Description about 2BA stainless steel coil
Usually 2BA finish is called in China market, the 2BA stainless steel surface is between BA and 2B, compare to BA ,2BA surface darker a little, and with better price than BA, so 2BA sometimes be used for some products to replace BA finish
2BA production process is the similar with BA finish, and always just only from the certain mills, currently this finish products seldom be exported, but be used well in domestic stainless steel market
The purpose and requirements of the bright annealing/BA process of stainless steel:
1)Elimination of work hardening for satisfactory metallurgical structure
The bright annealing furnace is mainly used for heat treatment of stainless steel in a protective atmosphere. When the performance requirements are different, the requirements of the metallurgical structure after bright annealing are different, and the process of bright heat treatment is also different.
Another key issue for the heat treatment of stainless steel cold-rolled strips is the requirement that the entire strip be uniform in width and length. Muffle Bright Annealing Furnace adopts a large size Muffle tube, which evenly organizes the heated air flow spirally around the outside of the Muffle tube to uniformly heat the strip. In order to ensure the uniform organization of the strip along the length, the line speed of the strip in the furnace must be kept constant. Therefore, before and after the modern vertical light heat treatment furnace is equipped with a precise adjustment of the roller tension adjustment device. It not only must make the strip import and export speed meet the requirements of heat treatment speed, and is not affected by the idle sleeve or full sleeve, but also establish and finely adjust the small tension of the strip according to the strip type of the strip to meet the requirements of the plate type. Claim.
2)Get a bright surface without oxidation
In bright annealing, the strip is heat treated under a H2 atmosphere. To achieve the requirements of the BA sheets , the protective atmosphere in the furnace must be controlled very strictly to avoid oxidation. How Oxidation Occurs Under H2 Protective Atmosphere
The main alloy composition of stainless steel strip is Fe, Cr, Ni, Mn, Ti, Si and so on. In the annealing temperature range, the oxidation of Fe and Ni is not a major problem. However, the oxidation zone of Cr, Mn, Si, Ti is just within the heating temperature range. It is the oxidation of these alloying elements that affects the surface brightness of the strip. In particular, the oxidation of chromium dechromizes the strip surface and reduces the corrosion resistance of the stainless steel. When the Cr content is 17% to 18% and the Ti content is 0.5%, the dew point of H2 must be lower than -60°C to avoid the oxidation of Cr and Ti within the heating range of 800°C to 1150°C.
In addition, how to maintain the purity of the shielding gas in the furnace is also a key issue. In this regard, the Muffle hood seals well and does not cause contamination of the protective atmosphere by electric heating of the furnace body material, providing a purer environmental space. In addition, the strip furnace entrance and exit of the vertical furnace are located in the lower part of the furnace, and the furnace pressure is stable. Therefore, compared with the horizontal furnace, the risk of air entering is much smaller. However, the import and export sealing boxes, strip conveying sections, tension regulating rollers, and furnace top guiding roller boxes of the bright annealing furnace should ensure the sealing requirements of a few parts per million (ppM), so that oxygen and water vapor cannot enter, and the gas is protected. Can't be released