简介:80yearshaspassedsinceduplexstainlesssteelswerefirstproducedandnowtheyhavedevelopedintoanintegralserieswiththeeffortsonR&Danddevelopmentoftechnology.Intherecentdecade,duplexstainlesssteelshavebeenacceptedbymoreandmorecustomersandincreasinglyused.ThefirstduplexgradeproducedinSwedenwas453E(26Cr-5Ni)inthe1930s,andthendevelopedinto329.Thesetwogradeswerecharacterizedbyhighcarboncontentandcalledthefirstgenerationofduplexstainlesssteels.Atthattime,itwasverydifficulttoaddnitrogenintothesteelsandmaintainthephaseequilibrium,thusinfluencingtheapplicationproperties,forexample,intergranularcorrosionpostwelding.Onemethodtosolvethisproblemistoalterthechemicalcomposition,likeaddingnitrogen,etc.AndthatcametorealitywiththedevelopmentofAODandmetallurgicaltheoryofstainlesssteels.Newseriesofduplexgrades,calledthesecondandthirdgenerationsduplex,havesuccessivelyemergedsincethe1980s.Thesegradesarecharacterizedbyhighamountsofalloyingelements,likechromium,molybdenumandnitrogen.Furthermore,superduplexstainlessgrades,likeS32750,S32760andS32707,weredevelopedforvariousharshserviceenvironmentswiththeiroutstandingcorrosionresistanceandworkability.Thesegradespossesscorrosionresistancecorrespondingtosuperausteniticgrades,orclosetonickel-basealloys,andareusedinocean-engineering,seawaterdesalinationandoilindustries,etc.Andtheapplicationofduplexstainlesssteelisexpendingintootherindustries.Forinstance,453Eisusedinthepulp&paperindustry.2205(S32205),amedium-alloyedgrade,hasbecomethemosttypicaloneintheduplexstainlesssteelfamilyandwidelyusedinmanyindustrieslikepulp&paper,chemicalandoil.Newapplicationsareemergingwithbetterunderstandingoftheduplexgrades.Modernduplexstainlesssteelsfeaturesmostthecorrosionresistanceandstrength,makingthemmostcost-efficientinmoreandmoreprojects.Int