J-Grooves on 3mm aluminium pipes?

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One of our products at work fequently leaves a distinguishing porosity, this has led me to investigate the design of the weld. The aluminium product is a pipe with a 3mm wall thickness and a diameter of 50mm (lengths vary). These pipes are partially socked over another pipe with a dimeter +/- 44mm and with a wall thickness of 8mm. The part which isn't socked over is also 50mm.The 3mm design isn't thick and I'm  doubting that aJ -groove isn't overkill.  I read on  several welding sites that J and U-grooves are usualy more aimed at materials thicker than 9.5mm and that a v-groove would be more suitable?

(The attachment is of a cross-section macro)Last edited by BT80; 14 Hours Ago at 01:06 PM.
Reply:Are the parts originally extrusions that are finish machined in your shop? How are they being cleaned? What do the parts look like after fit up but prior to the welding? Is the TIG process being used, if so, is it automated or done manually, and what filler? Does the porosity have any inclusions or just appear to be from gas bubbles? I'm no expert in this subject but believe the more information you can provide, the better the experts here can help you.
Reply:Both materials are from ISO-8062 Aluminium extrusions.The thicker matetial is also machined we buy the stock material however a contracted company CNC- Mills this material and cleans it post machining.We cut the thinner extrusion to desierd lengths in-house, no cleaning is performed.The process used is CMT (a subsidiary of MIG how ever it has its own process code though I'm under the impression its just being classed as MIG 131).The process is automated. The filler material is 2.0mm diameter ALMg5 wire.The cause of the porosity is not my issue. It is very clear this is due to oveheating, convincing the engineer (who just started his IWT diploma) is the issue.His predecessor had no clue and based most settings/ parameters on two examples configured by a hierd IWT hand one was a CMT examole the other a Mig-Pulse example. To save on costs the rest of the products were classed into either CMT or Pulse based on size and adjusted till a sufficient weld fusion was achived (even if that odly was only once out of a 100 attempts). These were then sent off for stress- testing (a legal requirement within the Netherlands). Once the results came back posetive the guy (not even a qulified IWT) wrote out the WPS which I have at my workstation and are full of errors and inducation that much information had been manufactured seeing as certain amperages were too high in relation to the associated voltages. (In CMT you adjust the wire feed rate which in turn influence the amps and voltage, its all tide together chageing one affects the others). Apart from that some of our larger and more robust products were being welded at lower amperages than some of our most delicate products. Other WPS's were given a range which coverd almost anything such as 150amps to 500amps this is a ridiculously large range.Some of our items with the same dimensions have v-groves yet this troubled product has a J-groove also not making sense is that most of the more robust items eg: 100x 8mm extrusions use V-groves yet some of our products including this particular product use J-groves yet are 50x 3mm and 50x 4mm stock. Both these items also have flat looking weld beads. I'm not the IWT guy at work so I can't legally change the WPS however I can play with the settings and hold a VTw-2 qualification which allows me to properly inspect the weld, by which my results are more inline with the machiens own calculated suggestion which  is a wire feed rate of 6.0 meters p/m approximately 140amps 25volts from memory fir 3mm thick aluminium. (Just as extra note the Fronius 5000i uses selected material  input and wire feed rate to calculate the material thickness it should be able to weld). I haven't got it perfect but my welds are constant and calculated for 3.6mm thick EN ISO-8062 Aluminium take that in comparison too 6.8mm for 3mm stock as best result from our engineer. However this all isn't my question. My question is, Is a j-groove not overkill for a welding 3mm thick aluminium?Last edited by BT80; 7 Hours Ago at 08:15 PM.
Reply:As an aside thought, if you can use a V groove and not a J groove, you’re wasting money on the machining process as well.  A J groove has got to be more expensive to have machined vs a V.
Reply:I'm only there till the end of this month after 7 years, but yeah it probably costs more.
Reply:Here is a cross-section of the Cnc machined part without a weld and with and without the 3mm pipe added. The J-groove in my opinion also has a wierd design rather than have face's with +/-15° slopes (common with u-grooves) its just 90° straight down and starts straight away with the radius?The width of the groove is also far larger than the depth which I would normaly expect the other way around? And the overall width in relation to the 3mm thick pipe seems to also be way to large (5mm distance)?The last image shows the size comparison between it and the largest 100x 8mm design which ironically usses a V-groove?The drawing shows the current situation in pink where yellow shows what I would find a more appropriate design if a J-groove needs to be implemented.

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Last edited by BT80; 9 Minutes Ago at 03:41 AM.