304H

304H stainless steel is the high-carbon version of 304 stainless steel, designed for superior performance in high-temperature environments. It is also referred to as the UNS S30409 / W.Nr. 1.4948 stainless steel.

304H stainless steel is the high-carbon version of 304 stainless steel, designed for superior performance in high-temperature environments. While 304L is known as the low-carbon alternative, 304H contains a controlled carbon content of 0.04%–0.10%, which significantly improves its strength at elevated temperatures between 427°C and 800°C.

One consideration is that 304H stainless steel becomes sensitized when exposed to 425–860°C, reducing its aqueous corrosion resistance. However, this is not an issue for high-temperature service where corrosion resistance in water-based environments is not required. For this reason, 304H is not recommended in applications where subsequent aqueous corrosion resistance is needed within the sensitization range.

Compared with 304L, 304H offers superior short-term and long-term creep strength above 500°C and also demonstrates better resistance to sensitization. Thanks to its excellent heat resistance and mechanical stability, 304H stainless steel is widely used in the manufacturing of ASME pressure vessels operating at temperatures above 525°C.