Grade 439
439 is a stabilised 20% chromium ferritic stainless steel, combining good corrosion resistance with high formability and weldability. This grade contains no nickel and is an economical alternative to grade 304 in many applications. Like all ferritic steels it is readily attracted to a magnet.
Grade 439
439 is a stabilised 20% chromium ferritic stainless steel, combining good corrosion resistance with high formability and weldability. This grade contains no nickel and is an economical alternative to grade 304 in many applications. Like all ferritic steels it is readily attracted to a magnet.
439 is most commonly available in sheet or coil up to about 2mm thick.
Corrosion Resistance
439 has good resistance in a wide variety of environments. The resistance of 439 to pitting and crevice corrosion in chloride environments is similar or superior to that of grade 304. Its PRE value of about 20 is above that of 304, confirmed by laboratory and service exposure testing. In outdoor exposure it performs similarly to 304. Chloride stress corrosion cracking (SCC) resistance of 439 is very high, as for all ferritic grades.
Its resistance to acids is generally slightly lower than that of 304, but performance varies for different acids.
Heat Resistance
439 resists oxidation in intermittent service up to 920°C and to 870°C in continuous service but it may become brittle at room temperature after prolonged heating in the 400 – 500°C range. This effect can be corrected by subsequent annealing.
Heat Treatment
Annealing
Heat to approximately 925°C, hold for only a few minutes and then water quench or quickly air cool. Slow cooling from 500-400°C will cause embrittlement. 439 is not hardenable by thermal treatment.
Welding
Welding of 439 can be readily carried out by all the common electric processes. As 439 has very low carbon and nitrogen contents and is stabilised by additions of titanium and / or niobium it has good resistance to sensitisation and hence intergranular corrosion. Like most ferritic grades it is subject to significant grain growth in the heat affected zones of welds. Heat input should therefore be kept to a minimum, and welding of thicknesses over 2mm become more difficult. Welding sections above 3mm is generally not recommended.
Gas shielding of the arc, weld metal and back side of the weld is important to minimise air contact. Shielding gases recommended for TIG (GTAW) are Argon or Argon + Helium. For MIG (GMAW) shielding is by Argon + 2% of Oxygen or Argon + 2% Carbon Dioxide or Argon + 2% CO2 + Helium. Use Grade 308L or 316L (or 316LSi) filler rod.
Machining
439 is easier to machine than the standard austenitic grades such as 304, but the grade is not currently available as a bar.
Fabrication
439 has a higher yield strength, lower tensile strength and lower work hardening rate compared to
Someoperations will therefore be easier, and some will require a little more force.
Stainless Steel 439 Grade Data Sheet
Mechanical and physical properties are very similar to those of common carbon steels, so formability is also very familiar for those fabricators with experience in carbon steel.
The lower ductility of 439 restricts some very severe operations. 439 has very good drawing capability; exceeding that of 304, but it has limited ability to stretch form. As these two processes are often combined in a single forming operation some changes to settings or tooling compared to the austenitic grades may be needed. Very severe cold working may not be possible, or may only be possible with an intermediate anneal.
Typical Applications
General sheet metal fabrication, bench tops, catering equipment, equipment cabinets, flues, process equipment, tank cladding.
Specified Properties
Because 439 is a very new alloy its properties are not yet included in any national or international specifications. The following composition and mechanical properties are typical, not specification limits. CompositionSpecification(%)(Typical values)
Specified Properties
Because 439 is a very new alloy its properties are not yet included in any national or international specifications. The following composition and mechanical properties are typical, not specification limits. CompositionSpecification(%)(Typical values)
| Grade | C | Mn | Si | P | S | Cr | N | Ti+Nb |
| 439 | 0.02 | 0.2 | 0.1 | 0.03 | 0.003 | 20 | 0.01 | 0.3 |
| Note: Because of on-going product development some minor changes may be made to this composition. | ||||||||
Mechanical Properties
| Grade | TensileStrength (MPa) | YieldStrength 0.2% Proof (MPa) | Elongation (%in 50mm) min. | Hardness VickersHV |
| 439 | 460 | 320 | 30 | 160 |
| Note: Because of on-going product development some minor changes may be made to these properties. | ||||
PhysicalProperties(Typical values in the annealed condition)
| Grade | Density (kg/m3) | Elastic Modules (GPa) | MeanCoefficientofThermal Expansion | Thermal Conductivity | Specific Heat | Electrical Resistivity |
| 0-100°C (µm/m/°C) | at100°C (W/m.K) | 0-100°C (J/kg.K) | (nΩ.m) | |||
| 439 | 7750 | 205 | 10.5 | 23 | 440 | 600 |
GradeSpecificationComparison
| Grade | UNS No | Euronorm | Swedish SS | Japanese JIS | |
| No | Name | ||||
| 439 | – | – | – | – | – |
| Note:No national or international specifications cover this grade as yet. | |||||
Stainless Steel 439 Grade Data Sheet
PossibleAlternativeGrades
| Grade | Whyitmightbechoseninsteadof439 |
| 304 | Better ductility is required for severe forming. Better weldability in heavy sections is needed. Product is required in thicknesses above those of 439. |
| 430 | Lower cost is required, and reduced weldability, formability and corrosion resistance can be tolerated. |
| 444 | Higher corrosion resistance is required, particularly in chloride environments. |
