Both types of steel Ingot being made into Refined Steel Ingots (note both types of bar produce the same Refined Steel Ingot)
Refined Steel is an item used to create most of the items in Mekanism. It is made by putting Steel Ingots in an Enrichment Chamber.
An alternative method is to use the Metallurgic infuser, using Compressed Carbon and Enriched Iron to create Refined Steel Dust, which can then be smelted into Refined Steel ingots. [1]
The Metallurgic infuser interface showing the alternative method of creating Refined Steel