Ultra 6XN
EN 1.4529, ASTM UNS N08367, UNS N08926

General characteristics

6% Mo, high Ni, and N alloyed austenitic grade with extremely high resistance to both uniform and localized corrosion. Commonly used in applications to withstand chlorinated sea water also used in flue gas cleaning.

Typical applications

  • In applications to withstand chlorinated sea water
  • Flue gas cleaning
  • Process equipment in chemical industry
  • Bleaching equipment in the pulp and paper industry
  • Desalination
  • Seawater handling
  • Hydrometallurgy
  • Food and beverage
  • Pharmaceuticals
  • Heat exchangers


Product forms, available sizes and finishes


Product typeFinishesThicknessWidth
Cold rolled coil and sheet2E0,40-6,35≤ 1524
Hot rolled coil and plateHot rolled white7,93-8,00≤ 1524
Quarto plateHot rolled white7,00-40,00≤ 2700
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 chemical composition is given as % by weight.

TypicalUltra 6XN0.0120.524.86.50.20Cu:0.6
ASTM A240/A240MUNS N08367<0.030<220.0-22.023.5-25.56.0-7.00.18-0.25Si:<1 P:<0.040 S:<0.030 Cu:<0.75
ASTM A240/A240MUNS N08926<0.020<219.0-21.024.0-26.06.0-7.00.15-0.25Si:<0.50 P:<0.030 S:<0.010 Cu:0.50-1.50
EN 10088-21.4529<0.020<119.0-21.024.0-26.06.0-7.00.15-0.25Si:<0.50 P:<0.030 S:<0.010 Cu:0.50-1.50
Mechanical properties

The mechanical properties of the available products are given in the table below.


StandardGradeRp0.2Rp1.0RmElongationImpact strengthRockwellHBHV
Product type: Hot rolled quarto plate
Typical (thickness 15 mm)Ultra 6XN32034070050180

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 Uniform corrosion occurs when all, or at least a large section, of the passive layer is destroyed. This typically occurs in acids or in hot alkaline solutions. The influence of the alloy composition on the resistance to uniform corrosion may vary significantly between different environments; chromium is essential for ensuring the passivity of stainless steels, nickel helps reduce the corrosion rate of depassivated steel, molybdenum enhances passivity (except for strongly oxidising environments, such as warm concentrated nitric acid) and copper has a positive effect in the presence of reducing acids such as dilute sulphuric acid. In an environment with constant temperature and chemical composition, uniform corrosion occurs at a steady rate. This rate is often expressed as a loss of thickness per unit time, e.g. mm/y. Stainless steels are normally considered to be resistant to uniform corrosion in environments in which the corrosion rate does not exceed 0.1 mm/y. Impurities may drastically affect the corrosivity of acid solutions. For guidance on materials selection in a large number of environments capable of causing uniform corrosion, the tables and iso-corrosion diagrams in Outokumpu Corrosion Handbook may be consulted.

Pitting and Crevice corrosion
Chloride ions in a neutral or acidic environment facilitate local breakdown of the passive layer. As a result, pitting and crevice corrosion can propagate at a high rate, causing corrosion failure in a short time. Since the attack is small and may be covered by corrosion products or hidden in a crevice, it often remains undiscovered until perforation or leakage occurs. Resistance to pitting corrosion is determined mainly by the content of chromium, molybdenum and nitrogen in the stainless steel. This is often illustrated using the pitting resistance equivalent (PRE) for the material, which can be calculated using the formula: PRE = %Cr + 3.3 x %Mo + 16 x %N. The PRE value can be used for rough comparisons of different materials. A more reliable means, however, is to rank the steel according to the critical pitting temperature (CPT) of the material. There are several different methods available, for example ASTM G 150 that uses the Avesta Cell with a 1M NaCl solution (35 000 ppm or mg/l chloride ions). The CPT-values are shown in the table below. Higher contents of chromium, molybdenum and nitrogen also enhance the crevice corrosion resistance of the stainless steel. Typical values of the critical crevice corrosion temperature (CCT) in 6% FeCl3 + 1% HCl according to ASTM G48 Method F are included in the table below. The CPT and CCT values vary with product form and surface finish, the values given are for ground surfaces. Both ASTM G150 and G48 are methods for ranking the relative pitting or crevice corrosion resistance for the different stainless steels but they do not give the maximum temperature for using these alloys in real service environments.

CPT according to ASTM G150
 Wet ground to 320 grit


Pitting corrosion resistanceCrevice corrosion resistance

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

*) Austenitic stainless steel grades may be magnetizable to a certain degree after cold deformation, e.g. in temper rolled condition.


Outokumpu 4529 can be welded with all conventional welding methods like:

Shielded metal arc welding (SMAW)
Gas tungsten arc welding, TIG (GTAW)
Gas metal arc welding, MIG (GMAW)
Flux-cored arc welding (FCAW)
Plasma arc welding (PAW)
Submerged arc welding (SAW)

An over-alloyed nickel-base filler should be used to overcome molybdenum segregatin. If autogenous welding is performed and no post weld heat treatment is used, the weld will have a reduced coroosion resistance. When welding thick gauges, the maximum heat input is 1.5 kJ/mm


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. The most commonly used international product standards are given in the table below.


ASTM A240/A240MUNS N08367; UNS N08926
EN 10088-21.4529