Ovality and Flatness generated after Heat Treatment of Rolled Rings

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Chennaiite

Never-say-die
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#2
Please suggest why the ovality is generated after normalzing of rolled ring
I have encountered this problem in Hardening & Tempering. For me, what you have asked is a million dollar question. I have conducted enough experiments to conclude the problem, but ended up losing to Heat treatment process. Causes include Geometry of the part (in your case wall thickness may be less), location of part in the trolley, stacking method in the trolley, metallurgical specification of the part before HT, Furnace controls, etc. BTW, not just rolled part, even Forged & Machined parts do not make exempt from this problem.
BTW, thanks for raising this point.
 

bobdoering

Stop X-bar/R Madness!!
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#3
I have conducted enough experiments to conclude the problem, but ended up losing to Heat treatment process. Causes include Geometry of the part (in your case wall thickness may be less), location of part in the trolley, stacking method in the trolley, metallurgical specification of the part before HT, Furnace controls, etc. BTW, not just rolled part, even Forged & Machined parts do not make exempt from this problem.
Any time you try to heat treat to a final geometric condition - whether it is a dimension or form feature - you are risking capability doom (unless you have a wide open tolerance.) It is as difficult as dialing in the height of a loaf of bread from the oven.
 
M

machrk

#4
Please suggest why the ovality is generated after normalzing of rolled ring

Distortion can occur during heat treatment processes - are parts being uniformly heated all the way through ? Was there some residual stress prior to heat treatment ? Are parts constrained from expansion - contraction in any way during the heating & cooling processes ? A metallurgical forensic "CSI" approach can help if you are having ongoing problems - all too often there isn't just a single cause to a problem - there may be multiple factors acting together..

I'd also suggest that you try the Eng-Tips forum website - lots of folks there with shop floor workshop knowledge on how to avoid probs like this - start here

cheers
@SteelyQueen aka machrk (also @KerrieAnne) :)
(Mechanical Testing Lab & QMS Manager - Bachelor of Metallurgy)
 
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