Well its been done a time or two I'm not actually sure if you're being sarcastic or not so I'll assume not. The Bessemer Process isn't complex, not even as much as a lot of routinely employed tech from the general fantasy era-mish-mash. The actual device could be explained to any competent engineer of almost any era and built. Iron ore is anything but uncommon, production has always been about labor and fuel. Steel had already been getting cheaper and more plentiful for a century or so before Bessmeer but right on the spot it dropped to about a fifth the price, but that was invented in 1850 something, we already had railroads by then but they didn't really get cheap until then. Bessemer itself doesn't matter, its just the highest tech steel production means I know I could show and explain to someone from antiquity. What matters is that you can make around a million suits of heavy jousting armor with the same metal as a you'd need to drop a rail line from Paris to Berlin, and if you had the typical fantasy-Europe with the big cities connected by a ten thousand or so kilometers of rail nobody is going to be dragging peasant clad in cloth and armed with pitchforks off to war, led by a few nobles in shining armor.
Now steam engines are another story, those aren't that terribly complicated but they're complicated enough that anyone smart enough to make them is going to be thinking about other applications and modifications. Of course someone can always wave the magic wand and have it powered by a magic widget.
That's what I meant about nitpicking though, a person could shoehorn in a reason why metal was still rare but they still had railroads, and they probably not even need to bother at all.
- Albert Einstein
King of Cairhien 20-7-2
Chancellor of the Landsraad, Archduke of Is'Mod