Which type of stainless steel is most commonly used for high-temperature applications?

The choice of grade 309 stainless steel for high-temperature applications is based on its composition and characteristics that make it suitable for such environments. Grade 309 stainless steel contains a higher percentage of nickel compared to other stainless steel grades. This higher nickel content enhances its oxidation resistance and allows it to maintain strength even at elevated temperatures, which is crucial in applications like furnace construction, heat treatment, and industrial processes.

Additionally, grade 309 exhibits excellent resistance to oxidation and scaling in high-temperature exposure, making it a preferred material for components that operate under these conditions. Its ability to maintain structural integrity and resist deterioration helps to ensure longevity and performance in applications where other stainless steels might fail or degrade.

In contrast, other options like 316, while offering good corrosion resistance, are not primarily designed for high-temperature environments. Grade 430 is a ferritic stainless steel that has lower nickel content and is generally more suited for applications that don't demand high-temperature performance, as it can become brittle under such conditions. Grade 201, although less expensive and somewhat better in some aspects than 430, also lacks the heat resistance and ductility required for high-temperature applications.

Thus, the characteristics of grade 309 make it the most suitable choice for high-temperature applications among the given options