If you ask in advance they will obviously have to say no since it doesn't fit within the allowed size. However, I am almost certain that you will not even see a lifted eyebrow at the gate if you bring it as carry-on.
SAS is very relaxed in regards to carry-on, in particular if you compare to US carriers. (Also, SAS does not have the carry-on problems US carriers have, so they can afford to be relaxed, i.e. most people still check in bags on European carriers as it is free).