Stainless steel grade 409 ( UNS S40900 )Applications This type of grade 409 stainless steels are widely used for : Automotive exhaust tubing Catalytic converter systemsChemical Formulation   C:≤ 0.08  ,   Mn：≤1.00,  Si：≤1.00,  Cr：10.5~11.75,  Ni :≤0.50,  P：≤0.045,  S：≤0.03,  Ti：(6C~0.75)        Type 409 steels are available in highly stabilized forms, such as S40910, S40920, S40930, which stability of is provided by the presence of niobium, titanium in the composition. Introduction   409 stainless steels used to be called " the cheapest stainless steels ".    It is commonly considered as a chromium stainless steel, which have excellent corrosion  resistance, heat resistance and fatigue resistance. It can realize the exhaust system components  for a longer life time and a lightweight designs.   With high temperature resistance, the engine can work in high efficiency, at the same time,  reduce the thickness of exhaust system , can reduce the emissions. 409 stainless steels are  cheaper than other stainless steels, with a good flexibility, high yield, easy to replace, are  recyclable and environmentally friendly new materials. At present, Most famous major automobile  manufacturers have used type 409 stainless steel materials for their production. The automobile exhaust system can collect and disposal the emissions, which is high temperature, high speed combustion come from the engine. Then exhausts gas overboard and reduces the noise level  of the high velocity gas flow. The automobile exhaust system is the longest components of the auto  parts, which must bear strict temperature change ( from -20℃ to 850℃ ) and high frequenvy  vibration. The 409 stainless steels can work as the heat from -20℃ to 650℃.      Recently, as the global increasingly stringent environment target, the short distance urban  driving increasing, and the spread of Winter snow remover, the standard of using exhaust system is  getting more and more stringent. From standard Europe Ⅱ to Europe Ⅳ, the traditional steel can  not meet the technical requirements. We estimate each car need 409 stainless steels appr 35kgs -  65kgs in the futuer.Composition                  Table 1 -  Composition ranges of type 409 stainless steelsMechanical Properties              Table 2 - Mechanical properties of type 409 stainless steels                 Physical Properties             Table 3 - Physical properties of annealed type 409 stainless steelsType Specification ComparisonPossible replace with:Heat Resistance   Type 409 stainless steels can work at tempertatures up to 675℃ during continuous operation, and up to 815℃ under intermittent conditions. This is very important to service environments.Heat Treatment    For 409 stainless steels, annealing is carried out at temperatures from 790℃ to 900℃, followed by air cooling.Welding Performance    Type 409 stainless steels must be pre-heated to temperatures of 150 to 260°C before welding. Care should be taken to weld grade 409 steels with minimum heat, in order to mitigate grain growth.Ductility of the welded products can be improved by annealing post-welding at temperatures of 760 to 815°C.