Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Inspection & Qualification / Worm holes in FCAW
- - By CB05829 Date 12-13-2012 09:36 Edited 12-13-2012 09:48
Can anyone give any sugestions as to why these occur.  ESAB 1/16 wire, A572, all mill scale is removed, preheat of 400DEG. This is usually in the root but not allways. These penatrate deep into the backup ring. Pics are to large to post, tried. if you want to see them maybe their is another way. Thanks for any help. Chris
Attachment: 000_0139.JPG (862k)
Parent - By newinsp (**) Date 12-13-2012 15:57
Preheat eliminates moisture in the base metal as a possibility. 
Sulfur content of .05 should not cause any problems.

Possibilities:

Other contaminant in the base material.
Contaminated wire.
Contaminated shielding gas, through leaks or improper distance.
Travel speed too fast (according to BOC gases). 

I had this problem once, back in the 90s, but can't remember what the culprit was.  I think it was a problem with a shielding gas line, like a hole.
Parent - By welderbrent (*****) Date 12-13-2012 16:11 Edited 12-13-2012 16:14
Are you sure the backing rings are correct material and clean?  What wire are you using, E70T or E71T??  What position?  70 works best flat, hot, fast; 71 works best slightly cooler, slower, and for all position. 

Worm holes, if you are talking the tracks laying on the surface after you remove the slag, can often be a result of removing the slag too soon or having the wire feed speed not quite right per the voltage.  Usually you increase the WFS and they will go away. 

Shielding is always a consideration, check for correct gas, pressure and line leaks.  Down in a CJP too much gas can be as much of a problem as too little gas.  Causes too much turbulence and moves itself away from the needed area without proper coverage.

400* seems a little high for the pre-heat.  Any particular reason?  2-300* even for thicker sections should be fine unless you were dealing with a higher carbon content which should not be the case with 572.  With a high pre-heat, are your fitups tight? 

Have a Great Day,  Brent
Parent - By Lawrence (*****) Date 12-14-2012 04:49
I use alot of ESAB 710X   and the main reason we see "worm tracks" with that particular electrode is when operators run with less than the factory recommended electrode extension (contact tip to work distance)

I believe the functional reason is a lack of or insufficient preheat (resistence) in the electrode wire.

Your basemetal preheat has nothing to do with this issue.
- - By 803056 (*****) Date 12-14-2012 00:58
Check your voltage and the electrode extension. Excessive voltage can result in porosity, but with slag filling the poreholes. If the electrode extension is too short, you can have excessive current. I suggest you go to the manufacturer's website to see what welding parameters are suggested. I would start with the median value for voltage and wire feed speed. Be sure to see what the___14 manufacturer suggests for he electrode extension or contact tip to work distance. It is an important welding variable the welder must be mindful of. Verify you are using the correct shielding gas if you are using gas shielded electrode.

It has been my experience that when welders are experiencing problems it is because they are setting their parameters based on what they did on their last project rather than consulting the manufacturer. Just because the electrode is the same classification, does not mean the parameters of electrode supplied by manufacturer "X" is the same as the same classification supplied by manufacturer "Y".

Use wire feed speed when setting up the wire feeder. DO NOT USE AMPERAGE. Amperage is dependent on WFS and the electrode extension. Excessive extension will reduce current; too shot an extension will result in excessive current. Excessive current often results in porosity due to the partial pressure of carbon dioxide produced by the decomposition of the flux core. Chicken tracks or more correctly called elongated porosity can result from the partial pressure of carbon dioxide produced. The partial pressure of the carbon dioxide is proportional to the current. In short; excessive current equates to excessive partial pressure of the carbon dioxide equates to excessive porosity.  

Good luck - Al
Parent - - By CB05829 Date 12-14-2012 09:25
OK! got a pic uploaded. See previous post.

   I will be more specific. The backing is A-36 all other materials are A-572 GR50. All materials are ground to a white finish. We are using AWS A5.20;E71T ESAB wire in the flat position, with CO2 shielding gas with a flow rate of 35 to 45 cfh, cup size 3/4". This is verified at the cup with a flow meter before any welding is performed. Contact tube to work is 1" to 1.25.  We use a volt/amp meter to set the welding machines the welders are not to adjust them after that.  I usually set them around 29.5V and 365A. We also use a mockup of the joint to get the most accurate readings while welding the root passes, after the root passes are done we will remeter them for the interpasses. Are WPS indicates that a travel speed of 8-22 ipm. This is one thing that I have not monitored, I will be watching this more closely just to verify what the welder is running at.

