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Up Topic Welding Industry / Inspection & Qualification / Porosity vs. End Crater
- - By k-maes Date 03-10-2016 18:55
Hello, and thanks for the help in advance.

A little about me before I get to my issue.

     My name is Keith and I have three years inspection experience (a year under my belt as a CAWI) with another two to go experience wise to obtain my CWI. I scored well enough on the exam to be able to just pay the upgrade fee and, as soon as I gain two more years experience (for a total of five years experience), I will be a CWI. My company primarily builds exhaust after treatment systems (thin wall stainless, mostly 1mm-4mm thickness with some flanges that are ~10mm) using ISO and customer specifications as reference for welding requirements.

Now to my question;
     I have some engineers who are arguing that an "end" crater (defined by AWS, A3.0M/A3.0:2010 as "A depression in the weld face at the termination of a weld bead.") is no different than (as they like to call it) "single pore porosity" where porosity (defined by AWS, A3.0M/A3.0:2010 as "Cavity type discontinuities formed by gas entrapment during solidification or in a thermal spray deposit."), in my understanding, is basically caused by some sort of pollution in the weld puddle during the welding process and an "end" crater is caused NOT by pollution, rather the rapid cooling of the puddle, at the terminus of the weld, without having ample filler.

The problem is this, the customer specification, in regards to craters and porosity, reads (respectively);

"The stops (crater) of arc welds shall not be considered as part of the acceptable weld length unless they meet the required fused leg and throat dimensions as specified in this standard or weld releases. An unacceptable weld stop (crater) is a condition at the end of a weld where the fused legs or throat dimension falls below the minimum requirement."

"Individual pinholes separated by at least their own diameter and other scatter surface porosity is allowable. The total length of porosity (sum of diameters) should not exceed 6.4 mm in any 25 mm (1/4 inch in any 1 inch) of weld.
The maximum pinhole diameter should not exceed 1.6 mm (1/16 in.)"

On some of the shorter welds produced here, the end crater actually cuts the effective length of the weld in half. If my understanding of the customer specification is correct, craters such as this would necessarily need to be filled in order to pass spec. as long as the leg and throat dimensions at that specific location fall below what is required by dimensions called out for in the specification. The engineers define a crater as porosity and as long as the diameter of the crater is less than 1.6mm it is acceptable.

Can I get a little help here? Am I wrong in my understanding or is there something besides AWS, A3.0M/A3.0:2010 that can be used concretely to help them understand that these end craters must be filled in order for the weld to pass.
Parent - - By welderbrent (*****) Date 03-10-2016 22:49

1) It's obvious these guys are not structural, welding, or mechanical engineers.  What discipline and who do they represent?
2) What code are you working to?  Beyond your references to D1.1 which probably does not really apply?
3) What process are you using?
4) Not sure what they are really saying, but termination craters and porosity are no where near the same.  You get cracking very often from craters (can we say 'crater cracking'?)  But the roundness of porosity is why it is often considered acceptable in many codes, like drilling a hole to STOP a crack.  Cracks don't form from porosity.
5) Dare I say it?  You want to know what type of info you can give them?  NONE.  You can't fix stupid.

He Is In Control, Have a Great Day,  Brent
Parent - - By Tyrone (***) Date 03-11-2016 12:28
Welcome to the AWS Forum k-maes!

It is absolutely a "crater crack".  You got it right.  Rapid cooling, causes the solidification crack.  Imagine trying to argue with the Customer that it's not a crack but porosity, and you don't have to fix it?  They may think twice about using your company in the future.

Proper crater fill technique...problem solved.

Parent - By TimGary (****) Date 03-11-2016 13:25
Proper crater fill technique... amen Tyrone.

Crater fill technique -

Option 1 - At the end of the weld, stop forward travel and back up about 1/4" before terminating the arc. This fixes the shallow crater / weld length issue, but may still leave behind a single hole porosity.

Option 2 - At the end of the weld, terminate the arc, but before moving the gun away, momentarily push the trigger again to fill the crater with a spot tack. This fixes the shallow crater issue, as well as the single hole porosity issue. The only potential drawback is that if the Welder is not careful, the spot tack may be placed off center, which is not very cosmetic.

Option 3 - (My favorite) Before making the weld, place a tack where you know you have to stop the weld. Then complete the weld and tie into the tack. This kills three birds with one stone - You know where to stop the weld, instead of guessing (intermittent welds), as long as you don't run completely over the tack there is no crater fill issue, this greatly reduces the chance of leaving behind a single hole porosity.

