worn paper thin

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I have an aluminum transmission case that I would like to repair.I have a problem spot where the case is paper thin,most of the case is solid 1/4" or better.I would like to back this spot up because I know once I put the heat to it the base is going to open up or fall away.I am thinking on backing this spot with mild steel or aluminum.Its a one shot deal and I don't have anything that I can use to practice on.I have Hi Freq but I have also tried DCEN with some good results.Opinions please!!Thanks, Ron
Reply:You post is sort of vague. DC tig would not be my 1st choice for thin alum. I also have no idea what your skill level is with welding alum. If you have only one shot at this, and you have to ask a general question of this nature, I'm going to say your best bet is to take it to someone who is experienced in doing these types of repairs. Here's my thought behind this...Alum tranny case says cast alum to me. Cast alum, can be very good, or very poor as far as weldability is concerned. Add in chances are high the case is saturated with oil, and chances that you will have good results drops. I see all sorts of issues with crap in the material screwing up the weld.2nd issue is the fact it's thin. I'm not sure what "Thin" means in this case. 1/16" or thinner, or simply something that's say 1/8". Thin material, especially alum tends to be harder to weld. Add in the possibility of a poor casting and oil contamination, and there's a good chance this simply won't be doable for the average person.You might have better results with a "patch" where you cut out the bad area and weld in a replacement piece, or you simply cover the damaged area with new material and leave the original alone.Really we need more info to really be any help..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Thanks DSW, This case has had a repair which I felt was poor,it was just a cover with very little penetration.I don't believe that it has been used after the old repair.I have heated the area a few times to clean and expose the cracks and I have it quite clean.It is cast.I am a good welder but most of my work is construction,fabrication and repair.I have welded Hi Freq aluminum but it certainly isn't my forte and my mention of DC was simply that of trying this after I read about it on a discussion forum and it worked alright and I was throwing it out for discussion and feedback more than anything else.I know how fickle aluminum is and I am trying to avoid having that weak spot which feathers down to a hole about 1/8" wide and about 1/2" long, blow open when I get to it.My thinking is if I can back this spot up with something to keep it contained,like a piece of aluminum or steel.We used to stick carbon air arc rods in holes that we didn't want to fill with weld and my thinking is along that line,it may not be by the book but it worked. I don't have control of my heat so its going to be a feel thing.I mean don't have a peddle.Last edited by nmaineron; 01-05-2013 at 01:24 PM.
Reply:Tig alum with no pedal will be fairly tricky. I've seen it done, but combined with something that's thin and little to no experience with alum tig,  I see a recipe for disaster here. Keep in mind with alum, you want to have your amps way up at the start,so you get a puddle started fast, then usually you back off the amps with the pedal and fly as the material heats up. With no pedal, your only way to do heat control will be travel speed for the most part increasing your challenge. You had better be really good at tig in general if you want to pull this off well. If you try and keep the amps low, all you will do is heat up the whole piece since alum is such a great heat sink. As soon as the puddle is ready to form, the whole piece will be almost molten, and then suddenly it will all want to go at one time and the puddle will drop out backer or no. I'd get some sheet alum in the same approximate thickness and do a bunch of practice before you go at the real one. You might also want to invest in the pedal for this project.As far as backing, yes you can back it up with copper, brass, carbon etc. I'd avoid alum, since if you go to deep, you might weld it in place. Steel might work as well, but I'd opt for something that's a better heat sink myself to try and keep the back as cool as possible.Picts of the tranny would help you get more suggestions as well as a list of what equipment you have to try and do this repair with..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:pics I hopeutside bottom of case Attached ImagesLast edited by nmaineron; 01-06-2013 at 12:47 AM.
Reply:another: looking into the case Attached Images
Reply:anotherops my old lathe,another project Attached ImagesLast edited by nmaineron; 01-06-2013 at 12:44 AM.
Reply:my tools: Attached Images
Reply:do you know if I can plug a pedal into the start button receptacle?
