Got to practice welding an intercooler today

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So I got a call from a friend a few weeks back telling me he broke a weld on his 4" front mount intercooler pushing medium boost, 28-30psi. He asked if I could weld it and I said probably not but I can try, so he brought it to a performance shop and they fixed it for $30.A week later the same thing happens but on the other side of the intercooler. Where the end tank and the core meet. So he brought to the local machine shop that does all of our engine builds for everyone in the area. He re-welded every bead on the intercooler. I get a call from him today saying it cracked yet a 3rd time and he wanted me to look at it and try welding it. So I figured I would because he said it doesn't matter it's pretty much garbage and he is going to order a new one. Few questions and such about this. Each guy that welded it heated it up with a small propane torch and said it welds better that way. The machinist heated it up for maybe 10 seconds at most. Would that even help, heating it up for such little time? The core is 12" tall, 4" thick and 40+ inches long. So it's not small.He put it on my bench and he pre heated it, sprayed it with acetone and use a wire brush. I had him doing this for like 10 minutes. The crack (sorry no pics) was in the middle of the weld bead over where the last guy welded. So I figured I would give it a shot, I had put my welder as high as it would go 125amps and tried to weld it. It would puddle no problem and I could dip my filler, but it welded almost like cast. But it wasn't. Seemed to have a lot of impurities in it. I made a few beads here and even cranked up the argon to 30, but when I lifted the torch, my newly placed beads also had a crack right down the center of them. My first thought was maybe the metal is moving causing it to crack so I tried moving the torch from one piece of metal to the next and still my welds were cracked right down the center. What would cause this?Also the other side of the intercooler was still ice cold. I thought with aluminum the entire piece had to heat up? He is going to put it back on his car and go back to school for the week (which is fine since it's running speed density, it won't affect anything) and when he gets a new one if nobody wants his I can keep it. So it would be nice to play with some more.Also for you guys that do this for a living, when something like this comes in the door, how do you know what filler to use for aluminum? Can you guys tell what is it by just looking at it?Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:What filler are using? Etc?
Reply:You don't usually need to preheat an intercooler (unless you only have 125amps lol). Intercooler tanks are usually about 1/8" thick, so 125 amps is spot on for that. The problem is in the corners and areas of bulk where the heat has multiple paths out. Sometimes brackets are 1/4" thick, this is about the only time I've run into heat issues. For filler just use 4043. The tank design, being a pressure vessel, is more important that 'the weld'. If the tank has huge surface area between the corners,ribs, etc it will bow under pressure repeatedly until it stress fractures. As an example, you can drill a half in hole through both sides of the tank, pass a rod through and (plug, fillet) weld it to both sides. This will stiffen up these areas a lot. If you're brave enough, you can try quickly pressuring the intercooler to the run pressure and see where any flex is in the tank. as for the weld being all nasty, you will need to brush/etch off the **** and have your wave balance setting set correctly. There is likely traces of oil in the tank which will totally mess up the weld. I suppose it's also possible that the intercooler is coated or even anodized, although unlikely.Welding/Fab Pics: www.UtahWeld.com
Reply:Are you grinding out the old cracked welds, or just putting more on top of the old ones?Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Oh my phone so I won't go into detail. I was using 4043 1/16 filler and welding ontop of the old ones.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:If you're going to try pressurizing it, you may want to pressurize it with water, if at all possible. If we're talking about 30 psi, that's a lot of potential energy, in the form of compressed air, if something blew off. But fill it almost completely with water, then add air at the very end just to pressurize it, and there's almost no energy available to try and cause damage, if something blows. There's a reason that pressure vessels are tested with something incompressible (like water), not air, so you don't level the room if something goes wrong
Reply:4043 is what I typically use, I would grind out the weld and then clean the metal with acetone, this will help clean the area of an oil, I've even flushed the tanks with acetone and then dawn and water.
