Weldability forging vs. casting ? 1

[annpo]

Is there any difference in weldability between forging and casting parts?

Assume general that I have two parts: one made by forging process, second is casted.
The chemical composition, carbon equivalent CE is equal for bought pieces.

In detail I’m considering the weldability of pipe P91 and casting ASTM A217-12CA ( 9% Cr steel).

 

[swall]

No difference.

 

[TVP]

Essentially no difference. Perhaps a small effect of dissolved gases in the casting.

 

[CoryPad]

If the cast part has chemical segregation, then it can have lower weldability.

 

[metengr]

As I read through your post, the last statement caught my attention. The devil is in the details. You realize you are dealing with a creep strength enhanced ferritic steel.

I have seen some real problems with large 91 castings because of poor casting quality and how weld repairs were performed on the castings. Because of the welding precautions required for this type of steel (preheat, interpass temperature, narrow PWHT band, and filler metal Ni+Mn content), and the concern with Type IV creep damage in elevated temperature service in the surrounding base metal heat affected zone, I would shy away from large 91 castings.

Assuming all things being equal, which is unrealistic for this alloy, weldability would be similar and all precautions must be strictly enforced. Since you will most likely have to weld repair 91 castings versus a wrought material, I would select the wrought material for component fabrication.

 

[Guest102023]

metengr is right, 'weldability' is a variable property (or aggregation of properties).

There are indeed some devilish details for an exotic ferritic alloy like P91, and weldability gets considerably more complicated, with PWHT entering into the equation.

BTW, I have heard of SCC issues specific to C12A castings - can anyone educate me on this? I am not referring to the type of SCC that can happen to not-yet-PWHT weldments.

 

[stanweld]

While experiencing cracking in C12A valve castings, they were caused by thermal fatigue - not SCC.