First a safety tip: With too much current you could overheat the coils and start a fire, You should start with a smaller current and work your way up, making sure that nothing is getting too hot.
Wikipedia actually has a nice clear explanation of the field calculation with the relevant formulas:http://en.wikipedia.org/wiki/Solenoid
The different permeabilities you're finding for iron reflect the large sensitivity of its permeability to metallurgical details. By the way, μo
= 4π * 10-7
Henries per meter is the permeability of free space.
It looks to me, based on your numbers (and using the same formula that appears in the wikipedia link) that your bare field (without the iron) would be about 5*10-2
(whoops- older version was wrong, see below) Tesla if you manage to safely get to 10 A current. Your iron would be driven beyond the range where its response to the field is linear. It would be near saturation- as magnetized as it can get. That would mean a field of around 1.5 Tesla internally for the most magnetized part. Once you get near saturation, there's little point in increasing the current- another reason to start with a small current and work your way up.
Without a picture, it's a little hard for me to tell the geometry well enough to figure out what the fields will be at the ends of your flanges. Generally, to get a large field you want the solenoid core to be completely filled with the iron, and you don't want it to get thicker at the ends, since that spreads out the field lines.
(published on 04/02/2010)