Reply:If you're welding crack sensitive parent metal alloys, like 6061 to 6061, these will be prone to "hot cracking" as you are describing experiencing, if not diluted adequately with filler rod for changing the metallurgy to one that is not as crack sensitive.The cure for this problem should be metallurgical, as follows: Rather than re-melting the old weld and hoping it doesn't "hot crack", instead try grinding it out, and then redepositing fresh filler of a recommended alloy (and I agree that 4043 is generally the appropriate one to use for an intercooler, since it gets hot, although it is always good to know what parent alloys you are deadling with) in it's place.  Whatever you do, don't just melt the crack sensitive parent alloys together autogenously - that crack right down the middle will just keep coming back.  (It might be a tiny hairline crack very hard to see, but is a crack nonetheless...)  You will want to dilute the molten puddle with 4043 to reduce the hot cracking.  To prevent too much parent metals from being present, avoid over penetrating into the parent metals.Also regarding the intercooler not heating up much while welding, you need to keep in mind that it is a device engineered for dissipating heat to the atmosphere very quickly.  Because it dissipates heat so readily, it will generally require more amps to weld than you are used to (especially welding near the core), for the thickness of whatever metal you are welding.  And it will also cool off very quickly after welding.I would try and degrease the back side of whatever you are welding because like others have said, oils are hydrocarbons in them, which are really bad news if they get in the area of a molten aluminum puddle.  The hydrogen has an affinity for liquid (molten) aluminum, but can't stay in the aluminum as it cools, so it converts to gas bubbles upon solidification (causing the dreaded "porosity" which = weak, unsound welds.)Automotive intake tracts typically have the blowby vapors from the crankcase recirculated into the intake tract before the compressor inlet.  This causes everything in the air tract downstream of that point (including the intercooler) to become "oiled".  You need to remove this oil before you weld to avoid the back side of your weld from becoming contaminated by the oil, and this is not a simple matter.
Reply:Originally Posted by GambleAlso for you guys that do this for a living, when something like this comes in the door, how do you know what filler to use for aluminum? Can you guys tell what is it by just looking at it?
Reply:He was in a rush and I didn't have time. It was going back on the car one way or another. Besides it will be mine when his new one comes in so I would like to try again.Something like this though, how would you clean the back side? It's welded all around already.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Originally Posted by GambleHe was in a rush and I didn't have time. It was going back on the car one way or another. Besides it will be mine when his new one comes in so I would like to try again.Something like this though, how would you clean the back side? It's welded all around already.
Reply:Do this outside, in a well ventilated area:Pour gasoline into intercooler, swish all around, and dump/shake out. (repeat until the gasoline comes out as clean as it went in.)Pour acetone into intercooler, swish all around, dump/shake out (this will get out most of the slower evaporating gasoline.)Then, set up a fan, or low temp heated breeze blowing through the intercooler (gently heated preferably, like from a hair dryer or a heat gun on a low temperature setting.  Note that using very much heat here could be dangerous.)  No not use any electric tools or smoke, etc in the area of the fumes.  Did I already mention, to do it outside in a well ventilated area?Let the air circulate until the air coming out no longer smells like solvent.  If you are not sure if there's any solvent smell, let the air circulate some more, better safe than sorry.  Don't want to weld around potentially explosive vapors.After all that, the inside will be totally bone dry, free of all oil.
Reply:Originally Posted by zapsterYup.Experience has it's advantages...And if you have to ask how to do it in the first place...It's easy enough but why ask if you took the job?Don't make a project out of a simple repair......zap!
Reply:40" long? Is this thing on a diesel or 900hp car? That's a huge frontal area!Hobart EZ-Tig newbie.
Reply:Good practice material.
Reply:Originally Posted by chimmike40" long? Is this thing on a diesel or 900hp car? That's a huge frontal area!
Reply:what brand of IC is it?
Reply:Forced Performance. My friend said they stopped selling them because they were prone to cracking.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:do you know if they made it in house or bought Chinese stuff?
Reply:Originally Posted by GambleForced Performance. My friend said they stopped selling them because they were prone to cracking.
Reply:FP does a lot of their stuff in house. Everything they make is really good, minus this core. But I've also heard their welder isn't very good. I heard that the wastgate flanges he welded onto turbos fell off. So I don't know. Never happened to me so i can't comment.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Originally Posted by chimmike40" long? Is this thing on a diesel or 900hp car? That's a huge frontal area!
Reply:meh, I have no problem with a 25"L, 3.5"thick core on a 400whp 4cyl turbo Methanol injection is what helps the most around here, especially with BAT's at cruise around 110 during the summer!Hobart EZ-Tig newbie.