Indexed on: 07 Feb '09Published on: 07 Feb '09Published in: Metallurgist
This paper presents the results of transmission-electron-microscope and scanning-electron-microscope studies of the fine structure of wire rod made from Sv-08G2S silicon-manganese welding steel, including electron microscope images used to identify the structural components of the wire-rod metal and determine the dislocation density. The wire-rod microstructure was compared against that obtained when a new, optimized process was developed for heat-treatment of the wire rod in a Stelmor line. We show that the wire rod has the highest ductility when the production flow includes long-term holding of the wire-rod coils under quasi-isothermal conditions (under insulated hoods with a cooling rate 0.2–0.3°C/sec) in such a way as to minimize the number of bainite-martensite areas when the structureless martensite (hardenite) content does not exceed 5%. The resulting process and optimized microstructure enabled us to achieve a relative deformation of 98% when direct-drawing wire rod from Sv-08G2S alloy steel.