[tccack]

Was thinking about metal preparation after spending a lot of time removing paint from the ends of tubing before welding.
Is there any issues with using sand or garnet blasting before tig welding? This is on plain mild steel, not stainless etc.
Would the sand blaster leave any grit in the metal or would a simple wipe down after be okay?

What about alumnium? I have been having issues with slagging on alumnium, which I think is the clear anodising. Even after light brushing and good hard wipe over with acetone the weld still gets dirty. This is regardless of the ac balance setting, which I have had to lean towards penetration in order to get the weld moving along.

Ta

Tony

[ajlskater1]

For mild steel you are fine sand blasting it, just wipe it down good after. If this was for critical application, I would not recommend this but for normal stuff you are fine. I would not do this on aluminum. I have never welded sand blasted aluminum but I would think it could get stuck in the aluminum because its softer than steel. Anodising on aluminum is hard to weld. What I do is pulse the foot pedal instead of welding normal. For me it helps.me punch the anodising without leaving a heavey cleaning action around the weld, because most.people do.not want to see that.

.

[weldin mike 27]

Hey,

We used to do a large mild steel job where, after welding and heat treatment there would be a weld shoot, shot blasting if the welds to aid defect detection. Welded really nice. On aluminium i have heard of using crushed up apricot stones as the blasting media, among other wierd things. Tuff enough to take off surface coatings and grime but not harsh enoigh to damage the soft metal.
Mick

[tccack]

Re the ally... I do the same thing with the ally I think is anodised. Its only about 3mm so I maintain the heat with about 80 amps, then pulse via the pedal to 150 for about half a second to sort of push the puddle along. Keeping constant 150 causes the base material to just melt away to soup.

Perhaps a "soft" blasting material may be the solution for ally then. I've heard of apricot stones too. They use it for painted plastics like bumpers and boat decks etc.
Cant go through a recycling blasting machine though like garnet. Even soda is more or less single use I think.

[TamJeff]

What kind of machine are you using? I weld a lot of anodized. I use balanced welding on AC, pulsed at high amperage. It will float the anodized to the surface of the weld. I use 5356 rod and straight argon.

Here is a normal weld on anodized. No prep with the coating whatsoever. The anodized actually helps keep from getting soot outside of the weld zone. You will typically get a light film of cloudy smoke outside the weld zone. Wipe it off with a plastic free paper towel (notice the scorched paper shop towel) while it is still hot and before the aluminum smoke oxidizes. Also, you may get some black soot around the initial tacks. It helps if you wipe that off before continuing with the rest of the weld.



Hope this helps.

[tccack]

What kind of machine are you using? I weld a lot of anodized. I use balanced welding on AC, pulsed at high amperage. It will float the anodized to the surface of the weld. I use 5356 rod and straight argon.

Lovely looking welds... I have a Miller Syncro 250 AC/DC. I set the balance up towards 9 which would equate to about 60% negative (max being 68%)
Pure argon but not sure what grade the filler is. 5356 I assume. Theres no marks on them so doubt they are 4xxx series.

Here is a normal weld on anodized. No prep with the coating whatsoever. The anodized actually helps keep from getting soot outside of the weld zone. You will typically get a light film of cloudy smoke outside the weld zone. Wipe it off with a plastic free paper towel (notice the scorched paper shop towel) while it is still hot and before the aluminum smoke oxidizes. Also, you may get some black soot around the initial tacks. It helps if you wipe that off before continuing with the rest of the weld.

What is the metal thickness and amperage you are using for the example in the photo?

[ajlskater1]

A good way to tell if your a using 5356 or other 5000 or 6000 series rods and not 4043 or other 4000 series rods is a drop test. Just drop the rod if it sounds like a stainless rod you are using a 5000 or6000 series rod. If it has a dull sound than you have a 4000 series. You can also tell when welding but that is hard to explain. You have a really good machine for welding aluminum. My buddy has a digital syncrowave.

