Outokumpu grade 4509 is a dual stabilized ferritic stainless steel having 18% chromium content. The material is also commonly called AISI 441, albeit this designation is missing in the ASTM standard. However, the code markings UNS S43940 and S43932 are equivalent to the European code 1.4509.
Corrosion resistance of grade 4509 is comparable to the austenitic grade 4301 (AISI 304) in some applications even though there is e.g. lower resistance to crevice corrosion. This means that grade 4509 is a perfect choice for similar, but selected applications as the austenitic grade 4301. Additionally, grade 4509l can be used in all the applications where grades 4510 (AISI 439) and 4520 (430 Ti) are used.
Outokumpu 4509 grade has good weldability thanks to a dual stabilization by titanium and niobium. Stabilization eliminates sensitization and helps to get equi-axed grain strain structure to the welded area. Filler materials used for austenitic 300-series materials can be used for 4509 grade. A typical microstructure of the weld seam can be seen in image 1.
Stabilization improves also formability and helps to prevent forming defects like roping, which is typical for the grade 1.4016. Elongation to fracture values up to 30% (A80) can be achieved.
Microstructure of the grade 4509 weld seam
Typical applications for the grade 4509 are different type of automotive segment applications, e.g. exhaust tubes and mufflers. Applications are mainly located in the hot end of the exhaust system, where better hot corrosion resistance and improved formability are needed.
Material is widely used in architectural applications like elevators and doorframes. Additionally, various structures in catering and household are among the application areas.
Grade 4509 is available from Outokumpu Tornio Works in hot rolled, 2E and cold rolled 2B delivery conditions. Thickness range varies from the 0,60mm to 2,00mm on cold rolled products and for RAPTM2E from 1,50mm to 4,50mm. Hot rolled material is available from 3,00mm to 6,00mm. Also wet polished surface finishes 3N and 4N are available.
For more information, contact:
Pasi Aspegren
Product Expert – Ferritics
Outokumpu Tornio Works, Finland
Phone: +358 16 454 208
Email: pasi.aspegren(at)Outokumpu.com