Q460NH is a high-strength structural weathering steel designed primarily for excellent mechanical properties and atmospheric corrosion resistance at ambient temperatures. It does not possess the special high-temperature properties of heat-resistant steels, boiler steels, or stainless steels, so it is not suitable for long-term service in high-temperature conditions.
1. Recommended Temperature Limits
Continuous operating temperature: ≤ 200°CWithin this range, strength decreases slightly, surface oxidation is minimal, and basic performance remains stable.
Short-term occasional exposure: up to 250°CBrief exposure causes no obvious damage, but prolonged use leads to obvious performance degradation.
Above 300°C: Not recommendedSevere strength loss, rapid oxidation, and structural risks may occur.
2. Performance Changes at Elevated Temperatures
Significant loss of mechanical strengthYield and tensile strength decrease noticeably as temperature rises, so it can no longer reliably meet the design requirements for Q460-grade high-strength structures.
Failure of the weathering patinaInstead of forming a dense, protective rust layer, the surface produces thick, brittle, loose oxide scale that easily spalls, destroying its weathering resistance.
Microstructure degradationProlonged high temperature causes microstructure softening, grain coarsening, and reduced toughness and fatigue resistance.
Creep and deformation risksUnder continuous load at high temperatures, the steel may slowly deform or even develop cracks over time.
3. Suitable and Unsuitable Applications
Suitable
Normal atmospheric environments (−20°C to 120°C)
Outdoor bridges, buildings, machinery, and vehicles under standard temperature conditions
Unsuitable
Flues, chimneys, boiler casings, and engine exhaust systems
Equipment near furnaces, combustion chambers, or continuous heat sources
Long-term high-temperature pipelines or structural components
Any environment with sustained temperatures above 250°C
