SUS316L and SUS321 stainless steel: in-depth analysis of the working temperature environment
I. Material properties and core differences
SUS316L: Contains molybdenum (Mo, 2–3%) and extremely low carbon (C≤0.03%). Its core advantage is medium-temperature corrosion resistance (such as chloride ion environment), but its high-temperature oxidation resistance is weak.
SUS321: Adds titanium (Ti, ≥5×C%), stabilizes the grain boundary through titanium carbide (TiC), and has outstanding high-temperature anti-sensitization ability, but its chloride ion corrosion resistance is weaker than 316L.
II. Comparison of working temperature environment
SUS316L: medium-temperature corrosion resistance
Continuous use temperature: ≤800°C (1472°F).
Performance: In the range of 600–800°C, it has excellent resistance to chloride ion corrosion (such as seawater and salt solution), but its oxidation resistance decreases with increasing temperature at high temperatures, and it is necessary to avoid long-term exposure to temperatures above 800°C.
SUS316L stainless steel applications:
Chemical equipment: reactors, heat exchangers (containing chloride ion media).
Marine engineering: desalination pipelines, ship accessories (resistant to salt spray corrosion).
Food and medical: disinfection equipment (≤150°C), pharmaceutical machinery (resistant to acid cleaning fluid).
Intermittent use temperature: short-term tolerance of 870°C (1600°F), but avoid the 450–860°C range (prone to intergranular corrosion due to carbide precipitation).
Limitations:
The strength drops sharply at high temperatures (＞800°C), which is not suitable for long-term load-bearing or high-temperature oxidizing environments (such as coal-fired boilers).
No annealing is required after welding, but heat input must be controlled to avoid sensitization risks.
SUS321: High temperature resistance
Continuous use temperature: 427–816°C (800–1500°F).
Performance: Titanium stabilization treatment makes it completely immune to intergranular corrosion in the range of 427–816°C, and its high temperature strength (creep resistance, stress cracking resistance) is significantly better than 316L, meeting the requirements of ASME boiler and pressure vessel specifications for high temperature pressure-bearing parts.
Applications of SUS321 stainless steel:
Energy field: power station boiler superheater (long-term exposure to 500–800°C high temperature steam).
Automotive industry: exhaust system (resistant to high exhaust temperature, long-term stability below 816°C).
Heat treatment equipment: heating furnace components (frequent thermal cycles, resistance to thermal fatigue).
Intermittent use temperature: short-term resistance to 871°C (1600°F), good oxidation resistance (such as 1000 hours of exposure to 871°C only increases weight by 0.338 mg/cm²).
Limitations of SUS321 stainless steel:
It does not contain molybdenum, and its pitting resistance in high chloride ion environments is weaker than 316L. It is not recommended for use in marine or strong chloride media. Solution treatment (1010–1150°C water cooling) is required after welding to relieve stress.
.jpg)
.jpg)
.jpg)