[Otto Nobedder]

I have nothing against (carefully) sand-blasting a repair area, since that is not the end of my prep. There is still grinding of bevels, wire wheel or brush, and sometimes an acetone or laquer thinner wipe or two if the metal has been exposed to oils.

That said, for a critical weld that sees pressure and/or "temperature shock", I do it all the "hard way", so there is no doubt about anything I may have introduced to the weld.

Steve S

[TamJeff]

What is the metal thickness and amperage you are using for the example in the photo?

It's sched 40 (.113 wall roughly or approx 1/8") manually pulsed at 250 amps at approx 1 pulse per second and one pulse per puddle. I have a momentary switch mounted on the torch handle. The other post that mentions fluctuating the pedal is indeed the best pedal method for anodized. It would look the same if I had used the pedal, just that it's inconvenient for the type of positioning I am usually in.

You can kind of tell what you are up against in this photo. You can see where it looks like I started going a little cold on this edge with loss of the definitive, clean line. That was because I was likely over it and I was on the verge of ruining my pattern to where you say. . ."good enough, leave it alone before you wreck it." This shows how the arc stream shapes the puddle that is not obscured with soot. The anodizing is such that anything outside the actual brunt of the shape of the arc stream, does not want to penetrate the anodized coating. It's more attracted to the raw aluminum you have punched thru with the arc itself.


Some anodized is thick. You can also use the pulse pedal in reverse travel. The gas/arc stream will keep the contaminate pushed back and give great shielding on the weld. I do a half step wash in the process to smooth out the heavy ripples and excess build up that reverse travel can often have. Almost like a reverse whip and pause, if that makes any sense. This is where the higher amperage helps as well.

[TamJeff]

I have nothing against (carefully) sand-blasting a repair area, since that is not the end of my prep. There is still grinding of bevels, wire wheel or brush, and sometimes an acetone or laquer thinner wipe or two if the metal has been exposed to oils.

That said, for a critical weld that sees pressure and/or "temperature shock", I do it all the "hard way", so there is no doubt about anything I may have introduced to the weld.

Steve S

I agree with this. I just don't have time to clean it and it is decorative in this situation. I would essentially have to carefully clean hundreds of joints in a day without going outside of the precise weld zone. I do clean all my mill finish stuff though. I worked for a place that built sidewalk rails for D.O.T. It was the nastiest pipe I have ever touched. It reeked of what I figure had to be pigeon and rat droppings. I got fired/quit for cleaning the crust from weld joints with a wire brush. Not because it was wrong, but that the owner was a greedy slave driver.

I would expect your environment to require x-ray quality consistency.

[tccack]

A good way to tell if your a using 5356 or other 5000 or 6000 series rods and not 4043 or other 4000 series rods is a drop test. Just drop the rod if it sounds like a stainless rod you are using a 5000 or6000 series rod. If it has a dull sound than you have a 4000 series. You can also tell when welding but that is hard to explain. You have a really good machine for welding aluminum. My buddy has a digital syncrowave.

Good tip, I'll check that sound out and see...

[Otto Nobedder]

I would expect your environment to require x-ray quality consistency.

You'd think! I suppose they "expect" it, but they don't police the welds enough to assure it.

Not even on most of the liquid hydrogen stuff, except extreme pressure piping. I always treat every weld like it'll be x-rayed, and this keeps me from doing rework. It's given me a reputation, where the client doesn't even require x-ray on my inner vessel repairs. This stuns me! When the repair is a quarter-million, why not shoot some film for a few dollars more, for everyone's peace of mind? I'd sure as hell feel better, since my ass is hanging out, too!

Steve S

[nova_70_383]

i have welded sand blasted aluminum. it was not anodized, but the sand gets jammed in the pores of the metal. this leaves dirt floating in the weld puddle. i would steel shot, or bead blast. i have welded aluminum that was shot blasted with no problems. just my experience.