Overview

Type 439 stainless steel, also known as UNS S43900 and EN-DIN 1.4510, is a stabilized 20% chromium ferritic stainless steel that combines good corrosion resistance with high formability and weldability. This grade contains no nickel and is an economical alternative to grade 304 in many applications. It is readily attracted to a magnet and is most commonly available in sheet or coil up to about 2mm thick  .

General Properties

Nominal Composition: C ≤ 0.070%, Mn ≤ 1.0%, P ≤ 0.040%, S ≤ 0.030%, Si ≤ 1.00%, Cr 17.00%-19.00%, Ni ≤ 0.50%, Ti 0.20%-1.10%, Al 0.15%, N ≤ 0.040%, Fe balance .

Physical Properties: Density 0.278 lb./in3 (7685 kg/m3), Modulus of Elasticity (E) 28.4 x 103 ksi (193 x 103MPa), Electrical Resistivity 24.0 μ ohm.in (60.0 μ ohm.cm) .

Applications

Type 439 stainless steel is used in applications that require oxidation and corrosion resistance, particularly in areas where temperatures may exceed the oxidation limit of Type 409 or where aqueous corrosion resistance, especially to chlorides, is needed. Applications include tubular manifolds and other exhaust system components

Corrosion Resistance

439 stainless steel is resistant to attack by potable water and many mildly or moderately corrosive chemical environments that are oxidizing in nature. It has superior pitting resistance to Type 304 in various chloride solutions and is not subject to stress corrosion cracking which may cause premature failure of austenitic steels in chloride-bearing environments.

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.

Machinability

439 is easier to machine than the standard austenitic grades such as 304 .

Welding

439 stainless steel is weldable by the usual stainless steel methods including spot welding, TIG, MIG, laser, and high-frequency tube welding. Properly welded, grade 439 alloy retains the corrosion resistance and almost all of the mechanical properties of the base metal in the weld fusion and heat-affected zones.

Hot Working 

Hot working for 439 stainless steel should be done at 1500 – 2000°F (816 – 1093°C).

Cold Working

439 stainless steel Can be cold worked but may require more force compared to austenitic grades.

Annealing

Stainless steel 439 alloy should be annealed between 1450 and 1600°F (790 and 871°C) and quickly cooled. Slow cooling from 500-400°C will cause embrittlement .

Hardening

439 is not hardenable by thermal treatment .