Applicable High-Temperature Range
It can maintain stable performance in the temperature range of 200°C to 400°C for long-term use:
In this temperature range, the alloy elements (Cu, Cr, Ni) in Q355NH can still form and maintain a stable self-healing patina, which continues to play a corrosion-resistant role
Its core mechanical properties (yield strength ≥355 MPa, tensile strength 470-630 MPa) will only have a slight decline (less than 10%), which can still meet the requirements of general structural use
Limitations in Higher Temperature Environments
When the temperature exceeds 400°C, the performance of Q355NH will be affected to varying degrees:
Corrosion resistance decline: The patina structure will be destroyed, and the alloy elements will accelerate oxidation, forming a loose, non-protective oxide layer, which will lose the self-healing ability, and the corrosion rate will increase significantly
Mechanical properties decline: When the temperature exceeds 500°C, the internal microstructure of the steel will begin to change, the yield strength and tensile strength will decrease sharply, and the load-bearing capacity will be difficult to guarantee
Key Notes for High-Temperature Use
If used in the range of 200-400°C, it is necessary to avoid long-term contact with corrosive media (such as high-temperature steam containing chloride ions), which will accelerate the damage of the patina
Regular inspection of the surface oxide layer is required. If the patina is found to be damaged, it can be repaired by applying a weathering steel rust accelerator
It is not recommended to use Q355NH in environments with long-term temperatures exceeding 400°C. Special heat-resistant steel should be selected instead
