From The Steel Mill to The Shop Floor: How is Light Gauge Steel Made?

Blast furnace / basic oxygen furnace route (BOS)

 

The process of creating steel from iron ore starts with the Blast Furnace / Basic Oxygen furnace route (BOS). It is currently the dominant method of steel production responsible for 67-70% of global steel output.

First the blast furnaces purify iron ore into iron, with coke (a purer form of coal) as its fuel source, and limestone as the purifying agent. 

Hot blasts of air are blown from the bottom of the furnace, raising temperatures to a point where the iron ore melts and separates into various compounds. 

Liquid iron is tapped from the furnace, including byproducts such as slag, which is used in making roads, cement and in some cases as a fertilizer for acidic soils. 

Next, the liquid iron needs to be further purified to create steel. Here is where the liquid iron is treated with blasts of pure oxygen. The oxygen further raises temperatures inside the furnace, and oxidizes the molten iron. In other words, it separates impurities inside the iron, and allows for the extraction of pure liquid steel. 

Electric Arc Furnace (EAF) 

The EAF method uses scrap steel or recyclable steel as its primary material, instead of iron ore. 

Powerful industrial magnets pick up scrap steel and place it inside a furnace. Giant electrodes are lowered into the furnace from the top, releasing electric arcs that are hot enough to melt down the scrap into liquid steel. 

Compared to BOS steel, the electric arc furnace method is  more environmentally friendly as it is more energy efficient and emits lower amounts of greenhouse emissions. The United States for example uses electric arc furnaces for 70% of its total steel output.

Environmental Impact of Steel Production

The steelmaking industry tends comes under fire due to its impact on the environment. The global steel production industry generates between 7-9% of all global greenhouse gas emissions. 

At the same time, we must not forget that steel is 100% recyclable, meaning it can be re-used over and over again after being recycled, without losing its properties. 

This lessens its overall life-cycle impact, and considering how this material essentially moves the modern world, we can cut the steel production industry some slack. 

If we were to compare the environmental impact of the two methods, the blast Furnace / Basic Oxygen steelmaking represents the largest portion of of emissions with 80% of the pollution released during the purification of iron from iron ore. This opens up grounds for researching other alternatives to coke or coal as the primary source of fuel. 

EAF on the other hand is much more energy efficient, using less than half the energy required by a blast furnace. At the same time, the electricity used by these types of furnaces needs to be fueled, and it is using done by coal. Some plants are now using renewable sources to power their electricity, namely wind and solar. 

Cold rolling light gauge steel 

Let’s look at the cold rolling process which cold formed steel derives its name from.   

Once liquid steel has been tapped from the basic oxygen furnace or electric arc furnace, it is cast into shapes of varying widths and lengths. 

It is allowed to cool down to room temperature, and passed through a series of rollers that compress the steel down to thicknesses of up to 0.2 mms, which is why it is also called sheet metal. The metal is also passed through rollers that form C, Z and U sections depending on future usage. 

Behind the scenes, architects, structural engineers, MEP trades virtually design their framing using software such as MWF, which works in Autodesk Revit. 

Once their virtual model is designed, it is easily fed into CNC machinery that cuts sheet metal down into the exact specifications as those provided in the virtual model. 

And voila! At the very end of this process is the light gauge steel framing that forms the essential skeleton of a home, a hospital, a primary school or a shopping center. While it mostly remains unseen, the framing supports major loads, and acts as a surface upon which sheathing, wall cladding and other fixtures are added.