We at Arc-Zone recommend our ArcTime tungsten... it works really well on all metals, all machines, and you don't have to keep switching tungstens. It's also sold as TriMix here in the states, or MultiStrike:
http://www.cob-industries.com/multistrike.htm
http://diamondground.com/tungstenmaterial.html
and of course,
http://www.arc-zone.com/catalog/web_store.cgi?page=amparctime_cream.html
--CE