Type 409 Stainless Steel(UNS S40900) is a stabilized ferritic
stainless steel that provides improved oxidation and corrosion
resistance compared to carbon steel. Ease of fabrication combined
with its corrosion resistance and economy have significantly
broadened its utilization in automotive exhaust and other
non-automotive applications.
ASTM A240 defines three (3) sub categories of Type 409 stainless
steel; UNS S40910, UNS S40920 and UNS S40930. Each of these
designations has a slightly different Ti or Nb stabilization
requirement. Each of these compositions can be supplied as UNS
S40900 unless the purchaser specifically identifies a specific
composition.
It is produced with enhanced formability characteristics known as
High Performance” or Ultra Form” in the industry.
Specifications
ASTM A240
Typical Applications: Automotive exhaust systems applications such as manifolds exhaust
pipes, catalytic converters, mufflers, tail pipes and other
components. Non-automotive exhaust applications such as home
heating systems, automotive thermostats and fuel filters,
electrical transformer cases, caskets and heat exchanger tubing.
Chemical Composition: (ASTM A240)
Element | UNS S40910 | UNS S40920 | UNS S40930 |
Carbon | 0.030 max. | 0.030 max. | 0.030 max |
Manganese | 1.00 max. | 1.00 max. | 1.00 max. |
Sulfur | 0.020 max. | 0.020 max | 0.020 max |
Phosphorus | 0.040 max. | 0.040 max. | 0.040 max. |
Silicon | 1.00 max. | 1.00 max. | 1.00 max. |
Chromium | 10.5 11.7 | 10.5 11.7 | 10.5 11.7 |
Nickel | 0.50 max. | 0.50 max. | 0.50 max. |
Nitrogen | 0.030 max. | 0.030 max. | 0.030 max. |
Titanium | 6x(C+N) min. 0.50 max. | 8X(C+N)min. / 0.15 0.50 | 0.05 min. |
Niobium | 0.17 max. | 0.10 max. | |
Ti + Nb | | | [0.08+8x(C+N)] min. 0.75 max. |
Mechanical Properties
Type | Yield Strength 0.2% offset (KSI) | Tensile Strength (KSI) | % Elongation (2" Gauge length) | Hardness Rockwell |
S40910 | 25 min. | 55 min | 20 min. | HRB 88 max. |
S40920 | 25 min. | 55 min. | 20 min. | HRB 88 max. |
S40930 | 25 min. | 55 min. | 20 min. | HRB 88 max. |
Physical Properties
Density (lb./ in^2) @ RT | | 0.28 |
Modulus of Elasticity in Tension (psi x 10^6) | | 29 |
Specific Heat (BTU/°F/lb.) | 32 to 212 °F | 0.114 |
Thermal Conductivity (BTU/hr/ft^2/ft) | 212°F | 14.4 |
Mean Coefficient of Thermal Expansion (in. x 10^-6 per °F) | 32 to 212°F | 5.84 |
| 32 to 500°F | 6.12 |
| 32 to 900°F | 6.60 |
| 32 to 1,200°F | 6.86 |
Electrical Resistivity (micro ohms - cm) | at 70°F | 60.0 |
Oxidation Resistance - Continuous Service(°F) | | 1450 |
Forming
409 stainless can be cut, blanked stretch formed and drawn without
difficulty. The formability characteristics of Type 409 are very
similar to carbon steel.
Welding
Type 409is readily welded using the conventional weld
