Welding A449 Studs

[scottmnj]

I have a project where the designer specified that A449 studs be welded to a steel member to serve as connection hardware. The studs are 3/4" dia and welded with a 1/4" fillet all around. Studs are failing when hit with a light to moderate blow from a lump hammer. The studs are breaking clean through just above the weld. The studs appear to be crystalized. I think the die may have been cast the minute A449 was specified. Was this an obvious design oversight?

 

[gtaw]

Yes.

A449 are quenched and tempered materials that will produce a martensitic microstructure when welded without due consideration for the carbon equivalency, preheat, and whether a low hydrogen welding process is used.

All metals by definition are crystalline structures. The failure wasn't the result of crystallization; it was the result of the particular microstructure that was formed as a result of the rapid cooling rate of the welding operation.


Best regards - Al

 

[Duwe6]

They will require a significant preheat to prevent the 'toe cracks' you are experiencing. Where is the WPS - welding procedure to cover these dissimilar metals and your actual thicknesses? Without a properly qualified WPS, everybody on your job is just guessing.

If there is a WPS, check the preheat requirements. Either the welders are not following these requirements, or the WPS is wrong. If it is the WPS, make the welding contractor qualify using the actual thicknesses they are working with, and you witness the welding of the test coupon. It is possible that an experienced welder welded up a test coupon using 200 - 300°F preheat [because he knew that preheat was needed] and nobody recorded that variable.