I agree with Tytus, although I'll add that when you design using steel, you should probably design the robot differently than you would with aluminum. See if you can find pictures of 1501's robot from the 2007 season.
edit: look at the pictures on the lower half of this page, the steel tube frame of the 1501 robot can be seen
http://photos.project1726.org/thumbn...lbum=21&page=6