Aluminum plug welding problems.

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Hi everyone, some people here know that im not writing well in english, because it's not my first language.At my job im facing a probleme that i already solved, the thing is because i always want to learn im asking questions about all possibility, even on a ''solved issues'', that could help to improve my work in the future if i know more than one way to work!My setting at work is:-250 Miller Sync-#6 ceramic cup-1/8 red tungsten -argon gas-normal collet body, no gas lenseIm not welding aluminum for years, i start about couple months ago at work for the shop needs.here'sthe situation i have to plug weld this top plate on this 1/2 square bar, i tried different option, i tried to pre-heat the 1/2 bar a little, but it seem to be useless because the bar doesn't take long to start melting, so im considering that my tig torch heating is enough for this and my machine as enough power to heat the 1/2 top bar.now when i fit the 1/8 thick top plate on it, and start to weld, there 2 things happen, the first is if im staying on the top of the plate and try to weld through my plug weld hole, the whole 1/8 plate start to melt and fall appart, but the things if if i don't stay enough longer on the plug weld, i won't be able to create any puddle through the plug, so i start to drop some filler rod in it, but what happen ? Its just stick, and then i can breack the bracket by hand!Personally if i had to enginneer this piece, i would make it of carbon steel and then galvanized, because its easier to make small plug weld on thin material on thin steel, thin aluminum on thick aluminum seem to be a probleme, they don't weld as well as steel.The way i solved the probleme ? I only screw the top plate into the 1/2 bar with type F screws (self tap screw) its stronger than the weld. Attached ImagesLast edited by LayoutMan; 03-30-2013 at 03:17 PM.Calculator > Bevel Square
Reply:Just some basics to cover. Are you wire brushing the aluminum with a stainless steel brush to remove the aluminum oxide first? Follow up with a solvent clean before you attempt to weld. The oxide of aluminum has a higher melting point and you will melt the underlying aluminum while trying to melt through the oxide.I'd also say you might want to preheat the 1/2 x 1/2 bar first. Aluminum is a good conductor of heat and that big bar will suck all the heat away from your plug hole and have you vaporizing the 1/8 bar before the 1/2 inch piece gets hot enough at the weld point.That's just my opinion.PapaLincoln Idealarc 250 (circa 1962)Lincoln Weldpak 155 w/Mig KitLincoln Squarewave TIG 175
Reply:If I had to plug weld it with a hole that small, I would punch the plate with a 1/2" square hole instead of round.  That way the square shaft would stick through the hole flush.  Much easier to weld that way.If the hole has to be round, then machine a shoulder on the square shaft so it sticks through.Both of these solutions make fast fit-up and easier welding.Dave J.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:By those 2 solutions do you mean that it will be easier if there is actually no ''plug'' and the 1/2 X 1/2 pass through the hole and stay flush with the top of the 1/8 ? still pre-heating the square 1/2 bar and weld it ?sounds great, i did not think about it!!Calculator > Bevel Square
Reply:Yes that's what I mean - if any pre-heat is needed, it would be slight.Starting the arc on the middle of the 1/2" square and then working over to the flat plate may be all that would be required.On steel when I set it up this way, I taper the inner piece to create a single bevel groove weld.  If both are thick I also chamfer the hole with a drill bit for a double bevel.Dave J.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Did you try starting the puddle in te center of the hole and moving outward to the edge?  That way the puddles started on the 1/2" piece and yu can tie the edges of the hole in easily.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Originally Posted by Drf255Did you try starting the puddle in te center of the hole and moving outward to the edge?  That way the puddles started on the 1/2" piece and yu can tie the edges of the hole in easily.
Reply:I tried everything, but i understand your idea DRF255, the thing is at the second that the arc start to touch the 1/8 plate, it doesn't take long to start melting apart and scrap the whole little 1/8 plate, its just literally melt by the center really fast (aluminum is good to melt fast by surprise haha) One other probleme is i don't have a control pedal, only torch button (poor shop setup i know but i work with what i have) so its really hard to control what you do, and the other thing is, the reason why they are plug welded is because they want no weld in the outer joint, like hairline joint, so the little ''head'' of 1/2X1/2 that i have to plugweld it have to be clean and perfect, but you can easily guess what happen if the hole is larger than what i have, the joint will look like turd all arround because its melting.Calculator > Bevel Square
Reply:I had some 1/2 square aluminum, so I thought I'd try MinnesotaDave's suggestion . . . except the hole through the plate is 7/16.  I set the machine at 60 Hz - set to match your Syncrowave65% balance . . . about 9 on your Syncrowave150 amps3/32 Lanthanated tungsten#7 cup18 CFH argon with a gas lens3/32 4043 fillerThat's about as close as I can get to a setup you can run on your machine.  I have a foot pedal, but used full current immediately and shut off abruptly at the end of the weld.  I started the weld on the center of the square stock until a puddle started to develop (about 5 seconds), then moved out to the edge of the plate.  By the time I finished, the part was too hot, but did not sag.  I think the smaller 7/16 hole helped protect the edge of the hole.  Something else to try is to pulse the current near the end of the weld to help control the heat.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:Nicely done - that is what I was talking about, but your demo explains it a lot better Dave J.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.