The Midwest Plant is a steel finishing facility, where we further treat steel made at our Gary Works facility. These processes include:
Cold Reduction Mills
At Midwest, we have two Cold Reduction Mills where we reduce the thickness of the steel strip down to as little as 0.0075 inches. The steel strip enters the mill where at high speed it passes through a series of rolls which stretch the steel strip reducing its thickness. After reduction, the steel strip is coiled in preparation for shipment or further processing.
The main difference between hot rolled and cold rolled steel is the process; hot rolling refers to processing done with heat where cold rolling refers to processing done at near room temperature. Hot rolled steels are softer and easier to form where cold rolled steel is typically harder and stronger with better surface quality and shape.
Galvanize Coating Lines
At Midwest, we have two continuous Galvanizing Lines. In a galvanizing line, the steel strip first passes through a cleaning section where any residual dirt and/or oil is removed. The steel strip then enters an annealing furnace where the strip is heated and held to a desired temperature to meet the customers physical property requirements. As the steel strip exits the annealing furnace, it is immersed in a molten zinc bath where it is coated. As the coated strip exits the bath, it passes through an airknife, where air is blown on the coated strip to meet the desired coating weight thickness. The coated strip passes through a skin pass mill to improve the shape before being coiled in preparation for shipment.
First, the steel strip passes through a cleaning section where initially a caustic cleaning solution is used then an acid wash and rinse occur to remove any residual dirt and/or oil from the steel strip and prepare the steel strip for electroplating. Next, the steel strip passes through tanks containing the tin solution and electrically charged anodes; here, the steel strip is coated with the tin. After electroplating, the coated strip is rinsed and coiled in preparation for shipment.
As described above, water is utilized in the finishing of flat-rolled steel products. It can be categorized into the following types:
Water treatment system
Non-contact cooling water: This is water that does not come into contact with any products or chemicals.
An example would be water used in a heat exchanger, which is a piece of equipment used to transfer heat between two or more fluids. The non-contact cooling water is contained in an enclosed tube and does not come into contact with the other fluids.
Process water: This is water that does come into direct contact with the steel, chemicals or industrial gasses.
All of our process water is captured and conveyed to one of our waste water treatment systems. These systems are designed to treat the waste water to levels as required in our NPDES (National Pollutant Discharge Elimination System) permit prior to discharge. For more on permitting, click HERE.