Bright annealing is the heat treatment of strip steel in an H2 protective atmosphere. To meet the requirements of BA board, it is necessary to strictly control the protective atmosphere inside the furnace and try to avoid oxidation. How does oxidation occur under H2 protection atmosphere

The main alloy components of stainless strip steel include Fe, Cr, Ni, Mn, Ti, Si, etc. Within the annealing temperature range, the oxidation of Fe and Ni is not the main problem. But the oxidation range of Cr, Mn, Si, and Ti happens to be within the heating temperature range. It is the oxidation of these alloy elements that affects the surface brightness of the strip steel. Especially the oxidation of chromium causes the surface of the strip steel to remove chromium, which can reduce the corrosion resistance of stainless steel. When the Cr content is between 17% to 18% and the Ti content is 0.5%, the H2 dew point must be below -60 ℃ to avoid the oxidation of Cr and Ti within the heating range of 800C to 1150 ℃.

In addition, how to maintain the purity of the protective gas in the furnace is also a key issue. In this regard, the muffle cover has good sealing performance and does not pollute the protective atmosphere like the electric heating furnace material, providing a relatively pure environmental space. In addition, the strip steel inlet and outlet of the vertical furnace are located at the lower part of the furnace, ensuring stable furnace pressure. Therefore, compared to the horizontal furnace, the danger of air entering is much smaller. However, the inlet and outlet sealing boxes, steel conveying sections, tension adjustment rollers, and furnace top guide roller boxes of the bright annealing furnace should ensure that they meet the sealing requirements of parts per million (ppM level), so that oxygen and water vapor cannot enter and protective gases cannot escape.