porosity? help!

[welder_one]

i do alot of heavy aluminum and just recently i started getting alot of porosity in the surface of the welds. i use an xmt 304 with an xr-a push pull feeder with a 30 foot xr edge gun. i use 0.35 5356 certed content wire from hobartbros. i tried a different spool, no change and different bottle, no change. i checked that i am getting 25 to 27 cfh flow at the nozzle. i am preheating to 300. chemically etching and cleaning the parts. and using a fresh ss wire brush between each pass. the specs on this post are 1 inch plate with 5x5 3/8 square tube. 45 degree bevel complete penetration. 1 inch by 1 inch fillet weld. these are spec'd by disney engineers and i am not happy with trying to send this to them. any thoughts would be greatly appreciated, please.


here is a pic of one side

[jwsrep]

First thing that comes to my mind when porosity is mentioned is gas coverage. Check and make sure all gas fittings are tight. Leak test your whole system. You could be asperating somewhere in the gas stream either externally or internally.

Also what are your parameters for doing these welds? Voltage, Amperage, wire feed speed? Are you pulsing?

[welder_one]

i am not pulsing, i only use that for very thin stuff. i know that pulse will trap porosity. i am running about 26 to 28 volts and 765 to 865 ipm on wire speed. the amperage, i am not sure (too busy looking at the weld to see the display...lol). i put new o-rings on the gun where it plugs into the feeder. i am not dropping any pressure between bottle and feeder as for the gun and cable? i would'nt know where to begin. i am using miller nozzle #50 and an 0.40 contact tip. i put brand new consumables in right before the piece in the pic. when i cut the weld, there wasn't any visible porosity. i sent one off to be x-rayed and the company said that the porosity is in the surface. 3 pores per linear 4 inches of weld inernally. what would cause porosity on the surface? do you know what "worm tracking" is? someone suggested that it might be that, i don't know, i have never heard of it.

[aametalmaster]

Don't know if this applies but on some jobs we did we had to shut all the doors and turn off the fans to stop porisity, sucked in the summer...Bob

[welder_one]

Don't know if this applies but on some jobs we did we had to shut all the doors and turn off the fans to stop porisity, sucked in the summer...Bob

heh... didn't even think about that one, another try tomorrow. but i still don't know what worm tracking is (maybe just some hillbilly terminology)...lol

[Darmik]

Porisity

what is your flow meter set at?

When you are welding are you changing your gun angle once in a while;
while welding?

How far away is the tip to work distance?

The problem that you have there is not worm tracks.

I don't think you have a leaky system.

Check your travel speed you might be going faster than the gas can cover you.

Before you started to weld the piece how well did you clean the material?

Is the nozzel clogged up with spatter in side?

Are you using anything like mig dip for the nozzel?

And last but not least is there any lite to medium air current where your welding.

[SundownIII]

Welder_One,

You mentioned that you had changed out your gas bottle but didn't mention what gas you were running. I'm assuming straight Argon.

You may want to try an Argon/Helium mix. As the metal thickness increases the helium will help provide more heat and wetting ability. I would recommend a flow rate in the range of 30-35 CFH with the helium mix.

[welder_one]

darmik, to answer your questions in order:
i have the meter pegged at about 60 cfh to get 27 at the nozzle. i did ask about that at first and i was told that pressure and flow gets lost in a 30 foot gun. maybe something there

i try to keep a 7 to 12 degree angle (push)at all times

about a 3/8 stick out

we have treating tanks for the aluminum, first tank is hot soap, #2 and #3 are rinse, #4 is etching:nitric and sulfuric acid mix #5 is rinse #6 is aladine and chromic acid, #7 is rinse. i run these parts through the tanks except for the last 2 the chrome and rinse tank. once dry, i use mek to cleanany oily residue, then stainless wire brush to remove "fresh" oxides immediately prior to welding

i keep 5 nozzles clean and rotate them out as they build up with spatter, when the last one is being used i will clean them all up real good again. it seems to keep production up that way. i am very a**l with keeping cleen consumables.

i dont use nozzle gel for aluminum, the wax cause poor welds. on steel i will though..

there is always a slight breeze where i weld. there is a huge exhaust fan above my tables and the plant is an open plant. it is about 400 yards long and about 100 yards wide. there is not really any way to keep breeze under control. i do use welding curtains and screens to block most of it.

that is an interesting point about travel speed too fast though, i dunno, i am "grabbing for straws here"

[welder_one]

Welder_One,

You mentioned that you had changed out your gas bottle but didn't mention what gas you were running. I'm assuming straight Argon.

