There's a similar tech called long range mineral scanners, you can use this to search for materials to mine on the world map, but its generally more efficient to use the ground scanners for steel. There's usually around 12-16 tiles of 300 steel each per deposit, so that will tide you over for a long time. You can find more steel via technology, the best method is deep drilling and the ground radar, build the radar and let you scientist work on it for a few days and it'll ping up underground resources, including steel. Of course, you'll need silver or other commodities to trade for the steel, I'd recommend art or drugs for that. If you have micro electronics researched, build the comms panel and the orbital trade beacon, you can trade with space ships as well as ground caravans now. Strongly recommended you have pack animals for that, as colonists won't be able to carry any meaningful amount of steel by themselves. Ideally you'll need to buy some, either from traders visiting you (Usually bulk goods traders), or sending out a caravan to a neighboring town. However, you will want a more premiant solution. If you haven't probed every rock cropping you have, might be worth doing so to find any hidden veins.
