Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Inspection & Qualification / SAW Porosity
- - By Logan Mayfield (**) Date 02-27-2008 20:48
We have some 48" pipe on hand that was spiral welded with Sub-arc.  There is enough porosity in it to be rejected.  I was asked what would cause porosity in SAW and all I can think of is base metal contamination(oil, millscale, improper joint preperation) or inadequate flux coverage. 

I have limited SAW experience but as a CWI these are the causes I can easily put together.  I would think that this pipe was done automatically so I would doubt that wire stickout would be an issue especially since it is not gas shielded and longer stickouts are acceptable.  Also, being submurged in granular flux, I would not peg travel speed as a cause either. 

Are there other probable causes that I am overlooking? 
Parent - - By js55 (*****) Date 02-27-2008 21:34
What's the porosity look like. Wormhole? Cluster? Linear? etc.
What wire and flux?
What alloy?
Agglomerated? Fused?
Did you watch the weld?
Where are you weldig?
Do you have flux controls?
Are you re-using your flux?
Parent - - By Logan Mayfield (**) Date 02-27-2008 22:01
This is pipe that was purchased from a supplier that we are using to make our product.  I don't know the specifics of there manufacturing process.  I am just inquiring about other possible obvious causes of porosity with the SAW process.  There is single pore porosity measuring up to 3/32" in diameter as well as cluster porosity measuring up to 5/8" in lenght.  It is carbon steel pipe.
Parent - - By CWI555 (*****) Date 02-27-2008 22:21
There are a lot of possible causes, one of which could be damp flux.
Parent - - By Logan Mayfield (**) Date 02-27-2008 22:30
So moisture in the base metal could also be a cause if not preheated?
Parent - - By CWI555 (*****) Date 02-27-2008 23:00 Edited 02-27-2008 23:03
I seriously doubt it's moister in the base metal. I was refering to Moister in the flux. Please refer to JS55 post for further options.
If you could post a couple of pictures depicting what your looking at, it would be helpful. 

Regards,
Gerald
Parent - - By Logan Mayfield (**) Date 02-27-2008 23:11
Here are some pics.
Parent - - By Logan Mayfield (**) Date 02-27-2008 23:20
Sorry, the pictures I was going to attach are over the maximum allowed bytes.  They are about 1,500,000 each.
Attachment: IMG_0925.JPG (851k)
Attachment: IMG_0929.JPG (570k)
Attachment: IMG_0932.JPG (719k)
Parent - - By aevald (*****) Date 02-27-2008 23:49
Hello Logan Mayfield, try right clicking on your pictures, when you do this you may see some choices for processing the picture, on my particular computer it says "open with", once you have clicked on this there is a choice called "microsoft office picture manager", click on this to edit or modify the picture. One of the choices when you open this program, will allow you to resize the picture specifically for publishing it to the internet, the choice on my computer is either Web-large or Web-small. After you have selected this and specified which choice you want, close the picture, it will ask you whether you want to save, select save and when you go to "attach" the picture to your post it will attach without having any issues. Hope this works for you on your computer, no guarantees unfortunately. Best regards, Allan
Parent - By Logan Mayfield (**) Date 02-28-2008 14:35
Thanks aevald, my program was a bit different but I was able to resize the pics.

The grind marks you see is how we recieved the product from the supplier also.  I would think that some of these pores would have been visable before we blasted it. 
Parent - By js55 (*****) Date 02-27-2008 22:27
Cluster porosity usually indicates an extreme shielding problem. Generally when you get cluster porosity with SAW you have an arc destabilization you can see, or hear.
Single pore porosity could be anything from H2 to N2/O2 to flux burden (though flux burden porosity is almost never that big).
You mentioned travel speed, and indicated it probably wasn't too fast. I'd take a look at it though. Especially for the single pore variety, especially if the single pore variety seems oriented to the toe of the weld-the fastest cooling zone. But again, not likely with 3/32" pores.
I'd take a look at a flux moisture problem first. The clusters are most likely something else though. IMO.
Parent - - By James Corbin (**) Date 02-28-2008 02:45
How old is the flux? (Moisture pickup from time or damaged bags)
Are you using reclaimed flux? (Contamination from dirt, other foreign material and or mix percentage)
Are you using unused flux swept off the floor? (Contamination from dirt, other foreign material and or mix percentage)
How are you drying your flux? (Drying oven time & temperature issues)

Just thoughts
Parent - - By CWI555 (*****) Date 02-28-2008 12:32
All good questions.
Parent - - By 803056 (*****) Date 02-28-2008 13:19
One source of porosity when welding with SAW that utilizes unfused flux that is recycled, i.e., vaccuumed and screened, is there may be too many fines in the recycled flux or the flux depth is too great to allow the gases to escape easily. The results can be porosity.

Best regards - Al 
Parent - By Logan Mayfield (**) Date 02-28-2008 14:38
Everyone input is appreciated.  I never thought about some of the possible causes that have been suggested.  I can see how each would be feseable however...
Parent - By RBeldyk (**) Date 02-28-2008 14:54
Rust Porosity

Possible Causes
*  Insufficient Voltage
*  Excessive Amperage 
*  Wrong Welding Polarity
*  Excessive Travel Speed
*  Dirty Weld Joint
Corrective Actions
*  Increase Voltage
*  Decrease Amperage (wfs)
*  Use DC+ Polarity 
*  Decrease Travel Speed 
*  Clean Weld Joint Completely

Organic Porosity

Possible Cause
*  Wrong Welding Polarity
*  Excessive Travel Speed
*  Organic Contaminants such as Grease in the Weld Joint   

Corrective Actions
*  Use DC+ Welding  Polarity
*  Decrease Travel Speed
*  De-Grease Joint Completely and Dry the Weld Joint

Arc Blow Porosity

Possible Causes
*  Excessive Amperage 
*  Excessive Welding Voltage
*  Improper Welding Polarity
*  Small Electrode Diameter

Corrective Actions
*  Reduce Amperage (WFS)
*  Reduce Voltage
*  Use DC+ or AC Polarity
*  Increase Electrode Diameter
Up Topic Welding Industry / Inspection & Qualification / SAW Porosity

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill