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Up Topic Welding Industry / Inspection & Qualification / Weaving more then 3 times the rod dia?
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Parent - - By JTMcC (***) Date 03-07-2005 02:58
We have been seeing a trend to requiring narrower bead widths for the last 8 years or so, under all common codes. Quite a change from 10 years ago. A big bore downhill pipe weld that used to get a puddle cap, now gets a 3 bead cap, and they want you to split the weld earlier. Structural welds in seismic areas are requiring narrower passes. I found it annoying at first, but we have "learned to love it".
Not that this has any bearing on the original question, but the trend is definitly toward narrowness.

JTMcC.
Parent - - By Jim Hughes (***) Date 03-07-2005 03:46
Okay!!
Thanks
Parent - - By JTMcC (***) Date 03-07-2005 05:06
Well then let me explain further so maybe you can understand. We generally work under api 1104, ASME and less frequently AWS D1.1 or D1.5.
In our work, under all of those codes, we have been seeing the trend toward narrower beads for years now. Simple. It may not jive with your experience, but that's no reason to write a smart mouthed response to me.
In southern California, and other seismic there are limits on bead width of structural welds.
Cross country pipeline work has been on a slow but constant move toward splitting the passes sooner, and requiring a multiple bead cap where 10 years ago a puddle cap was standard.
How the procedure is qualified, is dependant upon whatever a particular gas company wants, period. And if they want a 3 bead cap on .500 wall, then that's just what everyone has to do.
My "talk about trends" is not to be taken as a personal afront by you or anyone else, that's just odd. And in my world you don't need to "encourage people to look at their WPS and follow it" as the welders have absolutely no choice but to do so, we commonly have close to one inspecter per welder, anyone who ignores the WPS is simply fired.
My part of the welding world is evidently a bit different from yours, but it exist's nonetheless.

JTMcC.
Parent - - By Lawrence (*****) Date 03-07-2005 12:55

Hey JTMcC.

You said several times something about a, "move toward splitting the passes sooner"

I'm no pipeliner but would like to understand that term. What does it mean and what advantage is gained?

Thanks
Parent - By JTMcC (***) Date 03-08-2005 13:55
Using two narrow passes side by side, where in the past one wider pass would have been used.

JTMcC.
Parent - - By Jim Hughes (***) Date 03-07-2005 14:42
Sorry JTMcC, did not mean to offend. Please accept my appology. Just trying to get the original post to look at the WPS. Could of said it better.
Jim
Parent - By JTMcC (***) Date 03-08-2005 13:52
No sweat.

JTMcC.
Parent - - By ssbn727 (*****) Date 03-07-2005 06:06
Hey Jim , JTMcC!

Easy Gents! If anyone should apologize it's the person that posted the original post BECAUSE, HE LEFT OUT ALL OF THE IMPORTANT DETAILS until later follow ups, thereby intentionally or not, confusing us!!!! "A picture can say a thousand words"... Being that all we have are words to formulate our own input, responses, opinions, etc., it is imperative to include as many details as possible olmpkwelder474... By adhering to this simple yet effective principle, we can all avoid all or at least, most of this confusion, misunderstanding and ill will towards each other!!!

On this thread alone, we have over 175 years combined welding experience, possibly 200 years experience!!!!!
let's try to respect each others different backgrounds...

"CAN WE ALL GET ALONG???" OF COURSE WE CAN!!!

Respectfully,
SSBN727 Run Silent... Run Deep!!!
Parent - - By DGXL (***) Date 03-07-2005 17:35
I did not see anything smart-ass about the reply from Jim to JTM.

On the West Coast we have to consider seismic activity in addition to other design factors. "Splitting welds" means a reduction in the bead or layer width. A reduction in the bead/layer thickness is also common here. This is to minimize heat input and the HAZ. But, many of the powers that be (building officials, engineers, etc.) who have little to no knowledge of welding apply more stringent requirements, regardless of the service or application. (Not an engineering bashing comment.)

Weave beads were found to have performed less than satisfactory after the Northridge Earthquake. Much had to do with the technique implemented by the welders in addition to many other problems. So, to make it "easy" on everyone, a reduction in the weld metal deposit is the "trend" (don't get upset for me using the T word). Issued a GMAW WPS using a 0.045" electrode which denotes oscillation 5 times the electrode dia. last year. It was rejected until I had an engineer from the manufacturer verify if the "weave" was excessive, which they (the manufacturer) determined as NOT. See, engineers can be of help...

