What is ferritic stainless steel?

What is ferritic stainless steel?

409 stainless steel is a heat-resistant ferritic stainless steel, and the automobile exhaust parts made with it have good oxidation resistance and corrosion resistance. This stainless steel alloy can be made into automotive mufflers, manifolds, exhaust pipes, catalytic converters, mufflers and exhaust pipes. The excellent formability, weldability and corrosion resistance of 409 stainless steel make it used in many other fields, such as culverts, home heating furnaces, automotive thermostators, fuel filter transformer housings and agricultural equipment.

409 ferritic stainless steels are good in most areas, but intergranular corrosion can occur in welding heat affected zones in some industrial applications. The titanium and niobium content of the alloy is carefully matched to resist the sensitivity and intergranular corrosion that may arise in the weld heat-affected zone or other thermal exposure of the parent metal. Stable element ratio balance, no annealing after welding to restore ductility, you can get good weldability. Its formability and toughness will also be enhanced.

409HP stainless steel is a patented chemical composition of stainless steel. Like other 409 alloys, the 11% chromium content makes it more resistant to corrosion than carbon steel. This stainless steel has sufficient oxidation resistance and corrosion resistance to make it ideal for automotive emissions system applications. Alloys containing 18% chromium can be used for hot side discharge. The 409HP alloy has good machinability and is fully utilized in applications other than automotive.
In terms of stress fracture, the fracture data of 409 and 439 alloys are very close to each other at 649℃, while the fracture resistance time of 439 alloy will be slightly longer under special stresses. And because of the high chromium content in 439 alloy, the fracture resistance time of the material will be longer when the stress is 10.3MPa or lower at 816℃.

In terms of toughness, like other ferritic stainless steels, under the impact load, with the reduction of temperature, there will be a transition from ductility to brittleness. The tough-brittleness transition temperature is a function of many factors, including heat treatment, microstructure, stress state, loading rate, notch sharpness, thickness, and material uniformity. Generally 4.77mm and above thickness of 409 stainless steel plate, the DBTT value is higher than room temperature, indicating that the plate may be difficult to process due to brittle cracks.

In terms of corrosion resistance, 409 stainless steel alloy has a chromium content of 11%. Compared with carbon steel, the corrosion resistance of this stainless steel material is greatly improved. However, compared with other high-priced stainless steels with high chromium content, especially molybdenum content, its corrosion resistance is relatively low. However, 409 stainless steel can exhibit sufficient corrosion resistance and oxidation resistance in many automotive and non-automotive applications.