This guide will let you know how to make steel in Icarus. Go through the guide and follow the steps to make steel.
You will need Mortar and Pestle to make steel bloom, and also once you are in level 20, you need to make a concrete furnace, as shown in the image below.
Once you have Mortar and Pestle, you need to put them on the table and click on them. You will see that you need three iron ingots and one coal ore to make steel bloom.
When you have the steel bloom, you have to go to the Concrete Furnace machine. Tap on it and add steel bloom in it, and you will have your steel, as shown in the image below.