There are some touring/trekking triple cranks that use steel for wear resistance, particularly on the smaller rings which get used more. Two that come to mind are the Shimano Deore LX 48/36/26 (M583?) and the Sugino XD300. I think the Sugino is all steel while the Shimano used Alu for the big ring. While these certainly aren't top-of-the-line cranksets, they aren't department store grade either.