  Thanks to all of you for your input. I will be talking to the welders on some of the possible reasons this could occur.  I know that they are as frustrated as we are, as they are the ones that have to fix it.  One last thing, the 400Deg preheat is mostly to prevent warpage.
  
   Thank again
   Chris
Parent - - By welderbrent (*****) Date 12-14-2012 12:20
You are very welcome.  Let us know what you find.

I'm going to guess, either turn the volts down 'a little', or, turn the WFS up a little.  The specs may be good with those settings, but I think you are a little high and the volts per the amps/WFS being run.

Just my two tin pennies worth.

Have a Great Day,  Brent
Parent - By eekpod (****) Date 12-14-2012 14:36
I found that that mainly happens when welding rusty dirty material.
In my opinion it's gas trapped under the slag that creates that disconuity.

I don't have it happen when the base metal is clean, but weld on runst dirty materail and I'll get that all day long.

Run a few tests for yourself and see, it's simple enough.  DOn't change any other parameters just rusty vs clean.

Good luck
Parent - By unclematt (***) Date 12-14-2012 15:14
Hello;
I have run across this problem when welding long seams on box girders used in crane fabrication. Weld 40 or 50 feet and one would pop up. Very frustrating. Are you using an anti splatter or nozzle dip? I am not sure there is a correlation but sometimes I found if it was put on thick in places there would be a "wormhole" or "wagon track" in the vicinity. Quite possibly just a coincidence. I hope you get the problem solved. Nothing like putting on a slick cap, straight and uniform, only to knock the slag off and find these suckers.

Have a good one;
Matt
- - By 803056 (*****) Date 12-14-2012 22:35 Edited 12-15-2012 21:36
Well Chris, you left out some important details, so I will simply refer you to a link with the suggested parameters for ESAB's FCAW electrode. Good luck.

http://www.esabna.com/us/en/support/downloads/litDownloads/CoredWireBooklet/index.html#/11/

Just because the classification is the same, it does not mean the welding parameters will be the same. What works fine with one brand does not necessarily work for another brand or a different trade named electrode even when they are produced by the same manufacturer. Setting the parameters by the "seat of the pants" may work for some processes, but not FCAW. Amperage is a variable that depends on the wire feed speed and electrode extension. It should not serve as the basis of setting up the welding process. The three variables the welding procedure should list are arc voltage (read near the arc), wire feed speed, and electrode extension.

Amperage; it is a trap intended for fools to fall into. It looks good, it is sticky, gooey, taste sweet, and smells good, but it will bite you in the butt every time. Do your welders and yourself a favor, but black tape over the ammeter.

Al
Parent - - By eekpod (****) Date 12-17-2012 12:01
Al,

My intention was to point out that one cause of worm holes that I have figured out how to avoid was simply to make sure the base metal was clean, and that this might be a simple solution for him to try and eleviate his problem.  It is simple enough to run a few quick test welds on different material based on how rusty they are by using some scrap around the shop.

Yes I agree that there may be many other casues and Amps could be one of them.  I just thought this is a first step place to start.
Parent - By welderbrent (*****) Date 12-17-2012 14:55
Eekpod,

Careful, Al responded over to the side.  The OP is also a 'Chris' and stated his machine settings with Volts and Amps.

Can't speak for Al, but he was possibly responding to him.

Have a Great Day,  Brent
Parent - By jwright650 (*****) Date 12-17-2012 12:16 Edited 12-17-2012 12:28
Amperage is just one variable, but we found that when worm tracks showed up on the cap of welds, we had a welder running his VOLTAGE too high and travelling way too fast. He would sneak his machine up way out of the welding procedure parameters to make up time where he had been goofing off all morning. Once we nipped that in the bud, the worm tracks went away. I think he was travelling too quickly for the gasses to escape the slag and the gasses got trapped between the cap and the slag as the welds were solidifying. <--my opinion.

