Progression

[Ani18]

Dear experts,
"Vertical uphill progression qualifies for all position"!
The single statement is both valid for asme and aws code .
But what is the difference? Is there any difference between two?

 

[gtaw]

I believe you are referring to WPSs qualified for notch toughness. Vertical uphill progression maximizes the heat input in comparison to downhill progression. The higher heat input will reduce the cooling rate and maximize grain coarsening, which in turn adversely affects the values obtained when CVN testing is performed. On the other hand, downhill progression minimizes heat input, maximizes the cooling rate, and minimizes the probability of grain coarsening.

The consensus is that qualifying the WPS using uphill progression produces the highest heat input (as compared to the other welding positions), thus if the CVN values are acceptable using uphill progression, the CVN for the other positions will be higher.

It is my understanding that AWS still requires other positions be qualified, it just that CVN testing isn’t required for the other test positions if the WPS using vertical uphill progression passes.


Best regards - Al

 

[Ani18]

Thanks AI

 

[nabeel3]

Dear gtaw
I am a student of welding. Let me tell you that I was not able to understand the reason for the below statement u made.

"High heat input reduces the amount of the cooling rate". Can you please help me to understand why is it so?

 

[gtaw]

High heat input simply means more energy was put into the base metal. The base metal gets "hotter" or a larger volume of base metal gets heated, so it takes longer to cool down to ambient temperature.

My use of "cooling rate" may have been misleading.

Al

Best regards - Al