{"id":766,"date":"2020-01-22T10:41:59","date_gmt":"2020-01-22T05:11:59","guid":{"rendered":"https:\/\/www.ambicasteels.com\/blog\/?p=766"},"modified":"2024-11-08T12:19:06","modified_gmt":"2024-11-08T06:49:06","slug":"applications-and-uses-of-duplex-stainless-steels","status":"publish","type":"post","link":"https:\/\/www.ambicasteels.com\/blog\/applications-and-uses-of-duplex-stainless-steels\/","title":{"rendered":"Applications and Uses of Duplex Stainless Steels"},"content":{"rendered":"
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\"Applications<\/p>\n

Stainless steels<\/strong>\u00a0are preferred for their superior corrosion resistance. Its derivatives are formed by altering composition of the various alloying elements. They are broadly divided into- austenitic, ferritic, martensitic, duplex and precipitation hardened stainless steels. This article will focus on the brief history, classification, properties and applications of Duplex Stainless steel.<\/p>\n

Duplex stainless steels<\/strong>\u00a0have a two-phase micro structure of austenitic and ferritic steels. Mechanical properties of\u00a0Duplex stainless steel<\/strong><\/a>\u00a0depend on the relative amounts of ferrite and austenite forming elements present in the composition. Main alloying elements (other than iron) for the most popular 2205 grade are Chromium (21 -23%), Nickel (4.5 \u2013 6.5%) and Molybdenum (2.5- 3.5%).<\/p>\n

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Duplex stainless steel<\/strong>\u00a0was first conceptualized in 1930s; during this period maintaining chemistry was difficult due to manufacturing constraints. Nonetheless, it was used for some applications. With advancement in technology, particularly with introduction of decarburization in 1960s, manufacturing of duplex stainless steel became practically feasible. Duplex 2205, which is considered the workhorse of duplex grades, was developed during this period. 1980s saw the birth of superior Super & Hyper duplex grades. These new grades can survive the most corrosive of environments. Duplex stainless steel was introduced to the oil and gas industry with the development of these superior Super and Hyper duplex grades.<\/p>\n

Classification of Duplex Stainless steel\u00a0<\/strong><\/h2>\n

Below are a few of the popular duplex stainless steel grades.<\/p>\n\n\n\n\n\n\n\n\n\n
<\/td>\n<\/tr>\n
Type<\/strong><\/td>\nGrades<\/strong><\/td>\n<\/tr>\n
Common name<\/strong><\/td>\nUNS Number<\/strong><\/td>\nBS EN number<\/strong><\/td>\n<\/tr>\n
Lean Duplex<\/strong><\/td>\n2304<\/td>\nS32304<\/td>\n1.4362<\/td>\n<\/tr>\n
Duplex<\/strong><\/td>\n2205 (F51, F60)<\/td>\nS31803, S32205<\/td>\n1.4462<\/td>\n<\/tr>\n
Super Duplex<\/strong><\/td>\n2507 (F53)<\/td>\nS32750<\/td>\n1.4410<\/td>\n<\/tr>\n
Hyper Duplex<\/strong><\/td>\nSandvik SAF2707<\/td>\nS32707<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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Properties of Duplex Stainless Steel\u00a0<\/strong>\u00a0<\/strong><\/h2>\n

Corrosion Resistance<\/h3>\n

Duplex Stainless Steel<\/strong>\u00a0grades have corrosion resistance properties equivalent or even superior to that of austenitic grades. Higher Chromium content paired with Molybdenum impart it higher resistance to pitting and crevice corrosion. Pitting Resistance Equivalent Number (PREN) is used to rank the grades based on their resistance to pitting. Higher the PREN number, higher will be its resistance to pitting corrosion.<\/p>\n

Stress Corrosion Cracking (SCC) Resistance<\/h3>\n

Austenitic grades<\/strong>\u00a0are susceptible to SCC whereas ferritic grades have higher resistance to it. Duplex Stainless steels have better SCC resistance compared to austenitic grades but inferior to ferritic stainless steel grades. In duplex stainless steel grades SCC initiates in austenitic region but is arrested at ferritic crystal structure present at the boundary, thus preventing propagation of crack and increasing uptime.<\/p>\n

Mechanical Strength
\n<\/strong><\/h3>\n

Duplex Stainless steels have higher mechanical strength than austenitic grades and ferritic grades. It permits use of thinner sections and helps in weight reduction. Machining of duplex stainless steel is difficult and slower compared to austenite, owing to its higher mechanical strength.<\/p>\n

Welding
\n<\/strong><\/h3>\n

Welding is difficult compared to austenite. Close control on heat input and cooling rate is required in order to avoid formation of undesired intermetallic phases.<\/p>\n

Advantage of Duplex stainless steel over its austenitic counter parts-\u00a0<\/strong><\/h2>\n