Hello, I've take over a new project that requires mass production welding of 316L barbed fittings to each end of a 316L tube using an existing laser welder.  I have very little experience welding by any means, let alone laser welding.  The laser welder supplier warned me that welding 316L to itself will cause solidification cracking.  Online research seems to support this.  Ideas to avoid cracking include either a) modifying the composition of the base parts to increase the ferrite content, or b) adding filler metal to do the same thing.  As I understand it, the additional ferrite would lock up the impurities that would otherwise cause intergranular cracking. 

316L Cr ranges from 16-18% and Ni is 11-14%.  Plotting these ranges on a Schaeffler diagram seem to indicate that I could purchase material one day that meets the criteria of 316L but is primarily Austenite and prone to solidification cracking, and then buy another batch from the same place a month later that has more ferrite and welds without cracking.  First, is my thinking correct? 

How do I ensure a consistent supply of weldable 316L?  We're a fairly small company.  Is it possible to work with a mill to tailor a "recipe" that is more weldable and can be re-run as needed?  The engineer in me seems to think that this is where I should concentrate my efforts, although I may end up battling with the Purchasing Dept. because they have preferred (e.g. low cost) suppliers, and we wouldn't buy enough to justify our own mill run, etc.

Is the alternative to accept whatever 316L Purchasing finds and modify it with a filler metal that increases the ferrite content? If so, what grade of filler metal is recommended?

Finally, is welding 316 to 316 more prone to solidification cracking than 316L to 316L?

Thanks in advance for your help.