409 Stainless Steel


General Properties

Alloy 409 is a general purpose, chromium, titanium stabilized, ferritic stainless steel whose primary application is automotive exhaust systems. It contains 11% chromium which is the minimum amount for the formation of the passive surface film which gives stainless steels their corrosion resistance. It combines good elevated temperature corrosion resistance with medium strength, good formability, and overall cost. Alloy 409 resists corrosion strongly compared to carbon steel and is used as an alternative to carbon steel in mildly challenging environments where its high resistance to corrosion and high temperature oxidation gives an advantage. It is commonly used in applications where appearance is a secondary quality to mechanical properties and corrosion resistance.

Applications:

Although Alloy 409 is designed principally for the automotive exhaust industry, it has been successfully used in other industrial applications as well. Some examples of applications that call for Alloy 409 include:

1.Automotive exhaust systems

2.Catalytic converters

3.Mufflers

4.Tailpipes

5.Farm equipment

6.Structural support and hangers

7.Transformer cases

8.Furnace components

9.Heat exchanger tubing

10.ASTM/ASME: UNS S40900

11.EURONORM: FeMi35Cr20Cu4Mo2

12.DIN: 2.4660

13.Resists atmospheric and exhaust gas corrosion

14.In most atmospheres a light surface rust will form which inhibits further corrosion but makes the surface less appealing

15.Generally classified as resistant to scaling in intermittent service up to 1499oF (815oC ) and up to 1247oF (675oC) in continuous service

16.Readily weldable

17.Pre-heat of 302 to 500oF (150 to 260oC) is recommended

18.Post-weld annealing at 1400 to 1499oF improved weld ductility

19.Post-weld annealing is not required when welding thin sections

20.Automotive exhaust tubing is typically welded without filler metal

Standards:

Corrosion Resistance:

Heat Resistance

Weldability

Chemical Properties:

 

C

Mn

Si

P

S

Cr

Ni

Ti

409

max:0.08

  max:1.0

max:1.0

max:0.045

max: 0.045

min: 10.5 max: 11.75

max: 0.5

min: 0.48  max: 0.75

Mechanical Properties:

Grade

Tensile Strength MPa (min)

Yield Strength 0.2% MPa(min)

Elongation %

Hardness (Brinell) MAX

Hardness (Rockwell B) MAX

409

380

207

20

207

95

Physical Properties:

Density
lbm/in3

Thermal Conductivity
(BTU/h ft. °F)

Electrical
Resistivity
(in x 10-6)

Modulus of
Elasticity
(psi x 106

Coefficient of
Thermal Expansion
(in/in)/
°F x 10-6

Specific Heat
(BTU/lb/
°F)

Melting
Range
(°F)

at 68°F: 0.280

9.4 at 212°F

28.3 at 68°F

29

5.84 at 32 – 212°F

0.114 at 68°F to 212°F

2500 to 2590

 

12.4 at 932 °F

39.4 at 752°F

 

6.60 at 32 – 1000°F

 

 

 

 

49.6 at 1652 °F

 

6.86 at 32 – 1500°F