[mdlimy]

Hi all,

I am having some trouble getting a very clean porosity free weld on a piece of cast aluminum. The weld needs to be free of all voids/pinholes because it is an o-ring groove that is being machined.

I have successfully welded two of these previously but it took several tries and gets very expensive paying my machinist to re machine every time we find out there is a pinhole in the o-ring groove sealing surface.

My process is as follows, and I know some of it sounds overkill at first, but I am trying everything i can to ensure a clean weld.

Cut away material 1/2" on either side of the damage and about 1/4" below the sealing surface. Using a very clean aluminum fluted carbide 1/4" burr.

Clean surrounding area with clean stainless brush, wipe down with acetone, heat lightly with map gas to remove any moisture

Using light amperage, run over the weld area to allow the cleaning action to clean. Then wire brush again.

Lay base weld, then cut away about 1/4 of the weld on all suraces to remove any of the crap that floated to the surface.

Repeat that last process until I have a clean and what seems to be porosity free weld in the area of the o-ring groove.

I do not care if there is slight porosity in the material below the groove, as long as the groove and 3/16" above the groove are porosity free.

I feel like my issue the final part of the weld where I have to transition into the substrate and there is no clean base filler for me to weld on. No matter what this is the case on both ends of the weld, the beginning and the end. My technique is to get in and out as quick as possible at that point, pump the pedal just enough to drop the filler in without keyholing the rest of the groove and pulling crud from the substrate. It looks like it works great, until its machined, I am always seeing a small bit of porosity near that area.

Any help is greatly appreciated! I would like to at least get some ideas to try before Monday hits, Ive been fighting this one for over a week and would like to finish it next week. If there is any info I left out, let me know.

-Thermal Arc 300gtsw
-40% dcep
-2% 3/32 lanthenated tungsten that is ground to a point then flattened(I am having trouble welding it with balled up thoriated)It is not spitting on me
-100% argon @ 20cfh
-medium size lense with a #8 cup (my go to setup that i use for majority of work)
-4943 MaxalTig filler, It was recomended for cast, I was previously using 4047 and I feel like the 4943 flows a bit better.

I dont have a before picture of the final machined one, but it went similar to previous ones which I have pictured here.

[Otto Nobedder]

Welcome, mdlimy,

High-vacuum work is what I do, and I can suggest several things.

The first that comes to mind is the "aerodynamics" of what you're welding. The laminar flow from the gas-lens I see in one of the pictures will tend to draw air in from the sides with a weld in that configuration. I'd suggest going to a standard collet and cup (#8, if that's a -20 torch or similar, as it appears to be). I'd also tape up some aluminum foil dams to trap enough argon that it must "spill out" of the weld area. I've even done one particular problem weld inside a sandblast cabinet purged to nitrogen to get all the moisture and oxygen out of the equation.

Second, you should take time to prove your gas line completely leak-tight. I won't go into the explanation, but any leakage in your gas system after the flow-meter WILL draw atmosphere into the line.

Third, it's not uncommon to have moisture in your argon. As Braehill will tell you, not every bottle filler will evacuate the bottle at each fill. Consider adding an inline dessicant cartridge (rated for compressed air at 150 psi... your argon after the flow-meter will be between 30-75 psi). It's also possible for the gas to be contaminated with CO2 or other gasses if your local filler must use the same manifold for different mixes.

Just some thoughts...

Steve S

[LtBadd]

Welcome, mdlimy,


The first that comes to mind is the "aerodynamics" of what you're welding. The laminar flow from the gas-lens I see in one of the pictures will tend to draw air in from the sides with a weld in that configuration. I'd suggest going to a standard collet and cup (#8, if that's a -20 torch or similar, as it appears to be). I'd also tape up some aluminum foil dams to trap enough argon that it must "spill out" of the weld area.
Just some thoughts...

