Nippon Yakin Kogyo NAS74N Corrosion Resistant Alloys

Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model : NAS74N

NAS74N (UNS S32750)
High Corrosion Resistant Super Duplex Stainless Steel

NAS74N is a super duplex stainless steel with a pitting resistance equivalent (PRE*) number higher than 40, which provides not only excellent corrosion resistance but also excellent strength properties. In particular, NAS74N has superior localized corrosion resistance compared with UNS S32205 (NAS329J3L, SUS329J3L), and UNS S32506 (NAS64, SUS329J4L). Therefore, industries utilize NAS74N for applications in severe environments, including chemical plants and desalination facilities, due to its superior corrosion resistance and mechanical properties Nippon Yakin supplies NAS74N in the form of plate, sheet, and strip.

*PRE = %Cr + 3.3 × %Mo + 16 × %N

Chemical Composition25Cr, 7Ni, 3.8Mo, 0.27N
Product Shape

Coil

Sheet

Plate

WorkabilityAttention should be paid to the strength behavior of NASTM which increases below 1000°C despite lower strength than Type 304 at high temperatures. Solution annealing is necessary after hot working.
WeldabilityConventional welding processes including GTAW (TIG), GMAW (MIG) can be used. Use filler metals for UNS S32750. It is advisable to avoid preheating when working with NAS74N, as it may lead to undesirable effects on the material’s properties.
Heat TreatmentSolution annealing of NASTM should be performed between 1025°C to 1125°C, followed by quick quenching to prevent brittleness.
PicklingWe apply a mixture of nitric and fluoric acids for pickling to effectively remove surface contaminants and enhance the material’s corrosion resistanceImmersion in fused salt before pickling is effective.
ApplicationsSeawater desalination plant, Environment-related equipment, Chemical plants, Seawater pump.
CertificationCan be manufactured to UNS S32750 in accordance with the NORSOK standard. Thickness up to 40mm.

Steel Grade/Standard

Nippon Yakin GradeJIS G 4304/4305ASTM A240EN 10088-2/10028-7
NAS 74NSUS 327L1UNS S327501.4410

Chemical Composition

SpecificationCSiMnPSNiCrMoCuN[wt %]
Specification (SUS 327L1)≤0.030≤0.80≤1.20≤0.035≤0.0206.00~8.0024.00~26.003.00~5.00≤0.500.24~0.32
Specification (UNS S32750)≤0.030≤0.80≤1.20≤0.035≤0.0206.00~8.0024.00~26.003.00~5.00≤0.500.24~0.32≥41
Specification (EN 1.4410)≤0.030≤1.00≤2.00≤0.035≤0.0156.00~8.0026.00~26.004.5

Physical Properties

Densityg/cm³7.8
Specific heatJ/kg·K453
Electrical resistivityµΩ·cm83
Thermal conductivityW/m·K12.3
Average coefficient of thermal expansion 10⁻⁶/°C30~100°C13.4
30~200°C13.7
30~300°C13.8
30~400°C14
Young’s modulusMPa19.7 × 10⁴
MagnetismY (magnetizable)
Melting range°C1390~1455

Mechanical Properties at Room Temperature

Specification0.2% proof stress [MPa]Tensile strength [MPa]Elongation [%]Hardness [HBW]Impact Value R.T./V-notch/Fullsiz [J]
Specification (SUS327L1)≥550≥795≥15≥310
Specification (UNS S32750)≥550≥795≥15≥310
Specification (EN 1.4410)≥530730~930≥20≥100 (long)
Hot-rolled plate 20mm58884938235298
Hot-rolled plate 8mm65588037255298

**EN 10088-2 hot rolled plate

Impact Value

 NAS74N

Corrosion Resistance

NAS74N has excellent localized corrosion resistance (pitting corrosion, crevice corrosion) and acid resistance in comparison with Type 304, Type 316L, NAS329J3L (UNS S32205), NAS64 (UNS S32506).

Pitting Corrosion Resistance

AlloyASTM G48 Method AASTM G48 Method C
22°C50°C
NAS329J3LOX
NAS64OO
NAS74NOO

Test conditions: ASTM G48 Method A (O: No pitting corrosion, ×: Pitting corrosion)

Test solution: 6%FeCl3
Test temperature: 22°C, 50°C (Recommended temperature in this test)
Test time: 72h

Crevice Corrosion Resistance

AlloyASTM G48 Method D
NAS329J3L25
NAS6430
NAS74N45

Test conditions: ASTM G48 Method D
Test solution: 6%FeCl3 + 1%HCl
Test time: 72h

Acid Resistance

Alloy5%10%20%40%60%80%
NAS329J3L0.010.174.65365.91456106.4
NAS64< 0.010.021.07191.9105460.72
NAS74N0.020.021.3079.91548.699.53

Test time: 24h

Corrosion rate in sulfuric acid at 80°C (mm/y)

Alloy5%10%20%40%60%80%
NAS329J3L0.010.174.65365.91456106.4
NAS64< 0.010.021.07191.9105460.72
NAS74N0.020.021.3079.91548.699.53

Test time: 24h

Corrosion rate in hydrochloric acid at 80°C (mm/y)

Alloy0.1%1%2%3%
NAS329J3L0.020.0331.1060.62
NAS640.010.0112.9430.51
NAS74N0.010.010.0144.75

Workability

Manufacturers must pay attention to the strength behavior of NAS74N, which experiences a significant increase below 1000°C despite having lower strength than Type 304 at high temperatures. After hot working, they should carry out solution annealing. Additionally, they must consider the cold workability of NAS74N due to its higher proof stress and lower elongation compared to Type 304

Weldability

Conventional welding processes including GTAW (TIG), GMAW (MIG/MA) can be used. We recommend using filler metals for UNS S32750 to ensure optimal welding performance and structural integrity. Neither preheating nor post-weld heat treatment is necessary. Interpass temperature should be no more than 100°C in order to prevent precipitation of intermetallic compounds of σ phases that result in brittleness.

Heat Treatment

Perform solution annealing of NAS74N within the temperature range of 1025°C to 1125°C. After this process, quickly dip the material into water or use other approved methods according to ASTM A480/A480M. This practice helps prevent brittleness at 475°C and inhibits the formation of σ phases.

Pickling

We apply a mixture of nitric and fluoric acids for pickling to effectively remove surface impurities and enhance corrosion resistance. In addition, due to its higher corrosion resistance, immersion into fused salt bath before pickling is significantly effective to take scale off. And further occasion shot blasting before pickling is extremely effective.

Applications

Seawater desalination plant, Environment-related equipment, Chemical plants, Seawater pump.

Certification

It is possible to manufacture UNS S32750 in accordance with the NORSOK standard below. The thickness is up to 40mm.

  • NORSOK M-650
  • NORSOK M-630 MDS D55

 

 

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