Ranked

I was playing my first provisional ranked game (solo queue) and the results really surprised me.

My team had won the game and all of us did a great job whilst playing. I ended of with a KDA of 7/1/6 with and farm of 173 minions. To my surprise I was placed in "Iron 2" as a starting queue and there's only one question to it: why?

Can someone explain this to me? I was playing flawless and we won our game, yet I'm placed in the lowest ELO. I kind of demand an explanation.