Steve S

Along this thought I believe turning your gas down to at least 15cfh could be helpful, especially if you're going to go to a standard collet body.
Another thought is the weld wire, did you clean this right before welding? Also after cleaning the wire watch where you're laying it so it's not contaminated. Use a new clean sst wire brush. And last but not least watch your torch angle.

Richard

[big gear head]

What is the parent metal? Is it a casting or 6061, or 7075?

You may need to use a dam to keep air from pulling in from the back side.

[dave powelson]

welding porous al casting

-There's porosity in the parent casting, revealed by the groove machining.
-Porosity is normal in 'normal' castings and can be more prevalent in the thinner
sections.
-Castings can be made to a higher level of minimum porosity--at added expense.
X-ray of the machined area prior to machining would help define the extent and
degree of porosity. Yup, all of this costs bux--but your rework is costly as well.

(Your's truly, contracted 3x with same casting house for production of an A356 investment
cast, exquisitely thin, hollow and detailed turbine engine part---to Mil Spec's, meeting an
X-ray standard for porosity, 100 % penetrant inspect., post cast machining and processing. It can be done.)
An possible option is to have the groove cast in.

-Are you trying to save castings that you contracted to have made or is this work
and re-work being done for others?

Either way--you've been supplied with castings that really aren't acceptable for
the end function. Those lettle holes can create much larger air/argon gas bubbles
in the puddle when subjected to thousands of degrees of intense heat.

Ditto all the comments on setup and changing various aspects of the welding.
For damming, try flat blockoff plate set inside a tad, flat plating on the outside wall,
set below the cutout.

Cranking the 40% DCEP down to 30 (equivalent of 70% balance in 'Miller' terms)
--for more heat input, playing with the AC freq.--cranking it just high enough to get stiff arc, will help.
(I had a 300 GTSW for 15 years until it died)

Make a very thin overlay on the cutout, brush it and look with magnification if needed for any porosity holes.
Cheater glasses or inserts can help.
Gently, lightly, wash over them with a tad more filler.
(You've got to either boil it out or try to trap this stuff--below).
The other option is to wash with no filler, a tad and see if the hole has filled.
Carbide burring out any holes and washing over again and repeating as needed is another way.
Any subsequent passes need to be low heat & thin. It's really easy to pull up a porosity bubble, thru the filler puddle.
Slamming on one big, thick pass after overlay, hoping that it doesn't bubble, doesn't work.
PM me if you wish.

[mdlimy]

First I would like to thank everyone for taking the time to type out all this very valuable information. This is my first post on the forum but I know it wont be my last, I am very impressed with everyone that has taken valuable time to help me out!

Welcome, mdlimy,

High-vacuum work is what I do, and I can suggest several things.

The first that comes to mind is the "aerodynamics" of what you're welding. The laminar flow from the gas-lens I see in one of the pictures will tend to draw air in from the sides with a weld in that configuration. I'd suggest going to a standard collet and cup (#8, if that's a -20 torch or similar, as it appears to be). I'd also tape up some aluminum foil dams to trap enough argon that it must "spill out" of the weld area. I've even done one particular problem weld inside a sandblast cabinet purged to nitrogen to get all the moisture and oxygen out of the equation.

Second, you should take time to prove your gas line completely leak-tight. I won't go into the explanation, but any leakage in your gas system after the flow-meter WILL draw atmosphere into the line.

Third, it's not uncommon to have moisture in your argon. As Braehill will tell you, not every bottle filler will evacuate the bottle at each fill. Consider adding an inline dessicant cartridge (rated for compressed air at 150 psi... your argon after the flow-meter will be between 30-75 psi). It's also possible for the gas to be contaminated with CO2 or other gasses if your local filler must use the same manifold for different mixes.

Just some thoughts...

Steve S

Steve, Thank you for the advice. I did previously dam up around the weld area for the shielding gas, but I did not see much of a difference in weld quality so I stopped doing that, I will try again with tin foil. I will also swap to a standard collet instead of the gas lense, I have heard this is better for aluminum welding anyways.