Parent - - By k-maes Date 03-11-2016 16:29

1) Two are first year out of college Welding Engineers from Ferris State, one is a manufacturing engineer and the third (who has been here the longest is a controls engineer whose formal education is in controls and is echoing a contractor who is also a CWI/ CWE. So, That sort of explains where the mindset is coming from. Three don't know any better (yet) and are merely echoing the third who has a tendency to not want to listen to anyone who is not also an engineer or supervisor (which I am not). 

2)We are working to the customer's own welding specification (which I can't actually name due to liability) which is heavily based on D1.1 which is why I can get away with using A3.0M for definitions.

3) Automatic MIG

4) As for what they are saying, I think they are merely trying to decrease cycle time AND assert authority over my mouth as I'm really the only person in the building who knows the specifications.

5) Say it, PLEASE! That way I'm not the only one.
Parent - By Lawrence (*****) Date 03-11-2016 16:53
You tell those puppies to send the same image you have posted here to Dave Murray their department chair at Ferris and ask him if that's a defect or not.  He will set them straight in a heartbeat.

Probably you would rather train them politely rather than shaming them... But a Ferris grad should really know better.

They should certainly know how to set a weld termination sequence on your production unit to make that craterCRACK go away.
Parent - By k-maes Date 03-11-2016 16:32
Thank all of you for your responses. I really appreciate the backup. You have helped me understand that my information is correct, the problem is, in fact, fixable and people just need to be willing to do the work.
Parent - By k-maes Date 03-16-2016 14:53

Thanks for the responses, they gave me not only the confirmation I needed but a couple laughs to boot. Please remember, the question wasn't about what does or does not make a welding engineer qualified. It was about the quality of welds. Thanks again.
- - By 803056 (*****) Date 03-12-2016 22:51
Ferris State does not have a welding engineering program, they have a welding technology curriculum.

The crater pore often is the result of the absence of shielding gas post flow. Post flow is an option with some GMAW power supplies and not available on others.

There is no mystery with porosity, when there is no shielding gas, atmospheric gases are absorbed in the molten weld pool. As the pool cools and the phase change between liquid and solid occurs, the solubility of the gas in the metal drops by a couple orders of magnitude. Some of the gases escapes into the air, some form the gas bubble that is entrapped in the weld pool while it is in the mushy state and presto - a pore hole appears.

The crater pore often appears in the weld crater of a GTAW when the welder doesn't hold the gas nozzle over the weld pool as it is cooling and in the process of solidifying. That's when you want to slap the welder across the back of the head and explain why there is a post flow knob on the control panel for the 100th time.

GMAW is no different, but we have grown accustom to turning a blind eye to the event because AWS D1.1 (the new Farm Code) has no criteria for porosity other than piping porosity. So, structural fabricators forgo the added cost of the post flow control and the manufacturer's simply don't offer it because the marketplace isn't demanding it.

Several of my clients that weld aluminum do have post flow on their machines for the sole purpose of eliminating the crater pore problem. They also have preflow to eliminate porosity at the beginning of their welds.

Best regards - Al
Parent - - By Lawrence (*****) Date 03-12-2016 23:58
Parent - - By 803056 (*****) Date 03-13-2016 00:13 Edited 03-13-2016 00:16
Welding Engineering Technology Degree
Bachelor Degree Program Welding Engineering Technology

There is a difference between an engineering curriculum and a technology curriculum.

Parent - - By Lawrence (*****) Date 03-13-2016 00:27
They graduate welding engineers Al... Good ones

Get over it
Parent - - By 803056 (*****) Date 03-13-2016 04:09 Edited 03-13-2016 04:12
You'll have to argue this point with the boys on the PF&Q committee that are developing the qualification documents for the Certified Welding Educator, Certified Welding Technician, Certified Welding Technologist, Certified Welding Engineer programs.

They are adamant there is a difference between a technician, technologist, and an engineer. It all has to do with the math and sciences included in the university's curriculum. Now, if they want to sit for the necessary examinations ..........

You and I both know people that are given the title "engineer" by their employer, but are they really engineers? My brother-in-law has the title "engineer" given by his employer, but he has never spent a day in a college classroom, never studied calculus, chemistry, physics, strength of materials, statics, or any other subject related to a typical engineering curriculum. What is the chance a prospective employer would recognize him as being qualified as an "engineer"?

If Ferris State offered a degree as a BS Welding Engineer, I'm sure they would advertise it as such, not as a degree in technology.

The employers might call them welding engineers, but I have met "welding engineers" given the title by their employer because they owned a buzz box and knew the rudiments of laying down a weld bead. Others are called welding engineers by their employers because they have to have someone they can throw out onto the firing line.

