I think Pearlite is cast iron that has been heated long enough for the
graphite to separate out and form into either layers (like
mother-of-pearl) or little balls. Usually it is called Malleable or
Ductile iron. I've been told to use nickel or type 312 stainless for
steel-to-whatever arc welds but they are expensive and hard to find as
MIG wire.

jw