It looks like the steel output is wrong as it is still set to 10 plates of output, which makes it worse than regular steel smelting.
In phase2 resources.lua, line 8, where you set the steel recipe:
data_util.multiply_recipe("se-iron-ingot-to-plate", 1.8) <-- right here you multiply iron instead of steel
data_util.change_ingredients("se-steel-ingot-to-plate", {"se-steel-ingot"}, {{"iron-plate", 36}, {"coal", 14}, {"se-vulcanite-block", 1}})
data_util.change_category("se-steel-ingot-to-plate", "smelting")
This also makes the iron recipe even better which is probably unintentional.