I have had issues with bottles not being completely evacuated, I did not know i could add an inline desiccant cartridge, I will definitely do this!

Welcome, mdlimy,


The first that comes to mind is the "aerodynamics" of what you're welding. The laminar flow from the gas-lens I see in one of the pictures will tend to draw air in from the sides with a weld in that configuration. I'd suggest going to a standard collet and cup (#8, if that's a -20 torch or similar, as it appears to be). I'd also tape up some aluminum foil dams to trap enough argon that it must "spill out" of the weld area.
Just some thoughts...

Steve S

Along this thought I believe turning your gas down to at least 15cfh could be helpful, especially if you're going to go to a standard collet body.
Another thought is the weld wire, did you clean this right before welding? Also after cleaning the wire watch where you're laying it so it's not contaminated. Use a new clean sst wire brush. And last but not least watch your torch angle.

Richard

Richard, I will try lowering the flow rate to 15cfh with the standard collet body.
I wipe down the filler material with a brand new cleanroom texwipe with acetone right before welding and do not set it down, I have been very meticulous with this as I know how much of a headache dirty filler can cause.

With this particualr part, the torch angle is very critical, maybe I could do better. I am trying to keep as close to 90* angle as possible, If i start to add angle it gets hard to feed the filler quickly without blowing it away. Any tips here? I give it a jab of heat when I add filler, and I try to get in and out as quick as possible.

What is the parent metal? Is it a casting or 6061, or 7075?

You may need to use a dam to keep air from pulling in from the back side.

Unfortunately I have no idea what the casting material is

I think creating a dam for the argon will help, Ill give it a shot!

welding porous al casting

-There's porosity in the parent casting, revealed by the groove machining.
-Porosity is normal in 'normal' castings and can be more prevalent in the thinner
sections.
-Castings can be made to a higher level of minimum porosity--at added expense.
X-ray of the machined area prior to machining would help define the extent and
degree of porosity. Yup, all of this costs bux--but your rework is costly as well.

(Your's truly, contracted 3x with same casting house for production of an A356 investment
cast, exquisitely thin, hollow and detailed turbine engine part---to Mil Spec's, meeting an
X-ray standard for porosity, 100 % penetrant inspect., post cast machining and processing. It can be done.)
An possible option is to have the groove cast in.

-Are you trying to save castings that you contracted to have made or is this work
and re-work being done for others?

Either way--you've been supplied with castings that really aren't acceptable for
the end function. Those lettle holes can create much larger air/argon gas bubbles
in the puddle when subjected to thousands of degrees of intense heat.

Ditto all the comments on setup and changing various aspects of the welding.
For damming, try flat blockoff plate set inside a tad, flat plating on the outside wall,
set below the cutout.

Cranking the 40% DCEP down to 30 (equivalent of 70% balance in 'Miller' terms)
--for more heat input, playing with the AC freq.--cranking it just high enough to get stiff arc, will help.
(I had a 300 GTSW for 15 years until it died)

Make a very thin overlay on the cutout, brush it and look with magnification if needed for any porosity holes.
Cheater glasses or inserts can help.
Gently, lightly, wash over them with a tad more filler.
(You've got to either boil it out or try to trap this stuff--below).
The other option is to wash with no filler, a tad and see if the hole has filled.
Carbide burring out any holes and washing over again and repeating as needed is another way.
Any subsequent passes need to be low heat & thin. It's really easy to pull up a porosity bubble, thru the filler puddle.
Slamming on one big, thick pass after overlay, hoping that it doesn't bubble, doesn't work.
PM me if you wish.

welding porous al casting

-There's porosity in the parent casting, revealed by the groove machining.
-Porosity is normal in 'normal' castings and can be more prevalent in the thinner
sections.
-Castings can be made to a higher level of minimum porosity--at added expense.
X-ray of the machined area prior to machining would help define the extent and
degree of porosity. Yup, all of this costs bux--but your rework is costly as well.