Reply:cut out all the bad area and weld in a 1/4" plate that's been carefully formed to fit the hole.Welding/Fab Pics: www.UtahWeld.com
Reply:I'm thinking that may be the best way to go here....I think it would be easier than trying to deal with the holes with no base around them. Attached Images
Reply:Create the appropriate size patch first, then cut a hole to fit the patch.  I learned that from a piano refinisher.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:I used to have the setup you do and it's incredibly difficult to weld aluminum with.  Sorry bro.I'd love to try it again, now that I have more hood time.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum
Reply:Well...we have an update.I really thought I had this licked...I got the holes covered and the initial cracks covered.at first it wasn't very pretty but it was solid, I took it slow and tried not to get it really hot...an inch at a time and grind any bad spots, let it cool clean it with a clean SS brush an try it again.all of a sudden it starts cracking,some away from the weld and some along side but away from the edge...I don't think I will try and salvage it but I may use it to try and figure a way to weld this stuff...and get a little more understanding of things aluminum...
Reply:Here is what I ended my attempt without clean up.All passes had cracks and the blue line is where it cracked last and by far the worst, would really like some feed back.Thanks,Ron Attached Images
Reply:http://weldingweb.com/vbb/showthread.php...highlight=3000I would suggest talking to this guy.  He welds heavy aluminum and lists preheating and postheating as part of the deal.castweld: "3000hp busted ford head"I'm a curious guy.... and now I'm going to have to try it tooDave 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:Originally Posted by nmaineronHere is what I ended my attempt without clean up.All passes had cracks and the blue line is where it cracked last and by far the worst, would really like some feed back.Thanks,Ron
Reply:Bad terms on my part DSW. By no clean up I meant that I didn't grind the welds out.I tried really hard not to get it hot,this took me 7-8 days to get that much down going an inch or two then completely cooling followed with a clean SS brush.I had no oil issues,I preheated and washed three or four to make sure I had it clean.If I had a bad spot in the weld I ground it out to solid and covered.I used 4043 wire with 90 - 120 amps AC.I don't have amp control. I couldn't use much heat because I didn't have a floor between the two worn holes.I ended up using a #4 cup to keep the heat contained and turned the argon down to about 12 to 15 psi from over 20.The cracks seem to migrate perpendicular to the weld at first so I drilled two 1/8" holes to see if I could keep them contained.On my last weld which are the two small strings on the right it opened up almost all the way across.I had no cracks within my welds,none that followed the fillet or down the middle,just out at an angle running away from the fillet.This piece is probably junk now,probably was when I got it but I would like to figure out how to do this right.Thanks for listening.RonLast edited by nmaineron; 01-22-2013 at 09:22 PM.
Reply:I'm still thinking that Castweld's statement in his post "3000hp busted ford head" about preheat and post heat is your solution.  No preheat on cast aluminum has to cause shrinkage based cracking problems....can anyone else verify this?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:I think your right Dave,I didn't preheat right at all and I did not post heat which is the first time I have come across this procedure.He doesn't say how long though! I can't use moms oven cause it's -10 below here and I don't have heat in the dog house!I think I'll dig around and find a trailor stove/oven to stick in the shop,it should be large enough to handle my needs
Reply:That is a very large amount of weld and the shrinkage is extensive. I would have backed it up with some other piece of cast aluminum and barely weld the piece in and then immediately peened the weld. then did the same thing again until it was welded all the way around. Main thing is never get a massive amount of weld all at once hot so that it shrinks so much.  It could have been patched with about 1/8 as much aluminum rod that way.  By the way I have a welding setup almost exactly the same as yours and am used to welding with out a pedal.  Its a bitch  Mac
Reply:I posted before I started with questions about if I should back it up or not an got only one opinion and another that suggested that I cut the area out and weld in a patch.I was going to go with the patch idea but thought that there would be more welding involved than initially expected.I tried really hard to keep my heat down,what I have there is about seven or eight days of welding an inch or so at a time.I'm interested in your peening comment,I have seen it used to do that with cast iron.