I read in an old AWS book that Titanium could be cooled using copper "chill blocks" on the piping. I wanted to know how effective are the blocks, where to get them and how can they be used i.e. during the weld process or afterwards to help with cooling. My own research has turned up that there are different types,but i don't know what's the max. cooling rate to avoid thermal stress. Can anybody help with this one?