EDIT:
Just looked up the ESO according to ESAB's catalog for .035" thru 1/16" E71T-1 and they recommend 3/8" thru 3/4", not the 1" thru 1.25" that the OP stated earlier.
Another note, they also suggest in the flat/horz postions these parameters: 25-34v, 180-400a, ESO 3/8"-3/4"
- - By 803056 (*****) Date 12-17-2012 20:02
I'll reiterate, many manufacturers make more than one electrode that meets the classification XYZ. Each is slightly different, but each meets the requirements for strength, position, etc, but the chemistry is not always the same. In the case of FCAW it is important to verify the welding parameters are correct for the particular brand name / trade name. The spcific shielding gas can also muck up the works if the user isn't aware the voltage must be correct for the shielding gas used.

I this case, our fiend Chris did not list the particulars of the electrode he is using, hence my words of caution.

Paul Harvey lives!

Best regards - Al
Parent - - By jwright650 (*****) Date 12-17-2012 20:15
Al,
I went back and read the OP and looked at the pics....deeper problem than what we had. Our problem was just worm tracks(no holes) and it was only on the cap/top of the bead and seemed to only be cosmetic as they barely had any depth at all. Someone else here in the forum called them "pot marks" when this was discussed before.
Parent - By 803056 (*****) Date 12-18-2012 01:13
AWS calls it elongated porosity. They are acceptable per D1.1 unless there is piping porosity associated with it. If there is piping porosity, AWS D1.1 Table 6.1 provides the appropriate acceptance criteria.

Al
- By Dualie (***) Date 12-18-2012 06:32
Had it happen to me today on some cap passes on full pens.    Running an Inverter off of some drop boxes i think the other trades were pulling to much juice off of the branch circuit and screwing with the input voltage too much.    After a grind out and re weld it was none the worse for wear.
- - By CB05829 Date 12-18-2012 11:12 Edited 12-18-2012 11:18
To clarify some things that I did not mention before. We are using 1/16 diameter wire. We also use a hand held type Fluke meter, we are able to get as close to the point of arc to get the most accurate amperage as possable. We do not use the volt/amp meters on the machine as they usualy are not even close to correct.
  As far as the parts being clean, all rust, mill scale, etc is removed prior to fit up and with the high preheat that we have all oils from the milliing is burned away. At the bottom of the worm track in the pic that is a very deep hole, The accual track its self will disappear with very little grinding.
  This is not an issue that we encounter all the time (one out of every few months) but when it does I would like to be able to give guidence to the welders as to some possabilities this could happen. I dont think that our perameters are the cause. Everything we do is checked and rechecked daily by third party inspectors. They are on site all day, everyday.

  Thanks for everyones input! I will be taking everything into consideration. This has been a very helpfull forum I will be using it more now that I have done it.
Attachment: 000_0139.JPG (866k)
Parent - - By eekpod (****) Date 12-18-2012 11:37
Al
I agree that the porosity is defined as elongated porosity as there is a nice definition and picture in section 4.2.5 of AWS B1.11 Guide for the Visual Examination of
Welds.
Table 6.1 in D1.1 doesn't mention elongated porosity specifically.  It does mention piping porosity.

Are you saying that if you have the elongated porosity without the piping at the end that it is acceptable?
In my intrepetation of Table 6.1, any time I had this elongated porosity that exceeded the dimensions in the table I would have it repaired.  I did this becasue the table didn't mention "elongated" but it was clearly porosity (confirmed from B1.11) so I considered it a discontinuity.  Yes there are/were times when they were small enough that I left them.

Becasue they never mentioned the different kinds of porosity in Table 6.1, when I encountered them, I always grouped them all together to see if they exceeded the requirements or not.

I'm curious to your thoughts
Thanks
Chris
(BTW I didn't realize the OP was named chris as well)
Parent - By ctacker (****) Date 03-27-2013 02:37
I know this is old, but the book of interpretations says this about surface porosity (elongated): http://www.aws.org/technical/interps/id1-91-010-09.pdf
Now I would like to hear from everyone on what the maximum size of a piping porosity that is allowed, on a statically loaded fillet weld on a non tubular member. (I know this but I have seen most inspectors blow this one)
Parent - By Lawrence (*****) Date 12-18-2012 12:37
I think Al has coverd this but I'm not sure you have digested his instruction/admonition

1.  Each FCAW electrode wire has a "sweet spot" and this best practice parameter is usually provided by the electrode vendor.

