Years ago while working as a weldin 4

[matschka]

Years ago while working as a welding engineer for the biggest construction contractor, we ran into a problem with not having enough welders for the nuclear project. The union could not supply us so we brought in (non-union people, non welding people) and trained and tested them to weld only socket welds. I was directly involved with this program as an instructor. Of course we trained the people on how to 'walk the cup' by simply laying the wire in the throat of the socket and proceeding to consume the filler wire and there by producing a good looking fillet weld. No weld wire dipping was required. When we started to test the coupons we sawed them in sections and polished them. We then performed a macroetch examination. Under magnification we found that very few test specimens had penetrated the 'root'.They got close but not enough penetration. We changed our training technique to melt out the root a little dip the filler rod in and move ahead, melt out the root, dip the filler rod. But after the root was deposited in this way they could 'walk' the cup to finish the socket weld. The test specimens were then cut, bent, and then macroetched. 'WOW" what a difference. Complete penetration plus, no question.
We came to the conclusion that simply laying the filler wire in the throat and welding over it, consuming the wire was stopping complete penetration but the finished weld looked pretty.
It is my opinion that this is the cause of some of the socket weld failures around the globe.
I also believe that their are pipe welds out there that have been welded using the same technique of just consuming over the filler wire and they have been x-rayed and look ok but
have cold lap where one weld bead lays over an underlying bead but is not completly fused. The defect is laying in a plane where the x-ray goes through but does not show the lack of fusion. However, ut would show this type of defect.

 

[matschka]

I also believe that the completed socket weld fillet should be reinforced with a another weld bead on the pipe side, top of the fished fillet. Thereby giving the pipe side weld a little more reinforcement. This would solve some fatigue problems in socket welds.

 

[MJCronin]

"It is my opinion that this is the cause of some of the socket weld failures around the globe."

Whaaaat ????? Where ????? References ? ......????/

Why has no one mentioned the cheating known as "slugging the weld" ?

This sleazy welder practice has been around since the beginning of welding (100+ years) and is the major reason why so many "Liberty Ships" were lost at sea in WWII

https://books.google.com/books?id=q...6MQ6AEIKjAA#v=onepage&q=slugging weld&f=false

https://books.google.com/books?id=4...6MQ6AEINzAC#v=onepage&q=slugging weld&f=false

This OP guy was a weld instructor and he was inventing new methods of slugging ?

This is why structures fail .....

MJCronin
Sr. Process Engineer

 

[matschka]

After over 60 years in this welding business, I assure you that the socket weld training and testing did not involve any 'slugging'. The term that I used, 'laying' the filler wire in the throat of the socket weld and consuming it has been misconstrued. The following is a more detailed explanation:
The weld puddle is started,the filler wire is added to the leading edge. The weld puddle is advanced by 'walking the cup' assuring both sides of the socket weld joint adjacent to the throat is being melted and consuming the filler wire at the same time, this is the weld puddle. Their is 'no' dipping or feeding the wire. Sometimes you may have to dip to keep the puddle consistent but generally one just walks the cup in the joint and consumes the filler wire at the leading edge of the puddle and the 2 sides obtaining a good puddle and continually moving forward.
How could 'slugging' occur as we bent and macroetched all the performance tests?
The point I was trying to make is that I think that 'walking the cup' will sometimes cause
a lack of penetration at the root. A welder should always assure himself that the exact 'root'
of a socket weld is penetrated. This can be accomplished by using a 'dipping' technique.

 

[matschka]

'This sleazy welder practice has been around since the beginning of welding (100+ years) and is the major reason why so many "Liberty Ships" were lost at sea in WWII'

WRONG, WRONG, WRONG. Do not jump to conclusions with out doing the necessary research.
Go to your search window and enter the following: what caused the liberty ship failures.
go to the following.

https://metallurgyandmaterials.wordpress.com/.../liberty-ship-failures

 

[matschka]

Also go to your search window and put in socket weld failures. Again, do the necessary research before jumping to conclusions.

 

[gtaw]

This is where I believe many of the welding standards have missed the boat. Most codes permit welders that have qualified by welding a grooved butt joint to weld both grooves and fillet welds. A welder qualified by passing a fillet weld is only qualified for fillets.

As indicated by the post, there may be an issue with obtaining proper fusion in the root of the fillet weld if the technique isn't correct. The technique described in the post is sometimes referred to as the "lay wire" technique. It works just fine for a grooved joint with a root opening and root face about the same dimension as the filler rod. The technique doesn't necessarily work on fillet welds.

My 40 years of experience testing welders is that many welders that qualify on a groove weld will fail a subsequent fillet weld test. However, welders that pass the fillet weld test rarely fail a subsequent grooved butt joint. My experience is inconsistent with what is permitted by many welding standard. The interesting point is it is the same for each of the arc welding processes. Its all about technique. The problem is more of an issue with semi-automatic processes using small diameter electrode.

The failure rate for qualifying welders using the fillet break test is so high I've changed my pricing structure. Instead of charging by the test, I simple have the contractor give me the scrap and cash it in at the nearest scrap iron dealer. On a serious note, it is rare to have a welder pass the fillet break test on the first go around. It is a problem the committees, i.e., ASME AWS, etc., refuse to recognize or chose to ignore.

