Which type of welding can give you a perfect weld quality for cast iron?

A major factor contributing to the difficulty of welding cast iron

is its lack of ductility. If cast irons are loaded beyond their yield

points, they break rather than deform to any significant extent. Weld

filler metal and part configuration should therefore be selected to

minimise welding stresses.

MMA, flux cored arc, MIG, TIG and gas welding processes are

normally used with nickel-based welding consumables to produce

high-quality welds, but cast iron and steel electrodes can also

produce satisfactory welds in certain alloys.

using MMA, flux core arc welding, MIG,TIG and Gas welding process can be perfect welding quality for cast iron 

SMAW IS A GOOD TECHNIQUE FOR CAST IRON.

for sound quality weld SMAW shoudl be used !!minimised stress and defects 

Shield Metal Arc Welding, also knows as SMAW has been proven to be the best welding process to weld cast iron with minized stress and defects.

arc welding, carbon-arc welding, oxyfuel gas welding, flux-cored arc welding, gas metal arc welding.

Tig wilding and Arc Wilden....

nickel based arc welding will give high qulaity of welding and low crack on welding,

Electro-slag Welding 

based on my experience as a welder for 10 years, in order to have a good quality of weld - for a Cast iron metal is an arc welding or SMAW Welding -is a kind  of metal that need more prepation in order to have a a high quality of weld (like surface cleaning, preheat etc.).