hi machine1
welcome to the machining zone
regards the different inserts
inserts for aluminium are a different grade of carbide and geomertry to those of steel grade
and you run them ie: at different rpm and feeds
because steel is harder then aluminium
my advise to you is to check your spec on the inserts supplyed by your supplier
same if you where cutting something that was very abrasive and tough check material spec i would be using cast iron grade inserts
k (grade) because the inserts will stand stand some heat which the cutting action creates
wait till you get to ceramics or diamond impreganated tooling then
the sparks realy fly (pun)
there is such a lot of data available regarding materials and inserts you need to study them which your suppliers will have
but as a machinist will tell you its experiance that tells
best regards
peter