SSBN727:
The last time someone used that phrase here in LA we had another riot!
;-)
Parent - By JTMcC (***) Date 03-08-2005 14:01
DGXL speaks of what we are seing, I'm not commenting on wether it's technically right or wrong. But it is being required of us more and more. And like was mentioned it's mostly a result of the Northridge quake in the structural world. And in the pipeline world I believe it's a result of the higher and higher grades of line pipe being welded.

JTMcC.
Parent - - By tab_1999 (**) Date 05-10-2005 21:51
I'm glad they make Codes and Standards. I also appreciate detailed WPS's that my present company has as well as the details referred to in the WPS.
Weld techniques ( weave or Stringer ) have an obvious impact on welds and can be " unintentionally" used to heat relieve or create stress risers. ( Have you ever noticed the difference in a plate test coupon that has been welded with stringers vs. weave? ) The bow is very noticeable.
The color criteria we use on our sanitary tube is a 3 or better ( that means no blue ) that appears to be the level that passivation starts to work. Even the layer wears off over time as the products pass through the lines.
I've only been a CWI for a little over 9 years but have welded in a construction environment for the past 25 and am still a State of Ohio approved welder. Its not too difficult to notice the color variations in SS based on the difficulty of the field welds vs shop welding.
Another note is that using 316 to weld 304 is not necessarily an upgrade. Sulphuric fuming acids and caustic acids act tremendously different. They are not interchangeable as I've seen numerous failures caused by mixing the materials and filler metals.
Just throwing out some history to some of the items listed above.
Have a Great Day!
Parent - - By Jim Hughes (***) Date 05-10-2005 23:03
Hello, I just read your responce. How do you know that passivation starts to work at blue? What about Gold? Explain your comment about color variation on field welds Vs. shop welds. Were you saying that stringers causes more bow? A little more detail would be great.

Jim
Parent - - By tab_1999 (**) Date 05-12-2005 13:00
Hi Jim,
I didn't mean to start another topic but to peak some thought about the difference in stringers and weaves. The test coupons are an easy example of using the same rods/ wire and amps with the 2 different techniques and Visibly seeing the Heat input difference. ( Thats All )
The color of blue is unacceptable to my present client. Light straw to silver is the goal. Pipe systems need to be cleaned prior to using the passivation process " as a rule of thumb ". We use a citrus-based solution.
The understanding that I took away from the discussion is that the pipe won't form the protective layer if the internal color isn't as noted above.
As to the shop vs field welds; When your welding in position its not as easy to run smoothly around the pipe 100% as it is on shop welds where you may have the latitude to roll the pipe in stands etc. ( faster vs slower travel speeds )

Have a Great Day
Parent - By Jim Hughes (***) Date 05-12-2005 16:21
Hi Tom, thanks for the reply. You mentioned a color chart in AWS, would you be able to tell me where that is found in AWS?
Thanks
Jim
Parent - By HgTX (***) Date 06-27-2005 23:06
Which one bows more? (I have my guess, but I'm likely to be wrong...)

Hg
Parent - - By Bill Mc (**) Date 03-23-2005 16:32
I have a question then since the concerns raised by everyone above are certainly valid:

If changing from stringer to weave technique is that important, why is changing this technique considered a non-essential variable in ASME section 9 for procedure qualification?
Parent - - By jon20013 (*****) Date 03-23-2005 17:17
Joint design is also a non-essential variable but one wouldn't change from a butt weld to a fillet weld. Same holds true with root opening. We have to keep in mind also that ASME IX does NOT contain all variables that might otherwise be imposed by the construction/fabrication codes.
Parent - By jwright650 (*****) Date 03-23-2005 19:35
Wow, you guys have been busy. Lots of discussion on this one. I'll have to print this one and read it when I get more time. Interesting points so far.
John Wright
Parent - - By chall (***) Date 03-23-2005 17:35
Like you, I am jumping into this late.

One possible answer could be that the difference between stringer and weave, primarily boils down to heat input.

When heat input is an engineering concern (generally linked to notch toughness) other supplemental essential variables that must be adhered to, take care of that issue. Heat input is addressed specifically.

