I require information on composition, mech properties and applications of this grade.  Found almost nothing so far on the www.   

410 is a popular form of martensitic stainless steel.  "UF" is often used on mill products to indicate the product has not had all the finishing operations and/or inpsections completed.

Without knowing anything else, that's the best I can come up with.

rp

I know 410, which is martensitic.  The grade I am looking for is ferritic, with Ti, Nb, and something called MCN (350ppm) added.   

Update:

Some heavy googling determined this is a proprietary grade, with a duplex structure.  Composition is 11.5Cr-1.4Mn-0.8Ni-0.13Ti-0.1Nb-MCN(350ppm).  Also, several complex stipulations about Ti and Nb minima.  No idea what MCN means (My brain reached acronym saturation back about 2005.)

In the case of 410UF, UF apparently indicates for 'utility ferritic'.  [I hope my quest is not 'ultimately futile'.]  It appears to be designed for improved weldability and low temperature toughness.  

The goal is to weld this with good low temperature impact properties.  
Any suggestions for a filler metal and process?  Since it is proprietary we are going from first principles (see composition above).  Any experience/advice is welcome; this corner of the stainless universe has avoided me and my career until now.  
 

Seeing as the composition does not include Carbon or Nitrogen explicitly so MCN sounds like 350ppm of carbon and nitrogen.  

Or is this UF for ultra form.
The current specs call out two different carbon ranges for 410, the lower on is ferritic, the higher martensitic.  The low carbon and low N will give good formability.

If this is dual stabilized with Ni added then it is similar to the 439 variants that are used for auto exhaust work.
In light gage this stuff will weld very well.  It is commonly welded autogenously.  Any filler would need to be matched.

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Plymouth Tube

UF indeed refers to 'utility ferrite'.  Columbus Steel in S. Africa started development of this class with 3CR12; their website was informative.  I am dealing with substantially thicker material (up to 20mm), and impacts at -40°C.  

EdStainless, thinks for the info on 439.  The application there is different, but there is probably similarity in the fundamental physical metallurgy.  

http://www.worldstainless.org/ISSF/Files/ISSF%20The%20Ferritic%20Solution%20English.pdf