Automotive exhaust systems are the main use for Alloy 409, a general-purpose ferritic stainless steel stabilized with chromium and titanium. The minimum quantity of chromium required for the production of the passive surface coating that gives stainless steels their corrosion resistance is found in it at 11%. It combines moderate strength, decent formability, and overall cost with strong elevated temperature corrosion resistance.
The combination of heat resistance and corrosion resistance found in Stainless Steel 409 Plates makes them an excellent choice for applications or situations that are neither heavily nor moderately corrosive. For use in oil equipment or vehicle exhaust pipes, SS UNS S40900 Plate has exceptional oxidation resistance in high temperatures.
As an alternative to carbon steel in mildly difficult conditions where its high resistance to corrosion and high-temperature oxidation gives an advantage, alloy 409 has a stronger corrosion resistance than carbon steel. It is frequently utilized in situations where mechanical qualities and corrosion resistance take precedence over appearance.
It is especially helpful in applications where corrosion or oxidation protection is required beyond what carbon steel and some coated steels can provide. Due to the presence of chromium, 409 has lower corrosion resistance but strong oxidation resistance and formability. Although the corrosion resistance of 409 is less than that of 304, 430, or 439 grades, it is still significantly superior to mild carbon steel. Roll forming, stretch bending, deep drawing or pressing can be used to create 409. When cold worked with mild roll forming methods like stretching or pressing, 409 does not harden when in the annealed condition. Grade 409 welding performance is acceptable. Because of the potential for grain structure growth in heat-affected zones, which may directly impair the mechanical properties, this stainless-steel material should not be utilized in impact-loaded constructions. Tubing and stampings for motor vehicle exhaust systems frequently employ the alloy 409.