Welding is not the best option, I would think. A mechanical fastener would be stronger. The expansion coefficients of the 2 metals are too great in difference. If it is a casting operation maybe you could cast in a steel weld tab?

Rick Sidebottom
Aspiring Metal Artist

Usually, when steel needs to be welded to aluminum, it is done with explosive welding. In the United States, there are only two or three companies in the whole country capable of doing this, and it is very expensive and specialised.

I smell a homework question here.

I'm with Ries on this one. Smells like a homework question to me, and one that isn't particularly tied to art metal work. Like Ries said, most alu/steel welds are explosion welds and not anything done on a casual basis, nor for joints involving heavy loading.

Typically, alu to steel welds are more of the aluminum to stainless steel sandwich composites used for cookware bottoms. These are done by both explosion welding (rarely) and friction welding (common). They don't tolerate much loading due to the variation in coefficients of thermal expansion and the variation in malleability/ductility.

Fusion welding of aluminum to steel has been tried a jillion times by hobbyists and experimenters, never with good results. Typically, the aluminum is vaporized by the time the steel reaches the melting point. Thus the need for solid-state welding processes.