B31.3 and Section IX - Impact Testing Procedure Qualification Position

[RobsVette]

Hello Everyone,

I am looking to gain some understanding of the requirements that recently changed regards to position of which to perform a PQR coupon for a weld procedure that requirements impact testing.

My understanding of Section IX changes is as follows.
- Prior to 2019 code - impact test procedures were required to be qualified in the vertical position with upwards weld progression.
- From the 2019 code and beyond - these procedures can be qualified in any position.

The understanding I am looking to gain is
- Why was it originally thought that vertical with weld progression up was required?
- What was found that drove the change in PQR qualification position requirement?

Any insight would be appreciated.
Thanks
Rob

 

[david339933]

See below: Excerpt from Walter Sperko's Summary of Changes Sec IX - 2019 Ed.

http://www.sperkoengineering.com/html/2019_addenda.pdf

The following supplementary essential variable was deleted. QW-405.2, A change from any position to the vertical position uphill progression. Verticaluphill progression (e.g., 3G, 5G, or 6G position) qualifies for all positions. This variable has been in Section IX since the early 1970s, predating the presence of heat input control variables. While conventional wisdom is that welding in the vertical position using uphill progression results in high heat input that degrades the weld toughness a lot. This is not true; if one welds vertically using a wide weave to qualify high heat input, a lot of interbead tempering occurs, and the toughness properties will be surprisingly good. Such a high-heat input qualification, unfortunately, can support using a stringer bead technique where one makes large beads with little interbead tempering resulting in degraded toughness. QW-405.2, then, was misleading. Heat input, as one can see from the above, is not the key factor that controls toughness. In Weldability of Steels, Stout and Doty showed in 1971 that both too high heat input and too low heat input degraded toughness. Recognizing that controlling heat input is not the crux of controlling toughness, Section IX committee has formed a task group to look at the whole question of how welding parameters and bead shape affect toughness and how to address them better. Any data from readers of this article is welcome.

 

[RobsVette]

Thank you, that is very helpful.

So is it correct to state that using the 2019 Edition of Section IX, if you wanted to qualify a procedure that required impact tests, you would be able to use any position?

And it seems like the reasoning for this was that when you weld vertically, you do alot more of temper bead style weld, where the puddle sits more on the previously deposited weld metal. This actually improves toughness and would theoretically allow the welder to increase heat input, without affecting the weld toughness. The natural conclusion would be that it is actually better to weld in the flat position so that the heat input has more of a direct impact on weld toughness due to less temper bead heat treatment?

What I still dont understand is, what does this have to do with to low a heat input? Would it be that welding position can sometimes make an excessive heat input acceptable but can also make a lack of heat input more acceptable as well?

And then last comment, it seems like you can definitely state that welding in the 3G position with weld progression being vertical up is not the best way to determine what the actual weld properties will be in the field. For a PQR test, this deletion would make me think that the 1G position is the best way to go because the welding heat input will have the greatest impact on the weld toughness.

Thank you again for the response.

 

[weldstan]

The heat input was always the issue. Position and progression may have added heat input but so what? The heat input governs but even that is not as big a problem as imagined. I have qualified impact test procedures with up to 60 Kj/in. I must admit the high heat inputs coupled with much too high interpass temps are highly detrimental to low temp toughness in carbon, low alloy steels and austenitic stainless steels

 

[RobsVette]

Weldstan, I would generally tend to agree with you. I guess its just interesting what the code requirements have been and now have been changed.

Also, I have not tried it but I would think austenitic stainless steel is probably the most forgiving cryogenic weld ever. As you said, if you took a normal piece of pipe of plate and welded it like you typically do and didn't even monitor heat input and just kept the interpass temperature reasonable, I would think your impact test results would be just fine.

Thanks for all the assistance.

 

[RobsVette]

Good Morning Everyone,

Sorry to revive this once again, but can you guys advise as to what the current position is for fillet weld qualification range, when it comes to supplementary essential variables for impact testing.

we are working to B31.3, and I was treating the qualification range as unlimited for fillet welds. That does not seem to be the going interpretation. It seems that the current through process on this is that even fillet welds are restricted to the range reduced qualification range.

This does not make a lot of sense to me because metallurgically, the impact of a fillet weld would be far less severe than the impact of a full penetration butt weld. I suppose an arguement could be made that the added metal from a SW coupling could accelerate the cooling after welding and produce non-desireable hardening due to the couplings acting like a heat sink because its a large volume of metal. Does anyone have any insight as to why the fillet range qualification range is different when dealing with cryogenic temperatures?

Thanks
Rob

 

[EL SUICIDA]

buenas tardes a todos, en resumen el comité se dio cuenta que la variable que importa para controlar los valores de tenacidad es el Heat-Imput, con realizar la cuenta según formula de ASME IX es suficiente sin que importe la progresión de soldadura. por ejemplo:

Si califico un procedimiento en "toda" posición con un máximo de 3000 Jouls, solo debo asegurarme que en producción no supere dicha cantidad de "Joules" en la posición de soldadura elegida.

saludos