Ferritic stainless steels application

Since ferritic stainless steels contain more carbon than other classes, they are relatively harder to weld and shape than other varieties, which have historically limited their applications. However, since the 1960s, processes such as argon oxygen decarburization have resulted in steels with less carbon, allowing for smaller concentrations of chromium to be used. As a result, the price for ferritic stainless steel has dramatically dropped, and a number of applications now employ these materials - more than 2/3 of which include automotive exhaust systems. 

One material that has wide application in the systems of DOE facilities is stainless steel. There are nearly 40 standard types of stainless steel and many other specialized types under various trade names. Through the modification of the kinds and quantities of alloying elements, the steel can be adapted to specific applications. Stainless steels are classified as austenitic or ferritic based on their lattice structure. Austenitic stainless steels, including 304 and 316, have a face-centered cubic structure of iron atoms with the carbon in interstitial solid solution. Ferritic stainless steels, including type 405, have a body-centered cubic iron lattice and contain no nickel. Ferritic steels are easier to weld and fabricate and are less susceptible to stress corrosion cracking than austenitic stainless steels. They have only moderate resistance to other types of chemical attack. 

Corrosion of Stainless Steels in Acids Stainless steels are iron-based alloys with chromium as the main alloying element. The most interesting alloys for technical applications are ferritic stainless steels, austentic stainless steels, and duplex stainless steels. The distinction between the stainless steels comes from their different crystallographic structures. Ferritic-martensitic stainless steels and martensitic stainless steels have less nickel and a higher carbon content and can be hardened by heat treatment. The corrosion behavior of these steels is mainly influenced by the formation of carbides, which generally increase the corrosion rate. 

High chromium contents increase the corrosion resistance of ferritic stainless steels in highly concentrated sulfuric acid. For example, the ferritic steel 1.4575 (main components 28% Cr, 4% Ni, 2% Mo) is successfully used for applications in this field. At temperatures above 120 °C, the alloy can be used at concentrations between... 

The next-higher grade of materials that are used in oil and gas industries are stainless steels. Almost all kinds of stainless steels are used in oil and gas industrial applications. Stainless steels are classified as ferritic, austenitic, duplex, and martensitic stainless steels. The main advantage of stainless steels is their high corrosion resistance. The most primitive stainless steel is ferritic stainless steel. 

Ferritic stainless steels in general are less resistant than the austenitics and are subject to caustic cracking. Cupronickel tubes are occasionally used for low- to medium-concentration caustic at mild temperatures and with restrictions on fluid velocity. These alloys are also resistant to hot 70% NaOH, but only in the complete absence of oxidants. Monel has a number of applications, but its use can be restricted by the slow development of color due to copper contamination. It is a frequent choice for processing equipment in the salt-recovery section of the diaphragm-cell process (Sections 9.3.2.S and 9.3.2.6). 

The technology base for the LFR is primarily derived from the Pb-Bi liquid alloy-cooled reactors employed by the Russian Alpha class submarines. Technologies developed from the integral fast reactor metal alloy fuel recycle and refabrication development, and from the advanced liquid metal reactor (ALMR) passive safety and modular design approach, may also be applicable to the LFR. The ferritic stainless steel and metal alloy fuel developed for sodium fast reactors may also be adaptable to the LFR for those concepts with reactor outlet temperatures in the range of BSO C. 

Susceptibility of duplex stainless steels to formation of undesirable intermetallic phases is typically done using ASTM A 923 (Test Methods for Detecting Detrimental Intermetallic Phase in Wrought Duplex Austenitic/Ferritic Stainless Steels). The application of ASTM A 923 to testing of weldments is recommended in TAPPI TIP 0402-29 [196]. 

Yang Z, Xia GG, Maupin GD, Stevenson JW (2006) Evaluation of perovskite overlay coatings on ferritic stainless steels for SOFC interconnect applications. J Electrochem Soc 153 A852-A1858... 

Z. Yang, G. Xia, C. Wang, Z. Nie, J. Templeton, J. Stevenson, and P. Singh, Investigation of AISl 441 Ferritic Stainless Steel and Development of Spinel Coatings for SOFC Interconnect Applications, PNNL Report 17568, (2008). 

Because the corrosion resistance of these stainless steels is dependent upon the chromium content, and because the carbon contents are generally higher than the ferritic alloys, it is logical that they are less corrosion resistant. However, their useful corrosion resistance in mild environments coupled with their high strengths made members of the martensitic family useful for certain stainless steel applications. Details of the specific family members are covered in Chapter 9. 

When considering specific alloys for high-temperature service, it is imperative to consider other properties besides the corrosion resistance. It would be futile, for example, to select a stainless steel with high-corrosion resistance for an application in which strength requirements could not be met. In general, austenitic stainless steels are substantially stronger than ferritic stainless steels at high temperatures, as indicated by a comparison of stress rupture properties (Fig. 15.15) and creep properties (Fig. 15.16) [3]. 

C.C. Silva, H.C. Miranda, H.B. de Sant Ana, J.R Farias 2013. Austenitic and ferritic stainless steel dissimilar weld metal evaluation for the applications as-coating in the petroleum processing equipment. Materials and Design 47, 1-8. 

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