Stainless steel pickling is affected by factors such as steel type, strip surface state, annealing conditions, etc. The process used is different and should be determined according to specific conditions. Acid Concentration Control (HNO3+HF) pickling reaction in mixed acid is relatively complicated. According to the concentration balance law of the general reaction formula and the actual experience of many manufacturers, the acid concentration of the mixed acid tank is usually controlled at 80-160g/l for HNO3, and 8-160g/l for HF. Between 30g/l. It should be pointed out that the concentration of HF should not be too high, otherwise the metal loss will increase and the surface will be rough. Most manufacturers adopt a pickling process combining sulfuric acid tank, nitric acid electrolytic tank and (HNO3+HF) mixed acid tank, in which the concentration of sulfuric acid tank is controlled between 150-200 g/l. Acid temperature control Increasing the temperature can increase the pickling effect as increasing the concentration. When the metal ion concentration exceeds 45g/l, the pickling effect of increasing the temperature is more obvious than increasing the concentration, so the “low concentration, high temperature” pickling process is often used. The higher the temperature of the acid solution, the faster the reaction speed and the better the pickling effect, but when the temperature is too high, the acid solution will evaporate seriously (especially HF acid), and the heat resistance of the pickling tank must also be considered, so the temperature Can not be too high, usually controlled at 50-60 ℃. The temperature of the acid liquid is usually controlled automatically. In order to prevent the abnormality of the instrument, it needs to be checked regularly. picture Fe ion concentration control During pickling, the acid solution will react with alloy elements such as Fe and Cr in the base metal to form metal salts (mainly Fe), and the acid concentration calculated by wet analysis includes the acid ions in the metal salts. Even if the acid concentration analyzed in this way is the same, the free acid content is different due to the different concentration of metal ions (iron ions) in the acid solution. That is, as the concentration of iron ions increases, the free acid content decreases, and the pickling effect decreases. In addition, if the concentration of metal ions in the solution is too high, insoluble fluorides will be formed, which will easily block the pump and piping. For this reason, the concentration of Fe ions should be managed to avoid over-pickling or poor pickling. The concentration of iron ions in the mixed acid tank should generally be controlled below 45g/l. In order to solve this problem, the AT-50 rapid analysis device is currently used to analyze the free acid content in the acid solution through electrochemical treatment. The basic working principle of the AT-50 rapid analysis device is to directly measure the amount of H+ and F- in the solution through the ion selective electrode, so as to calculate the concentration of the corresponding acid solution. To sum up, the core issue of the pickling process is to do a good job of acid management. In addition, it is also important to check frequently during the process of passing the board to prevent defects. The length of the pickling equipment is about half of the entire length of the deacidification unit. Defects often occur on the surface of the strip steel during the pass-through process, and they are covered. Defects are often discovered late. Therefore, it is necessary to strengthen spot inspections and establish a quality assurance system. .  

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