Charles Hall
Parent - - By jerrykroll (**) Date 03-23-2005 18:08
what a long thread !

I always thought "splitting a weld" was done to reduce/prevent the likelyhood of segregations forming repeatedly and which accumulate down through the center line of the weld joint, like piping in a casting. These segregations consist of the lower melting temperature "impurities" that freeze last and can cause centerline type cracks. Splitting kind of side steps or staggers this phenomena and the likelyhood of this type of discontinuity.

time to start a new forum topic item- takes too long to read this one in it's entirety
Parent - By JTMcC (***) Date 03-24-2005 03:58
One justification used for splitting into two passes comes directly from Lincoln, they say "In critical applications for low temperature service, it may be necessary to maximize the impact toughness properties of a weld. In this case one technique is to split the layers into two passes as soon as possible. The objective is to align fine-grained reheated zones along the centerline of the weld."

JTMcC.
Parent - By - Date 03-23-2005 23:27
Bill,
Your question concerning Sec. IX not making the weave/bead process an essential variable is certainly warranted. Most PQR's, included the AWS suggested format (QW-483) has a section of the PQR entitled, Technique (QW-410) that states whether the weld will be done using a bead or weave. Whatever is stated in there determines what technique is used. Also, Sec. IX does not differentiate between stainless steel essential variables and carbon steel variables. Even though it is not an essential variable according to Sec. IX, it becomes an essential variable if it is documented on the PQR and WPS and a weave or bead technique specified. If you have a WPS that the Welding Engineer has written and he specifies that only a bead technique be used, then, that essentially is an "essential" variable when welding stainless steel with that particular PQR and WPS.

CM
Parent - - By - Date 03-23-2005 18:22
As a Welding Engineer for one of the world's largest producer of stainless steel pipe, plate, bar, billet, and stainless steel consumables, let me respectfully give my opinion on the original forum question. First of, it is recommended that stainless steel be welded using the "bead" technique. Therefore, "weave" beads can lead to higher heat inputs which can be detrimetal to the integrity of some stainless steel weld properties. Regarding carbide precipitation and sensitization in low carbon grades of stainless steels....Sensitization occurs when unstabilizes stainless steel weldments are exposed, or slowly cooled in the temperature range of 750 to 1550 deg. F., form chromium rich carbides (M23C6)along the austenitic grain boundaries, thus making the weldment sensitive to intergranular corrosion. Generally, the level of precipitation and degree of sensitization are approximately proportional to the carbon content. If I may, I would like to address one particular item that was discussed in one of the responses regarding "color" of a weld. I, too, am a CWI and a CWE, so I find it rather disturbing that a CWI would recommend not brushing a stainless steel weld after completion, regardless of the pretty color. Yes, the pretty gold, or silver, or rainbow color indicates that the heat input was correct, the travel speed was good, and the shieldiing was acceptable. But, the absolute bottom line is that regardless, that color is a "chromium depeted oxide layer". Stainless steel is protected by an impervious, or invisible, layer of chrome for corrosion protection. With the high heat input of the weld process, that chromium is burned off, leaving the oxide layer. That is the color you are seeing. Removing that color will allow the oxidation in the air to let the stainless steel restore the chromium layer that is necessary for corrosion protection. Thank you all ofr allowing me to speak my piece.

CM
Parent - - By Jim Hughes (***) Date 03-23-2005 18:47
CM, where could I find this information about "color" needing to be brushed after welding? Also as a welding engineer what information do have on dry-washing a 304L or 316L weld for the purpose of alignment. I would love to speak with you off the forum, could you e-mail me back at jimhughes71@hotmail.com so I can get your e-mail address.
Thanks
Jim
Parent - By - Date 03-23-2005 21:01
Hi Jim,
I sent you my e-mail address so we can discuss the very big misconception of not needing to remove the "color" of a weld. As far as dry washing a weld to gain proper alignment, well the main thing wrong with that is that autogenous welding directly affects the properties and corrosion resistance of the stainless weld by not adding alloys back into the weld metal. This is mainly true due to the loss of chromium in the weld arc, which directly affects the ferrite number. As we know, chromium is a ferrite former and nickel is an austenite former. Dry washing usually applies to washing just part of the weld so that it will pull in one direction or the other. This can be a localized thermal cycle that can definitely affect the integrity of that particular weld. We can discuss this in more detail when I hear form you. Thanks...

