The steel mill is a facility that produces 1x [[steel]] every 35 seconds. [[Steel]] is used mainly for Construction Material rather than production input. The List of Buildings that use [[steel]] can be seen below.
1 Iron mine and 1 Coal mine can passively provide enough materials to support (1-2) steel mills.
Recommended build ratio is 4 Iron mine and 1 Coal mine for every 7 Steel mill.
For every 50x production it'll have 1 excessive [[Iron]] and for every 5x production, it will have 3 excessive [[Coal]].
</br>Excess material can be sold or stockpiled in case of bad regional modifiers.