You may want to try an Argon/Helium mix. As the metal thickness increases the helium will help provide more heat and wetting ability. I would recommend a flow rate in the range of 30-35 CFH with the helium mix.

i do use straight argon, the purchasing lady will not spring for another bottle though. i did ask her to order a 90/10 mix for steel so that i can spray transfer and was told "why, this is what we have always used here. we arent going to go and start changing things around because you want to"

[aametalmaster]

[QUOTE=welder_one;16594]
there is always a slight breeze where i weld. there is a huge exhaust fan above my tables and the plant is an open plant. it is about 400 yards long and about 100 yards wide. QUOTE]

Now that's a shop....Bob

[SundownIII]

Welder_One

Still think the problem stems from gas coverage. Wrong mix, not enough flow, or too much air movement. Seems like a lot of splatter in and adjacent to the bead. If I didn't know better, I'd almost say it looks like you're using C25 for a covering gas.

[BWS29128]

Now, SundownIII...don't go accusin' the poor guy of makin' one of MY mistakes!!!

[welder_one]

Welder_One

Still think the problem stems from gas coverage. Wrong mix, not enough flow, or too much air movement. Seems like a lot of splatter in and adjacent to the bead. If I didn't know better, I'd almost say it looks like you're using C25 for a covering gas.

the shield gas used is 100% argon. i did try another piece today and brought the weld curtains close and turned off the fan. i did not change the porosity, it also didnt take long at all for the safety officer to threaten me with a write up for welding with the exhaust fan off...lol even in the dead of winter i have to run the fans. the spatter that is present on the weld bead and sides came of with a hand brush. i did slow my travel speed down and that seemed to kill the porosity. i have 790 of these stobs to make for disney in orlando. i was trying to move too fast i guess. i will post more pics of the new coupons, after they come back from x-ray.


i still dont know what worm tracking is though...

[Darmik]

Worm tracks

It is a typical problem with flux core.
You'll have a perfect weld and when you chip the slag you'll find in the center of the weld or just off to one side a surface crater about one inch long can be longer though then bareies it self at the end in the weld.

It's like when supermans metor hit earth that long surface crater that he created and then he came to a dead stop.the only difference is the worm hole goes down after the stop.

I hope this explains it.I wish I had a pic.the next time it happens to me I will take a pic of it.not very nice when your trying to pass a test.It's a fail if you get this.

I'm glad slowing your travel speed down helped out.

[jwsrep]

darmik, to answer your questions in order:
i have the meter pegged at about 60 cfh to get 27 at the nozzle. i did ask about that at first and i was told that pressure and flow gets lost in a 30 foot gun. maybe something there

i try to keep a 7 to 12 degree angle (push)at all times

about a 3/8 stick out

we have treating tanks for the aluminum, first tank is hot soap, #2 and #3 are rinse, #4 is etching:nitric and sulfuric acid mix #5 is rinse #6 is aladine and chromic acid, #7 is rinse. i run these parts through the tanks except for the last 2 the chrome and rinse tank. once dry, i use mek to cleanany oily residue, then stainless wire brush to remove "fresh" oxides immediately prior to welding

i keep 5 nozzles clean and rotate them out as they build up with spatter, when the last one is being used i will clean them all up real good again. it seems to keep production up that way. i am very a**l with keeping cleen consumables.

i dont use nozzle gel for aluminum, the wax cause poor welds. on steel i will though..

there is always a slight breeze where i weld. there is a huge exhaust fan above my tables and the plant is an open plant. it is about 400 yards long and about 100 yards wide. there is not really any way to keep breeze under control. i do use welding curtains and screens to block most of it.

that is an interesting point about travel speed too fast though, i dunno, i am "grabbing for straws here"

Allrighty then, let's take the first part of this post you said: "i have the meter pegged at about 60 cfh to get 27 at the nozzle."
How are you sure of this? Setting the fg at 60 CFH to get 27 CFH at the nozzle, are you measuring the flowrate with a gas flow indicator? Are you running a 100' hose? 200' hose? How can you be getting that much of a flowrate drop? Then you said " did ask about that at first and i was told that pressure and flow gets lost in a 30 foot gun." To which I say no way Jose. 30' of gas hose thru a torch will not affect the flowrate at all....nada.

See, SundownIII and I are of the same thought process on this. Porosity = gas flow/impurity problem....99% of the time.

After your post of setting the flowrate at 60CFH I almost have to draw the conclusion of 2 points.

#1) Too high of flowrate. You can create a turbulence effect when your flowrate is too high. The turbulence actually draws "air" into the gas column and the nitrogen, not to mention the oxygen creates porosity.

#2) You have a gas leak somewhere in the system and you are asperating the system.

As far as the fan goes, unless you have it directly blowing at your weld station I doubt this is the problem, unless it's a wind tunnel fan.
I have several customers that have fans blowing in their area and does not affect aluminum welding.

Ohh BTW the reason I asked about parameters is because welding at high voltage ranges (over doing it) can cause poor weldments. You at those ranges you mentioned are okay.

Like Darmik said about worm tracks, usually a flux core problem due to improper eso (electrical stick out) or improper voltage.