Qualification for miniature work

By Truta Date 03-17-2011 20:35

Hello,
What are the applicable standards or guides for qualification of miniature welds? I mean, for example, micro-tig or micro-plasma on capillary tubes, bellows, TIG welding of thin-walled pipes ( say 0.40 mm or less, Incoloy, Kovar, Zircaloy). AWS B2.1 paragraph 2.3.7 is ok? Suggestion for testing the weldments?
Thank you in advance
C. T.

By OBEWAN

Date 03-17-2011 20:44 Edited 03-17-2011 20:53

I used to work on bellows and most of the specs were in house company specs. The smallest we welded were .002" wall thickness titanium with micro plasma.

The QA was all done with macros and a scope for each production set-up and the product was 100% leak inspected with a helium mass spectrometer. There are actually published standards for mass spectrometer inspection that can corelate minute leak rates to defect sizes but it has been way too long ago for me to remember what those standards were. You could try searching for mass spectrometer leak test information and you might find them.

Update:

I found this article which gives the actual equation to calculate defect size if enough parameters are known:

http://www.atcinc.net/pdf/Advanced-Leak-Testing-Methods.pdf

By Truta Date 03-17-2011 21:21

Thank you for the reply
Question : "with macros and a scope" means "with macrophotography and a microscope"? ( I am not a native English speaker)
Actually I have availabe a lot of testing devices, including a Helium leak test detector with qualified tech.
But my problem is how to convince the Welding Chief Engineer at my job to try to apply with no exception the general ASME qualification tests ( tensile, etc) to miniature work.
I forgot to mention that most of my work is small scale or prototype work.
C. T.

By OBEWAN

Date 03-17-2011 21:30

Photography is possible but not always a requirement. Generally, macro means with magnification but less than 30X.