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Re: [MW:20944] Porosity in Al weld with Ar

By Materials & Welding
Dear Maulik:
 
  • Pulsed arc, if adjusted properly, will almost eliminate porosity and if there are still porosity in the weld, they may be result of deviating from Al-welding cleanliness rule (clean base metal, clean filler metal and clean shielding gas). Filler metals, if stored for a long time, can cause porosity. Use high quality and new filler wires. Super glaze Al filler wires are reliable ones (Lincoln). Gas shall be supplied by a reliable supplier and certificates should be available (chemical analysis of the gas). Base metal cleanliness shall not only be achieved by solvent cleaning. Sometimes humidity and air penetrates into oxide layer and is not easy to remove by solvents.   
  • Lower the thickness of Weld beads the better (to allow gas to escape from weld before it solidifies).
  • During depositing next layer, you can re-melt previous weld and gas may have the opportunity to escape. Again it is better to deposit weld layers with low thickness.
  • Generally, bevel angles in Al-welding shall be larger than steel (e.g. 90 deg instead of 75).
  • Bevel angle shall not be symmetrical for 2G joints (for example:  20 deg bevel for lower plate and 50 deg for upper plate - you do not have to use these exact angles though, the idea shall be understood and adopted for your own case). In 4G, it is more difficult though and the only joint geometry option is to increase bevel angle.
  • As a last resort, TIG dressing becomes handy when you are desperate...!!!


Best Regards

Ramin Kondori

Sr. QA/QC engineer

Yadavaran Oilfield Project

SIPC (SINOPEC)



On Thu, May 29, 2014 at 7:47 AM, kannayeram gnanapandithan <kgpandithan@gmail.com> wrote:
increase ur flow rate

THANKS & BEST REGARDS
KG.PANDITHAN, AWS-CWI, CSWIP 3.1
CONSULTANT-WELDING & QUALITY


On Wed, May 28, 2014 at 11:38 PM, Maulik <mlkthakkar2@gmail.com> wrote:
Dear experts,

Please guide me regarding following query:

We are leading fabricator of Al light weight vessels utilizing GMAW-P process. However, we found extensive porosity problems in most of times during 2G and 4G positional welding only when utilizing 99.995% Ar as a shielding gas. In 3G and 1G position seam is getting clear with no indication. We are also using He+Ar as a shielding gas & level of porosity drastically decrease due very known technical reason " getting hot arc welding".

However due to some constraints for short span of time, we are not able to utilize He+Ar for all seams & have to use Ar as shielding gas.

In view if above please suggest how to effectively utilize Ar shielding gas without RT failure, particular to welding in 2G and 4G positions.

Base Metal: AA5083
Filler Wire: ER5183
Thickness: 4 mm
Process: GMAW-P
Shielding Gas: 99.995% Ar with moisture content <2 ppm.

WPS parameters
I-90-120 AMP (2G position)
V-18-19 V
Travel Speed-350-450 mm/min

Regards,
Maulik H. Thakkar
Welding Engg & Metallurgist
L&T, Hazira, Surat
09924732922

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