Looking at different stainless-steel families, we find lower alloyed ferritic stainless steels, high alloyed austenitic, and duplex stainless steels. All different grades are used in a wide range of temperatures, corrosion environments, and applications. The challenge is developing different materials and product forms in a way that they can outperform their standard property portfolio to increase process efficiency and equipment lifetime and reduce costs. How is this achievable?
Duplex stainless steels with an austenitic and ferritic phase show excellent corrosion resistance and double the strength compared to standard austenitic steels, decreasing material costs.
Composite and bi-metallic tubes are used where process conditions require properties and cost evaluations that cannot be met only by one material.
The paper shows successful installations of duplex stainless steels, composite, and bi-metallic tubes in different industries.
Different solutions are provided to the industry to avoid corrosion in demanding environments. It can be done by optimization of process conditions, coating, and cathodic protection, for example. Another way is to select material grades like stainless steel, nickel alloys, or zirconium and titanium to improve the equipment's lifetime.
Bi-metallic tubes are a cost-efficient product for use in the fertilizer industry.
Composite tubes are used as superheaters, water walls, and floor tubes in black liquor recovery and biomass-to-energy boilers.
All the product forms listed so far help to make processes safer, increase service life and reduce costs.
The development of new corrosion-resistant steels, such as duplex steels, was enabled by innovations in the steel industry. With the introduction of the metallurgical processes AOD (Argon Oxygen Decarburization) and VOD (Vacuum Oxygen Decarburization), it has become possible to reduce and control carbon. In addition, other elements, such as nitrogen, can now be controlled precisely and used as an alloying element in various concentrations. Duplex stainless steel contains two phases, austenite and ferrite. The structure offers several advantages over austenitic steels in terms of higher mechanical strength, superior corrosion resistance, and lower price because of the lower nickel content.
