Strange arguing going on here. Some stuff is cast, some isn't. The original Jumar is a cast frame. The Petzl Ascension is stamped.
Every carabiner out there is probably forged out of aluminum bar stock, as that's the right way to make something light that has to catch a big fall.
Smart rescue units have dumped their old steel carabiners as "unnecessarily strong" or set them aside for training only. If you want some I'm sure I can get a good deal on them.