A 106Gr.B susceptibility to crack

[Qman3481]

Hello fellow colleagues,
I'm a NDT engineer (Level III in RT,UT,MT,PT) and recently I had a issue with a colleague about materials being radiographed. We were testing welds in A 106Gr.B, 12" in diameter and 9,53mm thickness. The issue is that the other guy say that this kind of material has susceptibility to transverse cracking. I don´t agree. Can you help me with this issue?
Regards, Qman3481

 

[DefenderJ]

I am assuming you are talking about cracking of welds

ASTM A106 Gr.B is the main material of pipe construction in the alumina refinery I work in.

I would say this material has no susceptibilty to cracking from welding under normal welding practice and conditions.

It is relativley low strength and has a modest CEV.

 

[Qman3481]

Greetings DefenderJ,
Thanks for the quick contribuition!
Yes it's weld. I need to defend my position based on documents. Where can I find this kind of statement? I need to prepare a response. The CE values calculated always goes over 0,4. Isn´t this the value to much?
I tried to reason with the guy but he was strict! The weld shop has no crack history so far!...and we are working there for 3 years now, radiographing 40 to 50 welds per day!
Regards.

 

[rustbuster]

There is an old paper here for carbon steels

http://www.osti.gov/bridge/purl.cov...218FC4D1CD19?purl=/505296-Hp6dMj/webviewable/

In 30 years I dont think I have seen transverse cracking in A106 B that wasn't related to service, environment, or mechanical forces.

Good luck with you're debate, I would ask him to provide evidence of this phenomina....

 

[Qman3481]

Hello rustbuster,
Thanks for your contribution!
I've asked for evidence....Still waiting!!!
Regards

 

[unclesyd]

I have a lot of references on welding problems with a good part of them concerning pipe welding and there is no mention of problems with the subject pipe material. The only problems and analysis are from in service problems, not fabrication.

This is not saying that someone hasn't had a problem but you may have to take the lack of field reports concerning cracking in welding the material as proof there isn't a common problem. I haven't met the person that will categorically state that you want have a weld crack at sometime when welding CS.

I have many years experience with fabrication of SA106 GrB in some very highly constrained piping weldments. jacketed piping, without any problems other than an occasional welder problem.

Having said all the above there is one problem with welding the subject material or any CS that was caused by the TIG welding electrode. The problem was not well published.
In an effort to prevent CS TIG wire from rusting it was Cu plated. The only problem was that the plating was too thick and under certain conditions the Cu would cause cracking in the weld metal. It was essentially the same as if you were making a cracked weld specimen for a standard.

 

[Qman3481]

Salutations Unclesyd,
I share your opinion on this subject and I thank you for your contribution.
I think the guy didn´t interpret the standard correctly. We will wait until someone takes an oficial position and after that I will decide what to do.
Nevertheless, thank you!
Regards.

 

[gtaw]

A carbon equivalency of 0.4 is different from a carbon content of 0.4.

The carbon equivalency formula used will provide guidelines on how the information is to be applied. There are several CE formulas to select from and each will result in a different CE value depending on the alloying elements under consideration.

From a weldability standpoint, 0.3% carbon is often considered the upper limit to ensure ease of welding. That is not to say you cannot weld steels with higher carbon content, it simply means that preheat is often required and the degree of restraint plays a more important role in obtaining successful welds.

Carbon equivalency is the sum effects of the alloying constituents under consideration. As mentioned already, there are several CE formulas that can be used. The guidelines provided with the specific CE formula used are applied only when that formula is used, they are not universally applied to every CE formula. The CE will typically be higher than the carbon content because alloying constituents such as manganese, silicon, chrome, nickel, copper, etc. increase the CE. However, those alloys do not have the same influence on hardenability and cracking problems as does the equivalent amount of carbon, thus each alloying constituent is assigned a different factor depending on the equation used. CE values on the order of 0.6 are frequently welded without extreme measures being required. Again, the CE is dependent on the alloys considered by the specific equation used to calculate CE.

ASTM A106 is a carbon manganese alloy that is used for higher temperatures than ASTM A53 for example. The ASTM A53 is a carbon steel alloy that requires higher carbon content than the A106 for the same strength. The added carbon content of A53 makes it more susceptible to graphitization when subjected to high temperature for extended periods of time. The A106, being alloyed with manganese and carbon has a lower carbon content and is not as prone to graphitization as is the A53.

Both ASTM A53 and A106 are considered to be easily welded and neither have a history of either longitudinal or transverse cracks if the proper filler metal is used and the proper welding technique is used to ensure sound welds.


Best regards - Al

 

[deco0404]

Qman,

I spent almost 20 years in an alumina refinery as a radiographer. All standard piping was 106Gr.b., and I think I can safely say that I X-rayed thousands of these welds. The only time I ever saw a weld crack was on a system with high temperature caustic as the service where they had forgotten to perform PWHT. Your guy is talking rubbish if he is talking about cracking in any kind of normal ( hi-temp caustic needs to be heat-treated to prevent embrittlement, so is not considered normal) service, as you are most likely aware however, any metal will crack in the right environment..........

Declan