347 stainless round bar (ASTM A276; GB 06Cr18Ni11Nb) is a niobium-stabilized austenitic stainless steel with a specialized composition: 17.0–19.0% chromium (Cr), 9.0–13.0% nickel (Ni), 0.70–1.00% niobium (Nb), and ≤0.08% carbon (C).
Niobium forms stable carbides (NbC) that prevent chromium carbide precipitation during welding, eliminating intergranular corrosion in heat-affected zones-critical for high-temperature welded components like furnace tubes and heat exchangers. Its mechanical properties include 515 MPa minimum tensile strength, 205 MPa yield strength, and 40% elongation, maintaining performance up to 800°C. 347 is equivalent to EN 1.4550 and is widely used in petrochemical and power industries, with Made-in-China listings marketing it as "347 Weld-Stable Stainless Round Bar."