Magnesium Gearbox Fix

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I'm in the middle of replacing the engine in a formula car and found a rather large crack in the bell housing of the gearbox ....The crack was repaired some time ago, but it was (of course) fixed incorrectly.  I discovered the previous repairer just simply laid a bead over the crack. Consequently the crack just propagated right through the layover weld.  So.....below is the proper fix.Material: Cast Magnesium  (what a pain in the arse this stuff is to weld)Filler: AZ61T50Tool:  1/8" pure W @ ~130 A w/ cleaning action1st: Identify the problem2nd:  Grind out the old weld and make sure to continue completely through the crack into base metal.  3rd:  Clean the weld area to be sure that no oil or junk will be near the HAZ.4th: Lay a single root pass (NOT PICTUREd) in the gouge and then grind it out...This step was completed because all of the junk (oils, fuel...etc) that has gotten embedded in the base metal over time, has a tendency to get sucked into the first weld pass...this of course results in a highly contaminated and porous weld.5th:  Lay another (clean) root pass and then cap it with a weave.TOOL6th: get paid....ahhhh  P.S.  the inside of the housing gets the same treatmentLast edited by spiral-cut-bevel; 04-08-2008 at 09:54 PM.-Graham-Mechanical EngineerAutosport Mechanic/Fabricator
Reply:You guys gotta quit posting work like this. It makes me nuts. LOLI didn't know you could weld magnesium honestly, i thought it caught fire or something. LOL I guess that wouldnt make sense or else it would have exploded during the casting of the box itself... LMFAO! Seriously, cool stuff you have going there!
Reply:Originally Posted by Jasondt2001You guys gotta quit posting work like this. It makes me nuts. LOLI didn't know you could weld magnesium honestly, i thought it caught fire or something. LOL I guess that wouldnt make sense or else it would have exploded during the casting of the box itself... LMFAO! Seriously, cool stuff you have going there!
Reply:Nice work....I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Magnesium....sheesh. I Still can't weld aluminum like you guys do. Funny that you made this post right after I bought my kids some magnesium sticks for starting fires. I bought it at Cabela's in Phoenix, AZ. Cool. They are all "fired" up to try it out!! hehehehe Sorry...I couldn't resist.Lincoln Power Mig 210MP MIGLincoln Power Mig 350MP - MIG and Push-PullLincoln TIG 300-300Lincoln Hobby-Weld 110v  Thanks JLAMESCK TIG TORCH, gas diffuser, pyrex cupThermal Dynamics Cutmaster 101My brain
Reply:Is welding mag about like welding aluminum as far as settings and the way it flows?  I've welded plenty of aluminum but know nothing about magnesium.DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:Originally Posted by littlefuzzIs welding mag about like welding aluminum as far as settings and the way it flows?  I've welded plenty of aluminum but know nothing about magnesium.
Reply:Originally Posted by Joker11Magnesium....sheesh. I Still can't weld aluminum like you guys do. Funny that you made this post right after I bought my kids some magnesium sticks for starting fires. I bought it at Cabela's in Phoenix, AZ. Cool. They are all "fired" up to try it out!! hehehehe Sorry...I couldn't resist.
Reply:thanks, don't know if I'd ever need the info but you never know.DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:One thing that Graham forgot to mention is the cost of mag filler- boy is it spendy, £180/kg (UK)
Reply:Originally Posted by hotrodderOne thing that Graham forgot to mention is the cost of mag filler- boy is it spendy, £180/kg (UK)
Reply:I would add one additional item in here, and that is if you haven't welded Mg before, and you are going to practice, do it on something much smaller than a transmission bell housing.  Additionally, do it somewhere where an extremely intense fire isn't going to kill you, destroy your shop, burn down your property, etc...  If you've never seen a Mg fire, then I would recommend getting some Mg ribbon first and cutting it into a 3 inch strip and lighting it on fire with a blow torch.  First thing you will notice is that when it catches, you can't see a damn thing, it's as bright white a flame as you ever want to be around.  Second thing you will notice is that the heat is intense (I use Mg to ignite thermite).  If you count a 3 inch ribbon as around 1 gram of Mg, then multiply that by whatever you are going to weld, and multiply the fire the same way...you will get real cautious real quick.As a note, I've never welded Mg., but I have used it for "other" things.--Wintermute"No man's knowledge here can go beyond his experience." - John Lockewww.improvised-engineering.comManufacturer Agnostic:Blood----------Sweat---------Tears----|------------------|----------------|----Lincoln Red, Miller Blue, Esab Yellow
Reply:all good points wintermute....thanks -Graham-Mechanical EngineerAutosport Mechanic/Fabricator
Reply:I've repaird a few Magnesium cases and odd ball parts in the past.  Cleanliness is a big priority. I would clean the weld area with a solvent, grind out the crack, drill out the end of the crack then finish up with a die grinder and a burr bit(to get the embeded abrasive material out of the weld area).  And lots of brushing is involved.  I have to follow up after welds to catch the impurities that would still boil out of the root weld.  If possible, I would use a skill saw to nibble the material away so I could skip the abrasive wheels.  I've used the dust for colorful sparkles, but never had anything do a fiery meltdown on me.  And I've gotten the parts pretty hot after a few back to back passes.Common sense in an uncommon degree is what the world calls wisdom.
Reply:A big hunk of mag is very difficult to set alight- it's too good a conductor of heat. The fire risk (as pointed out) is from grinding/maching swarf- don't clean it up or if some is missed, it can be set off by a spark at a later date. As we're onto safety now, a class D fire extinguisher is a good idea. Never try and put out a mag fire with water!!!Graham, i guess we're spoiled in the UK, some speciality fillers are available in a pack of 12 lengths. Even more expensive on a £/kg basis but handy for small one off jobs- having to buy a kg or a couple of lbs effectively means a one off mag job isn't worth it for most people
Reply:Nice work.Can you visually tell the difference between Magnesium or Aluminum or Cast steel or Cast iron before you start welding?  How do you test for Mg if not Visual?
Reply:Mag is noticably lighter than aluminium, generally a different colour (can't really put into words acurately except to say it's a slightly different hue and darker). It machines better than Al too.A simple test is with vinegar. Vinegar will not react with Al but does with mag- quickly producing foam. The pyromaniac in you might prefer to collect some shavings from the part and try to set fire to it It's becoming far more common too, appearing a lot in cars these days- drivtrain castings, seat frames, door frames, steering wheels and a bunch more too. Car makers like it because less weight = better economy and it casts and machines so well
Reply:Originally Posted by tapwelderNice work.Can you visually tell the difference between Magnesium or Aluminum or Cast steel or Cast iron before you start welding?  How do you test for Mg if not Visual?
Reply:good job, nice repairChuckASME Pressure Vessel welder
Reply:Great job and tutorial man!where does that gearbox goes into?My Babies: HF Drill pressHF Pipe Bender3   4.5" Black and Decker angle grindersLincoln Electric PROMIG 175that´s it!
Reply:Lookin' good Grahme! ...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:Originally Posted by chopper5good job, nice repair