Socket weld leaks at overlap/crater 1

[TheRyno]

Hi All, I'm trying to decrease frequency of weld leaks in an automated GMAW-P socket weld process.

It is a weld between a "cap" and a tube which are pressed together, then welded in an automated rotating fixture.

It is SAE 1010 steel, and the cap has wall thickness .080" and the tube is .049"

The weld only ever leaks at the overlap pass, at the crater and its always on the tube side of the weld.

Any suggestions for crater options or burnback etc. ?

see picture for clarity of the part.

Thanks

 

[StoneCold]

Can you continue the weld around. So you are welding 365 degrees instead of 360, resulting in a little weld overlap at the end of the weld?

Regards
Stonecold

 

[TheRyno]

Yes, the weld goes past 360 degrees, about 3/8" overlap.

 

[stanweld]

What you are more than likley experiencing is gas evolution at the tie-in loacation. If you have appropriate controls, slow down the travel speed and slightly increase the wire feed speed to permit the gas to escape at the tie in location. IF you have down sloping current control, use it after you have passed the tie-in location.

A competent, manual welder would readily compensate. Essentially, you need to mimic what he would do wiyh your automatic process.

 

[EdStainless]

current ramp up at the beginning of the weld and ramp down after the completion will help.
The ramp at the start acts as a pre-heat on this metal so that when you come around and weld over it you get good fusion with less gas evolution.

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Plymouth Tube

 

[Tmoose]

Is it a closed vessel?

 

[Duwe6]

Program it to do what an experienced welder does: breal the arc at 365°, hesitate 1 to 1.5 seconda and then 'blip' the gun for crater fill.

Also possible that the porosity is from gas evolution from lack-of-cleanliness. GMAW, being fluxless, has almost zero tolerance for oil, etc.

 

[WBH]

TheRyno,

What is causing the weld to leak?

Are you blowing thru the .049" tube wall or not fusing?

I agree with stanweld, your parameters need to be modified, however the condition causing the leak will depend on how you modify. Another parameter to consider is the diameter of the wire.

If you are blowing thru you could decrease the overlap to avoid excessive heat input.

 

[TheRyno]

Thanks for the responses so far.

WBH:
The weld leaks always on the tube side of the weld, see the attached pic for clarity. It seems to be lack of fusion on the thin wall and creates a pinhole leak path.

 

[Compositepro]

AS Tmoose asked, is the tube a closed volume or is it free to vent?

 

[WBH]

TheRyno,

Were you able to remedy this issue? If so how did you accomplish?

 

[TheRyno]

The volume is open to vent. The leaks still occur, they are only about 1% of total parts, but they always still leak at the same location. I haven't had much time to do further trials but might be able to soon. Again I appreciate the help from everyone.

 

[WBH]

If your are pressing the parts together with significant force, welding, immediately releasing the force you may be creating cracks at the weld termination.

Suggest dye penetrate testing these areas.