AS41 Magnesium Alloy Case Welding the tricks

23rd June 2009
The Magnesium/Aluminium case design of the AS41 case i renown for being one of the lightest design engine cases even by today's standards. This was the brilliant invention of the VW factories in Germany who originally built the engine to power planes. The downside of this design is that the Magnesium/Aluminium alloy was a mixture that was hard to weld. The obvious risk of this being igniting the Magnesium whilst welding so that the hole part you were welding burned with a large flash eating away its form. Traditionally welding these materials takes a great deal of experience as the welder needs to be aware of the composition and must apply only enough heat to weld and not combust. It is also paramount that you have a hammer with you available to beat the crap out of the area you are welding so as to knock the burning magnesium out of the area. The downside of this is that i can leave a larger hole than you start with. Crucial to the weld is also the composition of rod that you use and traditionally the flame is better controlled by a tig welder. Most people believe wrongly you need an Aluminium rod with a Magnesium content to weld the AS41 case. The result of this I found out quite quickly was not the answer and the shop that I asked to weld the case up produced the hole filled and taped but not surprisingly the plug they had welded in did not bond to the case and was simply able to be pulled out.

The correct welding rods to weld an AS41 case are in fact Magnesium rods with a low percentage of Aluminium. The actual percentage being 8% Aluminium to 92% Magnesium. These are available from Armour supplies Ltd in Hastings, East Sussex UK .

Withe the case welded so that the main gantry was plugged I was able to get the case re taped with the 3/8" NPT tap. I used a workshop for this and had to remove all the engine main studs so that it could be mounted in their mill. you can see from the photograph that I decided to have the area made bigger so that the thread had a good fetch into the casing.

The finished plug looks stronger and more durable than the original. I am very suprised this can be done and it blows a large rasberry in the faces of everyone that says it cannot be done or to put it a better way the people that have kept this a secret from us for a long time are now all aware we all know,. I look forward to seeing a lot more cases re welded in the future.

As the answer is a vertible YES!!!!!!!!!!!!!!!!!!!!