Get Literal Month From Date

I am trying to extract the month from a date field, and I am able to get the integer for the month, however, when I try to convert the integer to the literal, e.g. 3 to March, I am having issues.

I have a field called PROCES, which represents a date processed, which is numeric(8).... i.e. 20061231.

I am using:
SELECT datepart(mm,cast(convert(char(8),PROCES)as datetime))
which gives me the correct integer.

When I try:
SELECT datename(mm,datepart(mm,cast(convert(char(8),PROCES)as datetime)))

I get January for all records...?

Does anyone know why, and how to fix.

Thanks