Thin cast aluminum with TIG

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I am not a good tig welder.   I've only done it a dozen times or so.   I have run some pretty fair looking beads lately in aluminum in various alloys.  Some cast, mostly sheet and extruded.   Here I am new as hell doing this and my Dad brings home an automotive oil sump which has been cracked.  I get a lot of those favors he does for other people.   I'm pretty new at this.   Here's my plan...AC somewhere around 100 amps.  I haven't seen the thing yet but judging things like that I'd say 1/8 thick. 3/32 tung pure argon gas filter.    Sand all the crap off the surface beforehand.  Wash the oil out of the crack, steel wool and stainless brush.    Heat it with a soft torch and leech the oil out.       Use 4130 filler and do both sides.    That's MY plan.  Any advice from anyone who's done any motorcycle cases or oily cast aluminum cases of any kind would be appreciated.    Any advice on any cast aluminum pieces would also be appreciated.
Reply:Lets see some pics and have a look at it first.....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:won't weld very nicely with 4130 filler. try 4043 NO steel wool! degrease it, clean it up with scotchbrite and then scrub the weld area with the stainless brushV out the crack gently on both sides -preferably with a small burr on a die grinder- make sure you locate the ends of the crack and go slightly beyond! sometimes the part may have absorbed oil/crud. if i suspect this is the case i run an arc over the crack (just barely melting it) which tends to pull the contaminates out. remove any crudor, as said, post a pic and you'll get step by step instructions
Reply:Originally Posted by BeezerI am not a good tig welder.   I've only done it a dozen times or so.   I have run some pretty fair looking beads lately in aluminum in various alloys.  Some cast, mostly sheet and extruded.   Here I am new as hell doing this and my Dad brings home an automotive oil sump which has been cracked.  I get a lot of those favors he does for other people.   I'm pretty new at this.   Here's my plan...AC somewhere around 100 amps.  I haven't seen the thing yet but judging things like that I'd say 1/8 thick. 3/32 tung pure argon gas filter.    Sand all the crap off the surface beforehand.  Wash the oil out of the crack, steel wool and stainless brush.    Heat it with a soft torch and leech the oil out.       Use 4130 filler and do both sides.    That's MY plan.  Any advice from anyone who's done any motorcycle cases or oily cast aluminum cases of any kind would be appreciated.    Any advice on any cast aluminum pieces would also be appreciated.
Reply:Originally Posted by dave powelsonSome pic's of this oil pan, would really help.         (5000 series rod, is stronger than 4000 series rod, BTW.)
Reply:Originally Posted by hotrodderyes, and more ductile too but there's more to it than that. many castings are silicon based- there may be Mg and other elements present but Si is the primary addition because it aids the casting process. strength isn't the primary consideration- it's an oil pan, not structure. good advice to test it after but soapy water isn't ideal for this (if you're leak testing a tank that can be pressurised then yes). acetone/brake cleaner will do a better job of finding leaks in this case. even better, the penetrant from a DPI kit- it has excellent properties for this and is easy to detect too
Reply:Thanks guys.   I'll take it all into account and press on.  Thanks again.
Reply:You did mention "sanding" it.I don't recommend using sandpaper for any prep work, especially with softer materials.  Garnet can do some nasty things to a TIG weld.
Reply:Most sandpaper is made of aluminum oxide.  It is exactly what you don't want in your aluminum before you weld it.  Die grinder, or a grinder wheel made for aluminum.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Cast will have natural contaminates anyway so getting it perfectly clean is nominal. weld it like you own it