Austenitic SS Sanicro 28

Austenitic SS Sanicro 28

ALLOY 28 | N08028 | 1.4563 | X1NICRMO31-27-4 | Z1NCDU31-27-03

Austenitic SS Sanicro 28 is a high chromium-nickel-molybdenum containing alloy widely used in various chemical environments. The grade is generally known as alloy 28. It was specifically developed for resistance to corrosion in the phosphoric acid environment.

Phosphoric acid has its manufacturing technique involving large amount of impurities and varying content of halides. The Sanicro 28 has shown far more resistance to these impurities than any other high-grade alloys. Under contaminated 95% concentrated phosphoric acid, Sanicro 28 shows corrosion rate of 0.03 mm/year whereas, among other alloys only alloy 904L comes close with 0.10 mm/year.

Sanicro 28's chemical composition allows it to be used under highly acidic as well as chloride environments. Its high nickel content also makes it known as a nickel alloy. Chromium is a carbide former and 28% chromium in the alloy ensures superior resistance to corrosion. It also has a very high nickel content of 32% which further ensures superior strength even at elevated temperatures. Nickel has an ability to effectively resist corrosion during active state, hence with the help of its high nickel content, the grade can be used in highly acidic environments. Furthermore, the composition gives the alloy great impact strength, which makes it a very conducive alloy to be used in dynamic applications.

An addition of molybdenum of about 3-4% gives the grade a balanced composition. Molybdenum is a ferrite former and to balance the composition, austenitic former like nickel is present in the alloy. The addition of molybdenum ensures resistance to localized as well as uniformly distributed corrosion, which somewhat also improves its mechanical strength. The grade does not contain any element for carbide precipitation stabilization but still has good resistance to intergranular corrosion due to its chemical composition.

It is suitably used at elevated temperatures with adequate resistance to oxidation. However, the grade should normally be restricted to use above 600°C since, in that temperature range, precipitation of intermetallic phases might occur leading to embrittlement. After usage at elevated temperature, annealing is recommended. The grade also has excellent forming characteristics and can be bent by cold as well as hot working. Annealing might be required after hot bending, while cold bending does not require annealing

  • Chemical properties
  • Physical properties
  • General data
  • Standards Specifications
  • Forms of Supply
  • Corrosion Resistance
  • Heat Treatment
  • Weldability
  • Machining
  • Applications
  • Possible grade alternatives
Grade   Ni C Cr Mn Si P Mo S Fe Cu
Sanrico 28 Min. 30.00 - 26 - - - 3.00 - 29.01 0.60
Max. 34.00 0.030 28 2.50 1.00 0.030 4.00 0.035 - 1.40
Density 8.0 g/cm 3 / 0.29lb/in 3
Melting Point 1385 (°C) / 2525 (°F
Specific Heat 0.105 Btu/lb/°F
Thermal Conductivity @ 70°F 66 Btu•in/h/ft2/°F
Young’s Modulus 29
Electrical Resistivity 0.99 μΩ•m
Annealing 1100-1160°C (2010-2120°F),
Poisson Ratio  
Standard Sanrico 28
UNS N08028
EN X1NiCrMo31-27-4
AFNOR Z1NCDU31-27-03
Summary Standards
Standard Specification for Iron-Nickel-Chromium-Molybdenum Alloy (UNS N08028)* Plate, Sheet, and Strip ASTM B709
Pipes & Tubes
Summary Standards
Standard Specification for UNS N08028 Seamless Pipe and Tube ASTM B668

Shalco industries supply grade 347 in large quantities worldwide. It is available in different forms, particularly in pipes/tubes, fittings, flanges, washers.

Although the grade was initially highlighted for its use in phosphoric acid environments, it can also be conveniently used in highly acidic environments. Strong acids like hydrochloric acid, nitric acid, sulphuric acid, and nitric acid are efficiently resisted by this alloy. It has excellent resistance to sulphide cracking since it can efficiently resist hydrogen sulphide, carbon dioxide, chlorides and sulphides. Polythionic acid is largely found in petrochemical industries. The combination of molybdenum and nickel can suitably resist corrosion due to polythionic acid, hence, the grade is widely used in refineries and reactor systems. It is also used in oil refineries due to its adequate resistance to napthenic acid corrosion.

Localized corrosion like pitting and crevice corrosion are resisted exceptionally.

The grade has satisfactory resistance to oxidation. Under dry environment, around 600-700°C, the alloy formed a protective oxide layer. And under wet conditions, the oxide layer was around 600°C, before breaking it down by 700-750°C. The chromium evaporation in the presence of water vapour could not be restricted, and the chromium content fell short to resist oxidation. The grade can show suitable resistance to corrosion in presence of sodium hydroxide that is contaminated with chlorides. The grade also has fine resistance to inter-granular corrosion. When tested under highly corrosive media for 30 minutes at 650-700°C, the grade exceptionally resisted inter-granular corrosion.

The products of this grade are obtained in heat treated condition. Annealing is normally done after processing the alloy by heating it about 1100-1150°C, soaking appropriately and then quenching.

The grade has fine weldability. Conventional processes can be used like metal arc welding and gas shielded weldings like TIG (tungsten inert gas) and MIG (metal inert gas) welding. Normally no pre-heating and post-heating is required. The surface oxides should be properly removed after welding to ensure proper corrosion resistance of the alloy. The grade has high thermal expansion and therefore, the weld expansion should be taken care of. The grade has very low amount of impurity, which makes it very less prone to cracking during welding. Filler metals like Sanicro 60 can be used.

Conventional machining techniques can be used. Slow speeds and reduced feeds should be preferred.

Heat exchanger, pipes in oil and gas production, chemical processing, pollution control equipment, refineries, reactor systems, acid production, pickling equipment.

Grade Incoloy 825
Grade   Ni C Cu Mn Si Cr Fe S AI Mb Ti
Incoloy 825 Min 38.0 - 1.5 - - 19.5 22.0 - - 2.5 0.6
Max 46.0 0.05 3.0 1.0 0.50 23.5 - 0.03 2.0 3.5 1.2
Grade Hastelloy C276
Grade   Ni C Co Mn Si Cr W S V Fe P Mo
Hastelloy C276 Min Bal(50.99) - - - - 14.5 3.0 - - 4.0 - 15.0
Max - 0.010 2.5 1.00 0.08 16.5 4.5 - 0.35 7.0 0.04 17.0

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