Weak Weld, Need Help. AL Sand Casting and Aluminum Pipe

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Hi I'm working on project where I'm trying to weld:AL tube (6061) 3mm to:a sand casting (A.356.0)the parts are welded, Hard Anodized, then power coated.We are not sure if the shop really knows what's best result we can achieve is.We are trying to figure out why the weld keeps breaking.TESTWe have set the break test up and the weld breaks when the weight is placed 3ft out from the weld; weight is about 160lbsQuestions1-Can anyone tell use what the best result we can expect in terms of how much weight this weld should hold at 3ft out? is 300lbs possible? 600lbs? should the weld break or should the base metal bend and crack first?2- How does this weld look to everyone?3- We are going to request the shop try 4145 filler next and have the shop heat the parts before welding. Is their any other suggestions to making this weld stronger? The part does not operate in hot conditions. Application for use in salt water.Thanks, any help would be greatly appreciated.
Reply:Without knowing what your setup is, I would say you need more heat, that appears to be roughly 1/8" pipe welding to the casting, I'd say minimum 150-160amps and with the casting there to suck heat out you could be in the 180+amp range to get everything to flow properly. You could try pre-heating the casting some to make it easier to weld.
Reply:that weld has no penetration, just sitting on the surface.
Reply:It was welded too slow, so likely too little amps and hung around cooking it. What I'm looking at is a cleaning band that is much too wide as an indicator.In the beginning you said "I'm trying to weld." At the end you are talking about "the shop."Are you personally welding this or is someone else? What settings, filler material, and technique were used?How much weight is it designed to hold at 3 feet?Overall, the weld looks as if it was made by an inexperienced welder.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:I'm not really an aluminum guy. But from what I've read aluminum welds, unlike steel are often, if not nearly always, weaker than the base materials. You didn't say or I didn't notice what alloy this initial test was done with nor the process(I'm wondering if it was stick welded or oxy/acet ?). The pros are going to want to know the specs of the procedure and filler right down to the size of your shorts to be able to advise you properly. According to a chart in the Lincoln Aluminum GMAW Guide (which you can download as a pdf from their website) 4043 is the recommended filler for joining A356 to 6061 although I'm not sure if 4043 is the one that will not colour match well when anodized but if you're powder coating that might not matter, you'll want to experiment. Good luck and I hope you get more useful advice here. Meltedmetal
Reply:In addition to the critiques of the actual welding/beads, I am going to offer that the design parameters of the finished product ARE NOT satisfactory for ANY loading of the aluminum tube in the plane that you demonstrate in your photo with the arrow.ANY lateral loading of the weld is likely to result in failure of the weld or the tubing, or tear a chunk out of the structure you are welding the tube onto.If the tube is intended to deal with lateral loading in use, the design needs to be changed to incorporate some degree of bracing to the tube away from where it mates to the large casting member.If you are attempting to use the weight/leverage/break as simply a "test" to determine the soundness of the design and welding, you may be overdoing it.
Reply:That's a poor weld looks like someone did a start stop every 1/4inch on it and that's tig they left some big crater cracks that's why the weld broke they way it did it already had stress cracks in all the start stops.  Should be welded with 5356  you can tig or mig that joint
Reply:You cant weld dirty aluminum. It needs to be very clean material because it will bring about the contaminants. That aluminum looks incredibly dirty. Definitely certain it has porosity in that weld from not removing that film and just welding over it. gotta be why it broke apart like nothing! that film wont burn out and it is not strong. Need to clean that weld while welding!! That's why it broke!!
Reply:No grinding seems to have been done to the cast surface, there is no such thing as to clean, and did you preheat? to chase the water out of the casting?Swanny
Reply:It was welded too slow, so likely too little amps and hung around cooking it.
Reply:Thanks for all the input everyone. It's great to have some experienced eyes on this.@Walkerweld here is the design of the weld joint. I'm also under the same opinion of you, that this joint is really not meant support too much lateral force. In the field, this part does or can experience some lateral impact force from being dropped or pulled on. So we are trying to understand what the best result we can expect from weld. Once we know this, we can determine if we need a mechanical fix. Anyhow, we all know that something has to give; it's just a matter of when, Where, what and at how much force.1st test result 12/24/2013:3ft with 160lbs.Today the shop changed the filler to 5356 and cleaned the part by heating it.2nd test result 12/26/20134.26ft with 160lbs (weld is still breaking)We will keep testing with everyone's suggestions tomorrow. @abec: The continues weld with no start, stop is challenging as we need a mechanical way to hold and turn the part so the welding plane is horizontal to the ground?I found another good post on weld strength on this site and will take some of that into consideration:http://weldingweb.com/vbb/showthread.php...-weld-strengthAgain thanks for everyone's help on this.PS. I'll post some more photos tomorrow.
Reply:Why do you need to turn it? You can't weld vertical and overhead?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:Good luck with the joint but 160pounds 4ft out on the pipe is fairly decent without gussets or sleeving the inside or out side of the joint
Reply:Originally Posted by abecGood luck with the joint but 160pounds 4ft out on the pipe is fairly decent without gussets or sleeving the inside or out side of the joint
Reply:Cleaning the part by heating it is not good enough. There is a layer of oxide on all aluminum that must be removed shortly before welding. Read the section in the Lincoln literature on Welding Preparation and heed the advice here.---Meltedmetal
Reply:Not a pro here, but the weld shows some penetration on the pipe and none on the casting.  I'd bevel the pipe as well so you have a slightly larger valley.  The preheat the crap out of the casting.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Hi and welcome.You have little penetration to the root. You should bevel the pipe at least 30 degrees, run a hot root pass for base metal dilution, then a thick cover pass.Your first weld showed little base metal dilution, and 4043 is dependant on base meta dilution for strength. 5356 creates gas bubbles from the mag and needs to be run slow, but does not require base metel.dilution for strength. A good cover pass is still in order. I would recommend the bevel, 4943 filler, and 2 passes for proper reinforcement. The 4943 will have a bad anodize color match. But the paint will cover it.Don't forget with the pipe being so thick, and little penetration, you have a stress riser right at the joint. This is a good example of a breakaway joint.Good luck.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Scrub the hell out of it with a stainless brush, anywhere weld metal will be going needs to be extremely clean, scrub by hand cause using a power brush can just drive the contaminants into the surface of the metal.
Reply:Hi Everyone,Thanks for everyone’s help on this!Today we cleaned the part with a Stainless S. wire brush, heated up the casting, used 5356 filler, put a second pass on it and made sure we had good penetration.Test result was the same 4.26ft with 160lbs, however, this time the pipe broke, actually it ripped slowly. Before when the weld was failing, it was snapping like a cold icicle.The weld had great flex, about 1.5ft before it broke.We also tested two pieces of 6061 welded together. It flexed more but this could have been because the part was held a bit differently. However it still broke with 160lbs at 4.26ftThe AL tube is rated a 200Mpa and this test result is about what it is supposed to break at. So all in all, a great dayAgain, thanks for all your help on this.
Reply:Cool! You got it!Nice job!Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Glad it worked out for you 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:Taking some liberties here "Welding of the people, by the people, for the people"