Forta DX 2304
EN 1.4362, ASTM UNS S32304

General characteristics

Duplex grade with good resistance to localized corrosion and stress corrosion cracking in combination with high mechanical strength. Used in e.g. offshore topside applications since more than 20 years.


The grade is also available as Forta EDX 2304 with enhanced corrosion resistance and strength, but still within the same EN/ASTM standards as Forta DX 2304. The EDX version has a NORSOK approval from Aker Engineering & Technolgy ASaccording to NORSOKM standard M-650 Edition 4, September 2011 "Qualification of manufacturers of special materials".

Typical applications

  • Desalination plants
  • Firewalls and blast walls on offshore platforms
  • Bridges
  • Components for structural design
  • Storage tanks
  • Pressure vessels
  • Heat exchangers
  • Water heaters
  • Rotors, impellers and shafts

 

Product forms, available sizes and finishes

Flat

Product typeFinishesThicknessWidth
Cold rolled coil2B, 2BB, 2C, 2D, 2E, 2G, 2J0,50-6,0030-2040
Cold rolled sheet2B, 2BB, 2D, 2E, 2G, 2J0,50-6,00300-2040
Hot rolled coil, pickled1C, 1D, 1U3,00-10,0050-2040
Quarto plate1D5,00-100,00400-3200

Long

Product typeFinishesThicknessWidth
Cast billet127,00-180,00127-180
Cast slab165,00-305,001000-1580
Cold drawn bar round6,00-25,406-25
Forged billet round210,00-240,00210-240
Forged billet square200,00-240,00200-240
Hot rolled / Black bar square75,00-200,0075-200
Peeled / turned bar round70,00-170,0070-170
Rebar coilLP PI6,00-25,006-25
Rolled billet round75,00-210,0075-210
Rolled billet square75,00-200,0075-200
Wire rod (Rod coil) hex9,00-27,009-27
Wire rod (Rod coil) round6,50-27,007-27
Wire rod (Rod coil) square9,00-24,009-24
Chemical composition

The typical chemical composition for this grade is given in the table below, together with composition limits given for this grade according to different standards. The required standard will be fully met as specified on the order. The relatively low Ni and Mo content of Forta DX 2304 and Forta EDX 2304 makes these grades more price stable compared to common standard stainless steel grades.

The typical chemical composition for this grade is given in the table below, together with composition limits given for the product according to different standards. The required standard will be fully met as specified on the order.


The chemical composition is given as % by mass.

CMnCrNiMoNOther
Typical 0.0223.04.80.30.10Cu:0.30
ASME II A SA-240 ≤0.030≤2.5021.5-24.53.00-5.500.05-0.600.05-0.20Cu:0.05-0.60
ASTM A240 ≤0.030≤2.5021.5-24.53.0-5.50.05-0.600.05-0.20Cu:0.05-0.60
EN 10028-7 ≤0.030≤2.0022.0-24.03.5-5.50.10-0.600.05-0.20Cu:0.10-0.60
EN 10088-2 ≤0.030≤2.0022.0-24.53.5-5.50.10-0.600.05-0.20Cu:0.10-0.60
EN 10088-3 ≤0.030≤2.0022.0-24.03.5-5.50.10-0.600.05-0.20Cu:0.10-0.60
EN 10088-4 ≤0.030≤2.0022.0-24.03.5-5.50.10-0.600.05-0.20Cu:0.10-0.60
IS 6911 ≤0.030≤2.5021.5-24.53.0-5.50.05-0.600.05-0.20Cu:0.05-0.60
Mechanical properties

The duplex stainless steels have much higher mechanical strength compared to standard stainless steels. If the high strength of the duplex grades can be utilised, down gauging can be done in many applications leading to cost efficient solutions. The allowable design values may vary between product forms. The appropriate values are given in the relevant specifications.

The product types P= hot rolled plate, H=hot rolled strip and C=cold rolled coil and strip.

 

StandardRp0.2Rp1.0RmElongationImpact strengthRockwellHBHV
 MPaMPaMPa%J
Product type: Cold rolled coil and sheet
Typical (thickness 1 mm)62066079042
ASME II A SA-240 ≥ 400 ≥ 600 ≤ 290
ASTM A240 ≥ 400 ≥ 600 ≤ 32HRC ≤ 290
EN 10028-7 ≥ 420600-850 ≥ 20
EN 10088-2 ≥ 450650-850 ≥ 20
EN 10088-4 ≥ 450650-850 ≥ 20
IS 6911 ≥ 400 ≥ 600 ≤ 32HRC ≤ 290
Product type: Hot rolled coil and sheet
Typical (thickness 4 mm)60067076530235
ASME II A SA-240 ≥ 400 ≥ 600 ≤ 290
ASTM A240 ≥ 400 ≥ 600 ≤ 290
EN 10028-7 ≥ 420600-850 ≥ 20
EN 10088-2 ≥ 420650-850 ≥ 20
EN 10088-4 ≥ 420650-850 ≥ 20
IS 6911 ≥ 400 ≥ 600 ≤ 32HRC ≤ 290
Product type: Hot rolled quarto plate
Typical (thickness 15 mm)45067040210
ASME II A SA-240 ≥ 400 ≥ 600 ≤ 32HRC ≤ 290
ASTM A240 ≥ 400 ≥ 600 ≤ 32HRC ≤ 290
EN 10028-7 ≥ 400630-800 ≥ 25
EN 10088-2 ≥ 400630-800 ≥ 25
EN 10088-4 ≥ 400630-800 ≥ 25
IS 6911 ≥ 400 ≥ 600 ≤ 32HRC ≤ 290
Product type: Wire rod
Typical50070035

1)Elongation according to EN standard:
A80 for thickness below 3 mm.
A for thickness = 3 mm.
Elongation according to ASTM standard A2” or A50.

