grade

1. Choose the right metal for your operating environment

To determine which grade of steel will uphold best in a given environment, think about the conditions your final product will face. Extremely low pH, high stresses and high temperatures, and crevice corrosion negatively impact stainless steel performance.

Corrosion resistance is the main reason for choosing austenitic stainless grades. With any steel grade, high-quality structural design is the best defense against corrosion.

2. Consider your customers’ preferences

Many designers choose stainless steel for its aesthetic appearance, whether that appearance is a shiny, electro-polished “bright” finish, a dull “pickled” finish, a matte surface polished to a specific RMS, or a light-absorbing black oxide coating. Austenitic stainless steel can take any of these finishes plus the common addition of passivation.

Customers may also need certification for application-specific specifications. For instance, ASTM A213 and A249 should be used for boiler, super-heater, and heat-exchanger tubes, while ASTM A908 should be used for hard-drawn austenitic stainless steel industrial needle tubing. There are more than 12,000 ASTM standards, and each addresses a specification so customers know the technical standards tested for chemical composition, heat treatment or temper, and other physical and mechanical attributes.

3. Prioritize strength, ductility, and toughness

Strength: The stress a metal can withstand before it fractures or deforms

Ductility: The ability of a material to have its shape changed, such as being drawn out into a wire or thread, without losing strength or breaking

Toughness: The metal’s ability to deform and absorb energy before fracture

Stainless steel contains 10–30% chromium as its alloying element, which is what helps it resist corrosion. The nickel addition in austenitic grades provides the highest toughness and ductility among stainless grades. Grades high in chromium, molybdenum, and nickel are the most resistant to corrosion.

Alloy content is not the only aspect to consider when choosing a grade of stainless steel; the material’s processing also affects is mechanical response. The duration of time steel is held at different temperatures as part of its cooling process, as well as the total speed at which it is cooled, can affect its overall quality.

4. Factor in form and process

Austenitic stainless steel is widely available in bar, wire, tube, pipe, sheet, and plate forms; Most products require additional forming or machining before they can be used for their specific application.

When welding any stainless steel parts, embrittlement in the weld area is a top concern. Choose a lower carbon grade like 304, 304L, or 316L to reduce carbide formation.

5. Manage material cost and availability

Although high-performing austenitic stainless steels are the most expensive stainless steels up front, they are well worth the investment. Choosing a corrosion-resistant material well-suited to its application reduces maintenance, downtime, and replacement costs. Life-cycle costing methods can quantify current and future costs and create an “apples-to-apples“ comparison of different materials.