As for the Liberty Ships, out of the nearly three thousand built, around two hundred cracked in half with the failures initiating at the corners of hatch openings, but the majority of them were salvaged, towed to port, and welded back together to finish the voyage. They were considered a successful venture if they complete a one way trip to their destination. They were disposable shipping container! The life expectancy was five to seven years. The majority of the Liberty ship went on to serve nearly 35 years before being scrapped. They were still in use during the Vietnam War. There were multiple issues that involved in the welded failures. They included poor notch toughness in the plate. That was remedied by better control over the sulfur and phosphorus content and bidirectional rolling of the hull plate. Poor design details. Redesign included the elimination of sharp corner joints that acted as stress risers. Welding procedures that didn't consider notch toughness resulting from uncontrolled heat input and control of the plate chemistry. Without any doubt, the welder's skill does come into question. Unskilled workers were pulling off the sidewalk to become welders. They were trained to the point they could produce a simple weld. As they gained experience, they were assigned to more difficult welding tasks. Welding theory? Welders don't need no stinking welding theory. That attitude seems to persist in many shops.

Just saying.

Best regards - Al

 

[MJCronin]

Most socket welding failures on piping systems are due to fatigue failures of the weld on small bore systems subject to extreme or prolonged vibration.

Failure at the socket weld location is to be expected as this is where the system bending flexiblity transitions from "stiff" to "flexible".

Small bore piping systems subject to excessive vibration should be designed without socket welds.

MJCronin
Sr. Process Engineer

 

[matschka]

Thank you 'gtaw' for a great post concerning socket weld tests and welding technique and the
Liberty ships. Your comments were spot on.I agree 100% with all your comments.

 

[gtaw]

Thanks Matschka. It was good to see I'm not alone in my observations with regards to the difficulty many welders have with obtaining fusion to the root. Granted, there are a good number of welders that have no problem, they have developed the technique necessary to produce an acceptable fillet weld.

Best regards - Al

 

[XL83NL]

They were trained to the point they could produce a simple weld. As they gained experience, they were assigned to more difficult welding tasks. Welding theory? Welders don't need no stinking welding theory. That attitude seems to persist in many shops.

gtaw, please forgive me, but my native isnt English, it's Dutch. As such, properly spotting irony & sarcasm is sometimes diffuclt.

Is your point here that youre saying welders do need a welding theory?

 

[gtaw]

Hello XL83NL!

Exactly, if an employer wants welders with a strong technical understanding of welding, they have to step up to the plate and provide both opportunities for learning additional welding skills and the technical aspects of welding.

I differentiate between "rod burners" and "welders". A rod burner is an individual that may be skilled at using one welding process and a welder is an individual that has mastery of more than one welding process, but in addition to skill, they understand the technology that supports welding. What technology does a welder need to understand? How about welding symbols? How about some basic welding metallurgy? How about the root causes of weld defect? How about the use and application of a welding standard?

Welding is not considered to be a skilled trade in the United States. As a result, the majority of the people that use welding to earn a wage learn to weld on the job. They only know what the welder in the adjacent welding booth teaches him. That usually entails learning the skill, but no theory as to why you preheat, when preheating is necessary, the proper way to back gouge or why it is necessary. Many mistakes are made because the welder misinterprets the welding symbol, assuming he even knows how to read a drawing. I encounter welders on a daily basis that have no appreciation for what a material specification is, as a result, they make material substitutions because it is "steel" or because it is "aluminum". They don't do it with malice, they do it because they don't understand how minor differences in chemistry or heat treatment affects the mechanical properties.

I teach courses in welding for contractors that are engages in working to Navy welding standards. The training is mandated by the Navy as a condition of getting the contract. The welders are required to attend a class on theory and they have to pass a written examination. One of the subjects covered is the workmanship requirements of the welding standard. If they pass the written test, they move on the skills test, i.e., the hands-on welding portion of the test and weld either a plate or pipe assembly. It still amazes me to hear welders tell me “I’ve been welding for twenty years and no one has told me that before!”

The companies usually experience a reduction in reject rates after the training because the welders now understand why preheat is required, so they are less likely to skimp on the preheat. They understand how electrode extension affect amperage when welding with either gas metal arc or flux cored welding. They are less likely to use the wrong electrode because they now understand what the numbers on the filler metals actually mean. They understand why low hydrogen electrodes have to be stored at a high temperature and that you need to keep the electrode oven on all the time, not just when you are going to use the low hydrogen electrode.

As I told one “owner”, “If you want something change for the better, you can't simple keep doing what you’re doing now!”

Training isn’t cheap, but producing scrap is more expensive.


Best regards - Al

 

[XL83NL]

OK, that was my impression from your previous post as well. We see that here as well, though over recent years, such knowledge and theoretical skills have improved. One reason I can think of is that (at least here in NL) a lot of companies now have qualified and certified personnel at work as required by their QAQC manual, mainly driven by EU Directive CPR 305/2011/EC, which requires the application of EN 1090. There's been a lot of focus on getting these people (who make up e.g. welding plans - but welders as well) certified to become Welding Specialist, Welding Technician, etc. Just having that paper isnt enough, staying certified is another means in maintaining that knowledge level. From what Ive seen in front of the welding classes Ive teached, is that a lot of welders now understand basics of preheat, material selection, construction details (why use certain joints, or when especially not), welding symbols, welding apparatus & process fundamentals, metallurgical aspects, etc; it's part of their training.