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
350℃ will occur.
Short-term accidental heating500℃Beyond that, rapid mechanical property degradation.
Long-term high temperature (>450℃):Not recommended at all - serious oxidation and structural instability.
2. Performance changes at high temperature
200–300℃:Slight strength decrease; basically stable.
300–400℃:Yield strength drops significantly; accelerated surface oxidation.
Above 450℃: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 Q235far 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℃ surface temperature
5. What it CANNOT be used for
Long-term high-temperature pipelines
Furnace linings, high-temperature structural parts
