crater cracks at bracket edge

Date 10-30-2009 17:35 Edited 10-30-2009 17:56

we have around 200 brackets that have been returned to workshop for repair on cracks (look like crater cracks).
the cracks were detected by magnetic particle testing (MT) at erection site by buyer's QC.

our inspector is being questioned on why cracks were not detected or prevented in the workshop before site delivery.
the inspector explained that MT was not performed in the workshop because it is not a requirement for the brackets.

i would like to get your advise on how to prevent the cracks as shown in photo below (gouged portion).

the material is carbon steel of thk 16mm ; welded using fcaw / smaw process (7016 or 7018) ; single bevel - partial joint penetration (14mm depth)

thanks in advance

bert

By waccobird (****)

Date 10-30-2009 18:07

Are these galvanized parts? you might try a couple of shots with the camera. Do you have any that passed that you can take a picture of?

By 803056

Date 10-30-2009 18:31

Sorry Bert, I can't tell what is "cracked" in your photograph.

You said the joint was a partial joint penetration groove weld. Is the "crack" the other inspector is referring to the root side of the partial joint penetration groove weld?

Best regards - Al

By jwright650 (*****)

Date 10-30-2009 19:05

It does "appear" to have been hot dipped.....so.....the cracking may not have been there when it left the fab shop for the MT personnel to see.

By bert lee (**)

Date 10-31-2009 03:52 Edited 10-31-2009 03:56

hi all,

sorry, i have no clearer photo.

the cracks on edge have been removed (gouged marks) as shown in the photo.

the bevel was on the exterior side and the weld reinforcement was ground flush, it was paint coated not galvanized.

after the bracket was installed to erection site by fillet welding, MT was performed on the fillet weld, however, the edge portion (shop welded) was covered by MT too......that's where the problem starts.....when the buyer detected the crack on bracket edges...the bracket installation stopped and they sent some of the brackets for MT, which confimed the bracket edges cracks.... it seems the crack is shallow (minor) but when crack is heard by everyone...it become a major issue.

as an inspector, will you forsee this type of crack to happen when no abnormalities observed during the time of welding?

how you will handle this problem when the client say "as an inspector, you must detect this crack before releasing to site"

appreciate your advise / opinion.

thank you

bert

By 803056

Date 10-31-2009 05:33

Did you use extension tabs at the ends of the grooves to allow the welder to start the arc beyond the groove?

If not, there is a high probability that there is incomplete fusion at the begining of the groove where the arc is initiated.

The use of extension tabs, as called for in D1.1, will go a long way in eliminating the incomplete fusion at the ends of the grooves. Cut the tabs off when the weld is complete and grind to finish.

Best regards - Al

By bert lee (**)

Date 10-31-2009 06:05 Edited 10-31-2009 06:08

Al - that is the mistake, we did not use the run off tabs.

but the MT technician reported the defect as a crack instead of lack of fussion.

bert

By 803056

Date 10-31-2009 15:49

It sounds as if a possible solution is at hand.

Best regards - Al