Durable steel

Our society as it is today would not exist without steel.

Steel is not yet a perfectly honed super material when it comes to its manufacturing process and properties, however. Unfortunately, the manufacturing process of steel produces a higher volume of carbon dioxide than steel. For example, SSAB Europe’s steel plant in Raahe produces about 7% of Finland's CO2 emissions.

And we are also not able to make the most of steel as a material yet. While the strength of commercially mass produced steels has become many times higher in recent decades, the durability of the strongest steels is far from the theoretical strength of iron. On the other hand, the processing mechanical engineering industry has not kept up with material development. Companies remain unable to use high-strength steels efficiently in products.

The University of Oulu's Centre for Advanced Steel Research CASR has calculated that in the transport sector alone, high-strength steels could enable an up to 6-7% reduction in Finland’s CO2 emissions. This impact is based on making structures lighter by increasing the durability of steel.

The CASR has carried out sustained work together with the steel industry to develop and use new special steels. As a result of this RDI cooperation, the world's strongest mass produced steels and more environmentally friendly manufacturing technology have been developed in Raahe.

The Future Manufacturing Technologies research group (FMT) at the University of Oulu Kerttu Saalasti Institute, which is part of the CARS, conducts experimental usability research, gives demonstrations of manufacturing lightweight and durable steel structures, and pilots manufacturing at the ELME Studio in Nivala. The focus of the research is on transferring the best properties of special steels as superior factors in final products using cost-effective production methods.

Modern steel manufacturing includes not only the production of pig iron but also the modification and heat treatment phases to achieve the desired geometry and microstructure in the end product, which is a metal sheet or strip. Fossil energy sources are used in some heat treatments, while traditional resistance furnace technology is employed in others.

My group studies the suitability of electric induction heating for the metal and mechanical engineering industry. Rather than only introducing cleaner manufacturing technologies, we also aim to reduce energy consumption and the need for maintenance. An induction heater does not need to be preheated, which is why it only consumes electricity when heating steel, unlike conventional ovens, which are practically always on.

In addition to the environmental impacts, rapid induction heating opens up new opportunities for influencing the microstructure of steel and thus its properties. While conventional heating techniques can produce a heating speed of a few degrees per second and heat conduction through the piece is slow, induction heating enables the steel to be heated very quickly. In addition, the heat is generated directly inside the material, as the heating depth is adjustable.

Steel is developing rapidly, but only time will tell what the steel qualities of the future and their applications will be like. Finland has for long been a pioneer in the development and manufacturing of steel. Traditionally, we have also done well in its applications. The metal and mechanical engineering industry accounts for over one third of Finland's GDP and almost two thirds of the exports. Can Finnish expertise in specialist steels be harnessed into a new industrial success story? This question should be considered not only by large companies but also in the SME sector.



Author:

Antti Järvenpää, Research Director

The article was published in the newspaper Keskipohjanmaa on 27 November 2020.