(Your's truly, contracted 3x with same casting house for production of an A356 investment
cast, exquisitely thin, hollow and detailed turbine engine part---to Mil Spec's, meeting an
X-ray standard for porosity, 100 % penetrant inspect., post cast machining and processing. It can be done.)
An possible option is to have the groove cast in.

-Are you trying to save castings that you contracted to have made or is this work
and re-work being done for others?

Either way--you've been supplied with castings that really aren't acceptable for
the end function. Those lettle holes can create much larger air/argon gas bubbles
in the puddle when subjected to thousands of degrees of intense heat.

Ditto all the comments on setup and changing various aspects of the welding.
For damming, try flat blockoff plate set inside a tad, flat plating on the outside wall,
set below the cutout.

Cranking the 40% DCEP down to 30 (equivalent of 70% balance in 'Miller' terms)
--for more heat input, playing with the AC freq.--cranking it just high enough to get stiff arc, will help.
(I had a 300 GTSW for 15 years until it died)

Make a very thin overlay on the cutout, brush it and look with magnification if needed for any porosity holes.
Cheater glasses or inserts can help.
Gently, lightly, wash over them with a tad more filler.
(You've got to either boil it out or try to trap this stuff--below).
The other option is to wash with no filler, a tad and see if the hole has filled.
Carbide burring out any holes and washing over again and repeating as needed is another way.
Any subsequent passes need to be low heat & thin. It's really easy to pull up a porosity bubble, thru the filler puddle.
Slamming on one big, thick pass after overlay, hoping that it doesn't bubble, doesn't work.
PM me if you wish.

Dave, thanks for the tips, the process you described at the end of your post is what I am currently doing but I will try playing with the balance and frequency. I have found that a lower frequency seems to agitate the puddle less and I end up with less pinholes appearing. This thin part that I am welding doesn't require a hell of alot of heat so I am OK to keep the DCEP on the higher side(tungsten is in good shape), but will I see any advantages if I use more DCEN

This is work for a customer, they are old parts that are no long available and quite expensive, so the repair is well worth the money to them. Unfortunately they are parts that need to be fixed and I have committed to doing that repair. Fortunately, I have successfully repaired one and I know it can be done again, and the customer is happy at the end of the day. My goal now is to perfect this process.

I received another one today for repair, I will take pictures from start to finish for you guys to see the process. Wish me luck!

[mdlimy]

I started by cutting away material to remove the pinholes, I was very surprised how large it ended up being



After wire brushing, another pinhole appeared


I then created a shield to allow the argon to puddle around the weld, its crude but it works


Here is a closeup of the crap I'm working with



I swapped to a standard collet body, number 8 cup and 15cfh.

After making a light pass with no filler, to allow the cleaning action to do some work, this is what I ended up with


I cut it back and tried again, this time with fresh tungsten.....Nope.


After dealing with that, i decided to weld on some clean 6061 and see how she did. Here are the results...Clearly I have an issue directly related to the use of a standard collet.


I swapped back to a gas lense for the time being and tried welding the part to see if I noticed any difference with the shielding in place...I couldn't tell much of a difference and was still dealing with some crud pulling into the puddle at the end of my welds where I had to transition into the substrate.



I cut the weld down a little and ran over the top with some cleaning action and exposed an enormous void
always near the end of the weld close to the original material.


I will keep playing around some more today. What do you guys think?

[big gear head]

Reminds me of the Muncie 4 speed transmission cases that I've welded. In my case a few voids didn't matter, but you can't have them in that O ring groove.

I'm sure that you have tried this already, but sometimes I can dwell on a spot for a while and boil out the voids.

[kiwi2wheels]

A thought, are you running a name brand collet body and collet , e.g., Weldcraft or CK Worldwide, or ....?

Some no-name bodies have major burrs in the cross drillings and even the diameters are suspect.

