Carbon steel

Steel is an immensely important material. Made up of iron (Fe) and 0.06-2% carbon (C), plain carbon steel is the basis upon which all steels are built, including stainless steel and alloy steel. From relatively ductile and formable low carbon steels – referred to as mild steel, they make up the majority of all steel produced – through ultra strong high carbon steel, this group offers something for every type of application. Indeed, it surrounds us in our daily lives in applications including tinplate packaging and food cans, toys, buildings and bridges, automotive bodywork and components, and industrial components. The difficulty with carbon steels is that they have very high corrosion rate, in the order of 20-50 micrometres per year, when exposed to weathering. Therefore, if used outdoors or exposed to an oxidising environment, they must be protected, such as with galvanising, metal plating, powder coating or painting.

While steel has some incredible attributes, and is irreplaceable in many applications, its downfall is its relatively high density. Compared to engineering plastics, and nonferrous alloys, such as aluminium, it is quite heavy for the same thickness; and it can be expensive to form and fabricate. Plastics are injection moulded into complex and lightweight parts in a single step, which is hard to beat in many engineering applications. And aluminium can be extruded into complex shapes with very low investment costs. Even so, steel remains the most significant engineering and construction material, second only to concrete in terms of global production volumes, and has the highest recycling rates of all – its magnetic properties make it relatively easy to recover from mixed waste. Today, new steel products contain on average around 30% recycled steel.

Its carbon footprint is relatively low. According to World Steel Association, carbon steel production has an average of 1.91 kgCO2e/kg, with basic oxygen steelmaking (BOF) at 2.33 and accounting for around 70% of global production, and electric arc furnace (EAF) which is much more efficient and can take more scrap, at 0.66.