Parent - - By CWI555 (*****) Date 03-13-2016 19:32 Edited 03-14-2016 17:35

There are many companies that anoint welding, piping, etc engineers sans the degree. Some of them have self studied to the point of living up to the title, most not so much.
On the other side of that, there are folks that have a weld engineering degree that should get their money back. Particularly among the less than thirty crowd.

I don't claim to have the answers, but from either perspective, the end result is a severe shortage of truly qualified personnel. The majority out there are charlatans who slept at a motel six last night. My opinion for what it's worth.
Parent - - By 803056 (*****) Date 03-14-2016 00:16
That's where I come in, "I'm not a welding engineer, but I slept at a Holiday Express!"

I had high hopes for the AWS CWEng, but those hopes have been shattered. No one gets into the boy's club unless the degree has the right words printed on it.

Parent - - By k-maes Date 03-23-2016 15:54
Parent - By peterj357 (*) Date 03-23-2016 17:44
The yellow dimension is the length of the weld.  If the weld is acceptable, as pictured, is dependent to what your weld inspection and acceptance criteria are.
Parent - - By k-maes Date 03-23-2016 19:50
As shown in the above image, the weld stop (with crater) "shall not" be included in the measured length of the weld IF the cross sectional dimensions of that portion of the weld do not meet the requirements of the specification. Which gets back to my original question, can this end crater be considered (in any way, shape or form) a "pore".

The argument I am up against is more than semantics, it seems to be a way to get around having to use correct welding practices. I am the only weld inspector in the building and do not have the time on the job to be CWI. This is why I am depending on those CWIs here to give some witness as to the correctness of my understanding.

A) If it can be considered a pore, then, the weld stop can be included as part of the acceptable weld length.

B) If it can NOT be considered a pore, then, the acceptable weld length is much shorter and does not meet the print.
Parent - - By jwright650 (*****) Date 03-23-2016 20:19
What size fillet weld is required? I realize that you show it's length measured two ways, but the actual size matters too. Does the "crater" portion meet the fillet weld size requirement? Are you using AWS D1.1 as the acceptance criteria to meet?
Parent - By k-maes Date 03-24-2016 13:03
Weld size is relative to tMin. in the majority of our welding (also in this case) tMin = roughly 1.5mil. so the weld size only becomes an issue where the termination crater is located as the throat dimension drops to below the .7*tMin required by customer specification.
Parent - - By Trackergd (**) Date 03-23-2016 20:24
As I am looking at the picture, I cannot tell if the dark spot in the crater is an actual "hole" or just a dark spot.  If the cross section of the crater is less than the weld or the dark spot is a hole, I personally would not count it.  I would also not accept the under size section in the middle of the weld if it is less than the weld size callout.  With the length of the weld, it would be more than 10% of the weld.   Disclaimer: I'm not an actual CWI, but I did stay in a Motel 6 last night.  I am also the only weld inspector (B5.2 Weld Inspection Specialist) in my company, so I understand the predicament you are in.  I always err on the side of safety, even if it makes the Engineers and Fab manager angry, and since none of them have ever opened a code book and I own the only copies, I have survived intact thus far.
Parent - - By peterj357 (*) Date 03-23-2016 21:38
No, it isn't a pore, it is a weld termination, end crater or just crater, whichever you choose to call it. There appears to be a discontinuity within the crater, but it is a crater and not a "pore".  If the weld is required to be 25mm, I think the length of the required weld is met, as shown by the yellow dimension line. 

Now, with in the yellow dimension lines, does the weld meet whatever inspection and acceptance criteria you are using?  Is the weld size met throughout the required 25mm, including the depression from the weld termination?  Can the weld be undersized outside of the required 25mm? There appears to be a discontinuity, or the "pore" in question, in the center of the crater and is that discontinuity rounded or linear? Is that discontinuity acceptable to your applicable acceptance criteria?
Parent - - By k-maes Date 03-24-2016 13:07
It is actually a hole with a longitudinal crack starting. Which would put this in the "discrepant stop". zone and not to be included in the overall measurement.
Parent - By peterj357 (*) Date 03-24-2016 13:31
Your required weld length is 25mm, which you have exceeded.
There is hole with a crack at your weld termination site.  So fix the hole with the longitudinal crack and all should be well. Or if that size hole and longitudinal crack are acceptable to your inspection standards, then this shouldn't be an issue.
Up Topic Welding Industry / Inspection & Qualification / Porosity vs. End Crater

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