.

    Is the mass of the Al being annealed important? I just want to know what material properties affect the deformation caused by heating/cooling, so that the cage does not pull itself apart. (for ex. thermal expansion coefficient)
  7. Sep 23, 2014 #6
    From my own research that I've done, I believe the properties which are important when looking at the heating/cooling cycles are:

    - thermal expansion coefficient
    - tensile strength
    - creep strength

    If the cage is built out of a material (stainless steel, titanium, or carbon) which has a low expansion coefficient, and high tensile/creep strength. Then the cage shouldn't pull itself apart as easily when heated to 500 degrees C and then quenched in water. Does this make sense?
  8. Sep 23, 2014 #7


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    I would be worried about corrosion at elevated temps and the effect of repeated quenching cycles the most.
    Other properties can be designed around, the initial strength of the material wont matter much when it's corroding away or it becomes too brittle from quench cycles.

    Stress due to thermal expansion can be designed out (eg using expansion joints, slots, pin joints etc) Presumably the Al parts are free to expand/contract without constraint from the cage and vice versa so why does it matter if the cage temporarily deforms? as long as the Al isn't dropped right?

    Creep may not be a problem -depends on the design specs - is the cage hanging or sitting in the oven? (ie under self-weight only or Al mass too?) What loads are on the cage at annealing temp? for how long? Is dimensional accuracy even required? ie if it creeps 10mm will it still function? ie will it still fit through the oven door etc? Is 10mm of creep over 5 years acceptable? Can you design it so you can just redrill some holes 10mm away to counteract the creep after those 5 years? etc etc

    These and many other questions will probably be answered when you know exactly what the design specs are.
  9. Sep 24, 2014 #8
    Thank you for the help and additional questions.

    - Presumably the Al parts are free to expand/contract without constraint from the cage and vice versa: Correct, the Al is not constrained to the cage
    - Does it matter if the cage temporarily deforms? It does not matter whether the cage deforms as long as it comes back close to its original form so that it does not hit the side of the oven, and the four pick up points stay in the same spot. A crane lifts the cage into the oven by four pickup points, these points have to stay in the same position.

    - Is the cage hanging or sitting? Hanging
    - What loads are on the cage at annealing temp? Not sure yet
    - Is dimensional accuracy required? Yes, the cage just fits inside the oven
    - If it creeps 10mm will it still function? I'll get back to you on this one

    My plan was to pick a suitable material and then work on the design. Maybe it is a good idea for me to start on the design now while I look at materials. Do you have any literature or website I can read to help with designing a cage for this purpose?

    BTW the current material used is Stainless Steel 304
    From research I've gotten to Stainless Steel 330: RA330
    Which looks like a good replacement material.
  10. Oct 5, 2014 #9


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    What properties of 304 stainless are unacceptable for this application?

  11. Oct 6, 2014 #10
    The current problem is that the cycles of heating to 540 degrees C, dropping into water and cooling to 35 degrees C, causes the cage to "pull" itself apart. Now I understand this can be partly a problem with design, which is also an aspect I am looking at. However, I'd also like to find a "better" material.
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