And this

Re: CK24W
Simon,
I'm not sure if your using a gas lens or a standard collet body but I'm pretty sure that all CK24 torches use the old school split collets. Check to make sure your collet hasn't overheated and twisted, if it has it can go out against the inside of the torch and limit you gas flow. This is more likely in such a small torch with a rating of 180 amps, it puts a lot of heat back into the short components. Also check for leaks in your system, low pressure leaks will siphon atmosphere into your sheild gas. Also check that the o-ring on your back cap isn't split.

That's just a couple things off the top of my head.

Len
by Braehill
Thu Oct 02, 2014 11:32 pm
Forum: Tig Welding - Tig Welding Aluminum - Tig Welding Techniques - Aluminum Tig Welding
Topic: CK24W
Replies: 22
Views: 843

[Otto Nobedder]

There's something screwy going on here that's not related to the parent metal. If it were that porous and impure, it would not be in high-vacuum service. And, you've had success with it once before on an identical part. Something has changed.

Do you have a spare torch you can try? Have you added the dessicant cartridge yet?

Do you have a second bottle you can swap on to the machine?

I'm afraid this is going to be a challenge to diagnose, long-distance.

Steve S

[Metal_pig2001]

Hi to all

I realise that my question may be simplistic but id the pinhole that is found is more a pin-cavity as compared to a pin-tunnel that actually leads somewhere, is it a problem?
Is it possible to perform a leak test as you might do with a header tank etc?
With many castings, there may not be a hole initially, but when the metal is heated again then gas can come out of solution just like a soda has gas dissolved in the liquid. Is it possible that you are initiating those sorts of issues?

Regards
Ralph
Not a metallurgical specialist but aware of issues when doing some casting

[rick9345]

desiccant-Argon inline

http://www.amazon.com/Arrow-Pneumatic-P ... B003BJN0UO

any hardware/auto parts store for barb adapters

And clamps

"Better"

kiwi2wheels wrote:
To add to Rick's post, with the amounted of imported hoses and barbed fittings ( at least in Europe ) , the sizes of which don't seem to conform to any known norm..... I've found this version of the single ear also works well .

http://normapacific.com/Listing/Product ... ert+Clamps

[dave powelson]

This pic of the casting inside sez volumes--lots of porosity, etc. The machined grooves reveal the same. OP's main problem is
not his setup, but the trash part he's expected to 'fix'. I'd be surprised if this part actually maintained high vacuum and if it's
really prudent to use such a part in whatever the end use is, dependent on the cost of vacuum and/or part failure. Why are these parts being reworked? They may easily be leaking thru the walls and not the mating end faces….none of which is your problem.

Of course, quality collets, etc. should be used. The gypo china parts are expensive junk.

https://lh3.googleusercontent.com/-N4Sf ... G_2929.JPG

Below-at this point with porosity exposed, use 1/16" filler (if not already), switch to 1/16 electrode and crank heat down.
Try to get tiny puddling in a hole or two area. Use slow fade out of torch and long arc if needed to not make any craters or crater cracks. Stop. Start again on another area. Go back over lightly w/o filler and see if can 'boil out' the bubbles left. Touch up with carbide bur and repeat, ad infinitum.
This is a time and material job--hope you costed it that way or consider doing so.

https://lh3.googleusercontent.com/-56LW ... G_2931.JPG

[kiwi2wheels]

[quote="Otto Nobedder"]There's something screwy going on here that's not related to the parent metal. If it were that porous and impure, it would not be in high-vacuum service. And, you've had success with it once before on an identical part. Something has changed. .......................................


Are the problem castings all from the same batch ? Has there been a change of foundry ?

Or a change in their material supplier ?

[mdlimy]

I will try my best to reply to everyone's comments again, but today is a busy day!

I am using name brand parts on my Weldcraft torch, but I will check to make sure I am not trying to use a gas saver collet or something worn out with the standard body, I am sure I can figure out what the issue is, I just didn't have time to dig into it yesterday.

