Unusual Aluminum Issue.....

Date 06-03-2010 14:47

Hey guys,
I was approached by an automotive machine shop to do some aluminum & cast iron/steel welding on cracked parts. These fellows are outstanding machinists & their work on engines & associated engine parts is impeccable.....they know their "sheet".

Their problem is with repairing(welding) cracked aluminum heads on GM mfg., 4cyl engines, used on forklifts. These forklifts use propane fuel & after several tries to repair the cracks(w/TIG), the weld would not hold. The general consensus from investigation is that the propane somehow alters or severly contaminates the base aluminum casting.

I'm hoping that Lawrence & G.S. Crisi, or any of the well-knowledgeable members will have some input as to any information that would support the theory of propane damage to an aluminum casting & if a repair is possible or not.

Thanks guys.... Denny

By aevald

Date 06-03-2010 19:57

Hello Denny, this may be a bit simplistic, but are these heads "heat treated"? If they do have some sort of heat treatment then welding on them without "reintroducing" them to their original condition could certainly lead to a failure. Another consideration might go along the lines of casting type, "some" of GM's earlier aluminum components were high in silica content, which I believe makes them a very poor candidate for welding repair. I'm talking off the top of my head, so this might not apply at all to this situation, yet it may be something for consideration. Best regards, Allan

By Joseph P. Kane (****)

Date 06-03-2010 21:16

Are you sure that they are not Magnesium heads?

By 357max

Date 06-03-2010 21:41

Strike a gtaw arc on the "metal" and identify the arc's color; green - magnesium, white - aluminum

By DaveBoyer (*****)

Date 06-04-2010 02:22

My guess is that they might be made from an alloy that just doesn't lend itself to welding. After all, GM doesn't weld them, so it isn't a concern of theirs.

With regard to the idea of contamination from propane [I doubt it], do the same heads used on gasoline engines weld OK?

Propane is in the same chemical family as most of the components of gasoline, that is why I doubt welding these parts from a propane fueled engine would be any different than if from a gas engine.

By Tommyjoking (****)

Date 06-04-2010 02:51

Aluminum heads get damaged and repaired all the time....I have never heard of any particular series or brand that was "undoable", does not mean some are not tho like Dave said. Any time I ever had it done or welded them myself they always went to shop with an oven and got soaked. Never heard of a magnesium head but if you had some they will weld right up with aluminum filler and then promptly crack or the weld will just fall away as they cool.
Are the cracks being opened up prior to welding? Is the failure occurring after install or before? I reckon you have tried different fillers? What is the method and temp of your preheat? If I remember correct when I did this I used a 5xxx filler but I cant remember which.

By yorkiepap (***)

Date 06-04-2010 11:48

Hey guys,
I apologize for the brevity of the original post & will clarify a bit more.

The machine shop fellows don't do any welding repairs at all..... they send it all out. When they saw my cast iron repair & my info that I do all processes at my home shop, they were interested in having me do work for them. They indicated another fellow tried to TIG the heads with failure. Since I don't know what the other fellow did, I told them I would like them to bring one to my shop so I could look at it. The machine shop also has a cracked early Chevy Corvette L88 aluminum block that also needs cracks welded. This engine is the original that was located to be put back into the original car for collectors' value.

I never heard of a propane issue before with any metal, although I'm no engineer or metallurgist. I have welded many aluminum castings from intake manifolds to transmissions with no issues after a dedicated cleansing of the weld joint. Once they bring one to the shop, I will post some pics of damage & repair if the head is salvagable. Thanks for your input.....don't stop.

Denny

By Lawrence (*****)

Date 06-07-2010 17:32

Sorry Denny

I"ve been out of town (still am)

Never herd fuel contamination problems that were beyond a good vapor degrease.

If it's a complex casting with many thin to thick sections than a slow pre-heat and a blanket covering everything but the weld to control cooling is a good idea but I suspect this is not news to you :)

By jwright650 (*****)

Date 06-04-2010 12:05

Maybe this will help.....

http://www.mid-atlanticcasting.com/alum-casting-alloys_FEB05.pdf

I'm thinking that many of the aftermarket automotive performance heads and intakes(which have been succesfully repaired by welding) were ASTM A356. I remember seeing that stamped/cast on something, but it escapes me at the moment.

By Tommyjoking (****)

Date 06-04-2010 13:31

nice link!!