defectin welding 1

[11041977]

can anyone here help me in this trouble?
i m welding an A105 rod in A105 flange and i got always an hole at the end of weldign joint, like in the attached picture.
both parts are well cleaned and degreased, material used to join the 2 parts ESAB 12.64 1,2mm wire, gas 82-18.
thanks
matteo

 

[Ron]

This is a termination crater. Don't stop at the end of the weld. Continue past your termination point and then come back slightly with your electrode. It is a termination technique issue and that should solve it.

 

[11041977]

welding process is mag 135, not by electrode, machine didn t stop at the end of the weld but go ahead,i justy tryed it but didn t solve the problem in this way, what do you think about the exaclty torch position? can the position affect the welding?
thanks

 

[Ron]

Wire is still a form of electrode. As for position, it looks like you are using either a straight on position or backhand. Try a forehand position (pushing the weld pool instead of pulling it).

 

[stanweld]

This appears to be a single pass, automatic weld. With very tight fits, outgassing may occur at the termination point and the flaw appears to be resulting from same, rather than a crater crack. If your equipment has a current decay function, it could be used to provide extra filler metal at the weld terminous. Joint fit up can also be modified.

It could also be a termination crater. If so, follow Ron's recommendation and if you have the capability as stated above, it too will work.

 

[gtaw]

Just my opinion; but pushing is not a good idea when welding with GMAW (MAG). Using the push technique negates the purpose of the shielding gas, i.e., the shielding gas is pushed in front of the welding arc and do not shield the molten and solidifying weld pool as effectively.

Unless you are welding sheet metal gauges, one serious short coming of the push technique is obtaining proper fusion at the root of the joint. During my thirty years as a CWI that qualifies welders and provides welder instruction when their skills are lacking, I have never had a welder pass a fillet break test using the push technique using either the GMAW or gas shielded FCAW processes. The common reason for failing the break test and the macro etch examination is incomplete fusion in the root. Since the joint detail you show in the photograph is a socket joint, the push technique can result in incomplete fusion in the weld root. I suspect the incomplete fusion would be more of a concern than the porosity in the crater.

The response that I would agree with is to continue the weld slightly further past the point of initiation so the weld crater is slightly beyond the point where the weld was initiated. The "crater decay" concept also holds some possibilities or you can program the machine to give the weld crater one short additional shoot of energy. Terminate the weld and give it one last burst of power and electrode to fill the crater and provide some additional shielding gas to protect the weld crater as it solidifies.


Best regards - Al

 

[11041977]

yes, you are right, this is a single pass, automatic weld. the torch stands in front of the workpiece, not perfectly aligned with the piece, but dislocated a little in the LEFT side of the center respect rotation that is clockwise. SEE ATTACHED FILE
i already tryed all this possibilities: current decay function, continue past your termination point, what i never tryed is then come back slightly with electrode.
THANKS FOR THE HELP
MUNARI MATTEO
ITALY

 

[DVWE]

Terminate the weld and give it one last burst of power and electrode to fill the crater and provide some additional shielding gas to protect the weld crater as it solidifies.

This will be the key. I used to have the same problem of a similar joint, and we were able to program the robot to stop for a brief moment, and give it the last burst as stated above.

 

[Ron]

Munari...let us know how it works out.

 

[11041977]

this time i welded an A 105 flange with AISI 304 bar.
the problem is the same. this time i increased the space where the weld stop after past termination point and i used a pulling technique. the weld seems ok but i tryed to grind the weld joint and i found the crater.
see pics

 

[11041977]

second pic

 

[Duwe6]

May be a cleanliness problem. That assumes that you are programming a 'crater fill' cycle like gtaw & DVWE have previously suggested. FCAW 'flux-core' is *much* more tolerant of minor cleanliness issues -- there is flux to remove impurities. Running GMAW - MAG, you only have bare wire, thus both sides of a weld have to be squeaky clean.

 

[unclesyd]

If you have the time, somewhere in this website ED Craig points out your particular defect. Ed gets on the soap box quite often. Checkout his recommendation for shielding gases. His method of speed and feeds work very well.
Also look at the standoff distance and gas flow. I would also try slowing down the welding speed and amps. Sometimes it doesn't take very much

http://www.weldreality.com/spray_transfer_above100.htm