Your right, its more work than necessary. Grind the mill scale off and weld away.

 

If your going to sandblast the metal that is then going to be painted then go for it. If its for practice then just use your grinder. It is really up to you and its always nice to weld on clean steel.

 

I repair castings, (steel, alum. & brass), with TIG at the foundry where they are poured.
I sand blast the castings to clean them because it's easier in my circumstance, not to mention, sand blasting gets in where a grinder can't.
Sand blasting has not caused any problems with contamination or anything else.
If you are doing practice coupons, use whatever (grind or blast,) is easier or most convenient to clean the metal.

 

SAND blasting will impregnate into ALUMINUM so that is NOT an option...

Steel ..Well just make it REAL clean after before continuing..


...zap!

 

Zap is absolutely correct. (No more blasting alum. for me.)
I thought about it and it made sense, so..........
I did a little experiment and showed my boss the end result.
I figured showing everyone else would be a good thing.
After I blasted the peices, I wire brushed them (as always). Then proceede to weld.




Under the micro-scope, you can actually see small brown glass BBs, which were embeded grians of sand before welding.

 

I don't know how much I would be worried about that.
I get similar, yet macroscopic, glass spots on the surface, when GTAW welding steel with ER70-S2, which has a high silicon content.

And 4043 is 5% silicon. Yes, that "sand" is already alloyed with your filler, and the silicon in the alloy makes the weld more fluid, and wet better.

 

Yes, that "sand" is already alloyed with your filler, .

And how exactly does this happen to Aluminum alloy wire?
Unless you drop in on the beach beforehand..?

I don't have ANY of what is going on in this thread going on in my welds at any time...

And I can push 3/32" Red over 250 amps...



Nice Demo Papabear..:drinkup:

...zap!

 

There is no filler added to the welds.
Here is another pic of peices from the same stock, that was not sand blasted. No glass.
I get what you are saying rlit.:waving: I just find my results seem to back up what zap said.
Not to mention that I don't like the fact of having a contamited weld.:nono:

 

I am going to try a similar experiment with steel as soon as I get a chance. (More for my own curiosity than anything.)
Sorry for hi-jacking your thread carlito,:waving:
but I would guess this is giving you (and others) something to consider & remember.


Zap,
You are welcome.:laugh:
And thanks for teaching me something I never seriously considered.:drinkup:

 

Interesting..

I'm no scientist but that is a "Non Issue" amount per length of filler...


Back to the orig question.
Sandblasting Aluminum before welding is a :nono:


...zap!

 

Sandblasting may be a no-no for aluminum. Has anybody tested other media? I've seen crushed walnut shells used for very gentle media blasting. Inquiring minds want to know...

 

Baking soda? (commonly used to blast paint off airplanes...very gentle) Rice hulls? (used to use them to clean compressor blades on running gas turbine engines) Ground up corn cobs? Steel shot? (not for aluminum) Garnet? Aluminum oxide? (for aluminum, its there anyway), Black beauty? (coal slag - no silica) Plastic blasting media? Just throwing some ideas out there.

And what about chemical cleaning...hydrochloric acid (used for pickling steel).

BTW...great photos Pbear.

 

What about dry ice blasting? Anyone know if it could break through the oxide layer? It will remove rust but I doubt it would do aluminum oxide. Just wondering if anyone has any experience with the process.

http://www.coldjet.com/en/information/what-is-dry-ice-blasting.php

 

As promised; A similar experiment with steel. (With filler though - ER70S2)
Virtually no difference.

The first pic is on the peice cleaned up with a grinder;
tha second is is sand blasted, then wire brushed.

 

newbie here, but like all welders willing to discuss the trade.

for aluminum, even fairly old and not new, why not just abrade the oxide with a SS wire brush and let the TIG's AC lift the oxide and the hot argon or argon mix vaporize the flakes? I haven't been able to tell from the thread why blasting was being considered?

Unless there were a large area, sand blasting, even with a pencil or airbrush blaster seems like its more work than its worth in sheet and extrusions. My experience is limited to the 50series alloy sheet materials and the 60series alloy extrusions, but blasting seems more like a wide area surface treatment for paint prep?

White silica sand is nearly the same softness/hardness of 5086 H116 and blasts that material without any impregnation. After blasting, wire brush before welding like you would for all 50 & 60 series alloys and the welds are clean and non-porous using pure tungsten and pure argon on the old transformer power supplies and pure or mixed gas with %2 Ceriated electrode on the inverter.

Sand blasting steel is similar, why bother to blast a weld zone? Is the weld zone wide like hard facing an implement edge, bucket or tooth? Is this a cladding welding operation? A wire wheel, sander or grinder will clean off the [conventional seam type] weld zone and they're a whole lot less effort to set up and run.

Cheers,
Kevin Morin

 

Everyone thank Kevin Morin for redirecting Carlito's TIG coupon prepration question [sand-blast before TIG welding] away from the abrasionists, and back to how an experienced welder prebs their weldment.

Kevin covered the high points of Alumium prep, and why aluminun is generally welded A.C. to begin with - A.C. scavenges Aluminum/Oxide. Professionally, I have never witnessed aluminum preped by sandblasting, primarily because it is considered dirty and of poor technique. The resultant problems eg., corruption of the weld [popping of impregnated media], damaged margin . . . . . far out weight the benefit.

Carlito's original question was about sandblasting prep on steel. More on TIG/steel prep., next posting.

 

Thanks everyone for the replies.

The photos were very interested how the silica is actually melted to form glass beads.

I was definitely never planning to blast aluminum with sand, and have not even had good luck blasting aluminum with glass beads - it always turns out pitted and just not a great finish even at 30 PSI.

I definitely dont mind grinding my mild steel either, just wondered if the metal prepped by abrasive grinding vs sand blasting has any advantages for producing the best or cleanest molten metal for the final weldment. This can also have to do with looks - if we want a really smooth clean finish on mild steel we probably dont want to hit it with a grinding wheel, unless maybe a flap disk or even a DA sander as i`ve seen some work on here prepped. None of this is even worth arguing if we are welding 2" thick plate together for use on some tractor.

Thanks again for all the replies and info, very interesting how the sand sticks into the aluminum.

 

If you are worried about impregnating the aluminum parts you can purchase aluminum oxide as a blast media. It is very aggressive and will remove scale quickly.

Scott
http://www.welders360.com/

 

The pic with the glass was ALOX blasted.