When sourcing stainless steel for elevated temperature applications, understanding the distinction between standard, L (low carbon), and H (high carbon) grades is critical for B2B buyers and suppliers on Alibaba.com. The 304H grade represents a specialized variant of the ubiquitous 304 austenitic stainless steel, engineered specifically for service above 500°C (932°F).
The 'H' designation in 304H stands for 'high carbon,' but this terminology can be misleading. In stainless steel metallurgy, 'high carbon' for 304H means 0.04-0.10%, which is still relatively low compared to carbon steels. The purpose of this carbon range is to enhance short-term and long-term tensile and creep strength at temperatures exceeding 500°C, making it suitable for pressure vessel and boiler applications where structural integrity under thermal stress is paramount [3].
304H vs 304L vs 316: Technical Specification Comparison
| Property | 304H | 304L | 316 |
|---|---|---|---|
| Carbon Content | 0.04-0.10% | ≤0.030% | ≤0.08% |
| Tensile Strength | 515 MPa | 485 MPa | 515 MPa |
| Yield Strength | 205 MPa | 170 MPa | 205 MPa |
| Continuous Service Temp | 1500°F (815°C) | 800°F (427°C) | 1500°F (815°C) |
| Molybdenum Content | None | None | 2-3% |
| Cost Range | $1.60-3.50/kg | $1.50-3.45/kg | $2.50-3.50/kg |
| Primary Applications | Boilers, heat exchangers | Food processing, indoor | Marine, chemical, medical |
Temperature capabilities represent the most significant differentiator for 304H. According to Penn Stainless specifications, 304H supports continuous service at 920°C (1688°F) and intermittent service at 870°C (1598°F) [1]. Sandmeyer Steel confirms a maximum temperature of 1500°F (816°C) for sustained operation [2]. This makes 304H suitable for boilers, heat exchangers, steam exhaust systems, and power generation equipment where temperatures consistently exceed 500°C.
Pressure vessel codes such as AS1210 and AS4041 specify that standard grades cannot be used for parts operating at temperatures above 550°C. For these applications, materials with a carbon content of at least 0.04% are mandatory—making 304H the appropriate choice over 304L [3].
However, the elevated carbon content introduces a critical consideration: sensitization. When 304H is heated in the range of 425-860°C (797-1580°F), chromium carbides can precipitate at grain boundaries, reducing corrosion resistance in the heat-affected zone of welds [3]. This requires controlled welding procedures and often post-weld annealing at 1850-2050°F (1010-1120°C) followed by rapid cooling to restore corrosion resistance.
