Porosity in base material?

Date 09-04-2008 16:48

Recently we had a contractor weld 1100 Al, 1/2" thick-12"OD pipe end to end using a backing ring, a gap of 1/8 to1/16", using the TIG process. The customer wanted upwards of 20% of the welds to be x-rayed because of a "porosity condition" to the side of the weld. Can porosity occur in the base material and not on the weldment when welding aluminum? Every picture I have seen of this seems strange. Can the composition of the 1100 alloy be the culprit?

Help? The contractor doesn't know what to do next - the customer needs help as well.

By Kix

Date 09-04-2008 19:12

How far out of the weld is the porosity? Do you know for sure it's outside of the weld and just in the base material. How were the bevels cut into the pipe? Is the porosity visible to the surface?

By Sourdough (****)

Date 09-16-2008 01:11

I've never seen it. I would highly doubt that an alloy as dense would be the culprit. I would likely believe that your welder is the culprit.

By 803056

Date 09-17-2008 02:35

Aluminum pipe is most likely extruded. The plate is rolled. Any porosity, should any exist, in the base metal would most likely be "flattened" during the extrusion or rolling operations. I doubt there is porosity in the base metal.

I can imagine a situation where the film interpreter, being inexperienced, could mistake spatter for porosity. The difference would be obvious to an experienced film interpreter. Spatter would appear to be slightly lighter than the adjacent base metal and the porosity slightly darker than the surrounding base metal. Both would be rounded and possibly the same approximate diameter.

Best regards - Al

By CHGuilford (****)

Date 09-17-2008 16:21

How far from the weld metal is the porosity being found? If porosity does occur in the base metal, I would think you could find it anywhere in the pipe, not just in or near a weld.

By Tommyjoking (****)

Date 09-18-2008 12:59

brownhearl do you have any pictures you could post of this??? Letting some of the experts have a visual could do wonders on some insight. Also post filler/gas choices being used if possible.

ChGuilford is absolutely correct....if the base metal is suspect, has it not been shot outside the weld area (random locations)?