Austenitic Stainless Steels
Summary of Physical & Chemical Properties
With the rising cost of alloying elements such as nickel, the 201 grade of stainless has gained attention as an alternative to certain 300 series grades where corrosive environments are moderate to low. A higher quantity of manganese is added to this grade in order to reduce the nickel content and ultimately reduce the cost. Due to the higher levels of carbon in the 201 grade, weldability may not be as good as 304L grade and carbide precipitation may occur. Applications include sinks, restaurant equipment, automotive trim and appliances.
304 is the standard '18/8' stainless and known to be the most versatile and most widely used stainless steel. It is chosen for its suitability for use in highly corrosive environments, resistance to chromium carbide precipitation, high formability and high weldability. 304L grade is an extra low carbon version of 304 which offers additional resistance to carbide precipitation during welding, therefore eliminating the need for post weld annealing in most cases. Applications include kitchen equipment, welded components of chemical, textile, pharmaceutical and paper processing equipment, cosmetic automotive trim, air bag inflator tubes, automotive and truck exhaust components.
With higher levels of chromium and nickel than that of the 304 grade, 309 offers improved corrosion resistance in marine environments and certain lower pH applications. 309 also offers good strength and corrosion resistance at elevated temperatures. 309S is equivalent to 309 except for a specified lower carbon content which offers resistance to carbide precipitation and improved weldability. Applications include chemical processing equipment, boiler and heat exchanger tubes, furnace parts and automotive components.
This stainless grade is similar to that of the 304 grade, but with additions of molybdenum, greater corrosion resistance and improved high temperature strength is achieved. Corrosion resistance to lower pH and chloride solutions can be attributed to this particular grade's combination of stainless alloying elements. 316L grade is an extra low carbon version of 316 which offers additional resistance to carbide precipitation during welding, therefore eliminating the need for post weld annealing in most cases. Applications include parts exposed to marine atmospheres, furnace components, heat exchanger tubes, and exhaust manifolds.
Titanium is added to this grade as a carbon stabilizer to limit carbide precipitation during welding and intermittent high temperature cycling. Corrosion resistance properties are similar to that of the 304 grade but improved at higher temperature ranges normally conducive to carbide precipitation. Applications include oil refinery equipment, welded boiler and pressure vessels and diesel and heavy duty exhaust systems.