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Casting defects - bubbles in sheet


#1
We have had similar problems casting 18K and our advice from the
metalurgist at United Precious Metals was that we were probably
not hot enough. He said that if you are used to 14K it is a fairly
common mistake. Flask and metal hotter for higher kara 

Thats funny, the other day I called Hauser and Miller in St.Louis. I
enquired with their metalurgist as to my problem. I fabricate using
large 18kt gold sheet (4X6"). On occasion after rolling the sheet
looks great, but after anealing fair sized bubbles appear. The
metalugist had no good answer as he said they have problems too but
with 22kt. What’s this all about?

For all you beginners take heart, even the most experienced
goldsmiths have problems and we are always learning something new. I
have been at it for over 30 years and have learned a lot from
Orchid.

Robert


#2

Robert,

What you could be seeing is voids in the original cast bar that was
rolled down into the sheet. The breakdown operation will compress
the voids flat but never gets rid of them. When you stress relieve
the material with heat and it relaxes, the metal delaminates and you
can get what looks like bubbles. I’ve seen this especially with
platinum sheet.

Tino Volpe


#3
    What you could be seeing is voids in the original cast bar
that was rolled down into the sheet. The breakdown operation will
compress the voids flat but never gets rid of them. When you stress
relieve the material with heat and it relaxes, the metal
delaminates and you can get what looks like bubbles. I've seen this
especially with platinum sheet. 

It kind of sounds like Hydrogen damage… Send me the particulars
and I will look into it a bit.

jesse


#4

Tino

Then what do you think, higher temp and smaller voids? Could work.

Thanks Robert