its must be a secret thing so I wont ask again
if you dont want to stump up for groovy rods you can be bodgy and try using 309 stainless, a lot of preheat, peen and sloooow cool with blankets - it will end up marginally more brittle than a brittle thing though
for some light reading on the subject try these (courtesy of TWI library);
C.L.M.Cottrell, 'Welding cast irons', published by TWI, Abington, Cambridge, UK, 1986 and available from Woodhead Publishing, Abington, Cambridge, UK. e-mail: sales@woodhead-publishing.com
ISBN 0 85300 176 6
Guide for Welding Iron Castings - ANSI/AWS D11.2-89, American Welding Society, Miami, Florida, USA. e-mail: info@aws.org
ISBN 0 87171 295 4