Hi OBEWAN!
I would read the conclusions on page 327 in this book I posted below because it does give some insight, and definitely validates Jeff's argument. The book is titled: "Hot cracking phenomena in welds" By Thomas Böllinghaus, Horst Herold
http://books.google.com/books?id=OveDQzH5fPwC&pg=PA347&source=gbs_toc_r&cad=8#v=onepage&q=&f=falseHere are a few good articles:
http://nels.nii.ac.jp/els/110003380327.pdf?id=ART0003861463&type=pdf&lang=en&host=cinii&order_no=&ppv_type=0&lang_sw=&no=1252514979&cp=http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=isijinternational1989&cdvol=42&noissue=7&startpage=708&lang=en&from=jnlabstracthttp://www.msm.cam.ac.uk/phase-trans/2001/Ferrite_number.pdfhttp://www.msm.cam.ac.uk/phase-trans/abstracts/neural.review.pdfhttp://bunter.msm.cam.ac.uk/phase-trans/2002/solidification.stainless.steel.1991.pdfHere are a whole list of articles from the University of Cambridge in the UK:
http://www.googlesyndicatedsearch.com/u/cammsm?hl=en&domains=msm.cam.ac.uk&ie=ISO-8859-1&q=hot+cracking+in+welding&btnG=Search&sitesearch=msm.cam.ac.ukCheck this out to see if this may guide you in any way:
http://www.msm.cam.ac.uk/map/data/materials/weldhotmat-b.htmlhttp://www.msm.cam.ac.uk/map/data/materials/austenitic.data.htmlhttp://www.msm.cam.ac.uk/map/data/materials/fatnimat-b.htmlEDIT: A Note on Ferritic SS:
Ferritic stainless steels comprise approximately half of the 400 series stainless steels. These steels contain from 10.5 to 30 weight percent chromium along with other alloying elements, particularly molybdenum. Ferritic stainless steels are noted for their stress-corrosion cracking (SCC) resistance and good resistance to pitting and crevice corrosion in chloride environments, but have poor toughness, especially in the welded condition.
Ideally, ferritic stainless steels have the body-centered cubic (bcc) crystal structure known as ferrite at all temperatures below their melting temperatures. Many of these alloys are subject to the precipitation of undesirable intermetallic phases when exposed to certain temperature ranges. The higher-chromium alloys can be embrittled by precipitation of the tetragonal sigma phase, which is based on the compound FeCr.
Molybdenum promotes formation of the complex cubic chi phase, which has a nominal composition of Fe36Cr12Mo10. Embrittlement increases with increasing chromium plus molybdenum contents. It is generally agreed that the severe embrittlement which occurs upon long-term exposure is due to the decomposition of the iron-chromium ferrite phase into a mixture of iron-rich alpha and chromium-rich alpha-prime phases. This embrittlement is often called "alpha-prime embrittlement." Additional reactions such as chromium carbide and nitride precipitation may play a significant role in the more rapid, early stage 885 °F embrittlement.
The ferritic stainless steels have higher yield strengths and lower ductilities than austenitic stainless steels. Like carbon steels, and unlike austenitic stainless steels, the ferritic stainless alloys exhibit a transition from ductile-to-brittle behavior as the temperature is reduced, especially in notched impact tests. The ductile-to-brittle transition temperature (DBTT) for the ultrahigh-purity ferritic stainless steels is lower than that for standard ferritic stainless steels. It is typically below room temperature for the ultrahigh-purity ferritic stainless steels. Nickel additions lower the DBTT and there by slightly increase the thicknesses associated with high toughness. Nevertheless, with or without nickel, the ferritic stainless steels would need engineering review for anything other than thin walled applications as they are prone to brittle failure.
Anywho, that's enough out of me for today because I've got things to do people to see and places to go!!! ;) ;) ;) Hope this is helpful! :)
Respectfully,
Henry