4130 Filler Rod

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Received 2 gears from an old lathe, each missing one tooth.  Both approx 3 in dia.  I'm assuming they are made from 4130 material, but all attempts to re-build the tooth using 4130 filer rod, is not giving me satisfactory results.  The weld contain porosity, and no matter what I have tried, I can't seem to eliminate it.  Any suggestions??
Reply:What kind of lathe is it?  I have seen some lathe gears made from cast iron and plain carbon steel.  Some less expensive lathe gears were made from diecast, but I think you  would know diecast from steelAlso what kind of welding process are you using?  Porosity could indicate contamination on the part from soaked in oil etc, or possibly poor rod to material compatibility.   I know in tig welding 4130 tube e70s2 rod, it is bit tougher and ductile. Or use er80s-d2 where you need more strength and rigidity.  4130 rod would be used where you need to heat treat the item, but it not necessarily best for 4130.  I have also seen 308L rod used, it has good mechanical properties and good flow, but I haven't used it enough to tell you if it would work.  I have seen broken gear teeth successfully built up with oxy-acetalyene brazing rod and the teeth recut.Last edited by makethegun; 04-07-2010 at 08:48 PM.Reason: correction
Reply:What kind of lathe is it?  I have seen some lathe gears made from cast iron and plain carbon steel.  Some less expensive lathe gears were made from diecast, but I think you  would know diecast from steelAlso what kind of welding process are you using?  Porosity could indicate contamination on the part from soaked in oil etc, or possibly poor rod to material compatibility.   I know in tig welding 4130 tube e70s2 rod, it is bit tougher and ductile. Or use er80s-d2 where you need more strength and rigidity.   4130 rod would be used where you need to heat treat the item, but it not necessarily best for 4130.  I have also seen 308L rod used, it has good mechanical properties and good flow, but I haven't used it enough to tell you if it would work.  I have seen broken gear teeth successfully built up with oxy-acetalyene brazing rod and the teeth recut.
Reply:I have no idea what type of lathe that it was removed from.  I can tell the gear is not cast iron, or die cast.  Since the customer who gave it to me is a higher end machine shop, I'm sure it's from an older, but well built machine, as on of the gears still has it's bronze sleeves still in place..  I tried buttering the area to be welded hoping to burn out any oils prior to welding.  I'll give it one more attempt tomorrow before I change to a different filler.  My last attempt before changing filler, will be to fill the porosity with 308, as that has proved succesful when a situation such as this has occured in the past.
Reply:Originally Posted by ChgoWelderI have no idea what type of lathe that it was removed from.  I can tell the gear is not cast iron, or die cast.  Since the customer who gave it to me is a higher end machine shop, I'm sure it's from an older, but well built machine, as on of the gears still has it's bronze sleeves still in place..  I tried buttering the area to be welded hoping to burn out any oils prior to welding.  I'll give it one more attempt tomorrow before I change to a different filler.  My last attempt before changing filler, will be to fill the porosity with 308, as that has proved succesful when a situation such as this has occured in the past.
Reply:To finish this up, using a cut-off wheel, I was ablt to grind off enough of the 4103 which had porosity and get down to a good surface.  Using 308L I was able to reconstruct the teeth as necessary.  All is well.  Thanks for your help.
Reply:Try 309L for all of your uknown materials, you'll get a better result.
Reply:Interesting project, love to see photos.  I'm very curious as to how they recut the gear teeth after your welding was complete.  Did they recalculate the tooth profile and create a custom cutter for a vertical mill? (Or hand file, blue/grease, fit, hand file, blue refit, etc...)--zip
Reply:Normally I would have choosen to use 309 however the smallest dia rod I had available was 3/32. I had on hand .035 dia 308 and due to the size of the part, choose that instead.Zip, I'm not sure what process the customer will take.  They dropped off another project when picking up the gears, I'll ask on Monday, and post up that info for you.