Annealing experiments were conducted on BH steel to which 10 × 10^-6 boron was added. The annealing temperature,holding time, H2 content, and dew point were varied in the experiments in order to investigate their...Annealing experiments were conducted on BH steel to which 10 × 10^-6 boron was added. The annealing temperature,holding time, H2 content, and dew point were varied in the experiments in order to investigate their influences on the selective oxidation of boron. A higher annealing temperature and longer holding time is found to lead to a higher concentration of boron at the extreme surface, which reaches saturation after the steel sheet is held for a critical period of time that depends on the annealing temperature. The effect of H2 content on the selective oxidation of boron depends on the annealing temperature and dew point. It has almost no influence on the external oxidation of boron when the sheet is annealed at 820 ~Cin an atmosphere with a dew point of -40℃. At a dew point of - 10℃, a lower H2 content results in a lower peak value of boron in the subsurface area but deeper internal oxidation of boron. An increase in the dew point from -40℃ to - 10℃ can significantly promote internal oxidation of boron at depths of 50 - 200 nm from the surface. With the suppression of external oxidation of boron as well as manganese and silicon, a relatively clean surface with reduced and refined oxides can be achieved by increasing the dew point.展开更多
文摘Annealing experiments were conducted on BH steel to which 10 × 10^-6 boron was added. The annealing temperature,holding time, H2 content, and dew point were varied in the experiments in order to investigate their influences on the selective oxidation of boron. A higher annealing temperature and longer holding time is found to lead to a higher concentration of boron at the extreme surface, which reaches saturation after the steel sheet is held for a critical period of time that depends on the annealing temperature. The effect of H2 content on the selective oxidation of boron depends on the annealing temperature and dew point. It has almost no influence on the external oxidation of boron when the sheet is annealed at 820 ~Cin an atmosphere with a dew point of -40℃. At a dew point of - 10℃, a lower H2 content results in a lower peak value of boron in the subsurface area but deeper internal oxidation of boron. An increase in the dew point from -40℃ to - 10℃ can significantly promote internal oxidation of boron at depths of 50 - 200 nm from the surface. With the suppression of external oxidation of boron as well as manganese and silicon, a relatively clean surface with reduced and refined oxides can be achieved by increasing the dew point.
