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#624 04/24/09 04:31 AM
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Dear Sir,
I have a question about steel shots shape acceptance requirements.

On AMS-2431/1, or AMS-2431/2, page 6, figure 2, marginal shots, there are 3 samples, nodulated, elongated and twins.

For nodulated shots, there have 5 protuberances on the figure 2. if only have one protuberance on the surface, is it nodulated shots ? and what is probuberance size scale on whole shots.

For elongated shots, if one shot is very flat, how to judge, is round or elongated ?

Thank you very much.

#625 04/24/09 06:23 PM
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Yet another subjective test.

I would consider 1 protuberance on the surface to be modulated shot. As for the size of a protuberance at some point I assume you would define that shot as a twin. Either way as long as you are properly screening the shot it will remove most of these marginal particles. If not then running the charge through a spirolator will do the trick.

-Walter

#626 04/24/09 06:50 PM
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It is worth considering the objective of cast steel shot shape acceptance requirements. Shot peeners want the shot to be predominantly round (or at least roundish). They do not want to be supplied with grit. Hence the specifications divide shape into "Acceptable, Marginal and Unacceptable" categories. The diagrams of corresponding shapes are only illustrative - they are not comprehensive. Nodulation (caused by fusion during cooling) can involve one or more nodules. At one extreme there may be only one nodule, at the other there can be several. All are "Marginal". A very flat (pancake-shaped) particle is rare and is difficult to spot because it generally 'lies flat'. If the flatness is detected it would definitely be regarded as "elongated".

#627 04/27/09 05:56 PM
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I agree with Socrates the intent is to have round or near round shot particles. Because the atoinzation process yields made different shape it is necessary to determine acceptable shapes as defined in Figure 1. Marginal shapes including nodulated, elongated, and twins are acceptable as long as they number less than the allowable amount listed in Table 3. A nodulated marginal particle would be one containing at least one attached shot particle. An Elongated particle in most shot specifications define them as; a particle whose length is twice the width of the particle. Twins would be considered as two particles attached that are approximately the same size.

#628 05/01/09 11:18 AM
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[From Dr. John Cammett via Jack Champaigne]
There are no quantitative standards or definitions that apply here and such are really unnecessary. How relatively big does a protuberance need to be to have it and its mate classified as a twin? Literal interpretation of the English word, twin, would require that the mates be of equal size. Otherwise the smaller would be called a protuberance. If one were to get really fancy, then a protuberance could be named thus only if it falls below the smallest size permitted in the size distribution. Otherwise it could be called a "twin". As I stated at the outset, there are no established schemes here and I see no necessity to establish any. It is simply that all such misshaped particles with rounded edges are lumped together as marginal and the lumped percentage is used to determine acceptability of the media sample.

Any elongated particle is marginal provided that the largest dimension falls within the size distribution and it has no angular features. Otherwise it would be deemed unnaceptable. It is not important to create special names or to judge particular shape.


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