Not knowing the shape of the bottom of the point, nor how it fits the pipe,
I can't give you a really specific answer. If the base of the point has a
taper that fits into the pipe, my favorite join is a heat shrink attachment.
Heat the pipe to a red-yellow heat to expand it, then tightly insert the
tapering point base and immediately quench. You will not have any metals
mismatch to cause galvanic action, and it is a very clean looking permanent
join, with no unsightly weldment. It would not need to be painted if you
don't mind a rust patina.
Brass, copper, or silver brazing works well, and all are very strong, but
you will need to paint it for both aesthetic reasons, and to prevent
galvanic action between dissimilar metals. Often the flake carbon in the
cast iron can make brazing a challenge, but that can be overcome using
cleaning techniques to remove the surface carbon. Wire brushing doesn't
Welding works fine too using a high nickel rod, but that can cause aesthetic
problems due to the bright weldment when you are done if it is left
unpainted, so a better choice might be a rod such as Lincoln Ferroweld which
will rust along with the steel and the cast iron and form one uniform patina
if you don't paint it.
I hope that helps
Golden Age Forge