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  • 1.  3003 aluminum sheet warpage after powder coat

    Posted 04-06-2020 18:17
    Seeking aluminum grade and temper expertise for recommendations to eliminate part warpage. Grade 3003 has been utilized historically for sheet metal enclosures on some of our equipment products. Those were liquid spray painted for finished surfaces. We would like to change to a powder coat process that utilizes a 10 minute @ 400 F thermal step. Some (not all) parts are warping slightly after powder coat. Our parts are made from 48" wide roll stock with nominal sheet thickness of 0.063". We have heard that 5052 is common for sheet metal panels and enclosures. Can anyone recommend aluminum grades and tempers that will reduce/eliminate the post-coating warpage?​

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    Mike Winnen
    Director, Engineering Implementation
    Q-Lab
    Westlake, OH
    (440) 990-5924
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  • 2.  RE: 3003 aluminum sheet warpage after powder coat

    Posted 04-07-2020 09:43
    You do not mention the Orientation of the warpage.  Is the curvature's tangent longitudinal or transverse with respect to the original rolling direction (which I assume is controlled)?   By any chance is/was it coiled at some point in its manufacture, giving it a little bit of "set"?  At 400 F there could be stress relieving occurring; perhaps a pre-forming stress relief at 400 F might eliminate that. 

    Are you using annealed (O temper) sheet?  If it is instead in a work-hardened (H) condition, it might have some residual stress that 400 F exposure would relieve leading to distortion (as well as reducing the mechanical properties just a bit).

    I don't see how the alloy selection would affect warpage, but an "H" condition might.

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    Charles Himmelblau
    Retired
    Mountain View CA
    (650) 968-1121
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  • 3.  RE: 3003 aluminum sheet warpage after powder coat

    Posted 04-07-2020 11:35
    I do agree with Charles' first point. There is a stress relief action going in the material in coating process.

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    Sanjay Kulkarni
    Materials Engineer
    MSSC
    Troy, MI
    248-840-1056
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  • 4.  RE: 3003 aluminum sheet warpage after powder coat

    Posted 04-09-2020 08:18
    Thank you for your reply Sanjay.

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    Mike Winnen
    Director, Engineering Implementation
    Q-Lab
    Westlake OH
    4409905924
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  • 5.  RE: 3003 aluminum sheet warpage after powder coat

    Posted 04-09-2020 08:18
    Hello Charles. Thank you for your reply. As one example, the curvature of the warpage has a tangent parallel to the roll direction. We had observed warpage in some parts made with 3003-H14 (strain hardened only). It looks like using a temper which includes some stabilization will be helpful. We've selected 5052-H32 as a trial grade since it is not expected to strain harden as much as 3003 during sheet forming.

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    Mike Winnen
    Director, Engineering Implementation
    Q-Lab
    Westlake OH
    4409905924
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  • 6.  RE: 3003 aluminum sheet warpage after powder coat

    Posted 04-07-2020 14:12
    I'm not in total agreement that there must be stress relief happening.  Distortion during heat treating can be caused by differential expansion due to uneven heating as well.  If a part has sufficient temperature differential and the strains exceed the yield, then permanent deformation can occur.  Reaching the textbook yield stress may not be necessary, since that is a measure of an average property over many grain orientations. 

    The distortion can occur during heating OR cooling.  And the heating/cooling in a load can vary significantly with furnace location.

    I suggest doing some testing where identical parts are heated and cooled to the same temperature, but with much lower rate heating and cooling, to eliminate this as a factor.

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    Paul Tibbals
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  • 7.  RE: 3003 aluminum sheet warpage after powder coat

    Posted 04-09-2020 08:17
    Thank you for your reply Paul.

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    Mike Winnen
    Director, Engineering Implementation
    Q-Lab
    Westlake OH
    4409905924
    ------------------------------

    Education courses