The Armour Archive

My companys been having issues lately with porosity in various weld joints....we use TiG welding (argon atmosphere) for various steels, titanium, aluminum and inconel. Engineering thought it was poor cleaning or contamination in the hydroflouric and nitric acid baths. Turns out it was aluminum oxide sandpaper. All weld joints are supposed to be prepped with silicon carbide sand paper prior to etching and welding. They were using the aluminum oxide paper on all metals, and it was embedding aluminum in the parent material, then when heated with the torch, it would liquify and come to the surface, causing massive porosity (tiny sponge like air pockets) in the weld joints, significantly weakening them. Now, I know welding has limited application to armouring, mostly with helms, and the aerospace industry is quite a bit tighter in specs than armouring is, but i justt hought it would be worth mentioning to those of you that do a lot of welding, either in the shop for armour, or other uses.

Dont use aluminum oxide sand paper to prep metal for welding. Why use sandpaper on a weld joint? If you rough up the surfaces prior to joining, it'll give you a cleaner weld. I dont think it matters much with stick and MiG, but it makes a huge difference in TiG.

Just thought I'd mention it.

Thanks for sharing. I don't use TIG but knowledge is always good.

Pad

Wow...I just checked some of my sandpaper...aluminum oxide ! I have been setting myself up for disaster! Thanks, you probably just saved me hours of work

Well, like I said, it probably wouldnt matter much in stick welding helmet halves, but in aerospace, the weld joints have to withstand a lot of stress and pressure (we build hydraulic, water, oil, and fuel lines and other tubing and manifolds for engines) sometimes 600-800 PSI of pressure, so these joints have to hold...roughing up the ID and OD of the surfaces before etching improves the weld...since we use TiG, the welds are actually quite pretty....the bead is unbelievable, but we have to rough em up, alkaline clean the metal, then etch it, and weld it in the argon atmosphere. Doing all that makes the weld real pretty...we do no grinding, and very little wirebrushing...and then thats only done to blend out the discoloration. If you clean and prep your own weld projects, your bead will be much nicer and stronger, and you should save yourself a bit of time at the grinding wheel.

using a stiff wire brush or file will do the job just as well as the sand paper with out cross contamination.
just make shure you have your files and brushes either cleaned or dedicated use.

Exactly. In the polishing room, the greywheels, wirebrushes and files are all kept seperate. They're dedicated.

my files get up around 3 am every day, and sit there waiting to do something.. they don't stop until after midnight . they never ask for a day off, and never complain one bit about working conditions.

now THAT is dedicated..