I have ordered an inline desiccant from Mcmaster, I will have it tomorrow. LWS is bringing me a fresh bottle today and I will check all my hose connections when I swap out bottles.

Nothing is different between this parts and the other one that I successfully welded, but some are in worse condition than others.

It is not uncommon for me to see such beat up parts being used in high vac in this industry, generally they back with large pumps and multiple turbo pumps and can overcome any issues caused by porosity in the material similar to this part. But obviously knicks and holes in the oring sealing surface would cause a direct leak to atmosphere and cause issues.

The job is priced right and accounts for these kinds of problems, I would just like to get to the point where I know I am doing everything to the best of my ability and any issues are directly related to the material quality... I definitely feel like I am not there yet, I should be able to get this process down fairly well to the point that it only run into issues once in a while rather than on a consistent basis.

I am using 3/32 tungsten and 3/32 filler. The reason being, I feel the quality of the material require atleast 30% dcep and towards the end of the groove it gets into some very thick material requiring quite a bit of heat that I don't feel like 1/16" tungsten could handle....But I will definitely give it a shot and work in small areas trying to get rid of the pin holes.
The reason for 3/32 filler material is that I had a hard time getting it in the puddle without it balling up due to the higher amperage in some areas....but i believe this is more user error than anything, so I will also give this some practice.


Many good ideas and comments here, I will be sure to try every one of them and nail down what my issue is....I will start by getting a clean reliable weld using a standard collet body and #8 cup with fresh argon and a desiccant trap.

[dave powelson]

I will try my best to reply to everyone's comments again, but today is a busy day!

...............
I am using 3/32 tungsten and 3/32 filler. The reason being, I feel the quality of the material require atleast 30% dcep and towards the end of the groove it gets into some very thick material requiring quite a bit of heat that I don't feel like 1/16" tungsten could handle....But I will definitely give it a shot and work in small areas trying to get rid of the pin holes.
The reason for 3/32 filler material is that I had a hard time getting it in the puddle without it balling up due to the higher amperage in some areas....but i believe this is more user error than anything, so I will also give this some practice.


Many good ideas and comments here, I will be sure to try every one of them and nail down what my issue is....I will start by getting a clean reliable weld using a standard collet body and #8 cup with fresh argon and a desiccant trap.

".But I will definitely give it a shot and work in small areas trying to get rid of the pin holes."
---yes

My mantra when running my 300GTSW on woefully, big time porosity, inclusions in AL castings was
'Massive, focused heat succeeds where all other methods-fail'. If you crank AC balance down to the 10-20% on that TA, you will get max heat input. Stiffen the arc by increasing the AC Freq.--but the higher the AC freq.--the lower the total heat input. (This is the extent of the limited AC arc tailoring that the TA offers--it's not a dynasty.) For max. heat input, I've used 10% AC balance, 10 AC cps freq. which has the arc dancing around more--but one can still get the job done with torch technique. (At higher amp settings-like 150+, this lowest balance, lowest AC freq. will hit the part hard enough to vibrate it and even move it.)

This focused heat deals with embedded and thorough porosity better. It boils it out. The 1/16 electrode in this mode should be able to deal with the thin section and give you more finite control over the arc/puddle.
If this casting is trashy enough (and that inner sidewall pic looks like it may be--IOW the casting shot was maybe 20% virgin AL and 80% Coors Light recycled); a crust or dull oxidized skin may appear on top of this little puddle over a porosity hole. Poke the rod down thru the crust to feed it some good AL. Kinda like 'bump welding' anodized.
Then stop, carbide bur off the crust and inspect.

[Rick_H]

Poke the rod down thru the crust to feed it some good AL. Kinda like 'bump welding' anodized.
Then stop, carbide bur off the crust and inspect.

I second that, it helps with some of the dirty old castings I deal with....this is an interesting thread.

[Poland308]

This is a great line. I've got to save this one to many new things for me to try on cast. I need to get some scrap stuff to work on.