Q550NH is a high-strength atmospheric corrosion-resistant steel (weathering steel) with a minimum yield strength of 550 MPa. Its hardness typically ranges from 180–230 HB (Brinell Hardness) in the delivery state (usually hot-rolled or normalized). This places it in the medium-hardness range for structural steels, harder than low-carbon steels (e.g., Q235, ~120–150 HB) but softer than high-alloy or heat-treated steels (e.g., some alloy steels with hardness >300 HB).
Q550NH can generally be processed with ordinary high-speed steel (HSS), but its machinability is slightly lower than that of low-carbon steels due to its higher strength and alloy content (e.g., Cu, Cr, Ni for corrosion resistance). Here are key considerations:
: HSS tools can be used for simple operations (e.g., drilling, turning) but may wear faster than when machining softer steels. For higher efficiency or continuous production, carbide tools (e.g., WC-Co alloys) are recommended due to their better wear resistance and heat resistance.
: Compared to low-carbon steels, Q550NH may require lower cutting speeds and higher feed rates to reduce tool wear. Cooling lubricants are also advisable to dissipate heat and improve surface finish.
