Welding Tips and Tricks

I've been slowly teaching myself to TIG aluminum as I think I have MS and SS down. Only issue I am having is this gritty look to my welds. Not sure if its contamination or what? Im using acetone to clean the metal and filler, and a dedicated SS brush. Welder is a Miller Syncrowave 180SD, 100% argon @ 15cfh, green 3/32 tungsten. My filler rod is a few years old, but was kept dry in a tube the entire time. It happens at any balance setting, and sometimes it doesnt happen at all and I get shiny weld beads.
Any thoughts?
TIA

Even though your filler rod has been kept dry, it has still been sitting around for awhile which will cause oxidation to form on the filler rod. Try cleaning the filler rod and also try taking that top layer off the surface of your base metal. Oxidation can hide in those litte surface irregularities. Your base metal just doesn't look as clean as it should. Hope that helps. By the way, what grade filler and base metal do you have?

The base is 1/8" 6061, the filler was 1/8" 4043. I brushed it pretty good in the areas I welded, enough to produce aluminum dust. I also brushed my filler wire, but not very good as it was hard to do.

A Scotch green pad rubbed on the filler rod just before you use it will usually get off most of the oxidation.

Also if you have Orange Band Ceriated tungsten available I would use that. Ive gotten the best results with it. Ive used Red also but the Orange always seems to work alot better and more control. Just my 2 cents..Hope it helps..

Cleanliness is key all the way around clean you wire brush before use as well with the acetone. Also insure your shield gas is good. When we do 5xxx welding for crack alts on ships we have to check the moisture of our gas before beginning work. Good shielding from breezes needs to be established to keep shield gas in place but the big key Is make sure everything is clean very clean.

I have a theory about what is going on that although I can't prove, I'll share it anyway. I believe that"gritty" looking texture is relatively high-melting temperature grains (or crystals...) in the alloy growing large, and as the rest of alloy (the lower melting temperature stuff) solidifies around those grains, it can move those larger grains above the surface, kind of like pushing icebergs up out of the water just before the rest of the water freezes. Leading to well, what looks like little structures pushed up out beyond the surface. Or maybe a better analogy, is if you ever remember a chemistry experiment where you soaked a rope with sugar water and let the sugar water wick into the rope and dry and let sugar crystals grow, you will remember that as you waited longer, the crystals grew larger. Same thing I believe happens with metal grain/crystal structure as you hold an alloy in in between its liquidus and solidus tempetatures. Those temperatures are, the temperature at which an alloy *begins* to melt (that is, some of the components are beginning to become liquid, but there are at the same time, some solid "chunks", namesly, the crystals or grains) and liquidus temperature is the temperature at which *all* of the components of an alloy are liquid (no chunks at all, just a perfectly fluid liquid.)

Now the fix can be two different ways. You can "fix" the appearance of this metallurgically, by selecting a different alloy that doesn't make these kind of structures. For example, try using a 5356 filler rod (magnesium alloy) instead of 4043 (silicon alloy.) Magnesium grains and silicon grains have different characteristics in terms of size, melting temperature, and so on. So they will not behave the same. You might even wish to try 1100 filler rod (which is pure aluminum, so it will freeze much more suddenly.)

The other way you can fix it is by changing your welding technique. And what I would advise here is, get it to freeze faster. The faster the puddle freezes, the smaller the grain structure will be. The more time the puddle takes in the "slushy" temperature range (between solidus and liquidus temperature of the alloy) the more opportunity the grains have to grow larger in size, and also to get pushed around as the rest of the lower melting temperature components freeze. How do you do that? 1. don't pre-heat the metal. Start with it relatively cold. 2. Welding with more heat input power. Crank up the current. Trying mixing in some helium if you are using pure argon to increase the temperatures. By welding with more power, you will travel faster, and the heat will not have as much time to 'soak' into the surrounding weldment. Then when you progress your weld bead, the temperature of the molten puddle will drop through the liquidus-solidus temperature range more quickly, due to the relatively cooler metal pulling away the temperature from it more quickly. You could also try using something like a large copper backer bar or other techniques. Easiest thing is to crank up the current and increase the travel speed. And wait for your work to cool on one weld bead before beginning the next bead in the sequence.

I might be wrong about the grittiness being silicon crystals, and it might in fact be oxidation. I can't really prove that it's not. But whatever the cause of this "grittiness", I've found that changing the metallurgy and/or changing the welding technique as discussed above can be solutions to this appearance.

Have you tried a smaller filler wire? As you add filler it acts as a cooling agent to the weld puddle. A smaller size filler wire will increase puddle temps a little and allow you to travel faster. And why 4043? I'd be using 5356 in 3/32.
Gas quality can have this affect, make sure your torch lead is straight(so to speak) as a torch that has a coiled lead can cause interference and mess with you current.
I have encountered this exact looking weld problem, one time it was gas. I had an air cooled 26 torch and the high amps I was running perished the line going into the torch resulting is gas leaking out, although at the time I was getting a mix of gas leaking out( giving a mustard colour fleck to the weld) to air getting in dependent on what angle the torch was at. A quick check with a flow meter at the torch end will rule this out very quickly.
Another time it was the material. The material itself had impurities which came out in the weld and looked like this, only solution was to grind it out and re fill, grind out and re fill until clean weld is achieved. Not advisable with structural items.

Good luck and let us know what the out come is.

Cheers

This appears to be very typical of an air leak or using the wrong type of gas hose. I've messed around with different hose materials and the result was almost always the same as what the O/P is experiencing here. I've also had air leaks and had the gritty look. It is contamination but you can do a half way job of cleaning in still come out better than that.