Ferritic SS 441

Ferritic SS 441

Ferritic SS 441 is one of the superior grades used in the industry. With its exceptional chemical composition, having 18% chromium content and dual addition of titanium and niobium, it gives an excellent resistance to corrosion, high ductility and exceptional welding properties.

The composition gives the alloy a very fine grain structure, the grains equiaxed in all directions imparts commendable properties to the alloy. The intergranular corrosion of the alloy is low whilst the chromium content elevates the crevice resistance.

The alpha iron in the grain structure, like other Ferritic grades, imparts its magnetic properties.

The flat rolled metal of the grade retains its magnetic properties under all conditions. Normally, Ferritic steels do not give high temperature strength but with an additional columbium stabilisation in the alloy, there is further enhancing of the high temperature strength, creep-rupture strength and corrosion resistance properties. With appropriate heat treatment like annealing and columbium (niobium) stabilisation, the metal can give exceptional performance under load at elevated temperatures. Hence, properties like deep drawing, good weldability, and good brightness can be retained.

The dual addition of titanium and niobium enhances the welding property by restricting the formation of martensite at the heat affected zone, making the alloy ferritic at all conditions. Moreover, the carbon content (0.03%) reinforces the ductility of the alloy under all conditions. The grade has low work hardening rate, similar to other ferritic alloys, and hence the grade can be suitably deep drawn, cold formed, work stretched and machined. The grade is typically used in the gas exhaust systems due to its capability of resisting oxidation up to 900- 950°C. The chloride resistance of the grade is low, and crevice corrosion is possible depending upon chloride concentrations. With an efficient metal design, appropriate heat treatment, regular maintenance, the alloy can have commendable performance under various environments.

  • Chemical properties
  • Physical properties
  • General data
  • Standards Specifications
  • Forms of Supply
  • Corrosion Resistance
  • Heat Treatment
  • Weldability
  • Machining
  • Applications
  • Possible grade alternatives
Grade   C Ti Mn Si Cr S Nb P
SS 441 Min. -  0.10 - - 17.50 -  0.3+3 -
Max. 0.03 0.60 1.00 1.00 18.50 0.015 1.00 0.04
Density 7695 kg/m^3
Melting Point -
Thermal Conductivity @ 70°F 25 W/ mK
Specific Heat 460 J/ kgK
Electrical Resistivity 0.60
Young’s Modulus x 10ᵌ 220
Modulus of elasticity 220 GPa
Standard SS 441
UNS S43490
EN 1.4509
BS -
Pipes & Tubes
Summary Standards
Chromium and Chromium – Nickel Stainless Steel Plate, Sheet and Strip for Pressure Vessels and for General Applications. ASTM A240M
General Requirements for Flat Rolled Stainless and Heat-Resisting Steel Plate, Sheet and Strip ASTM 480M
Stainless Steel Technical delivery conditions for sheet, plate and strip of corrosion resisting steels for general purposes EN 10088-2 (1.4509)

Seamless Tubes

The grade 441 shows improved corrosion resistance than previous ferritic alloy grades. It is exceptionally resistant to stress corrosion cracking, cyclic oxidation, and creep resistance. The high temperature properties of the alloy are commendable due to its grain structure and chemical composition. The titanium and niobium addition in the alloy imparts the intergranular resistance properties to the alloy. Crevice corrosion and pitting resistance are retained by chromium in the alloy.

The alloy has low work hardening rate. Due to the exceptional chemical composition, the alloy remains ferritic at all conditions and the martensitic structure is restricted. The heat treatment might be needed to remove internal stresses after the processes. Annealing is usually performed to give the grade its ductility, and ability to perform at elevated temperatures.

The stabilising elements in the grade gives the alloy better weldability than previous ferritic grades. Martensite formation is restricted, which makes post weld heat treatment redundant. There might be grain growth due to high temperature at heat affected zone, so low heat input is recommended. Austenitic fillers are normally used in the welding processes. Conventional welding techniques can be suitably used. Gas Tungsten Arc Welding, Tungsten Inert Gas Welding, Electric current resistance welding, Electron beam welding are normally used.

Conventional machining techniques can be used. It is cold formed conveniently by standard procedures. Its excellent equiaxed grain structure improves its formability.

Catalytic converter shells, Clamps, Kitchen Catering and appliance, work surfaces, shelving, Automotive exhaust system components, Exhaust system parts, Heat exchangers, Wall panels and claddings, Elevators panels and doors, Tubes.

Grade SS 439
Grade   C Mn Si Fe Ti Cr Ni
SS 439 Min. - - - - - - -
Max. 0.070 1.00 1.0 78.33 1.1 18 0.50
Grade SS 18 CR-CB
Grade   C Mn Si Nb Ti Cr Ni S P N
18 CR-CB Min. - - -  0.3+(9xc 0.10  17.5 - - - -
Max. 0.03 1.00 1.0 0.9 0.50 19.5 1.00 0.03 0.04 0.03

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