What is the most used material in the world and the least researched?

José Manuel Torralba, IMDEA MATERIALES

We live in a world of steel. It’s so common that we use it as a metaphor for everyday life. Some people have nerves of steel, and the biceps of many muscular young individuals are made of ship steel. What is not a metaphor is that steel is everywhere we look: in food packaging, jewelry, buildings, refrigerators, railways, roads, surgical implants, cars, shopping carts, baby cribs, piano strings etc.

Steel is the second most consumed raw material globally after oil (steel alone accounts for 99% of metal consumption in the world!). And it’s also, pay attention, the most recycled metallic material: 100% of steel can be recycled, and 90% of the steel consumed is recycled. Iron ore, the primary raw material for its production, is abundant, and its handling is not hazardous to humans.

Furthermore, we are dealing with a material that is cheap to produce and can be molded, forged, and welded. It is strong, easy to manufacture, and lightweight when considering its specific strength (strength divided by density). If the Eiffel Tower were to be constructed with steel instead of iron today, it would be three to four times lighter than the current structure.

A hundred years from now, many of the trendy materials and alloys that are currently under extensive research will have ceased to be used due to their criticality, unhealthiness, strategic value, or scarcity. But steel will remain indispensable.

So, why isn’t it researched more? Is it forbidden, perhaps?

No one remembers steel

If you ask a group of experts to list ten new materials or ten advanced materials, it’s unlikely that they will think of steel. If you examine the content of ten master’s programs on new materials or advanced materials, you won’t find steel on the curriculum either. What’s worse, if you scrutinise any competitive call for projects in the field of Materials Science and Engineering, you’ll hardly find steel as a priority line for funding.

However, there is no structural material that has a greater influence on us as a society, in general, and as a technological society in particular. There is no structural material on which new technologies depend more than steel. Steel is also one of the materials that have the most impact, in various ways, on the so-called energy transition.

The virtues of pearlite

Steel is an alloy based on iron and carbon, along with other alloying elements. Its microstructure is governed by a reaction called eutectoid, which, in most cases, results in an ideal material known as pearlite. Perlite could be considered the perfect composite material if it weren’t for the fact that it’s not really a composite material.

Perlite consists of alternating layers of iron (ductile and soft) and iron carbide (brittle and hard), so intimately bonded and in such a perfect relationship that the result is a very strong material with acceptable ductility.

This microstructure of steel can be modified with thousands of possible heat treatments that offer performance spanning thousands of possible combinations of strength/hardness and ductility. In fact, there is no other family of alloys as versatile as steel.

To top it off, all manufacturing processes, shaping, and heat treatments are possibly the most reliable and reproducible among all existing alloys.

Steel’s Achilles’ heel: CO2 generation

Primary steel is obtained by reducing iron ore in the form of oxides in blast furnaces.

This is the Achilles’ heel of steel, as it generates vast amounts of CO₂ in this process. It’s the second industrial process, after cement manufacturing, in terms of CO₂ generation capacity. And in a world focused on achieving zero emissions, this is a problem. However, it’s a problem with a solution because steel can be produced without emitting CO₂ by replacing the necessary material for reduction, carbon (usually in the form of coke), with hydrogen.

Since we need steel in the entirety of the production of so-called alternative energies, it is urgent to increase R&D in alternative processes for primary steel production. And let’s not forget that steel is the most recycled alloy, so a large portion of the consumed steel is “secondary,” coming from recycling.

There is no material, no alloy, about which engineers or scientists know more. We understand all its intricacies. All simulation tools (starting with thermodynamic simulation), design, and development tools began by using steel as the material of study. The heat treatments of steel are the reference for the study of any other alloy. Materials Science is based on the physical metallurgy of steel. One of the first phase diagrams studied was the Fe-C diagram, and it is undoubtedly the most used diagram.

Our society needs investment in R&D for steel

Today and in the coming decades, steel is and will be a part of our lives, and we need to have the best steel possible.

Let’s bring steel back to the forefront of R&D investment. Like it or not, we are still in the Iron Age, and steel can still surprise us, just as it did 4,000 years ago when Egyptian armies were amazed by a new material that could cut through their bronze swords and shields like butter and gave them victory in battle.

José Manuel Torralba, Profesor at the Carlos III University in Madrid and IMDEA MATERIALES

This article was originally published in The Conversation. Read the original.