Duplex Stainless Steels

Duplex Stainless Steels

Duplex Stainless Steels Duplex stainless steels are accurately termed Duplex austenitic-ferritic stainless steels.

This terminology is derived from the approximately equal amounts of ferrites and austenite’s in the metallurgical structure. These steels have high chromium contents (18% to 28%) with low amounts of nickel (4.5% to 8%) and most grades contain molybdenum in the range of 2.5% to 4%.

Duplex steels are commonly referred to as lean duplex, duplex or super duplex in type. Lean duplex is achieved with the substitution of manganese where nickel may have been used and super duplex have chromium levels of 25% or more.

Characteristics of Duplex steels:

  • Good weldability and formability.
  • Higher tensile and yield strengths compared to standard austenitic and ferritic grades.
  • Increased resistance to stress corrosion cracking but do not match that of ferritic grades.
  • Small nitrogen addition enhances both strength and pitting resistance.
  • Increased level of passivity.

Grade and Typical application:

S31803 – (2205) – Superior corrosion resistance to 316L used in heat exchangers, gas scrubbers, fans, chemical tanks, marine and refinery applications.

S32304 – (2304) – Similar corrosion resistance to 316L with higher yield strength used in marine, mining, construction, food and power industries.

S32750 – (2507) – Extremely high corrosion resistance in severe marine, chloride and acid environments.

Stainless Steels for Hot Forging

Grade
EN #
AISI #
UNS #
EN Name
BS #
AISLF
1.4301/1.4307/1.4314
304/304L
S30400/S30403
X5CRNI18-10/X2CRNI18-9
304S15/304S31
AISLF1*
1.4301/1.4307
304/304L
S30400/S30403
X5CRNI18-10/X2CRNI18-9
-
AISTF
1.4541
321
S32100
X6CRNITI18-10
-
AISTF1*
1.4541/1.4544/1.4878
321/321H
S32100/S32109
X6CRNITI18-10/X8CRNITI18-10/X12CRNITI18-9
-
APMLF
1.4401/1.4404
316/316L
S31600/S31603
X5CRNIM017-12-2/X2CRNIM017-12-2/X2CRNIM017-13-2
-
APMLF1*
1.4401/1.4404
316/316L
S31600/S31603
X5CRNIM017-12-2/X2CRNIM017-12-2/X2CRNIM017-13-2
-
APMTF
1.4571
-
-
X6CRMIM0TI17-12-2
-
V174F
1.4542
630
S17400
X5CRNICUNB16-4
-
V174F/1*
1.4542
630
S17400
X5CRNICUNB16-4
-
VAL1F
1.4006
410
S41000
X12CR13
-

* for heavy forging parts.

Grades

Grade
EN #
AISI #
UNS #
EN Name
C225MN
1.4462
F51/F60
S31803/S32205
X2CRNIM0N22-5-3
V234N
1.4362
-
S32304
X2CRNIN23-4
V257MNC
1.4582
-
-
X4CRNIM0NB25-7
V2101MW
1.4162
-
S32101
-
*LDX2101®
1.4162
-
S32101
-

*Outokumpu registered trademark

Superduplex Stainless Steels

Characterised by higher contents of Cr, Mo, and N than standard duplex steels, resulting in increased corrosion resistance, these steels were developed for applications in aggressive chloride environments.

Grade
EN #
AISI #
UNS #
EN Name
V257M
1.4410
F53
S32750
X2CRNIM0N25-7-4
V257MWU
1.4501
F53
S32760
X2CRNIM0CUWN25-7-4