DUPLEX STAINLESS STEEL
The content of ferritic phase and Austenitic phase in duplex stainless steel are 50% separately and 30% at least if one phase is less.Content of Cr is between 18%-28% and Ni is 3%-10% in the condition of low C%.Also some stainless are with Mo,Cu,Nb,Ti,N,etc alloy elements.This kind of stainless is with both characteristics of austenitic and ferritic.Comparing with ferritic stainless,duplex stainless steel's plasticity and ductility are higher,keeps same 475℃ brittleness with ferritic stainless and high thermal conductivity,which is called super plasticity characteristic.Comparing with austenitic stainless,duplex stainless has a obvious improvement in strength,resistant nature for intergranular corrosion and chloride stress corrosion.
Application:
Duplex Stainless is usually used in oil refining,fertilizer,papermaking,petroleum and other fields with high request of resistant for sea,high temperature like exchanger,condenser's equipments.
Classify:
1.Low alloy duplex stainless,the representative grade is UNS S32304(23Cr-4Ni-0.1N),which is not with Mo,value of PREN is 32-33 and can take the place of 304 or 316 in anti-stress corrosion.
2.Middle alloy duplex stainless,the representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15N),value of PREN is 32-33,this material's anti-corrosion property is between 316L and 5%Mo+N austenitic stainless.
3.High alloy duplex stainless,which is normally with 25%Cr,Mo and N,also some of them are with Cu and Tu,the standard grade is UNS S32550,owns higher property of anti-corrosion then 22%Cr's duplex stainless.
4.Super duplex stainless,which is with high content of Mo and N,the representative grade is UNS S32750(25Cr-7Ni-3.7Mo-0.3N),some of them are also with Tu and Cu,PREN value is more than 40,these types materials can be used in special medium,which makes them be with good resistant for corrosion and mechanical property.Sometimes they can be instead for super austenitic stainless.
Representative Grades for Duplex Stainless:
Application:
Duplex Stainless is usually used in oil refining,fertilizer,papermaking,petroleum and other fields with high request of resistant for sea,high temperature like exchanger,condenser's equipments.
Classify:
1.Low alloy duplex stainless,the representative grade is UNS S32304(23Cr-4Ni-0.1N),which is not with Mo,value of PREN is 32-33 and can take the place of 304 or 316 in anti-stress corrosion.
2.Middle alloy duplex stainless,the representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15N),value of PREN is 32-33,this material's anti-corrosion property is between 316L and 5%Mo+N austenitic stainless.
3.High alloy duplex stainless,which is normally with 25%Cr,Mo and N,also some of them are with Cu and Tu,the standard grade is UNS S32550,owns higher property of anti-corrosion then 22%Cr's duplex stainless.
4.Super duplex stainless,which is with high content of Mo and N,the representative grade is UNS S32750(25Cr-7Ni-3.7Mo-0.3N),some of them are also with Tu and Cu,PREN value is more than 40,these types materials can be used in special medium,which makes them be with good resistant for corrosion and mechanical property.Sometimes they can be instead for super austenitic stainless.
Representative Grades for Duplex Stainless:
- UNS S31200
- UNS S31260
- UNS S31803
- UNS S32001
- UNS S32003
- UNS S32101
- UNS S32205(A240 2205)
- UNS S32304(A240 2304)
- UNS S32506
- UNS S32520
- UNS S32550(A240 255)
- UNS S32750(A240 2507)
- UNS S32760
- UNS S32900(A240 329)
- UNS S32906
- UNS S32950
- UNS S39274