The formation of zinc ash and zinc slag, zinc ash, and zinc slag seriously affects the quality of the dipped zinc layer and causes the coating to be rough and produce zinc nodules. Moreover, the cost of hot-dip Galvanised Steel Coil is greatly increased. Usually, 80-120kg of zinc is consumed per 1t of the plated workpiece. If the zinc ash and zinc slag are serious, the zinc consumption will be as high as 140-200kg. The main control of zinc carbon is to control the temperature and reduce the scum caused by the oxidation of the zinc liquid surface. Some domestic manufacturers cover with refractory sand, carbon ash, etc. In foreign countries, ceramic or glass balls with low thermal conductivity, high melting points, small specific gravity, and no reaction with zinc liquid are used, which can reduce heat dissipation and prevent oxidation. Attachment.
The zinc slag formation in the zinc liquid is mainly a zinc-iron alloy with extremely poor fluidity formed when the iron content dissolved in the zinc liquid exceeds the solubility at this temperature. The zinc content in the zinc slag can be as high as 95%—the key to the high cost of zinc. From the solubility curve of iron in a zinc solution, it can be seen that the amount of dissolved iron, that is, the amount of iron loss, is different at different temperatures and different holding times. At around 500°C, iron loss increases sharply with heating and holding time, almost in a linear relationship. Below or above the range of 480 to 510 °C, the iron loss increases slowly with time. Therefore, people will be 480 ~ 510 ℃, known as the malignant dissolution zone. In this temperature range, the zinc liquid erodes the workpiece and the zinc pot most seriously, and the iron loss increases significantly when the temperature exceeds 560 °C. When the temperature exceeds 660 °C, the zinc is destructive to the iron matrix, and the zinc slag will increase sharply. As a result, the plating cannot be carried out. . Therefore, plating is currently carried out in two regions of 450-480°C and 520-560°C.