Q235NH is a general-purpose atmospheric weathering steel, not designed for high-temperature service. Its high-temperature performance is basically the same as ordinary Q235 carbon steel-limited, and only suitable for short-term or low-temperature thermal environments.
1. Usable temperature range
Continuous service: ≤ 350°CAbove this temperature, obvious creep, softening, and strength loss will occur.
Short-term accidental heating: ≤ 500°CBeyond that, rapid mechanical property degradation.
Long-term high temperature (>450°C)：Not recommended at all - serious oxidation and structural instability.
2. Performance changes at high temperature
200–300°C:Slight strength decrease; basically stable.
300–400°C:Yield strength drops significantly; accelerated surface oxidation.
Above 450°C:Severe oxidation and scaling; matrix softens; risk of deformation.
3. Oxidation resistance at high temperature
Q235NH's weathering elements (Cu, Cr) provide slightly better oxidation resistance than Q235 at medium temperature, but far inferior to heat-resistant steels like 12Cr1MoV, 304/316 stainless.It will still form loose, thick oxide scale that falls off easily.
4. Typical high-temperature applications (only suitable for these)
Low-temperature flue pipes, vents
Engine covers, heat shields with short-term heat
Components near heat sources with ≤300°C surface temperature
5. What it CANNOT be used for
Boilers, pressure vessels at high temperature
Long-term high-temperature pipelines
Furnace linings, high-temperature structural parts
