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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Original Message:
Sent: 04-06-2020 17:26
From: Mike Winnen
Subject: 3003 aluminum sheet warpage after powder coat
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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