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up-fixing der car(ma)
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Aluminum content (metallurgy) of chain boxes, valve covers?
Approximately what is the percentage of each alloy (Al, Si, ?, ??) in parts like the valve covers and chain boxes? '78+ stuff.
Thanks, Scott
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Scott Kinder kindersport @ gmail.com |
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11-27-2006, 12:23 AM
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Location: Northern CA
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not sure but these "AL" parts can have lots of zinc in them making things tricky e.g. welding.
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Sold: 1989 3.2 coupe, 112k miles |
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11-28-2006, 05:14 PM
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the porsche cases weld really nicely along with all the chain boxes etc. I am not sure what alloy but as I said very nicly welded
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Ben 89 944,85.5 944 914-6 2.4s GT tribute. 914-6werkshop.com |
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11-29-2006, 08:41 AM
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up-fixing der car(ma)
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You're correct that high-Zn aluminum like 7xxx (7075 is probably most common) is tricky to weld, especially with a 4xxx wire! I don't think Porsche engine cases have much zinc in them, if any..perhaps .1% max.
From what it seems (just looked up some info on casting) that Porsche probably used something like 380.0 Al for the die-cast parts..which is about 8% Si, 3% Cu, and maybe a little, ~.2%, Fe. There really is no other alloy that makes sense for Porsche to use...the high(er) Si content seems to correlate with the fact that it was die-cast, and needs to flow into the mold well. Could be 356.0 Al alloy for the early sand-cast cases, about 7% Si, .3% Mg. This would explain why sand-cast Al is harder to make (reason for Porsche switching to die-cast on later Al parts) and also why I've noticed the early sand-cast cases seem to be stronger than the die-cast (less Si, no Cu and the addition of Mg) After a little research, looks like 4043 is the best welding wire for 380.0 and 4011 wire if 356.0. I have limited experience (none first-hand) with welding Al, but from the weld work I've seen, it didn't look like there was any trouble getting a smooth bead going and a "roll o coins" everyone learned something ! cheers Scott
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Scott Kinder kindersport @ gmail.com Last edited by YTNUKLR; 11-29-2006 at 04:03 PM.. |
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11-29-2006, 04:01 PM
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5052 make work better but I have done plenty with 4043
all have turned out really well. that said a good portion of the poor weldability is due to type of castings and typically porsche has used very high castings.. Sorry this is my thing ( I teach this stuff)
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Ben 89 944,85.5 944 914-6 2.4s GT tribute. 914-6werkshop.com |
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11-29-2006, 05:30 PM
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up-fixing der car(ma)
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no apology necessary! I have never welded aluminum myself, you would know better than I. I was just curious and looking into it. Plan to teach myself when I get some time with the MIG. Probably come to you and Milt Becker (Zeke) asking a bunch of stupid questions
  I was also trying to figure out basic metallurgy to see if it would make more sense to use acid or a caustic soda to oxidize the aluminum and turn it dark gray (to look more like Magnesium). Seems like caustic soda is a better bet. cheers
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Scott Kinder kindersport @ gmail.com |
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11-29-2006, 10:41 PM
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Surely caustic soda will dissolve the aluminium not oxidise the surface.
I am sure it will make cases quite bright but it will strip the oxide layer and then leave them prone to corrosion. Anodising usually uses sulphuric acid as an electrolyte and then a dye to change the colour as thin films of aluminium oxide are quite transparent. After using a dye it is normal practice to seal the surface to prevent any colour leaching. |
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11-30-2006, 07:38 AM
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