Corrosion resistance

Uniform corrosion

The resistance to uniform corrosion increases with high chromium content and the duplex stainless steels generally have a high chromium content. Forta DX 2304/Forta EDX 2304 is no exception. In strongly oxidising acids like nitric acid non-molybdenum alloyed steels are often more resistant than the molybdenum alloyed steels. Forta DX2304/Forta EDX 2304 is an excellent alternative due to high chromium content and low molybdenum content. More information about the resistance in different acids can be found in Outokumpu Corrosion Handbook. The corrosion tables can also be found from the here: Corrosion tables.

Pitting and crevice corrosion

The resistance to pitting and crevice corrosion increases with the content of chromium, molybdenum and nitrogen.

Pitting corrosion resistanceCrevice corrosion resistance
PRECPTCCT
2625±3<0

PRE Pitting Resistant Equivalent calculated using the formula: PRE = %Cr + 3.3 x %Mo + 16 x %N
CPT Corrosion Pitting Temperature as measured in the Avesta Cell (ASTM G 150), in a 1M NaCl solution (35,000 ppm or mg/l chloride ions).
CCT Critical Crevice Corrosion Temperature is the critical crevice corrosion temperature which is obtained by laboratory tests according to ASTM G 48 Method F

 

 

Physical properties

The physical properties at room temperature are shown in the table below. Data according to EN10088 or EN10095.

 

DensityModulus of elasticityThermal exp. at 100 °CThermal conductivityThermal capacityElectrical resistanceMagnetizable
kg/dm3GPa10-6/°CW/m°CJ/kg°CµΩm
7.820013155000.8Yes
Fabrication

Duplex stainless steel is suitable for all forming processes available for stainless steel. The high proof strength compared to austenitic and ferritics stainless steel can impose some differences in forming behaviour depending on chosen forming technique, such as an increased tendency to springback. This point is particularly relevant to forming of any high strength steel. If the forming process is not already decided, it is certainly possible to choose the most suitable one for duplex grades. Moreover, an excellent interplay between high proof strength, work hardening rate and elongation promote the duplex grades for light weight and cost-efficient applications with complex shapes. The impact of the high strength varies for different forming techniques. Common for all is that the estimated forming forces will be higher than for the corresponding austenitic and ferritic stainless steel grades. This effect will usually be lower than expected from just the increase in strength since the choice of duplex stainless steel is often associated with down gauging. It is important to consider that duplex stainless steel may also be more demanding for the tool materials and the lubricant. Also in this case attention should be given to the down gauging.

 

Machining

Duplex steels are generally more demanding to machine than conventional austenitic stainless steel such as 4404, due to the higher hardness.


The machinability can be illustrated by a machinability index, as illustrated in below figure. This index, which increases with improved machinability, is based on a combination of test data from several different machining operations. It provides a good description of machinability in relation to 4404. More information can be found in the machining guidelines which are available for each duplex grade.


 

Welding

Duplex steels generally have good weldability and can be welded using most of the welding methods used for austenitic stainless steel:

  • Shielded metal arc welding (SMAW)
  • Gas tungsten arc welding  TIG(GTAW)
  • Gas metal arc welding MIG (GMAW)
  • Flux-cored arc welding (FCW)
  • Plasma arc welding (PAW)
  • Submerged arc welding (SAW)
  • Laser welding
  • Resistance welding
  • High frequence welding

Due to the balanced composition, the heat-affected zone obtains a sufficiently high content of austenite to maintain a good resistance to localised corrosion. The individual duplex steels have slightly different welding characteristics. For more detailed information regarding the welding of individual grades, see the Outokumpu Welding Handbook or contact Outokumpu. The following general instructions should be followed:

 

  • The material should be welded without preheating.
  • The material should be allowed to cool between passes, preferably to below 150°C.
  • To obtain good weld metal properties in as welded condition, filler material shall be used.
  • The recommended arc energy should be kept within certain limits to achieve a good balance between ferrite and austenite in the weld. The heat input should be adapted to the steel grade and be adjusted in proportion to the thickness of the material to be welded.
  • Post-weld annealing after welding with filler is not necessary.
  • To ensure optimum pitting resistance when using GTAW and PAW methods, an addition of nitrogen in the shielding/purging gas is recommended.

Forta DX 2304 can be welded with high productivity methods (kg/h). For heavy gauge thickness, the use of heat input up to 3 KJ/mm can often be used without impairing weld metal properties. Suitable filler for welding Forta DX 2304 is ISO 23 7 NL or 22 9 3 NL.

More detailed information concerning welding procedures can be obtained from the Outokumpu Welding Handbook, available from our sales offices.

Standards & approvals

Outokumpu produce and certify materials to most international and national standards. Work is continuously on-going to get the different grades approved for relevant standards.

 

StandardDesignation
ASME SA-240M Code Sect. II. Part AUNS S32304
ASTM A240/A240MUNS S32304
EN 10028-7, PED 2014/68/EU1.4362
EN 10088-21.4362
EN 10088-31.4362
EN 10088-41.4362
IS 6911, AMENDMENT NO. 2ISS 2304