    1b. Those manufacturers suggestions apply to current and voltage as they relate to various wire feed speeds GASSES, AND POSITIONSThis can make a pretty big difference sometimes

    1c.  Example  ESAB and Lincoln both have More than one type of  E71T-1 that can be purchased in 1/16" diameter.

2.  You may be using the best equipment available to make sure your operators are staying within WPS parameters for current and voltage...  You also may be walking up and down the production floor watching to be sure your operators are keeping the contact tip to work distance/stickout within WPS ranges

2a.   This does not ensure that you are working at the "sweet spot" parameter ranges and distances for any particular brand of FCAW electrode wire.

Big finish/Moral of the Story....     Research the specific ranges and distances for the exact product you are using in production and educate you floor welders on the exact criteria.  Staying within WPS ranges may not be quite enough to avoide worm tracks...   You can always rewrite your WPS's to be a bit more strict and in keeping with manufacturers suggested ranges as long as they are still compliant with prequalified or PQR numbers.

Again.. I think Al's advice is best here... FCAW is designed to deal with mill scale and light rust... those are not the culpret unless your surface conditions are Gross..... it's a parameter or CTWD tweak that will fix your worm hole issue.
Parent - - By jwright650 (*****) Date 12-18-2012 12:43
If you have time...(meaning: be prepared to read for a few hours and then have your brain turn to mush trying to comprehend it all):eek:

Here is an older thread about "worm holes/chicken tracks" with some really deep discussion and technical speak with many, many links to investigate.

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=52732

Maybe you can sift through this and find some information that will be helpful. Most of what was posted by "stephan" was over my head, but very interesting.
Happy reading(grab a cup of coffee, get comfortable, and enjoy).
Parent - - By ssbn727 (*****) Date 12-25-2012 18:13
Hi John! MERRY CHRISTMAS TO EVERYBODY IN HERE AND OUT THERE!!!

I think we're on to something from this old thread you linked in your post...

I remember that thread and I had a hunch beforehand that it have something to do with what the OP in his third post mentioned regarding the burning of any residual oils left on the members would be burned off by the preheat... Here's what I'm talking about;

"As far as the parts being clean, all rust, mill scale, etc is removed prior to fit up and with the high preheat that we have all oils from the milliing is burned away."

And then I read this in the older thread you posted;

" XPERTFAB  Date 01-16-2007 21:12
Blaster,
Add one more parameter to you list of havoc wreaking situations for the FCAW wires mentioned.  That is the residue remaining from the sawing and machine coolants used in the fabrication process of components to be welded."

The red flags went up and then again, this is only one of he many possibilities which can only be verified @ the site where the welding is being performed...

So, without actually witnessing every step in prep, while welding is being performed, one cannot guess this problem you have especially if it only comes up;

"This is not an issue that we encounter all the time (one out of every few months)" only once in a while.

Respectfully,
Henry
Parent - - By Lawrence (*****) Date 12-25-2012 20:07
Merry Christmas Henry!
Parent - - By ssbn727 (*****) Date 12-26-2012 17:31
MERRY CHRISTMAS TO YOU TOO LARRY!!!

Respectfully,
Henry
Parent - By jwright650 (*****) Date 12-28-2012 01:18
Hi Henry....hope you had a great Christmas....and a Happy New year if I don't get to hear from you before then.
Parent - - By welderbrent (*****) Date 12-28-2012 14:25
Here too Henry,  Merry (late) Christmas, and most of all, Hoping you a Happy and Healthy New Year.

Stay out of those hospitals, they'll kill you in there.

Have a Great Day,  Brent
Parent - By CB05829 Date 01-11-2013 17:47
Just want to thank everyone for there imput on this matter, all is being taken into concideration. Hope everyone had a great holiday season.
I will be using this forum more now that I have had such a positive expierence.

Chris
Up Topic Welding Industry / Inspection & Qualification / Worm holes in FCAW

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill