Successful examples can be highlighted, such as developing stamped manifolds in automotive exhaust systems to substitute cast iron manifolds. Stamped manifolds considerably reduced the components’ weight while increasing vehicle performance, reducing emissions, and enhancing in-use performance with alloying strategies. These strategies included the addition of niobium in the chemical composition to increase fatigue and high temperature performance.
Maintaining the mechanical properties while avoiding creep phenomena are crucial characteristics for the component and increases catalysis efficiency.
Another recent example to be highlighted is the substitution of flat aluminium components in the battery pack of electric vehicles for stainless steels covers. It has allowed OEMs to find an interesting correlation between fire protection and mechanical performance with low thicknesses and corrosion resistance, while removing the need to e-coat the component necessary for carbon steel.
Returning to the second branch of development - substituting one stainless steel alloy for another - it is possible to see that the industry has dealt with this a lot over the years. Some market trends are good catalysts to promote this change, one of the foremost being the nickel price, and we’ll explore this a little bit more.
Returning to the circular approach, very good results can be obtained when the main players in the manufacturing chain work together. Alloying and steel making process strategies can enhance the metallurgical properties of a material. Adjustments in the manufacturing process can be applied to improve the weldability and formability of ferritic steels.
One prominent example is the substitution of austenitic stainless steel sinks for ferritic stainless steel sinks. This was only made possible by developing a special ferritic grade, with niobium and other chemical elements in the composition. A special process route was also developed, whereby the crystallographic texture and anisotropy of the material reached very interesting levels. At the end-user, special adjustments were made to the stamping process, by reducing the blank holder pressure, alleviating the die radius, increasing lubrication and adjusting the blank design. It is also important to mention that swapping austenitic grades for ferritic grades can positively affect the solution’s carbon footprint since we are removing nickel from the equation.
For many applications where surface quality and corrosion resistance are crucial, alternative grades have gained ground, such as duplex and molybdenum ferritic materials, which have replaced standard austenitic steels. Today, the doors and internal panels of many elevators are produced in DIN 1.4509 (441), UNS S43932 and even AISI 444. The same is true for industrial kitchens, white goods and architectural applications. For this last application, there are two important examples of soccer stadiums in Brazil, the Allianz Parque and the Arena Castelão, built for the 2014 FIFA World Cup.
The energy industry has also witnessed some modifications in the last decade, with austenitic grades or other alloys losing ground to stabilised ferritic stainless steels with high thermal conductivity for heat exchangers. As they are stabilised with titanium, niobium or even dual-stabilised with both, they can be easily welded and formed.
It is clear that the stainless steel industry has evolved a lot over the years and that technology has followed this evolution. Production volumes have risen in the last decade, particularly in Asian countries where most stainless production occurs. So I would like to conclude this article with a provocative reflection: stainless steel is a centenary material, really versatile and capable of adapting to complex environments. This is not so different than the moment that we are living in right now, so why don’t we inspire ourselves with the material that we work every day and also try to optimise developments by working in a more sustainable and integrative way?
To read the entire March 2021 issue of the Stainless Steel World Magazine.
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