Ti Weld Repair

[falco]

Hi everyone, perhaps somebody may be of assistance, I was inspecting a Ti weld Ti 6 AL 4V, I´m concern due that after repair it was cracked within the weld, it was repair and after another inspection it continues to crack and so on..I´m aware that some codes or spec. does not allow to repair more than 2 times, However I haven´t found any spec at the moment to support how many times it could be repaired, I´m really sure the welding procedure is incorrect. I´m not quite familiar with Ti welding therefore can someone please suggest me or inform where can I get information about this type of welds (spec) or if metallurgical speaking, if there is any risk of more severe damage after many repairs..will appreciate your assistance.

 

[metengr]

Go here first to understand welding of Ti

http://www.timet.com/pdfs/ti-handbook.pdf

 

[EdStainless]

Was the procedure qualified? What about the repair? If they hadn't done trial repairs and then tested them I would reject it. They first have to show that it is possible.
With Ti if you get too much oxygen or hydrogen (air, humidity) the welds will be very brittle. Have they checked weld hardness? I'll bet that it is too high.
They should have ground out a lot of metal before the repair. You grind and then perform NDT to show that you removed the entire crack before re-welding.

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Plymouth Tube

 

[stanweld]

If multiple repairs have produced the same bad result, determine the cause of failure before making another repair. At this point, I recommend that the existing weld be removed. For the reasons expressed by EdStainless, there is too great a potential for further contamination of the weld by making multiple repairs.

 

[mock1]

There could be a number of reasons that a crack formed, Bad mix in the gas, not using the correct tungsten, welding in the outdoors instead of controled environment, also thickness of the material. Was there a mixed gas used or pure? I've had a bad mix of Ar/He once that cost me three days of repairwork.
I agree with Edstainless, they should have documented that a certifiable repair was possible before trying it on the work piece.