1. Mechanism of toughness improvement
Grain refinement: Normalization involves heating Q295GNH to a temperature above the Ac3 critical point (typically 880–920°C) to form austenite, then cooling it in air. This process eliminates coarse or uneven grains formed during hot rolling, resulting in finer, more uniform ferrite-pearlite microstructures.
Reduction of inhomogeneity: It homogenizes the distribution of alloying elements (such as Cu, Cr, Ni) and carbides, reducing microstructural defects that cause stress concentration and brittle fracture.
2. Specific performance enhancements
Increased impact toughness: The refined grain structure and uniform microstructure allow the material to absorb more energy during impact, significantly improving its resistance to brittle failure (especially at lower temperatures).
Balanced strength and toughness: Unlike some heat treatments that sacrifice strength for toughness, normalization maintains or slightly enhances the steel's strength while primarily boosting toughness, making it suitable for structural applications requiring both properties.
