Type 409L (UNS S40903/1.4512)

  • Resistant to high temperature, exhaust gas and atmospheric corrosion
  • It is a cheaper version of grade 409 steel
  • Easily fabricated, and resistant to heat
  • Applicable to non-corrosive or lightly corrosive environments
  • Used in automotive exhaust systems
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Although stainless steel 409L is designed primarily for applications in automotive exhausts, it has been used successfully in other industrial applications such as home heating systems, electrical transformer cases, and automotive thermostats, and fuel filters.

Stainless steel type 409L has a relatively low chromium composition, which makes it a low-cost option for corrosion-resistant steel. In addition, it is has a good formability and welding performance and is also highly resistant to oxidation in high temperatures.

Steel grade 409L contains a good amount of chromium, the low composition of carbon, nitrogen, and titanium, which enhances the corrosion resistance, weldability and formability of its products.

Common Names: Grade 409L, UNS S409L00

Executive Standards:

  • ASTM A240
  • ASME SA240
  • API
  • EN 10088-2 (1.4512) 

Chemical Properties:

The chemical properties of grade 409L stainless steel are presented in terms of its chemical composition as shown below.

ElementContent (%)
Manganese, Mn1.0 max
Phosphorus0.04 max
Silicon, Si1.0 max
Chromium, Cr10.5 min, 11.7 max
Carbon, C0.03 max
Nickel, Ni0.5 max
Sulfur, S0.03 max
Titanium, Ti6(C+N) min, 0.05 max
Niobium, Nb0.17 max
Nitrogen, N0.03 max

Mechanical Properties:

ItemTensile TestHardness TestBend Test
0.2%Y.S.1%Y.S.T.S.EL (%)HRBWHV180∘

 Physical Properties:

The physical property of the 409L grade steel is shown below.

Density (kg/m³)7600
Elastic Modulus (GPa)208
Mean Coefficient of Thermal Expansion (mm/m/°C)11.0 (0-100°C), 11.7 (0-315°C), 12.4 (0-538°C)
Specific Heat 0-100°C (J/kg.K)460
Electrical Resistivity (nW.m)600
Thermal Conductivity(W/m.K)25.8 at 100°C and at 500°C

Key Features:

  • It has a lower chromium composition.
  • Has a good combination of heat and corrosion resistance
  • Good formability and excellent flexibility

Product Forms Available:

It can be cut, blanked stretch formed and drawn: Coils, Foils, Rolls, Plain Sheet, Shim Sheet, Perforated Sheet, and Chequered Plate


  • 409L steel is used in automotive exhaust systems
  • Heat exchangers
  • Catalytic converter systems
  • Culverts
  • Home heating systems
  • Automotive thermostats
  • Fuel filters

Possible Alternative Grades:

304, 321, and 3CR12


  • How is stainless steel grade 409L different from grade409?

409L contains less chromium than 409, and it is not as resistant to heat and corrosion as 409 version. This also makes it cheaper. Its heat resistance is up to up to 850°C and up to 650°C in continuous service.

  • What category of stainless steel do 409L belong to?

Ferritic steel types.

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