Need help, cast to brass

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A customer brought me this heat exchanger today.  Ends are cast steel?  It has some yellow sparks when I grind it.  Middle is brass.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:I tried all day to weld it.  First I used the Oxy torch to braize it.   I couldn't get the cast part hot enough to take the braize.   Once I did, it cooled and CRACK!.  So I tried some phos bronz rod and the tig torch.  It went on beautiful, stuck to the brass and the cast.   Let er sit and CRACK!SO I tried welding smaller beads.  We all know wide beads tend to crack more than small stringers.  Still the same thing.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:The phos bronz rod would pull away from the cast and actually break a thin piece off the cast.  NO problems sticking to the brass.  I also tried 15% silver braize with the tig torch and oxy torch.  Still the same result.  I even tried tigging a bead of 309 on the steel part then silver soldering the joint.  It cracked too.  Its gotta be a heat thing. Attached ImagesLast edited by David R; 09-14-2007 at 08:18 PM.Reason: Won't let me show the pics.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:spray transfer with silicon bronze wireChuckASME Pressure Vessel welder
Reply:GEEZ you are fast!  What about the cracking?  It does it when it cools.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:I tried "cold" welding it like an engine block. Still the same thing.  I even tried a 1/4" long bead.  It pulled away from the cast.  If I just run a couple of small beads I can see it pulling the crack together.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:there should be enough heat to cool slow so no crackingChuckASME Pressure Vessel welder
Reply:I tried running 3 beads in the other direction, but they cracked too.  I peened the beads like I would welding cast.  didn't help.David Attached ImagesReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by chopper5spray transfer with silicon bronze wire
Reply:did you try post heating it, or wrapping it in a blanket?Have we all gone mad?
Reply:99.9%argon 50 cfh 125F preheat 175 interpass tempi cant find my WPQ but this info should get you goingChuckASME Pressure Vessel welder
Reply:Originally Posted by sn0border88did you try post heating it, or wrapping it in a blanket?
Reply:I don't think you have a welding problem so much as a cooling problem.  What you will have to do is either try some post heating gradually allowing it to cool, or possibly pack it in sand while it is good and hot.  Sometimes that will slow the cooling to an acceptable rate.  Ultimately you have to find a way to slow the cooling.  Good luck ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Jackson, I agree.  I can get a nice weld, you saw it in the pics.  If it was all cast, I would preheat the bejesus out of it and weld away.  I can't preheat the brass near as much as I would like or I will have brass on the floor.   I told the guy, "I'll just braize it, pick it up later today"   I called him this afternoon.  Gonna try to get some silicone bronze wire and preheat the brass.ThanksDavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:That is nuts! You get all the fun jobs!City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by tanglediverThat is nuts! You get all the fun jobs!
Reply:I'd try holding some heat in the brass so it doesn't cool so much faster than the cast.With the number of attempts you've already made it's going to be tougher to get a good weld now. That area has to be drastically changed already.Anything worth doing is worth doing RIGHT
Reply:Have you tried silver solder?  There is much less heat so cracking would be less of an issue.  Some silver solder alloys are quite strong.
Reply:Originally Posted by David R  I also tried 15% silver braize with the tig torch and oxy torch.
Reply:This is all new to me..Get a big box of Vermiculite and pre heat..Weld..Post heat..Cover in Vermiculite and give it 24 hrs.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Well, today I did it.  Saturday if I ran one 1/4" bead, it would crack within 10 seconds.  It always pulled away from the cast steel.  Today I talked to the old guy at my LWS.  He is great to say the least.  He called an OLDER guy (seventy something).  He told me to preheat only the cast steel because it was cooling a lot faster than the brass.  Bottom line?  He was right.  I heated the cast steel to around 450, then went ahead and used Phos bronz rod (like silver solder) with the tig and welded the whole thing.   I added some heat after welding.  It never made any noise.  I did have a few leaks but that was from all the screwing around before, so I ground all the weld off and started fresh.  Preheat, weld and LEAVE IT ALONE.  I will pressure test tomorrow.  I think I got it.  If you want pics, I'll take the camera too.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:sounds like you got it sorted and yeah we need picshttp://datingsidorsingel.com/
Reply:Originally Posted by David R  If you want pics, I'll take the camera too...David
Reply:Tough little job, I hope you made some money on it.
Reply:Originally Posted by GLwelderTough little job, I hope you made some money on it.Originally Posted by GLwelderTough little job, I hope you made some money on it.
Reply:Remember the three P's of cast ironPreheatPost heatPray
Reply:Dave, I had the same problem with a pump housing. I heated the balls out of it with my weed burner, then TIG welded the crack with silicone bronze wire. I heated the SH^* out of it again then wrapped it in 2 welding blankets. Let it cool slooowwwww and it was fine.Disclaimer; "I am just an a$$hole welder, don't take it personally ."
Reply:Pray is key for a cast repair, as well as a lot of cursing along the way.Disclaimer; "I am just an a$$hole welder, don't take it personally ."
Reply:oK TESTING for understanding hereYou solved the prob by only pre heating the cast.!!??Trying to see the logic here..   the brass obviously cools quicker...ahhh maybe it was just not nessesary to preheat the brass because it would basically "preheat itself w/ the cast.....I quess  right?? weld it like you own it
Reply:How do you think this was originally joined together?
Reply:Ive lost my arse off on jobs like these;however, if I did not take them I would not expand my knowlege so hey you win some and loose some........ weld it like you own it
Reply:Originally Posted by lewrayIve lost my arse off on jobs like these;however, if I did not take them I would not expand my knowlege so hey you win some and loose some........
Reply:I wonder how metal spray would have worked in this situation.  I've seen them do some cool stuff with minimal preheat on cast iron.