409 stainless steel is a heat-resisting ferritic stainless steel providing good oxidation and corrosion resistance compared to carbon steel. This titanium stabilized grade is suitable for automotive exhaust systems, due to its good formability, weldability, and corrosion resistance, 409 stainless steel has been successfully used in other industrial applications as well.
Type 409 grade is ferritic stainless steel with less chromium (10.5 – 11.75%) and very little nickel (0.5% max). It combines good elevated temperature corrosion resistance with medium strength, good formability, and overall cost. It is less expensive to produce than 304.
409 Stainless Steel Overview
- Ferritic stainless steel with magnetic
- Cost-effective choice compared to 300 series stainless steel
- Excellent oxidation and corrosion resistance
- Good mechanical properties
- Typical applications in automotive exhaust systems and heat exchanger tube
409 Stainless Steel Chemical Composition
| Grade | C | Si | Mn | P | S | Cr | Ni | Ti | Fe |
|---|---|---|---|---|---|---|---|---|---|
| 409 | 0.08 | 1.00 | 1.00 | 0.045 | 0.045 | 10.5 – 11.75 | 0.5 | 6xC | Bal |
| TP409 | 0.08 | 1.00 | 1.00 | 0.045 | 0.030 | 10.5 – 11.7 | 0.5 | 6xC Min, 0.75 Max | Bal |
Max, %, 409 for ASTM A240 Plate, Sheet and Strip, TP409 for ASTM A268 seamless and welded tube
409 Stainless Steel 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 |
| TP409 | 380 | 170 | 20 | 207 | 95 |
409 for ASTM A240 Plate, Sheet and Strip, TP409 for ASTM A268 seamless and welded tube
409 Stainless Steel Physical Properties
| Melting Point | Density | Specific Gravity | Modulus Of Elasticity In Tension |
|---|---|---|---|
| 1480 – 1530 ℃ | 7.7g/Cm3 | 7.68 | 190 GPa |
Equivalent Grades Of 409 Stainless Steel
| USA ASTM | EU EN | Germany DIN | Japan JIS |
|---|---|---|---|
| 409 S40900 | X2CrTi12 | 1.4512 | SUS409L |
Corrosion Resistance
Grade 409 stainless steel has excellent resistance to exhaust gas and atmospheric corrosion, superior to that of 410 martensitic grades with 12% chromium and 3CR12. However, the corrosion resistance is lower than that of grade 430 steels containing 17% chromium. The surface of grade 409 steel is liable to mild corrosion, which limits the usage of steel for decorative purposes.
The corrosion resistance of 409 stainless steel is better than coated carbon steel, similar to that of Type 410 stainless steel, and less than that of Type 304/304L stainless steel. Type 409 is not suggested for cosmetic or surface-critical applications as light surface rusting can form during exposure to atmospheric conditions.
Welding
Grade 409 steels must be pre-heated to temperatures of 150 to 260°C before welding. Although grade 430 and 409 filler rods or electrodes can be used during the welding of grade 409 steels, grade 309 electrodes or filler rods are strongly recommended by AS 1554.6. Care should be taken to weld grade 409 steels with minimum heat, to mitigate grain growth.
The ductility of the welded products can be improved by annealing post-welding at temperatures of 760 to 815°C. However, this is not required for thin welded products. Welding of exhaust tubing of automobiles is carried out without filler rods.
Heat Treatment
Annealing of grade 409 steels is carried out at temperatures ranging from 790 to 900°C, followed by air-cooling. Thermal treatment does not harden grade 409 steels.
Typical Applications Of Type 409 Stainless Steel
- Automotive exhaust systems
- Catalytic converters
- Mufflers
- Tailpipes
- Farm equipment
- Structural support and hangers
- Transformer cases
- Furnace components
- Heat exchanger tube