Supra 444/4521
EN 1.4521, ASTM TYPE 444 / UNS S44400

General characteristics

Supra 444/4521 is a nickel-free, molybdenum alloyed ferritic stainless steel with very good corrosion resistance, good cold formability, and high strength. Supra 444/4521 allows for thinner walls in tanks and is not prone to stress-corrosion cracking.


Supra 444/4521 is a 2% molybdenum-alloyed ferritic stainless steel with medium chromium that can be used in many corrosive environments. As a ferritic stainless steel, it has high resistance to chloride-induced stress corrosion cracking. Because of its titanium alloying, Supra 444/4521 can be welded in all dimensions without becoming susceptible to intergranular corrosion.

Typical applications

  • Hot water tanks
  • Drinking water pipes

 

Product forms, available sizes and finishes

Flat

Product typeFinishesThicknessWidth
Black hot band1U3,00-8,501000-1550
Cold rolled coil2B, 2BB, 2C, 2D, 2E, 2F, 2G, 2J, 2K, 2R0,05-3,583-1620
Cold rolled sheet2B, 2BB, 2D, 2E, 2F, 2G, 2J, 2K, 2R0,30-3,5818-1620
Hot rolled coil, pickled1C, 1G, 1M, 1U2,80-6,00750-1350
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 on 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.

CMnCrNiMoNOther
Typical 0.0218.02.0Ti Nb
ASTM A240 ≤0.025≤1.0017.5-19.5≤1.001.75-2.50≤0.035
EN 10028-7 ≤0.025≤1.0017.00-20.001.80-2.50≤0.030
EN 10088-2 ≤0.025≤1.017.0-20.01.8-2.5≤0.030
EN 10088-4 ≤0.025≤1.017.0-20.01.8-2.5≤0.030
IS 6911 ≤0.025≤1.0017.5-19.5≤1.001.75-2.50≤0.035
Mechanical properties

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

 

StandardRp0.2Rp1.0RmElongationImpact strengthRockwellHBHV
 MPaMPaMPa%J
Product type: Cold rolled coil and sheet
Typical (thickness 1 mm)35037052550
ASTM A240 ≥ 275 ≥ 415 ≤ 96HRB ≤ 217
EN 10028-7 ≥ 320420-640 ≥ 20
EN 10088-2 ≥ 300420-640 ≥ 20
EN 10088-4 ≥ 300420-640
IS 6911 ≥ 275 ≥ 415 ≤ 96HRB ≤ 217
Product type: Hot rolled coil and sheet
Typical (thickness 4 mm)3804204503285
ASTM A240 ≥ 275 ≥ 415 ≤ 217
EN 10088-2 ≥ 280400-600 ≥ 20
EN 10088-4 ≥ 280400-600
IS 6911 ≥ 275 ≥ 415 ≤ 96HRB ≤ 217
Product type: Hot rolled quarto plate
Typical (thickness 15 mm)36040054026
ASTM A240 ≥ 275 ≥ 415 ≤ 217
EN 10028-7 ≥ 300420-620
EN 10088-2 ≥ 280420-620 ≥ 20
EN 10088-4 ≥ 300420-620
IS 6911 ≥ 275 ≥ 415 ≤ 96HRB ≤ 217

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

Supra 444/4521 has very 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. Supra 444/4521 may suffer from uniform corrosion in strong organic and mineral acids, as well as in hot concentrated alkaline solutions. More detailed information on the corrosion properties of Supra 444/4521 can be found in Outokumpu’s Corrosion Tables published in the Outokumpu Corrosion Handbook and on www.outokumpu.com.


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, and crevice geometry, if applicable. The presence of corrosion-inhibiting or accelerating compounds like e.g. transition metal ions or organic compounds may influence the corrosion behavior of Supra 444/4521. Due to its ferritic crystal structure, Supra 444/4521 is not prone to chloride-induced stress corrosion cracking.


Supra 444/4521 can be used for indoor and outdoor applications in rural areas and urban environments where chloride contamination is low. The best material performance is reached usually 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 to intergranular corrosion is strongly reduced when compared to non-stabilized ferritic grades. Supra 444/4521 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 850 °C. The presence of other corrosive compounds in the hot environment, like water or sulphur compounds may reduce the maximum service temperature significantly.


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

Pitting corrosion resistanceCrevice corrosion resistance
PRECPTCCT
25<10<0

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

Data according to EN 10088

 

DensityModulus of elasticityThermal exp. at 100 °CThermal conductivityThermal capacityElectrical resistanceMagnetizable
kg/dm3GPa10-6/°CW/m°CJ/kg°CµΩm
7.722010,4234300.80Yes
Fabrication

Forming

Supra 444/4521 can be formed using typical forming processes such as folding, bending, and drawing. It has higher minimum proof strength than a standard austenitic stainless steel like Core 304/4301 in combination with lower work hardening behavior. Due to the stabilization, the R-value is higher compared to non-stabilized ferritic stainless steels. These characteristics mean excellent deep-drawability.


Machining

Supra 444/4521 is relatively easy to machine. Compared to austenitic grades, it has lower tendency to form edges, which gives a larger machining window. Since the machinability is comparable to that of low-alloyed carbon steels, the same recommendations regarding choice of tool, cutting speed, and cutting feed apply.


Welding

Supra 444/4521 has good weldability and can be welded with common fusion and resistance welding methods. Conventional welding methods like MMA, MIG, MAG, TIG, SAW, LBW, or RSW, except gas welding, are applicable. Austenitic 19 12 3 L (316L) or 23 12 2 L (309MoL) filler metals can be used.


Low interstitial levels and added stabilizer have made enormous improvements to the welding characteristics of ferritic grades. Heat input should be minimized to reduce the grain growth in the HAZ. Dual-stabilization (Ti+Nb) of Supra 444/4521 improves autogenously welded joints by refining the grain structure in the weld metal. Stabilization prevents chromium carbide precipitation, which could otherwise lead to sensitization embrittlement. Consequently, the stabilized grades are practically immune to intergranular corrosion in the as-welded condition.


Shielding gases should be Ar/He based, mixed with a maximum of 2% oxygen to improve the arc stability. Hydrogen and nitrogen additions are forbidden.


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.

 

StandardDesignation
ASTM A240/A240MTYPE 444 / UNS S44400
EN 10028-7, PED 2014/68/EU1.4521
EN 10088-21.4521
EN 10088-41.4521
IS 6911, AMENDMENT NO. 2ISS 444