Alloy rocker cover welding?

Date 11-22-2000 10:52

Recently, we were asked to weld a General Motors V8 cast alloy rocker cover. Going by appearance, it seems to be of a die cast construction.
Due to some inlet manifold changes we were asked to remove the oil filler neck from one cover and weld it in position on the other cover.
When removed we had a hole of approx 65mm (2 1/2 in) diameter.
We cut a disc of 5052 aluminium to suit and welded it in position with TIG welding with 5356 filler rods. When cooling, cracking could be heard and on inspection the parent metal was found to be tearing away from the weld metal approx through the HAZ. After numerous tries we eventually got it sealed but it's not a job that I would be happy with myself.
Any thoughts by anyone on a procedure that may work on die cast aluminium? Perhaps a different alloy on the filler wire or the disc to be welded?
Looking forward to reading your comments.
Regards Andrew.

By BP Maas (**)

Date 11-22-2000 19:31

With your dissimiliar joint, 4145 is your filler rod. Preheat the rocker cover to 150 degrees F, make sure all oils are removed and use a degreased stainless steel brush to remove oxides. Use the TIG process with 100% argon. A square wave power source at a minimum.
I favor Millers Dynasty TIG welder for any aluminium with 2% Ceriated
tungsten sharpened to a point. Hz setting 230.
Let the cover cool normally in room temperature air.

Cheers, Brad

By awill4x4 (**)

Date 11-24-2000 12:10

Thanks for the information Brad, we have one more rocker cover to modify so I'll apply your information on that cover. We don't have any 4145 filler rod in stock. What do you think about using 4047 instead? Currently all our TIG machines are square wave non pulse machines and not inverter types so unfortunately we cannot modify the Hertz range as yet. Although, saying that, the welding technicians we use are investigating the possibility of converting our machines to pulse welding using some form of modified hertz control. I don't pretend to understand how they do it but they seem confident that it can be achieved. At least it will be far cheaper than buying new inverter machines.
regards Andrew.

By BP Maas (**)

Date 11-27-2000 19:40

I think you should be okay with 4047, since one of the considerations is melting temperature, filler must be lower than the base metals. 4047 is a low temp filler wire. Let me know how it went.

All the best, Brad

By awill4x4 (**)

Date 12-05-2000 11:54

Brad, our customer finally got around to bringing the other rocker cover in to be welded. We used your method and used 4047 filler wire and the job was definitely better than the 1st one. Still not quite as good as I hoped it would turn out but the customer went away happy, so that's what's important. It's made me realise one thing. The more I weld die cast aluminium, the more I dislike welding die cast aluminium :)
Thanks for your help.
Regards Andrew.