CM
Parent - - By - Date 03-23-2005 21:35
Jim,
Sorry for the mis-typed words. Sometime I type faster than my brain works. <smile>

CM
Parent - - By MBSims (****) Date 03-24-2005 04:42
Interesting discussion. I haven't seen one run this long in awhile. But getting back to the original question - why run 2 "stringers" instead of one weave? Our specifications for pressure piping always require a minimum of 2 weld layers (not necessarily stringers) and I wonder if this is what the fitter was concerned about. I have welded many socket welds with a root pass and a wide 2-to-1 fillet on top of it, but they all had 2 weld layers.

We normally don't have maximum weave width in our WPSs. In cases where heat input is a concern (e.g. notch toughness or sensitization), we specify a maximum heat input value and the travel speed is measured in the direction of weld progression (side-to-side travel speed not included). If the welder can weave and still meet the minimum travel speed needed to stay within the heat input limits, that would be acceptable. We have welded quite a few procedure qualifications with acceptable notch toughness values with wide weaves. I agree with the earlier statement that wide weaves will result in lower notch toughness values than stringers, however the values can still be acceptable. I've also seen machine GTAW welds made with 0.035 in. wire that were weaved up to 1 in. wide (28x weave!), but still passed the A262 sensitization tests. So, there are exceptions to weave limits based on electrode/wire diameter that produce sound welds.
Parent - - By jerrykroll (**) Date 03-25-2005 17:35
related info ....?

I seem to recollect that B31.1 requires a 2 pass minimum, along with a minimum 1/16 inch witdrawal on socket-type welds.
Parent - By tebrugge Date 04-26-2005 12:54
I have read this thread and its long .
My take is , by limiting how much may be deposited in one pass and then limiting how wide the welder can weave effectively puts a lower limit on travel speed , and is a way of controlling the heat input .
So when you use a given rod size and you may only weave so wide , if you do not move forward fast enough it will build up beyond the allowable limit . Some times this is about the only real restriction in the wps's .
Look at them ,they are mostly written to where , if you could possibly go outside the given parameters , you could not make the weld , especially , amperage .
Pre-heat , interpass heat and things that can be measured are easy to controll with specific directives .
However things like heat input are another ballgame as you are dealing with humans , and sometimes a bankshot is the only way.
"So" Limit the height ,limit the width , and you controll the forward speed and heat input very effectively.
Parent - By tab_1999 (**) Date 05-12-2005 12:45
Hi cm,
I hope you didn't interpret my response to mean that
I would condone leaving the color on a weld when I mentioned colors addressed on the AWS chart of 3 or better.
We use these for internal Inspection of Sanitary Tubing which has to be light straw to silver per our clients choice. This is the level required for their passivation to be effective.
" Just for the record "

Have a Great Day!
Parent - - By Bonniweldor (**) Date 06-22-2005 02:43
The tint of a SSt weld is required to be removed in order to obtain full corrosion resistance of the weldment material. Some corrosive media will exhibit accelerated corrosion of SSt initiated at the heat tint surface; salt water, for example.

Look up "rouging" of SSt on googoo.
Parent - By - Date 06-22-2005 16:47
Stainless steel is protected by an invisible, inpervious layer of chrome. When welding is done, the "color" on sees is a "chromium depleted oxide layer". This is not only on the weld, but in the HAZ as well. This color should be removed not only on the surface, but immediately below the surface. This was discussed in many of the posts above.


See the Avesta Pickling Handbook "Handbook for the Pickling and Cleaning of Stainless Steel". If you would like more information on pickling, I can send you 2 papers that were submitted to NACE and AWS for publication. You can e-mail if you would like this info.

chuck.meadows@outokumpu.com

CM
Parent - By - Date 06-29-2005 16:33
I typed in "googoo" and found it to be an on-line shopping web site. Couldn't find anything mentioning "rouging" there. Regardless, pickling is the recommended way to fully restore the corossion protection in the weldment material AND the HAZ. Maybe you meant "google"?
Up Topic Welding Industry / Inspection & Qualification / Weaving more then 3 times the rod dia?
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