| 词条 | Duplex stainless steel | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 释义 |
}} Duplex stainless steels[1][2][3] is the most recent family of stainless steels developed in the 1960's. They are called duplex (or austenitic-ferritic) grades because their metallurgical structure consists of two phases, austenite (face-centered cubic lattice) and ferrite (body centered cubic lattice) in roughly equal proportions. They are used for their good mechanical properties in the as-cast (and therefore as-welded condition) and/or their excellent corrosion resistance properties (particularly to stress corrosion cracking).[4] They tend to be divided in three sub groups, with a fourth sub group steadily emerging. They are: Grade 1.4462 which has been the grade initially developed. and represents the "mid-range" of properties and is perhaps the most used today Super-duplex grades which were developed later to meet specific demands of the oil& gas as well as those of the chemical industries. They offer a superior corrosion resistance but are more difficult to process. Faulty processing will result in poor performance and users are advised to deal with reputable suppliers/processors. Hyper Duplex Stainless Steel, (designated HDSS) is the latest type of dual phase stainless steel at grade EN 1.4658. This type of steel utilizes a unique blend of alloying agents added at specific times during the alloying production stage to deliver the mechanical characteristics that it possesses; more corrosion resistance at higher temperatures, with more strength. "To improve corrosion resistance and strength, modern duplex stainless steels are alloyed with chromium (Cr), molybdenum / tungsten (Mo/W), nitrogen (Ni) and nickel (N). The challenge of developing new, highly alloyed duplex stainless steels by increasing these alloying elements is to balance the alloying level to control the risk for formation of undesirable intermetallic phase."[5] Applications include deepwater offshore oil production. Lean Duplex grades, typically grade EN 1.4362, have been developed more recently for less demanding applications, particularly in the building & construction industry. Their corrosion resistance is closer to that of the standard austenitic grade EN 1.4401 (with a plus on resistance to stress corrosion cracking) and their mechanical properties are higher. This can be a great advantage when strength is important. This is the case in bridges, pressure vessels or tie bars. Chemical compositionsChemicals composition of grades from EN 10088-1 (2014) Standard are given in the table below:[6]
Mechanical propertiesMechanical properties from European Standard EN 10088-3 (2014)[6] (for product thickness below 160mm):
The minimum yield stress values are about twice as high as those of austenitic stainless steels. Duplex grades are therefore attractive when mechanical properties at room temperature are important because they allow thinner sections. References1. ^{{Cite book|title=Handbook of Stainless Steels|last=Peckner D, Bernstein I.M.|first=|publisher=McGraw Hill|year=1977|isbn=0-07-049147-X|location=|pages=Chapter 8}} 2. ^{{Cite book|title=Les Aciers Inoxydables|last=P.Lacombe, B. Baroux, G. Beranger|first=|publisher=Les Editions de Physique|year=1990|isbn=2-86883-142-7|location=|pages=Chapter 18}} 3. ^{{Cite web|url=http://www.imoa.info/download_files/stainless-steel/Duplex_Stainless_Steel_3rd_Edition.pdf|title=Practical Guidelines for the fabrication of Duplex Stainless Steels|last=|first=|date=2014|website=|archive-url=|archive-date=|dead-url=|access-date=}} 4. ^{{Cite web|url=https://www.nace.org/Corrosion-Central/Corrosion-101/Stress-Corrosion-Cracking-(SCC)/|title=NACE (National Association of Corrosion Engineers)|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}} 5. ^{{Cite web|url=https://www.materials.sandvik/en/knowledge-center/|title=Knowledge center — Sandvik Materials Technology|website=www.materials.sandvik|language=en|access-date=2019-03-25}} 6. ^1 {{Cite web|url=https://shop.bsigroup.com/SearchResults/?q=BS%20EN%2010088-1:2014|title=The standard is available from BSI Shop|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}} 1 : Stainless steel |
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