High-tensile steel bar remained heat treatment intensifying effect and oxide layer anti-corrosion research

The surface of hot rolled ribbed steel bar after remained-heat-treatment process readily corrodes and rusts on store and transportation process due to falling off of the surface of its oxide layer in the steel production. By studying different cooling intensity having what effect on rebar structure, mechanical property and the thickness and component of surface oxide layer, this paper analyses the influence factor of strengthening mechanism and anti-corrosion on the surface oxide layer of hot rolled ribbed steel bars (HRB). The result indicates that there is a certain extent improvement on the bar's yield strength and strength of extension after remained heat treatment, and that this change in large size bar is more distinct than which in small size's. The most distinct strengthening effect happens in a temperature on cooling table about 720 °C. Above 820 °C -the temperature on cooling table, all metallographic structure consist of ferrite and pearlite (F+P); under 725 °C, the sclerotic structure like bainite appears. With the temperature on cooling table arising, surface oxide layer thickens. In low temperature on cooling table, the sample integrates with matrix comparatively closely and has relatively better anti-corrode property.