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#1242 08/24/16 01:43 PM
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hi all,
We use 230 shots (ams2431/2) to peen aircraft parts.
Recently, we bought some shots from the supplier , and found some of the particles rusted (approximately 10%~20%) when performing a view examination for acceptance.

we considered the supplied shots do not meet the requirements which specified in ams2431/2 3.6
What do you think about that? The shots acceptable?

ams2431/2, 3.6 contamination
shot shall be clean and free of dirt, grit,oil or grease.



Last edited by tom and jerry; 08/24/16 01:46 PM.
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I'm not an expert on media but here is what I seem to remember: The new cast steel shot should have an oxide coating after the manufacturing process. This is generally not subject to rust. However, after using the media in the machine this layer is reduced or removed and rust may occur. This is why it is important to maintain the in-use media with the highest standards of quality.

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Rust is not "dirt, grit, oil or grease" so that rusty shot does not contravene the quoted specification. This implies that you could be forced to accept the shot, having purchased it. On the other hand it should not have been rusty. Steel shot as-manufactured is covered with a thin skin of iron oxide. Reputable manufacturers store their shot in air-tight containers to prevent water molecules in damp air reacting with the iron oxide to form hydrated iron oxide, aka rust. I suggest that you do not use the rusty shot but ask your supplier to replace it with rust-free shot.

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Good point, iron oxide in trace amounts is not harmful to the process or the results. 10 -20% iron oxide is natural if the shipping or storage atmosphere is high in humidity. Furthermore, defining Rusty is too subjective and perhaps should be included in the next Committee meeting.

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Thank you all.
We will ask the supplier to replace them.

It's difficult to describe what I observed using a microscope, but I am sure it not "a thin skin of iron oxide", it looks like ... heavily mildewed peanuts。

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We order media in steel buckets and media inside bucket is in plastic bags. Just to be sure.

I poured some shots in a golf putter club to make it more stable. Added a little water to be sure it stays inside smile It rusts almost instantly as you already know.

Good luck with supplier !


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