When grinding the edges of 2 pieces of 1/4 inch plate to be joined (to create a "V" for filling with weld material) is it common practice to use a grinding wheel used exclusively on aluminum?
Is this common practice to avoid contamination of the metal prior to welding?
Does the same hold true for wire wheel use on aluminum?
Thanks.
Depending on the aluminum grinding wheels do not usually work well as they tend to load up with aluminum. If you have this sort of problem just use a coarse file
They always teach you to wire brush aluminum with a wire wheel that is used solely for aluminum.
Frequently when certifying for aircraft TIG welding I was given aluminum tags that had been chemically cleaned and kept in some sort of bath that prevented contamination. Touching the edge to be welded was cause for failure.
I really don't know whether that is a normal practice as frankly, in the field, we didn't go to that extent. On the other hand aluminum corrodes almost instantly so anything that keeps it clean a bit longer must be good. But then, we use AC for aluminum that "cleans" the metal which makes one wonder whether the electrical cleaning is not as good as it should be or whether the mechanical cleaning is largely unnecessary :-)
Cheers,
Bruce (bruceinbangkokatgmaildotcom)
Grinding wheels for aluminum are very soft, and will disintegrate rapidly if use on steel. If you use a steel grinding wheel on aluminum it will load up quickly and be useless.
Sand paper flap-wheels are more reliable on aluminum and won't transfer as much material from a previous use.
In most critical aluminum fab jobs, no abrasives are ever used for aluminum weld prep since they can all leave embedded abrasive granules which can contaminate the weld. Strictly die grinders, air saws, and routers.
Aluminum boat shops use a device called a "maneater". A small air powered right-angle grinder with a milling cutter in it. They are well named, and are incredibly dangerous, but they can prep and edge for welding or removed a bad weld without contaminating the surface. Well maybe some blood, but nothing else.
The only wire wheels that should ever be used on aluminum are stainless steel. Using a steel wire wheel on aluminum almost guarantees iron contamination of the surface. This will make rust spots on the aluminum, since the iron particles and aluminum will create electricity . This is called Galvanic Corrosion, and it reacts very quickly.
So obviously don't use any abrasive or wire wheel between the metals if the work is important. For hobby stuff, who cares?
Bob, your post was blank.
The easy way to remember this- Aluminum and Steel Don't Mix. Use a clean, new Stainless steel brush on Al, and never use that brush for anything else! Dedicate some grinding wheels to Al, and never use them on anything else. Separate your Al and Fe grinding operations, or you might just discover why those two metals are the chief ingredients of Thermite.
Al is very subject to contamination, and even trace Fe contamination can cause your welds to fail.
It also depends on your application. Are you building a structure that will have to bear weight? Meet a code requirement? Could hurt someone if it (or a part of it) fails? Or are you repairing/building something that no-one else will use for any of the above? If you cannot envision the part getting used for any potentially hazardous situation, then use that rusty old brush, throw some sparks into a pile of Al and Fe grit to get it to combust, and who cares how you prep the edges....
Thanks for your comments.
If grinding isn't practical (ie, need to get the surface fairly flat), is a metal file (steel) OK to use for the task? Of course new, never used on ferrous metals. Are there stainless files?
This isn't a critical weld but I'd not like to see it rust if ferrous contaminants get in there.
Dave
A carbon steel file is fine to use. It is so much stronger than the Al, all it does is cut it, not contaminate it. Use a clean file, and give your workpiece a good brushing when done.
When you're done filing, clean the surfaces adjacent to the prepped edge with either a chemical deoxidizer or wire brush the heck out of them.
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