What does the GN45 mean in the Q355GNHD weathering steel plate?

GNH is the "high weather" Chinese phonetic alphabet, D is the grade, said the low temperature impact toughness requirements, the standard: GB / T 4171-2008 "weathering structural steel." High weathering steel is more resistant to atmospheric corrosion.
Introduction: Q345 series of high weathering structural steel plate, including 09CuPCrNi, Q345GNHL, SPA-H, Q355NH and other steel, such steel through the Cu, P, Cr, Ni alloying, metal substrate surface to form a protective layer, Which has a high resistance to atmospheric corrosion. Q355GNHD steel weather resistance than the welding structure with weathering steel is good, so called high weatherability structural steel. Q355GNHD steel is widely used in railway vehicles, all kinds of weathering building structural parts (especially for industrial atmospheric environment), bridge auxiliary structural parts and so on.
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