Core 441/4509
EN 1.4509, ASTM UNS S43940

General characteristics

Core 441/4509 is a nickel-free 17% chromium ferritic stainless steel originally designed for exhaust systems, with good corrosion resistance and high-temperature strength. Core 441/4509 is available with a single (niobium) or dual (niobium and titanium) stabilizer. Due to good formability and weldability, it is often a suitable replacement for Core 301/4310.

Core 441/4509 can be supplied with a wide range of functional and aesthetic surface finishes.

Typical applications

  • Indoor cladding
  • Restaurant equipment and appliances
  • Tubes
  • Heat exchangers


Product forms, available sizes and finishes


Product typeFinishesThicknessWidth
Black hot band1U2,50-8,501000-1550
Cold rolled coil2B, 2BB, 2C, 2D, 2E, 2F, 2G, 2H, 2J, 2K, 2M, 2R0,05-3,583-1550
Cold rolled sheet2B, 2BB, 2D, 2E, 2F, 2G, 2J, 2K, 2M, 2R0,30-3,5818-1550
Hot rolled coil, pickled1C, 1D, 1E, 1G, 1M, 1U2,00-8,0050-1550
Precision strip2R0,05-1,503-649
Chemical composition

The chemical composition may vary slightly between different product standards. The required standard will be fully met as specified in the order.

The typical chemical composition for this grade is given in the table below, together with composition limits given for the product according to different standards. The required standard will be fully met as specified on the order.

The chemical composition is given as % by mass.

Typical 0.0217.6Ti Nb
ASME II A SA-240 ≤0.030≤1.0017.0-19.0≤0.50≤0.030
ASME II A SA-240 ≤0.030≤1.0017.5-18.5Ti
ASTM A240 ≤0.030≤1.0017.0-19.0≤0.50≤0.030
ASTM A240 ≤0.030≤1.0017.5-18.5Ti
EN 10028-7 ≤0.030≤1.0017.50-18.50Ti
EN 10088-2 ≤0.030≤1.017.5-18.5Ti
EN 10088-4 ≤0.030≤1.017.5-18.5Ti
EN 10088-4 -5MEK ≤0.030≤1.017.5-18.5Ti
IS 6911 ≤0.030≤1.0017.0-19.0≤0.50≤0.30≤0.030
Mechanical properties

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


StandardRp0.2Rp1.0RmElongationImpact strengthRockwellHBHV
Product type: Cold rolled coil and sheet
Typical (thickness 1 mm)31033048055
ASTM A240 ≥ 205 ≥ 415 ≤ 89HRB ≤ 183
ASTM A240 ≥ 250 ≥ 430 ≤ 88HRB ≤ 180
EN 10088-2 ≥ 230430-630 ≥ 18
EN 10088-4 ≥ 230430-630 ≥ 18
IS 6911 ≥ 205 ≥ 415 ≤ 89HRB ≤ 183
Product type: Hot rolled coil and sheet
Typical (thickness 4 mm)3653955003178
IS 6911 ≥ 205 ≥ 415 ≤ 89HRB ≤ 183
Product type: Hot rolled quarto plate
IS 6911 ≥ 205 ≥ 415 ≤ 89HRB ≤ 183

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

Outokumpu Core 441/4509 has good corrosion resistance in solutions of many halogen-free organic and inorganic compounds over a wide temperature and concentration range. It can withstand many sufficiently diluted organic and mineral acids depending on the temperature and concentration of the solution. Core 441/4509 may suffer from uniform corrosion in strong organic and mineral acids, as well as in hot concentrated alkaline solutions. More detailed information on corrosion properties of Core 441/4509 can be found in Outokumpu’s Corrosion Tables published in the Outokumpu Corrosion Handbook and on Stainless Steel Finder.

In aqueous solutions containing halogenides, e.g. chlorides or bromides, pitting and crevice corrosion may occur depending on the halogenide concentration, temperature, pH-value, concentration of oxidizing compounds, or crevice geometry, if applicable. For short periods of time, for instance when cooking food in stainless steel dishes, Core 441/4509 can even tolerate relatively high chloride concentrations. The presence of corrosion inhibiting or accelerating compounds like e.g. transition metal ions or organic compounds may influence the corrosion behavior of Core 441/4509. Due to its ferritic crystal structure, Core 441/4509 is not prone to chloride-induced stress corrosion cracking.

Core 441/4509 can be used for indoor applications in rural areas and urban environments where chloride contamination is low. The best material performance is typically achieved with the help of adequate design, correct post-weld treatment, and regular cleaning during use (if applicable).


Due to its titanium and niobium content, the risk of sensitization for intergranular corrosion is strongly reduced when compared to non-stabilized ferritic grades. Core 441/4509 can be used in the temperature range in which chromium carbides would precipitate in non-stabilized ferritic grades. Its maximum service temperature in dry air is 950 °C. The presence of other corrosive compounds in the hot environment like water or sulfur compounds may reduce the maximum service temperature significantly.

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


For more information on corrosion resistance, please refer to the Outokumpu Corrosion Handbook or contact our corrosion experts.

Physical properties

Data according to EN 10088


DensityModulus of elasticityThermal exp. at 100 °CThermal conductivityThermal capacityElectrical resistanceMagnetizable

Core 441/4509 can be formed using typical forming processes like folding, bending, drawing, etc. It has slightly higher proof strength than standard austenitic stainless steel grade 1.4301 / AISI 304 in combination with lower work hardening. Due to the titanium stabilization, its R-value is higher compared to non-stabilized ferritic stainless steel. These characteristics mean excellent deep-drawability.


Conventional welding methods and filler materials applied to austenitic 300-series can be used. Heat input in welding should be kept to a minimum level. Welded structures generally show lower ductility compared to that of base material.

More detailed information concerning welding procedures can be obtained from the Outokumpu Welding Handbook, available from our sales offices.

Standards & approvals

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


ASME SA-240M Code Sect. II. Part AUNS S43940; UNS S43940
ASTM A240/A240MUNS S43940; UNS S43940
EN 10028-7, PED 2014/68/EU1.4509
EN 10088-21.4509
EN 10088-41.4509
IS 6911, AMENDMENT NO. 2ISS 439Ti1