Constituting approximately 25% of stainless steel production, ferritics are the second-largest type of stainless steel, after austenitics. Like all other stainless steels, they are resistant to corrosion, but their chemical composition sets them apart in many ways from other types. Besides rendering them magnetic, absence of certain alloying elements makes ferritics a more affordable alternative to common austenitic grades. Lack or minimal content of costly and price-volatile nickel in particular explains why ferritics are less expensive and therefore gaining in popularity, at least in certain industries and applications.
But there are many other benefits that ferritics have to offer. As pointed out by James Chater in his recent Stainless Steel Word News article, ferritics are characterised by a number of favourable properties. Compared to austenitics, they have a higher resistance to stress corrosion cracking and can, on occasions and for certain applications, show superior corrosion resistance, higher thermal fatigue resistance, improved deep drawability, and easier machinability and weldability.
Clearly, these advantages are considerable and enticing, especially when coupled with the fact that they come at a comparatively lower cost. To further exploit them, several manufacturers have successfully developed new ferritic grades, doing so by experimenting with novel alloy combinations and different manufacturing parameters and by adopting new techniques such as powder metallurgy.
One possible growth area for ferritic grades is nuclear power where high-temperature creep resistance and other thermal properties are of the essence. Similar needs are observed in the automotive industry, particularly in the manufacture of exhaust systems where the drive is towards greater heat resistance without using expensive alloys. Among the substitutes for costly elements in the two industries are zirconium, aluminium and copper. To achieve higher corrosion resistance, some manufacturers are raising the level of chromium to 21% and beyond, while other producers are exploring other possibilities such as use of ferritics in additive manufacturing (3D printing).
To find out more about recent developments among ferritic grades, read the full article by James Chater.
Photo courtesy of Sandvik