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Ferritic SS 446

Ferritic SS 446

ALLOY 446 | 1.4763 | S44600

Ferritic SS 446 has the best corrosion resistance among all the grades in 400 series, notably due to its high chromium content (26%). It is commonly used in applications having a high-temperature range about 1500°F to 2100°F because it has exceptional high-temperature resistance to oxidation and corrosion.

The strength of the metal might decrease a little at elevated temperatures but finds its place due to its resistance to oxidation in air, and resistance to various other media at elevated temperatures.

The alloy can also suitably resist cyclic oxidation. The grade has superior scaling resistance than the majority of 400 and 300 series alloys.

The welding material needs to be considered during processing since the material does not have equal scaling resistance compared to the base metal. The alloy is heat-resistant, and normally non-heat treatable. High-temperature applications require the metal to be stable with an imperturbable grain structure, this is made possible by the exceptional chemical composition of 446.

For forging the alloy, it needs to be hot-worked, particularly beginning at a temperature of 1100°C. By the end of the process, the temperature should be below 870°C for grain refinement and prevention of embrittlement. In the Sigma phase, (intermetallic phase in the metal around 560- 980°C) embrittlement is common in the alloy with long term exposure at elevated temperature.

The cold working becomes very difficult in the grade due to very high chromium content, hence, processes like bending, drawing and spinning will be difficult for the grade. For convenient forming and bending, the alloy will require slow forming speeds, edge preparation and suitable preheating. The alloy grade also has lesser ductility due to the chromium content, with carbon content restricted to 0.20%. The grade’s resistance to reducing sulphurous gases, and metals like molten copper, lead and tin, might find its uses into respective applications.

  • Chemical properties
  • Physical properties
  • General data
  • Standards Specifications
  • Forms of Supply
  • Corrosion Resistance
  • Heat Treatment
  • Weldability
  • Machining
  • Applications
  • Possible grade alternatives
Grade   C Ni Mn Si Cr Fe P S N
SS 446 Min. - - - - 23.0 69.22 - - -
Max. 0.020 0.75 1.50 1.00 27.0 - 0.040 0.030 0.25
Density 7.7 g/cm 3 / 0.28 lb/in 3³
Melting Point 1510 C°/2750 F°
Thermal Conductivity @ 70°F 21.6 W/mK          150 BTU in/hr.ft².°F
Specific Heat 20 C ° J/Kg C°
Electrical Resistivity 20 C°
Modulus of Elasticity 200 GPa   29000 ksi
Annealing 800 – 860 (°C) / 1650 – 1700 (°F
Poisson's Ratio 0.27-0.30
Quench Rapid Water
Standard SS 446
UNS S44600
WERKSTOFF NR. 1.4762/1.4763/1.4749(466-1)
EN X10CrAlSi25 / X10CrAlSi24
BS -
DIN X10CrAl24
JIS -
AFNOR Z12CAS25
Pipes & Tubes
Summary Standards
Standard Specification For Seamless Stainless Steel Mechanical Tubing ASTM A511
Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service ASTM A268

Pipes and fittings, fittings and flanges, washers.

The grade is commonly used at elevated temperatures due to its properties and hot corrosion resistance in various media. It is certainly the most stable resistant steel in the 400 series.

It provides resistance to cyclic oxidation, superior resistance to reducing gases, sulfidation, and oil- ash corrosion. It is a heat resisting steel that can resist molten copper and brass efficiently.

The grade is heat resisting, and non hardenable by heat treatment. Annealing is done for the grade to restore ductility. Annealing is carried around 800°C, followed by water quenching or air cooling. Slow cooling might result in loss of ductility especially during sigma phase. The temperature during annealing should be avoided to get above 900°C.

Conventional welding methods can be used, such as common fusion and electric resistance welding. Oxyacetylene welding is avoided in this grade. Welding material needs to be considered since the scaling resistance might become lesser than base metal. For better ductility, preheating may be carried out before welding to slow down the cooling rate of the heat affected zone. Post weld annealing can also be helpful. Pre-heating and post-heating around 150°C/ 300°C is recommended. Austenitic fillers are generally used.

Common machining processes can be suitably used. Slow speeds, sharp and carbide tooling, with rigid mounts are preferred. Powerful machinery might be required.

Furnace parts, x- ray tube bases, oil burner parts, neutral salt pot electrodes, kiln linings, glass moulds, boiler baffles, stack dampers, annealing boxes, soot blowers, spouts, recuperators, industrial mufflers.

Grade SS 442
Grade   C Mn Si P S Cr
SS 442 Min. - - - - - 18
Max. 0.20 1.0 1.0 0.04 0.03 23
Grade SS 310
Grade   C Mn Si P S Cr Ni
SS 310 Min. - - - - - 24.0 19.0
Max. 0.25 2.00 1.50 0.045 0.030 26.0 22.0

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