409L Stainless Steel Sheet

409L Stainless Steel Sheet

409L stainless steel has strong resistance for corrosion, high temperature and fatigue. It prolongs the using span and reduces the weight of the exhaust system components. Introduction & Application 409L has strong temperature resistance; it can be made high efficiency engine and exhaust...
Product description

409L stainless steel has strong resistance for corrosion, high temperature and fatigue. It prolongs the using span and reduces the weight of the exhaust system components.


Introduction & Application

409L has strong temperature resistance; it can be made high efficiency engine and exhaust system, and reduce the thickness of exhaust system and exhaust emissions.

409L has the advantages of low cost, good flexibility, high yield, easy to replace; it belongs to the new environmental product.


409L stainless steel has good corrosion resistance, suitable for prolonging service life of automobile and reducing weight. As recyclable environmentally friendly materials, major automobile manufacturers like GM, Ford, Volkswagen, Daimler Chrysler and others choose stainless steel in exhaust system. The automobile exhaust system disposes the high temperature, high speed combustion exhaust gas generated by the automobile engine and discharges it outside of the car. The main function of the exhaust system is reducing vibration and noise, reheating the exhaust gas and converting it to clean gas. The exhaust system is the longest component in vehicle parts. This system needs stand the influences like extreme large temperature change from -20℃ to 850℃, the high frequency shaking of high temperature, high speed exhaust gas. It is in the most complex environment in the vehicle. The temperature deadline of 409L can stand is -20~650℃.


Recently the using standard of exhaust system is becoming more strict due to the increasingly stringent standards environmental protection had on automobile exhaust, the raising number of short distance urban driving and dispersion of winter snow removal agent. From Euro II to Euro IV standard, the traditional stainless steel material can not meet the technique requirements. The high end motorcycle exhaust system has adopted 409L material already. The stainless steel amount used in each vehicle is 35KGS to 65KGS.


409L/S40903 Characteristics of Stainless Steel

409L/S40903 is a kind of ultra low carbon ferritic stainless stee; good oxidation performance and welding performance.


Mechanical Performance

409L/S40903 stainless steel forging technique and standard  

preheat /760℃ initial forging temperature/1040~1120℃ final forging temperature/705~790℃

Cooling Method: air cooling


409L/S40903 Heat Treatment of Stainless Steel

The annealing temperature is 780~950℃, quick cooling or slow cooling, Hardness: 197HBW.


409L/S40903 Usages of Stainless Steel

409L/S40903 stainless steel are mainly used for manufacturing the automobile exhaust treatment device.


Crystalline Characteristics

When 409L steel is crystallized, the two-phase region of solid and liquid is very small, less than 30 30℃. No γ phase at high temperature. Therefore, when the 409L stainless steel begin to crystallize after casting, due to the direct contact with mold surface, the super cooling degree of t liquid phase is rather large, and the mold surface also promotes non spontaneous nucleation. So the nucleation rate of liquid phase is very high and cause the formation of surface fine equiaxed grains.


The formation speed of the surface equiaxed grain region is very fast. The carbide of the titanium is too short to precipitate at this point.


Unlike the general steel, 409L steel does not form column crystal after the formation of fine equiax grain areas. Due to the narrow temperature range between the liquid and solid phase zone, the under-cooling zone is rather small when crystallizing and the column crystal is difficult to grow forward.


At the same time, after the formation of fine equiaxed grains area, after a period of time, titanium and carbon have time to diffuse to form titanium carbide particles, which promote non spontaneous nucleation.


These above two reasons making this area generate equiax crystal not columnar crystal. There is no columnar crystal but equiax crystal of different sizes on the cross section.


In the process of casting, when the billet temperature drops to 1100℃, if the carbon content is high, partial Cr and C will form carbide, causing poor chromium area around the carbide, there may be a small amount of delta phase.


At this time, there are two different phases in the steel, or the delta phase content is 32% to 6O%, which is the plastic area of the billet

The carbon content of 409L steel is very low, even if the delta phase appears, the amount is very small. Therefore, there will be no big impact on the performance.

409L steel has almost no alpha to gamma phase transition from high temperature to low temperature. So the grain is easy to grow and coarse ferrite organization would appear as a result. With its low strength, in continuous casting slab, elbow phenomenon might occur when cutting off the slab and going upward, affecting the normal production. The main problem of 409L steel crystallization is reduced performance caused by coarse grains. 

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